docs: complete the 5.4.4 changelog entry

The release script only picks up unscoped feat:/fix: subjects, so the
presence/simplex feature was missing from the generated entry.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Uc9V1v7iXruubpoLiSE24M

.gitignore

@@ -16,3 +16,4 @@ uv.lock
 .superpowers/
 rndc-key
 docs/superpowers/
+graphify-out/

CHANGELOG.md

@@ -2,6 +2,57 @@
 
 All notable changes to this project are documented here, organized by release.
 
+## [5.4.4]
+
+### Added
+- client reports per-protocol (IPv4/IPv6) internet presence: a connectivity probe (route check every ~5s, ICMP echo every ~60s, debounced) sends `p4`/`p6` flags on every heartbeat and a `connectivity` metric (presence, own address, gateway, RTT) via `network_monitor`
+- server monitors only the protocols a client reports as present; a protocol reported absent is shown as `absent` and raises no alert
+- host status (`up`, `simplex`, `overdue`, `down`, `unknown`) computed on the server: a host is overdue only when every present protocol is overdue; `simplex` (both present, one silent) has the same severity as `up` and is logged without notification
+- live and plugins pages show the host status, `simplex`/`absent` protocols and a Connectivity table
+- `hbc` config keys under `network_monitor`: `probe_enabled`, `probe_v4`, `probe_v6`, `probe_interval`
+
+### Changed
+- overdue and recovery alerts are raised per host, not per protocol: a single CRITICAL when the last present protocol goes overdue; a protocol coming back while another stayed up is logged as INFO instead of a RECOVER notification (also applies to clients that do not report presence)
+
+### Fixed
+- never park the last present family as absent, so a host that reports no protocol as present still alerts when it dies
+- keep the connectivity alert for a host overdue past the drop window across an `hbd` restart
+- `default_gateway` never raises; a protocol whose probe cannot run stays unknown rather than absent
+
+---
+
+## [5.4.3]
+
+### Fixed
+- fix RTT y-axis label clipping, add x-axis tickmarks, enlarge charts
+
+---
+
+## [5.4.2]
+
+### Fixed
+- preserve chart history across reconnects, show gaps for missing data
+
+---
+
+## [5.4.1]
+
+### Added
+- live-refresh Connectivity section and RTT charts every 30s
+- render RTT history chart per connection in Connectivity section
+- record RTT history per heartbeat for charting
+
+### Fixed
+- correct empty-state copy on Host Overview page
+- stop synthetic rtt_* keys from masking real plugin-data checks
+- use the latest RTT sample, not the oldest, in host info API
+- hide synthetic rtt history keys from plugin accordion list
+- remove extra blank line to pass flake8 E303 check
+- clear flap state when a host is dropped
+- correct plugin import path in docs, wire up orphaned footer template
+
+---
+
 ## [5.4.0]
 
 ### Added

CLAUDE.md

@@ -1,8 +1,97 @@
+# CLAUDE.md
+
+This file provides guidance to Claude Code (claude.ai/code) when working with code in this repository.
+
+## Working principles
+
 1. Don't assume. Don't hide confusion. Surface tradeoffs.
 2. Minimum code that solves the problem. Nothing speculative.
 3. Touch only what you must. Clean up only your own mess.
 4. Define success criteria. Loop until verified.
 
-This project's hbd daemon is deployed and in production on host w02 
+## Commands
-under user 'nagios', which you can reach via ssh nagios@w02.
+
- The hbc client is used on 30 hosts in multiple networks.
+```bash
+# Run tests
+pytest -q                        # all tests
+pytest tests/test_threshold.py   # single file
+pytest -k test_name              # single test
+
+# Lint and type check
+tox -e lint     # flake8 over hbd/ and tests/
+tox -e mypy     # mypy over hbd/
+
+# Install for development
+pip install -e ".[all,dev]"
+
+# Run server
+python -m hbd.server.cli serve -c .hb.yaml -f -v
+
+# Generate a password hash
+hbd passwd <username>
+```
+
+Tests live in `tests/` (pytest, imported as a package). A second directory `test/` contains only TLS fixtures (`.pem` files), not test code.
+
+Line length: 111 characters (`black`, `flake8`, both configured).
+
+## Architecture
+
+The system has two components: `hbc` (client) and `hbd` (server), both in the `hbd` Python package.
+
+```
+hbd/
+  common/    # proto.py (encode/decode), utils.py
+  client/    # hbc: plugins/, main.py, config.py, plugin.py
+  server/    # hbd: all server modules
+```
+
+### Server module map
+
+| Module | Role |
+|---|---|
+| `cli.py` | Argument parsing, entry point, daemon startup |
+| `main.py` | Asyncio runtime: starts UDP, HTTP, WebSocket; pickle save/load |
+| `hbdclass.py` | `Host` and `Connection` domain objects; DNS queue |
+| `udp.py` | UDP datagram listener; processes `HTB` and `PLG` messages; sets/resets overdue timers |
+| `http.py` | aiohttp web server; all REST API routes (`/api/0/`) and page routes |
+| `ws.py` | WebSocket broadcast to connected dashboard clients |
+| `notify.py` | Notification dispatch (Pushover, email, Mattermost, Matrix, Signal, SMS); `eventlog()` is the single choke-point for all alert events |
+| `threshold.py` | Threshold evaluation against plugin metrics; state transitions (OK/WARNING/CRITICAL/UNKNOWN) |
+| `monitor.py` | Timer cleanup on shutdown (reachability is event-driven via timers in `udp.py`, not polled) |
+| `data.py` | Shared in-memory message ring buffer |
+| `journal.py` | JSONL message journal with size-based rotation |
+| `users.py` | Session management, password hashing (PBKDF2), role checks |
+| `config.py` | Config loading and defaults |
+| `configio.py` | Config file read/write via `ruamel.yaml` (preserves comments) |
+| `settings.py` | Settings sections for the web UI settings page |
+| `dns.py` | `nsupdate` integration for dynamic DNS |
+| `oauth.py` | OAuth2 login (Gitea) |
+
+### Key data flows
+
+**Heartbeat received:** `udp.py` decodes the `HTB` datagram → updates `Connection` state in `hbdclass.py` → resets overdue asyncio timer → broadcasts via `ws.py` → `notify.py` fires connectivity alerts on state change.
+
+**Plugin data received:** `udp.py` decodes `PLG` datagram → stores on `Host` → `threshold.py` evaluates against configured thresholds → `notify.py` fires threshold alerts on state transitions.
+
+**State persistence:** `Host.hosts` dict + `data.msgs` ring + active sessions are pickled every 5 minutes and on clean shutdown. Asyncio timers are stripped before pickling (`Connection.__getstate__`).
+
+**Config reload:** SIGHUP → `configio.py` re-reads YAML → live-updates hosts, thresholds, users, notification channels. Port/cert/pickle/journal changes require a full restart.
+
+### Client plugin system
+
+Plugins in `hbd/client/plugins/` subclass `InfoPlugin` (collected once, on demand) or `MonitorPlugin` (periodic). `initialize()` returns `False` to self-disable. Data is sent as `PLG` UDP messages.
+
+`hbc_mini.py` (scripts/) and `hbc_mini.c` (scripts/c/) are standalone single-file clients with no external dependencies.
+
+### Protocol
+
+All UDP messages: `!<ID>: <zlib-compressed key=value payload>`. Encoding in `hbd/common/proto.py`. Lists/dicts encoded as JSON with `@` prefix; booleans as `1`/`0`.
+
+### Web UI
+
+Jinja2 templates in `hbd/server/templates/`. Static assets in `hbd/server/static/`. Live pages (`/live`, `/plugins`) use WebSocket connections for real-time push.
+
+### CI
+
+Gitea Actions workflow at `.gitea/workflows/release.yml`.

README.md

@@ -20,7 +20,7 @@ A lightweight UDP-based host monitoring system. Monitored hosts run a client (`h
   └────────────────────┘              └────────────────────────────┘
 ```
 
-**Package:** `hbd` v5.4.0
+**Package:** `hbd` v5.4.4
 **Python:** 3.11+
 
 ### Subpackages

docs/PLUGIN_DEVELOPMENT.md

@@ -21,7 +21,7 @@ Heartbeat's plugin system is designed to be simple yet powerful. Plugins are Pyt
 ### Key Concepts
 
 - **Plugin Registry**: Central registry that manages all loaded plugins
-- **Plugin Loader**: Automatically discovers and loads plugins from the `hbd/plugins/` directory
+- **Plugin Loader**: Automatically discovers and loads plugins from the `hbd/client/plugins/` directory
 - **Plugin Types**: InfoPlugin (static data) and MonitorPlugin (periodic metrics)
 - **Async/Await**: All plugin methods are async for non-blocking operation
 
@@ -64,7 +64,7 @@ Decide whether your plugin collects static information (InfoPlugin) or dynamic m
 
 ### Step 2: Create Plugin File
 
-Create a new Python file in `hbd/plugins/` directory:
+Create a new Python file in `hbd/client/plugins/` directory:
 
 ```python
 """
@@ -82,7 +82,7 @@ try:
 except ImportError:
     psutil = None
 
-from hbd.plugin import MonitorPlugin  # or InfoPlugin
+from hbd.client.plugin import MonitorPlugin  # or InfoPlugin
 
 logger = logging.getLogger(__name__)
 
@@ -193,7 +193,7 @@ from pathlib import Path
 # Add parent directory to path
 sys.path.insert(0, str(Path(__file__).parent))
 
-from hbd.plugins.my_awesome_plugin import MyAwesomePlugin
+from hbd.client.plugins.my_awesome_plugin import MyAwesomePlugin
 
 async def test():
     # Create plugin instance
@@ -224,7 +224,7 @@ Understanding the plugin lifecycle helps you implement plugins correctly:
 
 ```
 1. Plugin Discovery
-   └─> Loader scans hbd/plugins/ directory
+   └─> Loader scans hbd/client/plugins/ directory
    └─> Finds Python files (except those starting with _)
    └─> Imports modules
 
@@ -378,7 +378,7 @@ Document your plugin thoroughly:
 ### Example 1: Simple InfoPlugin
 
 ```python
-from hbd.plugin import InfoPlugin
+from hbd.client.plugin import InfoPlugin
 import platform
 
 class SimpleInfoPlugin(InfoPlugin):
@@ -406,7 +406,7 @@ plugin = SimpleInfoPlugin
 ### Example 2: MonitorPlugin with State
 
 ```python
-from hbd.plugin import MonitorPlugin
+from hbd.client.plugin import MonitorPlugin
 import time
 
 class CounterPlugin(MonitorPlugin):
@@ -442,7 +442,7 @@ plugin = CounterPlugin
 ### Example 3: Plugin with External Command
 
 ```python
-from hbd.plugin import MonitorPlugin
+from hbd.client.plugin import MonitorPlugin
 import asyncio
 
 class CommandPlugin(MonitorPlugin):
@@ -561,7 +561,7 @@ python -m hbd.hbc -c test_config.yaml --verbose
 
 ## Further Reading
 
-- [Plugin Framework Source](../hbd/plugin.py) - Core plugin implementation
+- [Plugin Framework Source](../hbd/client/plugin.py) - Core plugin implementation
-- [Built-in Plugins](../hbd/plugins/) - Examples of working plugins
+- [Built-in Plugins](../hbd/client/plugins/) - Examples of working plugins
 - [Nagios Integration](NAGIOS_INTEGRATION.md) - Running external plugins
 - [Configuration Guide](../hbd/config_example.yaml) - Full configuration reference

hbd/__init__.py

@@ -14,4 +14,4 @@ Install options:
 """
 
 __all__ = ["__version__"]
-__version__ = "5.4.0"
+__version__ = "5.4.4"

hbd/client/connectivity.py

@@ -0,0 +1,204 @@
+"""Per-protocol internet presence probe.
+
+Tier 1 (every tier1_interval seconds, sends no packets): a UDP connect() to the probe
+address reveals whether a route exists and which source address would be used.
+Tier 2 (every probe_interval seconds, sooner after a failure or a change of address or
+gateway): one ICMP echo to the probe address. Absence needs fail_limit consecutive
+failures (or no route at all); presence needs one success.
+
+The result is read by the heartbeat sender (p4/p6 flags on every HTB) and by the
+network_monitor plugin (connectivity metric) via the shared instance.
+"""
+
+import asyncio
+import logging
+import socket
+import sys
+import time
+from dataclasses import asdict, dataclass, replace
+from typing import Any, Awaitable, Callable, Dict, Optional, Set, Tuple
+
+from hbd.client import gateway as gateway_mod
+from hbd.client.pingutil import PingUnavailable, run_ping
+
+logger = logging.getLogger("hbc.connectivity")
+
+FAMILIES = ("ipv4", "ipv6")
+FLAG_KEYS = {"ipv4": "p4", "ipv6": "p6"}
+DEFAULT_PROBES = {"ipv4": "1.1.1.1", "ipv6": "2606:4700:4700::1111"}
+
+
+class ProbeUnavailable(Exception):
+    """The address family cannot be probed on this host (e.g. no IPv6 support)."""
+
+
+@dataclass
+class FamilyState:
+    present: Optional[bool] = None      # None = unknown (probe cannot run yet/at all)
+    addr: Optional[str] = None
+    gateway: Optional[str] = None
+    rtt: Optional[float] = None
+
+
+def local_address(family: str, target: str) -> Optional[str]:
+    """Source address the kernel would use to reach target, or None if there is no route.
+
+    A UDP connect() sends nothing. Raises ProbeUnavailable if the family is unsupported.
+    """
+    af = socket.AF_INET if family == "ipv4" else socket.AF_INET6
+    try:
+        sock = socket.socket(af, socket.SOCK_DGRAM)
+    except OSError as e:
+        raise ProbeUnavailable(str(e)) from e
+    try:
+        sock.connect((target, 9))
+        return str(sock.getsockname()[0])
+    except OSError:
+        return None
+    finally:
+        sock.close()
+
+
+async def ping_rtt(target: str, family: str) -> Optional[float]:
+    """One ICMP echo; returns RTT in ms or None if no reply."""
+    result = await run_ping(target, 1, 2, 4 if family == "ipv4" else 6)
+    rtt = result["rtt_avg"]
+    return None if rtt == float("inf") else rtt
+
+
+class Connectivity:
+    def __init__(
+        self,
+        probes: Optional[Dict[str, str]] = None,
+        probe_interval: float = 60.0,
+        retry_interval: float = 10.0,
+        tier1_interval: float = 5.0,
+        fail_limit: int = 2,
+        local_address_fn: Callable[[str, str], Optional[str]] = local_address,
+        ping_fn: Callable[[str, str], Awaitable[Optional[float]]] = ping_rtt,
+        gateway_fn: Callable[[str], Awaitable[Optional[str]]] = gateway_mod.default_gateway,
+        clock: Callable[[], float] = time.monotonic,
+    ):
+        self.probes = {**DEFAULT_PROBES, **(probes or {})}
+        self.probe_interval = probe_interval
+        self.retry_interval = retry_interval
+        self.tier1_interval = tier1_interval
+        self.fail_limit = fail_limit
+        self._local_address = local_address_fn
+        self._ping = ping_fn
+        self._gateway_fn = gateway_fn
+        self._clock = clock
+        # Reading the gateway is a cheap /proc read on Linux but a subprocess elsewhere,
+        # so elsewhere it is refreshed only when a tier-2 probe is due.
+        self._cheap_gateway = sys.platform.startswith("linux")
+        self.states: Dict[str, FamilyState] = {f: FamilyState() for f in FAMILIES}
+        self._fails: Dict[str, int] = {f: 0 for f in FAMILIES}
+        self._next_ping: Dict[str, float] = {f: 0.0 for f in FAMILIES}
+        self._last_key: Dict[str, Optional[Tuple[Optional[str], Optional[str]]]] = {
+            f: None for f in FAMILIES}
+        self._ping_disabled: Set[str] = set()
+
+    @classmethod
+    def from_config(cls, cfg: Optional[Dict[str, Any]]) -> "Connectivity":
+        cfg = cfg or {}
+        probes = {}
+        if cfg.get("probe_v4"):
+            probes["ipv4"] = str(cfg["probe_v4"])
+        if cfg.get("probe_v6"):
+            probes["ipv6"] = str(cfg["probe_v6"])
+        return cls(probes=probes, probe_interval=float(cfg.get("probe_interval", 60)))
+
+    # ---- readers (cheap; safe to call on every heartbeat) --------------------------
+    def snapshot(self) -> Dict[str, FamilyState]:
+        return {f: replace(s) for f, s in self.states.items()}
+
+    def flags(self) -> Dict[str, bool]:
+        """HTB flags for families whose presence is known."""
+        return {FLAG_KEYS[f]: s.present for f, s in self.states.items() if s.present is not None}
+
+    def as_metric(self) -> Dict[str, Dict[str, Any]]:
+        return {f: asdict(s) for f, s in self.states.items()}
+
+    # ---- probing -------------------------------------------------------------------
+    async def refresh(self) -> None:
+        for fam in FAMILIES:
+            try:
+                await self._refresh_family(fam)
+            except Exception:
+                logger.exception("connectivity probe failed for %s", fam)
+
+    async def run(self, stop: asyncio.Event) -> None:
+        while not stop.is_set():
+            await self.refresh()
+            try:
+                await asyncio.wait_for(stop.wait(), timeout=self.tier1_interval)
+            except asyncio.TimeoutError:
+                pass
+
+    async def _gateway(self, fam: str) -> Optional[str]:
+        try:
+            return await self._gateway_fn(fam)
+        except Exception:
+            return None
+
+    async def _refresh_family(self, fam: str) -> None:
+        st = self.states[fam]
+        try:
+            addr = self._local_address(fam, self.probes[fam])
+        except ProbeUnavailable:
+            st.present = None
+            return
+
+        if addr is None:                       # tier 1: no route => absent immediately
+            self._fails[fam] = 0
+            self._next_ping[fam] = 0.0
+            self._last_key[fam] = None
+            st.present, st.addr, st.gateway, st.rtt = False, None, None, None
+            return
+
+        now = self._clock()
+        gw = await self._gateway(fam) if self._cheap_gateway else st.gateway
+        key = (addr, gw)
+        due = key != self._last_key[fam] or now >= self._next_ping[fam]
+        if due and not self._cheap_gateway:
+            gw = await self._gateway(fam)
+            key = (addr, gw)
+        st.addr, st.gateway = addr, gw
+        self._last_key[fam] = key
+        if fam in self._ping_disabled:
+            st.present = None          # cannot probe: unknown, never absent, while a route exists
+        elif due:
+            await self._tier2(fam, st, now)
+
+    async def _tier2(self, fam: str, st: FamilyState, now: float) -> None:
+        try:
+            rtt = await self._ping(self.probes[fam], fam)
+        except PingUnavailable:
+            logger.warning("ping unavailable; %s presence stays unknown", fam)
+            self._ping_disabled.add(fam)
+            st.present = None
+            return
+        except (asyncio.TimeoutError, OSError):
+            rtt = None
+        if rtt is None:
+            self._fails[fam] += 1
+            self._next_ping[fam] = now + self.retry_interval
+            if self._fails[fam] >= self.fail_limit:
+                st.present, st.rtt = False, None
+        else:
+            self._fails[fam] = 0
+            self._next_ping[fam] = now + self.probe_interval
+            st.present, st.rtt = True, rtt
+
+
+# ---- shared instance (heartbeat sender and network_monitor plugin) -----------------
+_shared: Optional[Connectivity] = None
+
+
+def set_shared(conn: Optional[Connectivity]) -> None:
+    global _shared
+    _shared = conn
+
+
+def get_shared() -> Optional[Connectivity]:
+    return _shared

hbd/client/gateway.py

@@ -0,0 +1,103 @@
+"""Best-effort default-gateway lookup (informational only; never affects presence)."""
+
+import asyncio
+import re
+import socket
+import struct
+import sys
+from typing import List, Optional, Tuple
+
+_RTF_GATEWAY = 0x2
+_RTF_REJECT = 0x200
+
+
+def parse_proc_route_v4(text: str) -> Optional[str]:
+    """Default gateway from /proc/net/route (lowest metric wins)."""
+    best: Optional[Tuple[int, str]] = None
+    for line in text.splitlines()[1:]:
+        f = line.split()
+        if len(f) < 8:
+            continue
+        _iface, dest, gw, flags = f[0], f[1], f[2], f[3]  # noqa: F841
+        if dest != "00000000" or not int(flags, 16) & _RTF_GATEWAY:
+            continue
+        metric = int(f[6])
+        if best is None or metric < best[0]:
+            best = (metric, socket.inet_ntoa(struct.pack("<L", int(gw, 16))))
+    return best[1] if best else None
+
+
+def parse_proc_route_v6(text: str) -> Optional[str]:
+    """Default gateway from /proc/net/ipv6_route (lowest metric wins)."""
+    best: Optional[Tuple[int, str]] = None
+    for line in text.splitlines():
+        f = line.split()
+        if len(f) < 10:
+            continue
+        dest, plen, nexthop, metric, flags, iface = f[0], f[1], f[4], f[5], f[8], f[9]
+        if dest != "0" * 32 or plen != "00" or nexthop == "0" * 32 or iface == "lo":
+            continue
+        fl = int(flags, 16)
+        if not fl & _RTF_GATEWAY or fl & _RTF_REJECT:
+            continue
+        m = int(metric, 16)
+        if best is None or m < best[0]:
+            best = (m, socket.inet_ntop(socket.AF_INET6, bytes.fromhex(nexthop)))
+    return best[1] if best else None
+
+
+def parse_macos_route(text: str) -> Optional[str]:
+    """Gateway from `route -n get [-inet6] default`."""
+    m = re.search(r"^\s*gateway:\s*(\S+)", text, re.MULTILINE)
+    return m.group(1) if m else None
+
+
+def parse_windows_route(text: str, family: str) -> Optional[str]:
+    """Default gateway from `route print -4` / `route print -6` (lowest metric wins)."""
+    best: Optional[Tuple[int, str]] = None
+    for line in text.splitlines():
+        if family == "ipv4":
+            f = line.split()
+            if len(f) >= 5 and f[0] == "0.0.0.0" and f[1] == "0.0.0.0" and f[2] != "On-link":
+                cand = (int(f[4]), f[2])
+            else:
+                continue
+        else:
+            m = re.match(r"^\s*\d+\s+(\d+)\s+::/0\s+(\S+)\s*$", line)
+            if not m or m.group(2) == "On-link":
+                continue
+            cand = (int(m.group(1)), m.group(2))
+        if best is None or cand[0] < best[0]:
+            best = cand
+    return best[1] if best else None
+
+
+async def _run(cmd: List[str]) -> str:
+    proc = await asyncio.create_subprocess_exec(
+        *cmd, stdout=asyncio.subprocess.PIPE, stderr=asyncio.subprocess.DEVNULL,
+    )
+    try:
+        out, _ = await asyncio.wait_for(proc.communicate(), timeout=5)
+    except asyncio.TimeoutError:
+        proc.kill()
+        await proc.wait()
+        raise
+    return out.decode(errors="replace")
+
+
+async def default_gateway(family: str) -> Optional[str]:
+    """Return the default gateway address for "ipv4"/"ipv6", or None on any failure."""
+    v4 = family == "ipv4"
+    try:
+        if sys.platform.startswith("linux"):
+            with open("/proc/net/route" if v4 else "/proc/net/ipv6_route") as fh:
+                text = fh.read()
+            return parse_proc_route_v4(text) if v4 else parse_proc_route_v6(text)
+        if sys.platform == "darwin":
+            cmd = ["route", "-n", "get"] + ([] if v4 else ["-inet6"]) + ["default"]
+            return parse_macos_route(await _run(cmd))
+        if sys.platform == "win32":
+            return parse_windows_route(await _run(["route", "print", "-4" if v4 else "-6"]), family)
+    except Exception:
+        return None
+    return None

hbd/client/main.py

@@ -25,6 +25,7 @@ from .. import __version__
 
 # Import plugin system
 from .plugin import PluginRegistry, PluginLoader, InfoPlugin, MonitorPlugin
+from .connectivity import Connectivity, set_shared
 
 # Constants
 PORT = 50003
@@ -281,7 +282,16 @@ async def handle_update(conn: AsyncConnection, _msg: dict):  # pyright: ignore[r
     stop()
 
 
-async def heartbeat_sender(conn: AsyncConnection, interval: int):
+def build_heartbeat_msg(conn, interval: int, connectivity: Optional[Connectivity] = None) -> dict:
+    """HTB payload; carries p4/p6 presence flags when the probe knows them."""
+    msg = {"acks": conn.ackcount, "rtt": conn.rtts[-1], "interval": interval}
+    if connectivity is not None:
+        msg.update(connectivity.flags())
+    return msg
+
+
+async def heartbeat_sender(conn: AsyncConnection, interval: int,
+                           connectivity: Optional[Connectivity] = None):
     """Send periodic heartbeats, retrying the connection if it is not open.
 
     IPv6 connections that fail to open before their first successful send are
@@ -291,6 +301,7 @@ async def heartbeat_sender(conn: AsyncConnection, interval: int):
     Args:
         conn: Connection to send on
         interval: Heartbeat interval in seconds
+        connectivity: Optional probe whose presence flags are attached to every heartbeat
     """
     logger = logging.getLogger("hbc.heartbeat")
     IPV6_EARLY_FAIL_LIMIT = 3
@@ -328,11 +339,7 @@ async def heartbeat_sender(conn: AsyncConnection, interval: int):
                 continue
 
         try:
-            msg = {
+            msg = build_heartbeat_msg(conn, interval, connectivity)
-                "acks": conn.ackcount,
-                "rtt": conn.rtts[-1],
-                "interval": interval
-            }
             await conn.sendto(msg, "HTB")
 
         except asyncio.CancelledError:
@@ -619,9 +626,18 @@ async def async_main(args, config):
     loop.add_signal_handler(signal.SIGHUP, _sighup)
     
     # Start async tasks
+    # Per-protocol internet presence probe (shared with the network_monitor plugin)
+    net_cfg = dict((config.get("plugins") or {}).get("network_monitor")
+                   or config.get("network_monitor") or {})
+    connectivity = None
+    if net_cfg.get("probe_enabled", True):
+        connectivity = Connectivity.from_config(net_cfg)
+        set_shared(connectivity)
+        active_tasks.append(asyncio.create_task(connectivity.run(shutdown_event)))
+
     # Heartbeat senders (one per connection)
     for conn in connections:
-        task = asyncio.create_task(heartbeat_sender(conn, interval))
+        task = asyncio.create_task(heartbeat_sender(conn, interval, connectivity))
         active_tasks.append(task)
     
     # Plugin collector (uses all connections, but we'll use first one)

hbd/client/pingutil.py

@@ -0,0 +1,73 @@
+"""System ping helpers shared by ping_monitor and the connectivity probe."""
+
+import asyncio
+import re
+import sys
+from typing import Dict, List, Optional
+
+_INF = float("inf")
+
+
+class PingUnavailable(Exception):
+    """The system ping binary could not be executed."""
+
+
+def ping_command(host: str, count: int, timeout: int, family: Optional[int] = None) -> List[str]:
+    """Build the platform ping command. family is 4, 6 or None (let ping decide)."""
+    if sys.platform == "win32":
+        cmd = ["ping", "-n", str(count), "-w", str(timeout * 1000)]
+        if family:
+            cmd.append(f"-{family}")
+        return cmd + [host]
+    if sys.platform == "darwin" and family:
+        if family == 6:
+            return ["ping6", "-c", str(count), host]
+        return ["ping", "-c", str(count), "-W", str(timeout * 1000), host]
+    cmd = ["ping", "-c", str(count), "-W", str(timeout)]
+    if family:
+        cmd.append(f"-{family}")
+    return cmd + [host]
+
+
+def parse_ping_output(output: str) -> Dict[str, float]:
+    """Parse rtt_min/avg/max/loss from ping output (Linux, macOS, BSD)."""
+    loss = 100.0
+    loss_match = re.search(r"(\d+(?:\.\d+)?)\s*%\s*packet\s*loss", output)
+    if loss_match:
+        loss = float(loss_match.group(1))
+
+    # Linux: "rtt min/avg/max/mdev = x/x/x/x ms"; macOS: "round-trip min/avg/max/stddev = ..."
+    rtt_match = re.search(
+        r"(?:rtt|round-trip)\s+min/avg/max/\S+\s*=\s*([\d.]+)/([\d.]+)/([\d.]+)",
+        output,
+    )
+    if rtt_match:
+        return {
+            "rtt_min": float(rtt_match.group(1)),
+            "rtt_avg": float(rtt_match.group(2)),
+            "rtt_max": float(rtt_match.group(3)),
+            "loss": loss,
+        }
+    return {"rtt_min": _INF, "rtt_avg": _INF, "rtt_max": _INF, "loss": loss}
+
+
+async def run_ping(host: str, count: int, timeout: int, family: Optional[int] = None) -> Dict[str, float]:
+    """Run ping and return parsed metrics.
+
+    Raises PingUnavailable if the ping binary is missing and asyncio.TimeoutError
+    (after killing the process) if it hangs.
+    """
+    cmd = ping_command(host, count, timeout, family)
+    try:
+        proc = await asyncio.create_subprocess_exec(
+            *cmd, stdout=asyncio.subprocess.PIPE, stderr=asyncio.subprocess.PIPE,
+        )
+    except FileNotFoundError as e:
+        raise PingUnavailable(str(e)) from e
+    try:
+        stdout, _ = await asyncio.wait_for(proc.communicate(), timeout=timeout * count + 2)
+    except asyncio.TimeoutError:
+        proc.kill()
+        await proc.wait()
+        raise
+    return parse_ping_output(stdout.decode(errors="replace"))

hbd/client/plugins/network_monitor.py

@@ -13,6 +13,7 @@ except ImportError:
     psutil = None
 
 from hbd.client.plugin import MonitorPlugin
+from hbd.client.connectivity import get_shared
 
 logger = logging.getLogger(__name__)
 
@@ -32,6 +33,10 @@ class NetworkMonitorPlugin(MonitorPlugin):
         interfaces: List of interfaces to monitor (default: all)
         include_connections: Include connection statistics (default: True)
         include_addresses: Include interface addresses (default: False)
+        probe_enabled: Run the per-protocol internet presence probe (default: True)
+        probe_v4: IPv4 address to ping (default: 1.1.1.1)
+        probe_v6: IPv6 address to ping (default: 2606:4700:4700::1111)
+        probe_interval: Seconds between ICMP probes while healthy (default: 60)
     """
     
     name = "network_monitor"
@@ -103,6 +108,7 @@ class NetworkMonitorPlugin(MonitorPlugin):
               - etc.
             - addresses: Interface address information (if include_addresses)
               - Dict keyed by interface name with address details
+            - connectivity: per-protocol presence {ipv4, ipv6} -> {present, addr, gateway, rtt}
         """
         if psutil is None:
             logger.error("psutil not available")
@@ -229,6 +235,11 @@ class NetworkMonitorPlugin(MonitorPlugin):
         except Exception as e:
             logger.warning(f"Could not collect interface stats: {e}")
 
+        # Per-protocol internet presence, address and gateway (from the shared probe)
+        shared = get_shared()
+        if shared is not None:
+            metrics['connectivity'] = shared.as_metric()
+        
         return metrics
     
     async def cleanup(self):

hbd/client/plugins/ping_monitor.py

@@ -40,9 +40,9 @@ threshold_configs:
 
 import asyncio
 import re
-import sys
 from typing import Any, Dict, Optional
 
+from hbd.client.pingutil import PingUnavailable, run_ping
 from hbd.client.plugin import MonitorPlugin
 
 
@@ -84,51 +84,13 @@ class PingMonitorPlugin(MonitorPlugin):
 
     async def _ping(self, host: str) -> Dict[str, float]:
         """Run a system ping command and return rtt_min/avg/max/loss."""
-        if sys.platform == "win32":
-            cmd = ["ping", "-n", str(self.count), "-w", str(self.timeout * 1000), host]
-        else:
-            cmd = ["ping", "-c", str(self.count), "-W", str(self.timeout), host]
-
         try:
-            proc = await asyncio.create_subprocess_exec(
+            return await run_ping(host, self.count, self.timeout)
-                *cmd,
+        except (asyncio.TimeoutError, PingUnavailable, OSError) as e:
-                stdout=asyncio.subprocess.PIPE,
-                stderr=asyncio.subprocess.PIPE,
-            )
-            stdout, _ = await asyncio.wait_for(
-                proc.communicate(),
-                timeout=self.timeout * self.count + 2,
-            )
-            output = stdout.decode(errors="replace")
-        except (asyncio.TimeoutError, FileNotFoundError, OSError) as e:
             self.logger.warning("ping_monitor: ping failed for %s: %s", host, e)
             return {"rtt_min": float("inf"), "rtt_avg": float("inf"),
                     "rtt_max": float("inf"), "loss": 100.0}
 
-        # Parse packet loss
-        loss = 100.0
-        loss_match = re.search(r"(\d+(?:\.\d+)?)\s*%\s*packet\s*loss", output)
-        if loss_match:
-            loss = float(loss_match.group(1))
-
-        # Parse rtt min/avg/max — Linux: "rtt min/avg/max/mdev = x/x/x/x ms"
-        #                          macOS: "round-trip min/avg/max/stddev = x/x/x/x ms"
-        rtt_match = re.search(
-            r"(?:rtt|round-trip)\s+min/avg/max/\S+\s*=\s*([\d.]+)/([\d.]+)/([\d.]+)",
-            output,
-        )
-        if rtt_match:
-            return {
-                "rtt_min": float(rtt_match.group(1)),
-                "rtt_avg": float(rtt_match.group(2)),
-                "rtt_max": float(rtt_match.group(3)),
-                "loss": loss,
-            }
-
-        # Host unreachable or all packets lost
-        return {"rtt_min": float("inf"), "rtt_avg": float("inf"),
-                "rtt_max": float("inf"), "loss": loss}
-
     async def _collect_metrics(self) -> Dict[str, Any]:
         data: Dict[str, Any] = {}
         tasks = {host: asyncio.create_task(self._ping(host)) for host in self.hosts}

hbd/server/flap.py

@@ -100,6 +100,17 @@ def observe(host: str, service: str, level: str) -> str:
     return SUPPRESS
 
 
+def clear_host(host: str) -> None:
+    """Discard all flap state for *host* (called when a host is dropped).
+
+    A dropped host may be mid-flap with no RECOVER ever received, in which
+    case ``ok_since`` stays ``None`` and ``_sweep`` can never clear it on its
+    own — the state would otherwise persist forever.
+    """
+    for key in [k for k in _state if k[0] == host]:
+        del _state[key]
+
+
 def flapping_services(host: str) -> list:
     """Return the services of *host* that are currently flapping.
 

hbd/server/hbdclass.py

@@ -29,6 +29,7 @@ class Connection:
     UP = "up"
     DOWN = "down"
     OVERDUE = "overdue"
+    ABSENT = "absent"
 
     def __init__(self, host, cid, addr, afam):
         self.host = host
@@ -94,7 +95,9 @@ class Connection:
         now = time.time()
         if not Null:
             d["addr"] = self.addr
-            if self.rtts[-1]:
+            if self.state == Connection.ABSENT:
+                d["rtt"] = ""
+            elif self.rtts[-1]:
                 d["rtt"] = "%d" % round(self.rtts[-1])
             elif self.state == Connection.UNKNOWN:
                 d["rtt"] = ""
@@ -299,6 +302,8 @@ class Host:
         self.alert_states = {}
         # Stale-data timers: {plugin_name: asyncio.TimerHandle}
         self.plugin_timers = {}
+        # Client-reported protocol presence: {afam: {"present": bool, "ts": float}}
+        self.presence: dict = {}
         # User access control
         self.owner: str | None = None       # username of owner
         self.managers: list = []            # usernames with manager role
@@ -322,6 +327,7 @@ class Host:
             d["name"] = "<b>%s</b>" % d["name"]
         d["dyn"] = str(self.dyn)
         d["num"] = self.num
+        d["status"] = self.status()
         
         # Add alert counts (split by acknowledged status)
         warning_unacked = 0
@@ -444,6 +450,7 @@ class Host:
             _, os_data = latest_os
             hbc_version = os_data.get("hbc_version")
         ddict["hbc_version"] = hbc_version
+        ddict["status"] = self.status()
 
         return ddict
 
@@ -459,6 +466,47 @@ class Host:
         else:
             return addr.find(".") > 0
 
+    def set_presence(self, afam, present, now):
+        """Record the client's report of whether it has internet connectivity on afam."""
+        self.presence[afam] = {"present": bool(present), "ts": now}
+
+    def flag_present(self, afam):
+        """Client-reported presence; True when the client never reported (legacy clients)."""
+        entry = getattr(self, "presence", {}).get(afam)
+        return True if entry is None else entry["present"]
+
+    def family_present(self, afam):
+        """True if afam should be monitored: the client says it is present, or heartbeats
+        are demonstrably arriving on it (real traffic overrides a false "absent")."""
+        conn = self.connections.get(afam)
+        return self.flag_present(afam) or (conn is not None and conn.state == Connection.UP)
+
+    def status(self):
+        """Host-level status: down, overdue, simplex, up or unknown.
+
+        overdue: every present family is overdue. simplex: both present, one up, one overdue
+        (same severity as up). Families the client reports absent are not considered,
+        unless none is present: then every connection not parked as ABSENT is considered.
+        """
+        conns = self.connections
+        if any(c.state == Connection.DOWN for c in conns.values()):
+            return "down"
+        present = [c for afam, c in conns.items() if self.family_present(afam)]
+        if not present:
+            # The client reports no protocol present (e.g. its internet probe fails on every
+            # family) yet may still be heard: monitor whatever is not parked as absent, so a
+            # host that then dies is "overdue", not silently "unknown".
+            present = [c for c in conns.values() if c.state != Connection.ABSENT]
+        up = sum(c.state == Connection.UP for c in present)
+        overdue = sum(c.state == Connection.OVERDUE for c in present)
+        if up and overdue:
+            return "simplex"
+        if up:
+            return "up"
+        if overdue:
+            return "overdue"
+        return "unknown"
+
     def conndata(self, cid, addr, rtt, now):
         if addr[0:7] == "::ffff:":
             addr = addr[7:]
@@ -499,6 +547,8 @@ class Host:
             self.monitors = []
         if not hasattr(self, "plugin_timers"):
             self.plugin_timers = {}
+        if not hasattr(self, "presence"):
+            self.presence = {}
 
         pass
 

hbd/server/http.py

@@ -14,6 +14,7 @@ import logging
 from aiohttp import web
 import jinja2
 from . import data
+from . import flap as flap_mod
 from . import notify as notify_mod
 from . import settings as settings_mod
 from . import users as users_mod
@@ -209,6 +210,16 @@ def _mask_config_for_api(config) -> dict:
     return result
 
 
+def _visible_plugin_names(plugin_data: dict) -> list:
+    """Plugin names to render as accordion sections.
+
+    Excludes synthetic rtt_ipv4 / rtt_ipv6 history streams (written by
+    udp.py for charting) which aren't real client plugins and have no
+    accordion renderer.
+    """
+    return [p for p in plugin_data.keys() if not p.startswith("rtt_")]
+
+
 def _build_host_info(host, threshold_checker=None) -> dict:
     """Assemble the info payload for GET /api/0/hosts/{hostname}/info."""
     hbc_version = None
@@ -264,7 +275,7 @@ def _build_host_info(host, threshold_checker=None) -> dict:
             "family": getattr(conn, "afam", family),
             "addr": getattr(conn, "addr", ""),
             "state": getattr(conn, "state", ""),
-            "rtt": (getattr(conn, "rtts", None) or [None])[0],
+            "rtt": (getattr(conn, "rtts", None) or [None])[-1],
             "statetime": getattr(conn, "statetime", None),
             "lastbeat": getattr(conn, "lastbeat", None),
         }
@@ -439,6 +450,7 @@ async def start(
             return web.json_response({"error": "Forbidden"}, status=403)
         eventlog(uname, "INFO", "dropped")
         del hbdclass.Host.hosts[uname]
+        flap_mod.clear_host(uname)
         return web.Response(text="Done")
 
     async def register(request):
@@ -765,7 +777,7 @@ async def start(
             if host.plugin_data:
                 hosts_with_plugins.append({
                     "name": hostname,
-                    "plugins": list(host.plugin_data.keys()),
+                    "plugins": _visible_plugin_names(host.plugin_data),
                     "is_owner": _can_own_host(current_user, host),
                     "owner": host.owner,
                 })

hbd/server/templates/about.html

@@ -107,6 +107,8 @@
       </section>
     </div>
 
+    {% include 'foot.html' %}
+
     <script>
       (function() {
         var startEpoch = {{ start_epoch }};

hbd/server/templates/live.html

@@ -73,6 +73,7 @@
     .tipbox .up { color: var(--st-ok); font-weight: 700; }
     .tipbox .dn { color: var(--st-crit); font-weight: 700; }
     .tipbox .ov { color: var(--st-warn); font-weight: 700; }
+    .tipbox .ab { color: var(--st-faint); font-weight: 700; }
     .tipbox .meta { margin-top: 6px; padding-top: 6px; border-top: 1px solid var(--st-line-soft); font-size: 11px; color: var(--st-faint); }
 
     @media (max-width: 760px) {
@@ -134,18 +135,18 @@
       function worstConnection(data) {
         var worst = null;
         (data.connections || []).forEach(function (c) {
-          if (!c.state || c.state === 'unknown') return;
+          if (!c.state || c.state === 'unknown' || c.state === 'absent') return;
           if (!worst || (STATE_RANK[c.state] || 0) > (STATE_RANK[worst.state] || 0)) worst = c;
         });
         return worst;
       }
 
       function severity(data) {
-        var w = worstConnection(data);
+        var st = data.status;
         if ((data.alert_critical_unacked || 0) > 0 || (data.alert_critical_acked || 0) > 0) return 'crit';
-        if (w && w.state === 'down') return 'crit';
+        if (st === 'down') return 'crit';
         if ((data.alert_warning_unacked || 0) > 0 || (data.alert_warning_acked || 0) > 0) return 'warn';
-        if (w && w.state === 'overdue') return 'warn';
+        if (st === 'overdue') return 'warn';
         return 'ok';
       }
       var SEV_ORDER = { crit: 0, warn: 1, ok: 2 };
@@ -171,17 +172,17 @@
 
       // ---- host row rendering ---------------------------------------------
       function statusChip(data) {
-        var w = worstConnection(data);
+        var st = data.status;
-        if (!w) return '<span class="chip outline">—</span>';
+        if (!st || st === 'unknown') return '<span class="chip outline">—</span>';
-        var cls = w.state === 'up' ? 'ok' : (w.state === 'down' ? 'crit' : 'warn');
+        var cls = (st === 'up' || st === 'simplex') ? 'ok' : (st === 'down' ? 'crit' : 'warn');
-        return '<span class="chip ' + cls + '">' + escHtml(w.state) + '</span>';
+        return '<span class="chip ' + cls + '">' + escHtml(st) + '</span>';
       }
 
       function tipCard(data) {
         var rows = '';
         (data.connections || []).forEach(function (c) {
           if (!c.state || c.state === 'unknown') return;
-          var cls = c.state === 'up' ? 'up' : (c.state === 'down' ? 'dn' : 'ov');
+          var cls = c.state === 'up' ? 'up' : (c.state === 'down' ? 'dn' : (c.state === 'absent' ? 'ab' : 'ov'));
           var fam = (c.afam || '').replace('IPv', 'v');
           var rtt = (c.state === 'up' && c.rtts && c.rtts[0]) ? Math.round(c.rtts[0]) + ' ms' : '—';
           rows += '<tr><td>' + escHtml(fam) + '</td><td>' + escHtml(c.addr || '—') + '</td>'
@@ -247,7 +248,9 @@
         else if (data.hbc_version !== HBD_VERSION) {
           staleTag = '<span class="stale" title="agent v' + escHtml(String(data.hbc_version)) + ' ≠ server v' + HBD_VERSION + '">v' + escHtml(String(data.hbc_version)) + '</span>';
         }
-        var dotCls = w ? (w.state === 'up' ? sev : (w.state === 'down' ? 'down' : 'overdue')) : 'off';
+        var st = data.status;
+        var dotCls = (!st || st === 'unknown') ? 'off'
+          : ((st === 'up' || st === 'simplex') ? sev : (st === 'down' ? 'down' : 'overdue'));
         var flapTag = '';
         var flapping = data.flapping || [];
         if (flapping.length) {
@@ -286,11 +289,11 @@
         var total = 0, up = 0, overdue = 0, down = 0;
         Object.values(hostData).forEach(function (d) {
           total++;
-          var w = worstConnection(d);
+          var st = d.status;
-          if (!w) return;
+          if (!st || st === 'unknown') return;
-          if (w.state === 'up') up++;
+          if (st === 'up' || st === 'simplex') up++;
-          else if (w.state === 'overdue') overdue++;
+          else if (st === 'overdue') overdue++;
-          else if (w.state === 'down') down++;
+          else if (st === 'down') down++;
         });
         var parts = [total + ' hosts', up + ' up'];
         if (overdue) parts.push(overdue + ' overdue');

hbd/server/templates/menu.html

@@ -1,2 +0,0 @@
-<!-- <label for="drawer-toggle" id="drawer-toggle-label"></label>
-s<header>{{ header }}</header> -->

hbd/server/templates/plugins.html

@@ -290,8 +290,8 @@
 
       {% if not hosts %}
       <div class="no-data">
-        <p>No hosts with plugin data available</p>
+        <p>No hosts have connected yet</p>
-        <p style="font-size:0.9em;margin-top:10px;">Hosts will appear here once they start sending plugin metrics</p>
+        <p style="font-size:0.9em;margin-top:10px;">Hosts will appear here once they start sending heartbeats</p>
       </div>
       {% else %}
       <div id="hosts-container">
@@ -445,14 +445,18 @@
         </div>`;
 
         if (data.connections && data.connections.length) {
-          html += `<div class="info-thresholds-title">Connectivity</div>
+          html += `<div class="info-thresholds-title">Connectivity</div>`;
-            <table class="data-table"><thead><tr>
+          for (const c of data.connections) {
+            html += `<div class="info-note">${escHtml(c.family)} &middot; ${escHtml(c.addr || '—')} RTT</div>
+              <div id="rtt-chart-${hostname}-${escHtml(c.family)}" style="margin-bottom:8px;"></div>`;
+          }
+          html += `<table class="data-table"><thead><tr>
               <th>Family</th><th>Address</th><th>State</th>
               <th class="num">RTT</th><th>Last Change</th><th>Last Packet</th>
             </tr></thead><tbody>`;
           for (const c of data.connections) {
             const st = escHtml(c.state || '—');
-            const stCls = c.state === 'up' ? 'status-up' : (c.state ? 'status-down' : '');
+            const stCls = c.state === 'up' ? 'status-up' : (c.state === 'absent' ? '' : (c.state ? 'status-down' : ''));
             const rtt = (c.state === 'up' && c.rtt) ? Math.round(c.rtt) + ' ms' : '—';
             const chg = c.statetime ? new Date(c.statetime * 1000).toLocaleString() : '—';
             const seen = c.lastbeat ? new Date(c.lastbeat * 1000).toLocaleString() : '—';
@@ -495,6 +499,15 @@
         }
 
         el.innerHTML = html;
+
+        if (data.connections && data.connections.length) {
+          const rttThresholds = (data.thresholds || []).find(t => t.metric === 'rtt') || null;
+          for (const c of data.connections) {
+            fetchRttHistory(hostname, c.family)
+              .then(samples => renderRttChart(hostname, c.family, samples, rttThresholds))
+              .catch(() => {});
+          }
+        }
       }
 
       async function fetchHostGlance(hostname) {
@@ -809,84 +822,164 @@
         return json.samples || [];
       }
 
-      function renderCpuChart(hostname, samples) {
+      function renderTimeSeriesChart(elId, pts, opts) {
-        const el = document.getElementById(`cpu-chart-${hostname}`);
+        const el = document.getElementById(elId);
-        if (!el || !samples.length) return;
+        if (!el || pts.length < 2) { if (el) el.style.display = 'none'; return; }
 
-        const pts = samples
+        const unitSuffix = opts.unitSuffix || '';
-          .filter(s => s.data.cpu_percent != null)
+        const W = 690, H = 92, PAD = { top: 6, right: 8, bottom: 18, left: 28 };
-          .map(s => ({ t: s.timestamp, v: s.data.cpu_percent }));
-        if (pts.length < 2) { el.style.display = 'none'; return; }
-
-        const W = 600, H = 80, PAD = { top: 6, right: 8, bottom: 18, left: 28 };
-        const cW = W - PAD.left - PAD.right;
-        const cH = H - PAD.top - PAD.bottom;
 
         const tMin = pts[0].t, tMax = pts[pts.length - 1].t;
         const tRange = tMax - tMin || 1;
-        const x = t => PAD.left + ((t - tMin) / tRange) * cW;
 
-        // Auto-scale Y axis with 10% padding, clamped to [0, 100]
+        // Auto-scale Y axis with 10% padding, optionally clamped to opts.yDomain
         const vMin = Math.min(...pts.map(p => p.v));
         const vMax = Math.max(...pts.map(p => p.v));
         const vRange = vMax - vMin || 1;
         const vPad = Math.max(vRange * 0.1, 1);
-        const yLow  = Math.max(0,   vMin - vPad);
+        const domainLow  = Array.isArray(opts.yDomain) ? opts.yDomain[0] : 0;
-        const yHigh = Math.min(100, vMax + vPad);
+        const domainHigh = Array.isArray(opts.yDomain) ? opts.yDomain[1] : Infinity;
+        const yLow  = Math.max(domainLow,  vMin - vPad);
+        const yHigh = Math.min(domainHigh, vMax + vPad);
         const yRange = yHigh - yLow || 1;
-        const y = v => PAD.top + cH - ((v - yLow) / yRange) * cH;
 
-        // Build polyline points and filled area path
+        // Compute nice tick step for ~3-5 grid lines, then size the left
-        const linePoints = pts.map(p => `${x(p.t).toFixed(1)},${y(p.v).toFixed(1)}`).join(' ');
+        // margin to fit the widest label (values/units can run to 3+ digits,
-        const areaPath = `M${x(pts[0].t).toFixed(1)},${(PAD.top + cH).toFixed(1)} ` +
+        // e.g. RTT samples above 99ms) instead of a fixed guess that clips them.
-          pts.map(p => `L${x(p.t).toFixed(1)},${y(p.v).toFixed(1)}`).join(' ') +
-          ` L${x(pts[pts.length-1].t).toFixed(1)},${(PAD.top + cH).toFixed(1)} Z`;
-
-        // Color based on latest absolute CPU %
-        const latest = pts[pts.length - 1].v;
-        const strokeColor = latest > 90 ? '#e53935' : latest > 70 ? '#fb8c00' : '#43a047';
-        const fillColor   = latest > 90 ? '#ffcdd2' : latest > 70 ? '#ffe0b2' : '#c8e6c9';
-
-        // Compute nice tick step for ~3-5 grid lines
         const rawStep = yRange / 4;
         const mag = Math.pow(10, Math.floor(Math.log10(rawStep || 1)));
         const niceStep = [1, 2, 5, 10].map(f => f * mag).find(s => yRange / s <= 5) || mag * 10;
         const tickStart = Math.ceil(yLow / niceStep) * niceStep;
-        let gridLines = '';
+        const yTicks = [];
-        for (let v = tickStart; v <= yHigh + 0.001; v += niceStep) {
+        for (let v = tickStart; v <= yHigh + 0.001; v += niceStep) yTicks.push(v);
-          const yy = y(v).toFixed(1);
+        const yTickLabels = yTicks.map(v => (Number.isInteger(v) ? v : v.toFixed(1)) + unitSuffix);
-          const label = Number.isInteger(v) ? v : v.toFixed(1);
+        const maxLabelLen = yTickLabels.reduce((m, s) => Math.max(m, s.length), 0);
-          gridLines += `<line x1="${PAD.left}" y1="${yy}" x2="${PAD.left + cW}" y2="${yy}" stroke="#e0e0e0" stroke-width="1"/>`;
+        PAD.left = Math.max(28, Math.ceil(maxLabelLen * 5.5) + 10);
-          gridLines += `<text x="${(PAD.left - 3).toFixed(1)}" y="${yy}" text-anchor="end" dominant-baseline="middle" font-size="8" fill="#999">${label}</text>`;
+
+        const cW = W - PAD.left - PAD.right;
+        const cH = H - PAD.top - PAD.bottom;
+        const x = t => PAD.left + ((t - tMin) / tRange) * cW;
+        const y = v => PAD.top + cH - ((v - yLow) / yRange) * cH;
+
+        // Color based on latest value
+        const latest = pts[pts.length - 1].v;
+        const { stroke: strokeColor, fill: fillColor } = opts.colorFor(latest);
+
+        // Split into segments wherever the gap between consecutive samples is
+        // much larger than the typical spacing (e.g. the host was overdue/down
+        // for a while) — draw each segment separately so missing data reads as
+        // a visual gap instead of an interpolated line across dead time.
+        const deltas = [];
+        for (let i = 1; i < pts.length; i++) deltas.push(pts[i].t - pts[i - 1].t);
+        deltas.sort((a, b) => a - b);
+        const medianDelta = deltas[Math.floor(deltas.length / 2)];
+        const gapThreshold = medianDelta * 2.5;
+
+        const segments = [[pts[0]]];
+        for (let i = 1; i < pts.length; i++) {
+          if (pts[i].t - pts[i - 1].t > gapThreshold) segments.push([]);
+          segments[segments.length - 1].push(pts[i]);
         }
 
-        // X-axis time labels
+        let linePolylines = '';
+        let areaPaths = '';
+        for (const seg of segments) {
+          if (seg.length < 2) continue;
+          const segPoints = seg.map(p => `${x(p.t).toFixed(1)},${y(p.v).toFixed(1)}`).join(' ');
+          linePolylines += `<polyline points="${segPoints}" fill="none" stroke="${strokeColor}" stroke-width="1.5" stroke-linejoin="round"/>`;
+          const segArea = `M${x(seg[0].t).toFixed(1)},${(PAD.top + cH).toFixed(1)} ` +
+            seg.map(p => `L${x(p.t).toFixed(1)},${y(p.v).toFixed(1)}`).join(' ') +
+            ` L${x(seg[seg.length-1].t).toFixed(1)},${(PAD.top + cH).toFixed(1)} Z`;
+          areaPaths += `<path d="${segArea}" fill="${fillColor}" opacity="0.6"/>`;
+        }
+
+        let gridLines = '';
+        yTicks.forEach((v, i) => {
+          const yy = y(v).toFixed(1);
+          gridLines += `<line x1="${PAD.left}" y1="${yy}" x2="${PAD.left + cW}" y2="${yy}" stroke="#e0e0e0" stroke-width="1"/>`;
+          gridLines += `<text x="${(PAD.left - 3).toFixed(1)}" y="${yy}" text-anchor="end" dominant-baseline="middle" font-size="8" fill="#999">${yTickLabels[i]}</text>`;
+        });
+
+        // X-axis: start/end plus evenly spaced intermediate tickmarks + labels
         const fmt = ts => {
           const d = new Date(ts * 1000);
           return d.toLocaleTimeString([], { hour: '2-digit', minute: '2-digit' });
         };
-        const xLabels = `
+        const xTickCount = 5;
-          <text x="${PAD.left}" y="${H - 2}" text-anchor="start" font-size="8" fill="#999">${fmt(pts[0].t)}</text>
+        const xAxisY = (PAD.top + cH).toFixed(1);
-          <text x="${PAD.left + cW}" y="${H - 2}" text-anchor="end" font-size="8" fill="#999">${fmt(pts[pts.length-1].t)}</text>`;
+        let xAxisMarks = '';
+        let xLabels = '';
+        for (let i = 0; i < xTickCount; i++) {
+          const t = tMin + (tRange * i) / (xTickCount - 1);
+          const xx = x(t).toFixed(1);
+          const anchor = i === 0 ? 'start' : (i === xTickCount - 1 ? 'end' : 'middle');
+          xAxisMarks += `<line x1="${xx}" y1="${xAxisY}" x2="${xx}" y2="${(PAD.top + cH + 3).toFixed(1)}" stroke="#ccc" stroke-width="1"/>`;
+          xLabels += `<text x="${xx}" y="${H - 2}" text-anchor="${anchor}" font-size="8" fill="#999">${fmt(t)}</text>`;
+        }
 
         el.innerHTML = `<svg viewBox="0 0 ${W} ${H}" preserveAspectRatio="none"
           style="width:100%;height:${H}px;display:block;">
           <defs>
-            <clipPath id="cpu-clip-${hostname}">
+            <clipPath id="${opts.clipId}">
               <rect x="${PAD.left}" y="${PAD.top}" width="${cW}" height="${cH}"/>
             </clipPath>
           </defs>
           ${gridLines}
           <line x1="${PAD.left}" y1="${PAD.top}" x2="${PAD.left}" y2="${PAD.top + cH}" stroke="#ccc" stroke-width="1"/>
           <line x1="${PAD.left}" y1="${PAD.top + cH}" x2="${PAD.left + cW}" y2="${PAD.top + cH}" stroke="#ccc" stroke-width="1"/>
-          <g clip-path="url(#cpu-clip-${hostname})">
+          <g clip-path="url(#${opts.clipId})">
-            <path d="${areaPath}" fill="${fillColor}" opacity="0.6"/>
+            ${areaPaths}
-            <polyline points="${linePoints}" fill="none" stroke="${strokeColor}" stroke-width="1.5" stroke-linejoin="round"/>
+            ${linePolylines}
           </g>
+          ${xAxisMarks}
           ${xLabels}
         </svg>`;
       }
 
+      function renderCpuChart(hostname, samples) {
+        const pts = samples
+          .filter(s => s.data.cpu_percent != null)
+          .map(s => ({ t: s.timestamp, v: s.data.cpu_percent }));
+
+        renderTimeSeriesChart(`cpu-chart-${hostname}`, pts, {
+          yDomain: [0, 100],
+          clipId: `cpu-clip-${hostname}`,
+          colorFor: (latest) => ({
+            stroke: latest > 90 ? '#e53935' : latest > 70 ? '#fb8c00' : '#43a047',
+            fill:   latest > 90 ? '#ffcdd2' : latest > 70 ? '#ffe0b2' : '#c8e6c9',
+          }),
+        });
+      }
+
+      async function fetchRttHistory(hostname, family) {
+        const plugin = `rtt_${family.toLowerCase()}`;
+        const r = await fetch(`/api/0/hosts/${encodeURIComponent(hostname)}/plugins/${plugin}?limit=100`);
+        if (!r.ok) return [];
+        const json = await r.json();
+        return json.samples || [];
+      }
+
+      function renderRttChart(hostname, family, samples, rttThresholds) {
+        const pts = samples
+          .filter(s => s.data.rtt != null && s.data.rtt > 0)
+          .map(s => ({ t: s.timestamp, v: s.data.rtt }));
+
+        renderTimeSeriesChart(`rtt-chart-${hostname}-${family}`, pts, {
+          yDomain: 'auto',
+          clipId: `rtt-clip-${hostname}-${family}`,
+          unitSuffix: ' ms',
+          colorFor: (latest) => {
+            if (rttThresholds?.critical != null && latest > rttThresholds.critical) {
+              return { stroke: '#e53935', fill: '#ffcdd2' };
+            }
+            if (rttThresholds?.warning != null && latest > rttThresholds.warning) {
+              return { stroke: '#fb8c00', fill: '#ffe0b2' };
+            }
+            return { stroke: '#1976d2', fill: '#bbdefb' };
+          },
+        });
+      }
+
       function renderCpuTable(hostname, d) {
         const KEYS = [
           ['cpu_percent',      'CPU Usage',         'bar'],
@@ -1050,6 +1143,24 @@
       function renderNetworkTables(d) {
         let html = '';
 
+        if (d.connectivity) {
+          let t = '<table class="data-table"><thead><tr><th>Protocol</th><th>Internet</th>'
+            + '<th>Address</th><th>Gateway</th><th class="num">RTT</th></tr></thead><tbody>';
+          for (const fam of ['ipv4', 'ipv6']) {
+            const c = d.connectivity[fam];
+            if (!c) continue;
+            const known = c.present === true || c.present === false;
+            const cls = c.present === true ? 'status-up' : '';
+            const txt = c.present === true ? '✓ present' : (c.present === false ? 'absent' : '?');
+            t += `<tr><td>${fam === 'ipv4' ? 'IPv4' : 'IPv6'}</td>
+              <td class="${cls}">${txt}</td>
+              <td>${escHtml(c.addr || '—')}</td><td>${escHtml(c.gateway || '—')}</td>
+              <td class="num">${known && c.rtt != null ? Math.round(c.rtt) + ' ms' : '—'}</td></tr>`;
+          }
+          t += '</tbody></table>';
+          html += `<div class="table-section-label">Connectivity</div>${t}`;
+        }
+
         if (d.interfaces && Object.keys(d.interfaces).length) {
           const sample = Object.values(d.interfaces)[0];
           const hasDelta = 'bytes_sent_delta' in sample;
@@ -1293,6 +1404,11 @@
         document.querySelectorAll('.host-card:not(.collapsed)').forEach(card => {
           const hostname = card.dataset.hostname;
 
+          fetchHostInfo(hostname).then(data => {
+            infoCache[hostname] = data;
+            renderInfoSection(hostname, data);
+          }).catch(() => {});
+
           card.querySelectorAll('.plugin-accordion:not(.collapsed)').forEach(acc => {
             const pname = acc.dataset.plugin;
             if (!GLANCE_PLUGINS.includes(pname)) {

hbd/server/udp.py

@@ -194,6 +194,40 @@ def _set_connectivity_alert(host, afam, level_name):
     state.update(level, level_name)
 
 
+_PRESENCE_KEYS = {"p4": "IPv4", "p6": "IPv6"}
+
+
+def _apply_presence(host, msg, now, uname, ctx, skip_conn):
+    """Record client-reported protocol presence and settle the affected connections.
+
+    A family reported absent whose connection is already overdue/unknown is parked as
+    ABSENT (timer cancelled, connectivity alert cleared). One still UP is left alone; its
+    timer expiry parks it. A family reported present again while ABSENT restarts a grace
+    timer. The connection that carried this very heartbeat (skip_conn) is never touched.
+    """
+    cfg = ctx.get("config", {})
+    for key, afam in _PRESENCE_KEYS.items():
+        if key not in msg:
+            continue
+        present = bool(msg[key])
+        host.set_presence(afam, present, now)
+        conn = host.connections.get(afam)
+        if conn is None or conn is skip_conn:
+            continue
+        cls = conn.__class__
+        if not present:
+            if conn.getstate() in (cls.OVERDUE, cls.UNKNOWN):
+                conn.cancel_overdue_timer()
+                conn.newstate(cls.ABSENT, now)
+                _set_connectivity_alert(host, afam, "OK")
+        elif conn.getstate() == cls.ABSENT:
+            conn.newstate(cls.UNKNOWN, now)
+            interval = int(msg.get("interval", 0) or 0) or host.interval
+            if interval > 0:
+                on_overdue, _ = _make_timer_callbacks(uname, host, ctx)
+                conn.reset_overdue_timer(interval + cfg.get("grace", 2), on_overdue)
+
+
 def _make_timer_callbacks(uname, host, ctx):
     """Return (on_overdue, on_unknown) async callbacks for connection timer logic.
 
@@ -210,26 +244,52 @@ def _make_timer_callbacks(uname, host, ctx):
             msg_to_websockets("host", host.stateinfo())
 
     async def on_overdue(connection):
-        if connection.getstate() != connection.__class__.UP:
+        cls = connection.__class__
+        if connection.getstate() not in (cls.UP, cls.UNKNOWN):
             return
         now = time.time()
-        connection.newstate(connection.__class__.OVERDUE, now, cfg.get("grace", 2))
+        afam = connection.afam
-        msg = f"{connection.afam} overdue"
+        # Park only while some other family is still present: the last monitored family
-        eventlog(uname, "CRITICAL", msg)
+        # must never be parked silently, or a host whose client reports no internet on any
-        if host.watched:
+        # protocol would die without an alert.
-            asyncio.create_task(notify_mod.send_notification(
+        if not host.flag_present(afam) and any(
-                uname,
+                af != afam and host.family_present(af) for af in host.connections):
-                notify_mod.Notification(title=f"[CRITICAL] {uname}", body=msg, level="CRITICAL"),
+            # The client says this protocol has no connectivity: not an outage.
-            ))
+            connection.newstate(cls.ABSENT, now)
-        # Track in alert_states so the Alerts Dashboard shows this
+            connection.cancel_overdue_timer()
-        _set_connectivity_alert(host, connection.afam, "CRITICAL")
+            _set_connectivity_alert(host, afam, "OK")
-        if threshold_checker:
+            if msg_to_websockets:
-            threshold_checker.check_value(
+                msg_to_websockets("host", host.stateinfo())
-                host_name=uname,
+            return
-                metric_path="rtt",
+
-                value=float("inf"),
+        # If any connection is DOWN (clean shutdown reported) Host.status() is "down", so a
-                alert_states=host.alert_states,
+        # later overdue of the other family raises no separate event/alert; the shutdown did.
-            )
+        prev = host.status()
+        connection.newstate(cls.OVERDUE, now, cfg.get("grace", 2))
+        new = host.status()
+        if new == "overdue" and prev != "overdue":
+            names = ", ".join(sorted(af for af, c in host.connections.items()
+                                     if c.getstate() == cls.OVERDUE))
+            msg = f"{names} overdue"
+            eventlog(uname, "CRITICAL", msg)
+            if host.watched:
+                asyncio.create_task(notify_mod.send_notification(
+                    uname,
+                    notify_mod.Notification(title=f"[CRITICAL] {uname}", body=msg, level="CRITICAL"),
+                ))
+            # Track in alert_states so the Alerts Dashboard shows this
+            for af, c in host.connections.items():
+                if c.getstate() == cls.OVERDUE:
+                    _set_connectivity_alert(host, af, "CRITICAL")
+            if threshold_checker:
+                threshold_checker.check_value(
+                    host_name=uname,
+                    metric_path="rtt",
+                    value=float("inf"),
+                    alert_states=host.alert_states,
+                )
+        elif new == "simplex":
+            eventlog(uname, "INFO", f"{afam} overdue (simplex)")
         if msg_to_websockets:
             msg_to_websockets("host", host.stateinfo())
         connection.reset_overdue_timer(DROPOVERDUE, on_unknown)
@@ -270,6 +330,8 @@ def restore_connection_timers(hbdclass, ctx):
         interval = host.interval
         for afam, conn in list(host.connections.items()):
             state = conn.getstate()
+            if state == hbdclass.Connection.ABSENT:
+                continue
             if state == hbdclass.Connection.DOWN:
                 _set_connectivity_alert(host, afam, "CRITICAL")
                 continue
@@ -295,6 +357,7 @@ def restore_connection_timers(hbdclass, ctx):
                 restored += 1
 
             elif state == hbdclass.Connection.OVERDUE:
+                host_overdue = host.status() == "overdue"
                 elapsed_overdue = now - conn.statetime
                 remaining = DROPOVERDUE - elapsed_overdue
                 if remaining <= 1:
@@ -304,6 +367,9 @@ def restore_connection_timers(hbdclass, ctx):
                         "Marking %s/%s UNKNOWN (overdue %.1f days)",
                         uname, afam, elapsed_overdue / 86400,
                     )
+                    # A connection dropped to UNKNOWN keeps its alert, like the
+                    # UNKNOWN branch above and on_unknown do.
+                    host_overdue = True
                 else:
                     conn.reset_overdue_timer(remaining, on_unknown)
                     logger.debug(
@@ -313,12 +379,23 @@ def restore_connection_timers(hbdclass, ctx):
                 # Ensure the connectivity alert is set — it may be missing if
                 # hbd was shut down before the on_overdue callback had a chance
                 # to record it.
-                _set_connectivity_alert(host, afam, "CRITICAL")
+                if host_overdue:
+                    _set_connectivity_alert(host, afam, "CRITICAL")
                 restored += 1
 
     logger.info("Restored timers for %d connection(s)", restored)
 
 
+def _is_rtt_key(plugin_name: str) -> bool:
+    """True for synthetic RTT-history keys (rtt_ipv4/rtt_ipv6), not real plugin data."""
+    return plugin_name.startswith("rtt_")
+
+
+def _has_real_plugin_data(plugin_data: dict) -> bool:
+    """True if plugin_data holds any real (non-RTT) client-collected plugin data."""
+    return any(not _is_rtt_key(k) for k in plugin_data)
+
+
 def handle_datagram(msg: dict, addr, transport, ctx: dict):
     """Handle a parsed datagram message.
 
@@ -385,7 +462,7 @@ def handle_datagram(msg: dict, addr, transport, ctx: dict):
         host.doesack = msg.get("acks", -1)
         # send ACK back; ask client to resend plugin info when we have none yet
         rmsg = {"time": time.time()}
-        if not host.plugin_data:
+        if not _has_real_plugin_data(host.plugin_data):
             rmsg["request_update"] = 1
         opkt = dicttos("ACK", rmsg)
         try:
@@ -507,24 +584,36 @@ def handle_datagram(msg: dict, addr, transport, ctx: dict):
     if message:
         eventlog(uname, "INFO", message, service=service)
 
+    _apply_presence(host, msg, now, uname, ctx, conn)
+    prev_status = host.status()
+
     if conn.getstate() != hbdcls.Connection.UP:
         # Transition to UP and log/notify if appropriate
         lasts = conn.state
         d = conn.newstate(hbdcls.Connection.UP, now)
-        # On reboot, pre-boot plugin data and derived alerts are stale.
+        if boot:
-        # Cancel all plugin timers and wipe plugin state so timers restart
+            # On reboot, pre-boot plugin data and derived alerts are stale.
-        # cleanly from the first two post-boot samples.
+            # Cancel all plugin timers and wipe plugin state so timers restart
-        for pname in list(host.plugin_timers):
+            # cleanly from the first two post-boot samples. An ordinary
-            host.cancel_plugin_timer(pname)
+            # reconnect (no boot flag) doesn't invalidate the client's
-        host.plugin_data.clear()
+            # already-collected data, so it's left alone — this keeps chart
+            # history intact across a transient network blip.
+            for pname in list(host.plugin_timers):
+                host.cancel_plugin_timer(pname)
+            for pname in [k for k in host.plugin_data if not _is_rtt_key(k)]:
+                del host.plugin_data[pname]
         stale_plugin_keys = [
             k for k in host.alert_states
             if k not in ("rtt",) and not k.startswith("connectivity.")
         ]
         for k in stale_plugin_keys:
             del host.alert_states[k]
-        # Clear connectivity alert now that the host is back up
+        # Clear connectivity alert now that the host is back up; once the host is no longer
+        # overdue no family may keep a connectivity alert (e.g. the simplex case).
         _set_connectivity_alert(host, conn.afam, "OK")
+        if host.status() in ("up", "simplex"):
+            for af in host.connections:
+                _set_connectivity_alert(host, af, "OK")
         # Don't log/notify RECOVER for a brand-new host seen for the first time —
         # it was never down, it just hasn't been seen before.
         if not newh:
@@ -536,8 +625,11 @@ def handle_datagram(msg: dict, addr, transport, ctx: dict):
             else:
                 m = "%s back after being %s for %s" % (conn.afam, lasts, dur(d))
             if m:
-                eventlog(uname, "RECOVER", m)
+                # RECOVER (and a notification) only if the host itself was overdue/down;
-                if host.watched:
+                # a single family coming back while another stayed up is informational.
+                level = "RECOVER" if prev_status in ("overdue", "down", "unknown") else "INFO"
+                eventlog(uname, level, m)
+                if host.watched and level == "RECOVER":
                     asyncio.create_task(notify_mod.send_notification(
                         uname,
                         notify_mod.Notification(title=f"[RECOVER] {uname}", body=m, level="RECOVER"),
@@ -562,6 +654,10 @@ def handle_datagram(msg: dict, addr, transport, ctx: dict):
     if interval > 0:
         host.interval = interval
 
+    # Record RTT history for charting
+    if rtt is not None:
+        host.add_plugin_data(f"rtt_{conn.afam.lower()}", {"rtt": rtt}, timestamp=now)
+
     # Timer-based reachability monitoring
     # Reset overdue timer on every heartbeat
     if interval > 0 and conn.getstate() != hbdcls.Connection.DOWN:

pyproject.toml

@@ -4,7 +4,7 @@ build-backend = "setuptools.build_meta"
 
 [project]
 name = "hbd"
-version = "5.4.0"
+version = "5.4.4"
 description = "Heartbeat monitoring system — client (hbc) and server (hbd)"
 readme = "README.md"
 requires-python = ">=3.11"

scripts/hbc_mini.py

@@ -41,7 +41,7 @@ from pathlib import Path
 from typing import Any, Dict, List, Optional, Tuple
 
 # updated by scripts/bumpminor.sh
-__version__ = "5.4.0"
+__version__ = "5.4.4"
 
 # ---------------------------------------------------------------------------
 # Protocol  (mirrors hbd/common/proto.py)

tests/test_client_heartbeat.py

@@ -0,0 +1,28 @@
+from hbd.client.main import build_heartbeat_msg
+
+
+class _Conn:
+    ackcount = 3
+    rtts = [0, 12.5]
+
+
+class _Conn2:
+    def __init__(self, flags):
+        self._flags = flags
+
+    def flags(self):
+        return self._flags
+
+
+def test_heartbeat_without_connectivity_is_unchanged():
+    assert build_heartbeat_msg(_Conn(), 60) == {"acks": 3, "rtt": 12.5, "interval": 60}
+
+
+def test_heartbeat_carries_presence_flags():
+    msg = build_heartbeat_msg(_Conn(), 60, _Conn2({"p4": True, "p6": False}))
+    assert msg == {"acks": 3, "rtt": 12.5, "interval": 60, "p4": True, "p6": False}
+
+
+def test_heartbeat_omits_unknown_flags():
+    msg = build_heartbeat_msg(_Conn(), 60, _Conn2({}))
+    assert "p4" not in msg and "p6" not in msg

tests/test_connectivity.py

@@ -0,0 +1,173 @@
+import asyncio
+
+from hbd.client.connectivity import Connectivity, ProbeUnavailable
+from hbd.client.pingutil import PingUnavailable
+
+
+class Net:
+    """Scriptable network: addr None = no route, 'unavailable' = family unsupported."""
+
+    def __init__(self):
+        self.addr = {"ipv4": "192.0.2.5", "ipv6": "2001:db8::5"}
+        self.gw = {"ipv4": "192.0.2.1", "ipv6": "fe80::1"}
+        self.rtt = {"ipv4": 10.0, "ipv6": 20.0}   # None = ping fails, 'unavailable' = no ping binary
+        self.pings = []
+        self.now = 1000.0
+
+    def local(self, fam, target):
+        a = self.addr[fam]
+        if a == "unavailable":
+            raise ProbeUnavailable("no such family")
+        return a
+
+    async def ping(self, target, fam):
+        self.pings.append(fam)
+        r = self.rtt[fam]
+        if r == "unavailable":
+            raise PingUnavailable("no ping")
+        return r
+
+    async def gateway(self, fam):
+        return self.gw[fam]
+
+    def clock(self):
+        return self.now
+
+
+def make(net, **kw):
+    c = Connectivity(local_address_fn=net.local, ping_fn=net.ping, gateway_fn=net.gateway,
+                     clock=net.clock, **kw)
+    c._cheap_gateway = True
+    return c
+
+
+def refresh(c):
+    asyncio.run(c.refresh())
+
+
+def test_present_with_addr_gateway_rtt():
+    net = Net()
+    c = make(net)
+    refresh(c)
+    s = c.snapshot()["ipv4"]
+    assert (s.present, s.addr, s.gateway, s.rtt) == (True, "192.0.2.5", "192.0.2.1", 10.0)
+    assert c.flags() == {"p4": True, "p6": True}
+    assert c.as_metric()["ipv6"]["gateway"] == "fe80::1"
+
+
+def test_no_route_is_immediately_absent():
+    net = Net()
+    net.addr["ipv6"] = None
+    c = make(net)
+    refresh(c)
+    assert c.flags() == {"p4": True, "p6": False}
+    assert net.pings == ["ipv4"]          # no ping wasted on a family without a route
+    assert c.snapshot()["ipv6"].addr is None
+
+
+def test_ping_is_debounced_and_rate_limited():
+    net = Net()
+    c = make(net, probe_interval=60.0, retry_interval=10.0)
+    refresh(c)
+    refresh(c)                            # same instant: cached, no second ping
+    assert net.pings == ["ipv4", "ipv6"]
+    net.now += 60
+    net.rtt["ipv6"] = None                # first failure: still present (debounce)
+    refresh(c)
+    assert c.flags()["p6"] is True
+    net.now += 10                         # retry_interval elapsed: second failure flips it
+    refresh(c)
+    assert c.flags()["p6"] is False
+
+
+def test_first_probe_failing_once_is_unknown():
+    net = Net()
+    net.rtt["ipv4"] = None
+    c = make(net)
+    refresh(c)
+    assert "p4" not in c.flags() and c.flags()["p6"] is True
+
+
+def test_recovers_on_first_success():
+    net = Net()
+    net.rtt["ipv6"] = None
+    c = make(net, retry_interval=10.0)
+    refresh(c)
+    net.now += 10
+    refresh(c)
+    assert c.flags()["p6"] is False
+    net.rtt["ipv6"] = 25.0
+    net.now += 10
+    refresh(c)
+    assert c.flags()["p6"] is True
+
+
+def test_address_change_invalidates_cache():
+    net = Net()
+    c = make(net)
+    refresh(c)
+    net.addr["ipv4"] = "198.51.100.7"     # moved networks, no time has passed
+    refresh(c)
+    assert net.pings.count("ipv4") == 2
+    assert c.snapshot()["ipv4"].addr == "198.51.100.7"
+
+
+def test_gateway_change_invalidates_cache():
+    net = Net()
+    c = make(net)
+    refresh(c)
+    net.gw["ipv4"] = "192.0.2.254"
+    refresh(c)
+    assert net.pings.count("ipv4") == 2
+
+
+def test_route_loss_then_return_pings_immediately():
+    net = Net()
+    c = make(net)
+    refresh(c)
+    net.addr["ipv6"] = None
+    refresh(c)
+    net.addr["ipv6"] = "2001:db8::5"
+    refresh(c)
+    assert net.pings.count("ipv6") == 2 and c.flags()["p6"] is True
+
+
+def test_missing_ping_binary_leaves_presence_unknown_and_stops_retrying():
+    net = Net()
+    net.rtt["ipv4"] = "unavailable"
+    c = make(net)
+    refresh(c)
+    net.now += 600
+    refresh(c)
+    assert "p4" not in c.flags()
+    assert net.pings.count("ipv4") == 1
+
+
+def test_unsupported_family_is_unknown():
+    net = Net()
+    net.addr["ipv6"] = "unavailable"
+    c = make(net)
+    refresh(c)
+    assert "p6" not in c.flags() and c.flags()["p4"] is True
+
+
+def test_from_config():
+    c = Connectivity.from_config({"probe_v4": "9.9.9.9", "probe_interval": 30})
+    assert c.probes["ipv4"] == "9.9.9.9"
+    assert c.probes["ipv6"] == "2606:4700:4700::1111"
+    assert c.probe_interval == 30.0
+
+
+def test_ping_less_family_stays_unknown_after_route_returns():
+    net = Net()
+    net.rtt["ipv4"] = "unavailable"
+    c = make(net)
+    refresh(c)
+    assert "p4" not in c.flags()
+    net.addr["ipv4"] = None
+    refresh(c)
+    assert c.flags()["p4"] is False       # no route is definitive
+    net.addr["ipv4"] = "192.0.2.5"
+    refresh(c)
+    assert "p4" not in c.flags()
+    assert net.pings.count("ipv4") == 1   # missing binary is not retried

tests/test_flap.py

@@ -98,6 +98,26 @@ def test_alert_during_the_quiet_window_keeps_it_flapping():
     assert flap.flapping_services("h1") == ["cpu"]
 
 
+# --- host removal ------------------------------------------------------------
+
+def test_clear_host_drops_flapping_state_even_without_a_recover():
+    # A host dropped mid-flap (no RECOVER ever received) must not stay
+    # flapping forever: nothing will ever set ok_since for it again.
+    alerts(4)
+    assert flap.flapping_services("h1") == ["cpu"]
+    flap.clear_host("h1")
+    assert flap.flapping_services("h1") == []
+    assert flap.observe("h1", "cpu", "CRITICAL") == flap.PASS
+
+
+def test_clear_host_only_affects_the_named_host():
+    alerts(4, host="h1")
+    alerts(4, host="h2")
+    flap.clear_host("h1")
+    assert flap.flapping_services("h1") == []
+    assert flap.flapping_services("h2") == ["cpu"]
+
+
 # --- keying -----------------------------------------------------------------
 
 def test_services_and_hosts_are_tracked_independently():

tests/test_gateway.py

@@ -0,0 +1,75 @@
+import asyncio
+import struct
+
+from hbd.client import gateway
+
+PROC_V4 = (
+    "Iface\tDestination\tGateway \tFlags\tRefCnt\tUse\tMetric\tMask\t\tMTU\tWindow\tIRTT\n"
+    "wlan0\t00000000\t0100A8C0\t0003\t0\t0\t600\t00000000\t0\t0\t0\n"
+    "eth0\t00000000\t0101A8C0\t0003\t0\t0\t100\t00000000\t0\t0\t0\n"
+    "wlan0\t0000A8C0\t00000000\t0001\t0\t0\t600\t00FFFFFF\t0\t0\t0\n"
+)
+
+PROC_V6 = (
+    "00000000000000000000000000000000 00 00000000000000000000000000000000 00 "
+    "fe800000000000000000000000000001 00000400 00000001 00000000 00000003 wlan0\n"
+    "00000000000000000000000000000000 00 00000000000000000000000000000000 00 "
+    "00000000000000000000000000000000 ffffffff 00000001 00000000 00200200 lo\n"
+    "fe800000000000000000000000000000 40 00000000000000000000000000000000 00 "
+    "00000000000000000000000000000000 00000100 00000001 00000000 00000001 wlan0\n"
+)
+
+MACOS = """   route to: default
+destination: default
+       mask: default
+    gateway: 192.168.1.1
+  interface: en0
+"""
+
+WIN_V4 = """IPv4 Route Table
+Active Routes:
+Network Destination        Netmask          Gateway       Interface  Metric
+          0.0.0.0          0.0.0.0      192.168.1.1    192.168.1.50     25
+          0.0.0.0          0.0.0.0        10.0.0.1        10.0.0.9     50
+        127.0.0.0        255.0.0.0         On-link         127.0.0.1    331
+"""
+
+WIN_V6 = """IPv6 Route Table
+Active Routes:
+ If Metric Network Destination      Gateway
+ 12    281 ::/0                     fe80::1
+  1    331 ::1/128                  On-link
+"""
+
+
+def test_proc_v4_picks_lowest_metric_gateway():
+    assert gateway.parse_proc_route_v4(PROC_V4) == "192.168.1.1"  # eth0, metric 100
+
+
+def test_proc_v4_none_without_default_route():
+    assert gateway.parse_proc_route_v4(PROC_V4.splitlines()[0] + "\n") is None
+
+
+def test_proc_v6_skips_reject_and_non_default():
+    assert gateway.parse_proc_route_v6(PROC_V6) == "fe80::1"
+
+
+def test_macos():
+    assert gateway.parse_macos_route(MACOS) == "192.168.1.1"
+    assert gateway.parse_macos_route("route: writing to routing socket: not in table") is None
+
+
+def test_windows_v4_lowest_metric():
+    assert gateway.parse_windows_route(WIN_V4, "ipv4") == "192.168.1.1"
+
+
+def test_windows_v6():
+    assert gateway.parse_windows_route(WIN_V6, "ipv6") == "fe80::1"
+
+
+def test_default_gateway_never_raises_on_parser_error(monkeypatch):
+    """default_gateway catches all exceptions; never raises even if parser fails."""
+    monkeypatch.setattr("sys.platform", "linux")
+    monkeypatch.setattr(gateway, "parse_proc_route_v4", lambda _: (_ for _ in ()).throw(struct.error))
+    result = asyncio.run(gateway.default_gateway("ipv4"))
+    assert result is None

tests/test_host_status.py

@@ -0,0 +1,120 @@
+import time
+
+import pytest
+
+from hbd.server import hbdclass
+from hbd.server.hbdclass import Connection as C
+
+
+def _host(name):
+    hbdclass.Host.hosts.pop(name, None)
+    return hbdclass.Host(name)
+
+
+def _conn(host, afam, state):
+    addr = "192.0.2.1" if afam == "IPv4" else "2001:db8::1"
+    conn, _ = host.conndata(0, addr, None, 1000.0)
+    conn.state = state
+    return conn
+
+
+CASES = [
+    # v4 state, v6 state, presence flags, expected status
+    (C.UP, C.UP, {}, "up"),
+    (C.UP, C.OVERDUE, {}, "simplex"),                       # both present (legacy) => simplex
+    (C.UP, C.OVERDUE, {"IPv6": True}, "simplex"),
+    (C.UP, C.OVERDUE, {"IPv6": False}, "up"),               # v6 not present => not monitored
+    (C.OVERDUE, C.OVERDUE, {}, "overdue"),
+    (C.OVERDUE, C.ABSENT, {"IPv6": False}, "overdue"),      # only present family is overdue
+    (C.UP, C.ABSENT, {"IPv6": False}, "up"),
+    (C.DOWN, C.UP, {}, "down"),
+    (C.UNKNOWN, C.UNKNOWN, {}, "unknown"),
+    (C.OVERDUE, C.UNKNOWN, {}, "overdue"),
+    (C.UP, C.UNKNOWN, {}, "up"),
+    (C.OVERDUE, C.UP, {"IPv6": False}, "simplex"),          # HTB arriving => present despite flag
+]
+
+
+@pytest.mark.parametrize("s4,s6,flags,expected", CASES)
+def test_status_matrix(s4, s6, flags, expected):
+    h = _host("status-matrix")
+    _conn(h, "IPv4", s4)
+    _conn(h, "IPv6", s6)
+    for afam, present in flags.items():
+        h.set_presence(afam, present, time.time())
+    assert h.status() == expected
+
+
+def test_status_single_family_host():
+    h = _host("status-v4only")
+    _conn(h, "IPv4", C.UP)
+    assert h.status() == "up"
+    h.connections["IPv4"].state = C.OVERDUE
+    assert h.status() == "overdue"
+
+
+def test_status_no_connections_is_unknown():
+    assert _host("status-empty").status() == "unknown"
+
+
+def test_family_present_rules():
+    h = _host("fp")
+    v6 = _conn(h, "IPv6", C.OVERDUE)
+    assert h.family_present("IPv6") is True            # never reported => present
+    h.set_presence("IPv6", False, 1.0)
+    assert h.family_present("IPv6") is False
+    v6.state = C.UP                                    # real traffic overrides the flag
+    assert h.family_present("IPv6") is True
+    assert h.flag_present("IPv6") is False
+
+
+def test_stateinfo_and_statedict_expose_status():
+    h = _host("status-exposed")
+    _conn(h, "IPv4", C.UP)
+    assert h.stateinfo()["status"] == "up"
+    assert h.statedict()["status"] == "up"
+
+
+def test_absent_connection_statedict_is_neutral():
+    h = _host("absent-dict")
+    conn = _conn(h, "IPv6", C.ABSENT)
+    conn.rtts.append(42.0)
+    d = conn.statedict()
+    assert d["state"] == "absent" and d["rtt"] == "" and d["rttstate"] == "absent"
+
+
+def test_presence_survives_pickle_and_old_pickles_get_default():
+    import pickle
+    h = _host("pickled")
+    h.set_presence("IPv6", False, 5.0)
+    h2 = pickle.loads(pickle.dumps(h))
+    assert h2.presence == {"IPv6": {"present": False, "ts": 5.0}}
+    del h2.__dict__["presence"]                        # simulate a pre-feature pickle
+    h2.fixup()
+    assert h2.presence == {}
+
+
+def _all_absent(name, s4, s6=None):
+    h = _host(name)
+    _conn(h, "IPv4", s4)
+    h.set_presence("IPv4", False, time.time())
+    if s6 is not None:
+        _conn(h, "IPv6", s6)
+        h.set_presence("IPv6", False, time.time())
+    return h
+
+
+def test_all_absent_single_family_overdue_is_overdue():
+    assert _all_absent("abs-single", C.OVERDUE).status() == "overdue"
+
+
+def test_all_absent_dual_stack_one_absent_one_overdue_is_overdue():
+    assert _all_absent("abs-dual-od", C.ABSENT, C.OVERDUE).status() == "overdue"
+
+
+def test_all_absent_dual_stack_v6_up_is_up():
+    assert _all_absent("abs-dual-up", C.ABSENT, C.UP).status() == "up"
+
+
+def test_all_absent_all_unknown_is_unknown():
+    assert _all_absent("abs-unknown", C.UNKNOWN, C.UNKNOWN).status() == "unknown"

tests/test_http_host_info.py

@@ -1,5 +1,4 @@
 """Tests for _build_host_info helper in http.py."""
-import pytest
 from unittest.mock import MagicMock
 from hbd.server.http import _build_host_info
 
@@ -175,11 +174,11 @@ def test_build_host_info_covers_empty_when_exact_matches_only():
 
 
 class _FakeConnFull:
-    def __init__(self, afam, addr, state, rtt, statetime, lastbeat):
+    def __init__(self, afam, addr, state, rtt, statetime, lastbeat, rtts=None):
         self.afam = afam
         self.addr = addr
         self.state = state
-        self.rtts = [rtt]
+        self.rtts = rtts if rtts is not None else [rtt]
         self.statetime = statetime
         self.lastbeat = lastbeat
 
@@ -200,3 +199,14 @@ def test_build_host_info_connections_empty():
     host = _FakeHost()
     result = _build_host_info(host)
     assert result["connections"] == []
+
+
+def test_build_host_info_connection_rtt_uses_latest_sample():
+    """rtt should reflect the most recent sample, not the oldest retained one."""
+    host = _FakeHost(connections={
+        "IPv4": _FakeConnFull("IPv4", "10.0.0.5", "up", None, 1000.0, 2000.0,
+                              rtts=[100.0, 50.0, 14.2]),
+    })
+    result = _build_host_info(host)
+    conns = {c["family"]: c for c in result["connections"]}
+    assert conns["IPv4"]["rtt"] == 14.2

tests/test_http_plugins_page.py

@@ -0,0 +1,23 @@
+"""Tests for the plugin-accordion visibility filter in http.py."""
+from hbd.server.http import _visible_plugin_names
+
+
+def test_visible_plugin_names_excludes_rtt_history_keys():
+    plugin_data = {
+        "cpu_monitor": [],
+        "rtt_ipv4": [],
+        "rtt_ipv6": [],
+        "network_monitor": [],
+    }
+    result = _visible_plugin_names(plugin_data)
+    assert sorted(result) == ["cpu_monitor", "network_monitor"]
+
+
+def test_visible_plugin_names_empty_when_no_plugins():
+    assert _visible_plugin_names({}) == []
+
+
+def test_visible_plugin_names_keeps_names_not_prefixed_with_rtt_():
+    plugin_data = {"nagios_runner": [], "os_info": []}
+    result = _visible_plugin_names(plugin_data)
+    assert sorted(result) == ["nagios_runner", "os_info"]

tests/test_network_monitor_connectivity.py

@@ -0,0 +1,26 @@
+import asyncio
+
+from hbd.client import connectivity
+from hbd.client.plugins.network_monitor import NetworkMonitorPlugin
+
+
+class _FakeShared:
+    def as_metric(self):
+        return {"ipv4": {"present": True, "addr": "192.0.2.5", "gateway": "192.0.2.1", "rtt": 9.0},
+                "ipv6": {"present": False, "addr": None, "gateway": None, "rtt": None}}
+
+
+def test_collect_includes_connectivity_when_probe_running():
+    connectivity.set_shared(_FakeShared())
+    try:
+        data = asyncio.run(NetworkMonitorPlugin()._collect_metrics())
+    finally:
+        connectivity.set_shared(None)
+    assert data["connectivity"]["ipv4"]["present"] is True
+    assert data["connectivity"]["ipv6"]["present"] is False
+
+
+def test_collect_omits_connectivity_without_probe():
+    connectivity.set_shared(None)
+    data = asyncio.run(NetworkMonitorPlugin()._collect_metrics())
+    assert "connectivity" not in data

tests/test_pingutil.py

@@ -0,0 +1,60 @@
+import sys
+
+import pytest
+
+from hbd.client import pingutil
+
+LINUX_OK = """PING 1.1.1.1 (1.1.1.1) 56(84) bytes of data.
+64 bytes from 1.1.1.1: icmp_seq=1 ttl=57 time=11.2 ms
+
+--- 1.1.1.1 ping statistics ---
+1 packets transmitted, 1 received, 0% packet loss, time 0ms
+rtt min/avg/max/mdev = 11.234/11.234/11.234/0.000 ms
+"""
+
+MACOS_OK = """PING 1.1.1.1 (1.1.1.1): 56 data bytes
+64 bytes from 1.1.1.1: icmp_seq=0 ttl=57 time=12.3 ms
+
+--- 1.1.1.1 ping statistics ---
+1 packets transmitted, 1 packets received, 0.0% packet loss
+round-trip min/avg/max/stddev = 12.3/12.3/12.3/0.000 ms
+"""
+
+LOST = """--- 1.1.1.1 ping statistics ---
+1 packets transmitted, 0 received, 100% packet loss, time 0ms
+"""
+
+
+def test_parse_linux():
+    r = pingutil.parse_ping_output(LINUX_OK)
+    assert r == {"rtt_min": 11.234, "rtt_avg": 11.234, "rtt_max": 11.234, "loss": 0.0}
+
+
+def test_parse_macos():
+    r = pingutil.parse_ping_output(MACOS_OK)
+    assert r["rtt_avg"] == 12.3 and r["loss"] == 0.0
+
+
+def test_parse_lost():
+    r = pingutil.parse_ping_output(LOST)
+    assert r["rtt_avg"] == float("inf") and r["loss"] == 100.0
+
+
+def test_parse_garbage_is_unreachable():
+    r = pingutil.parse_ping_output("ping: connect: Network is unreachable")
+    assert r["rtt_avg"] == float("inf") and r["loss"] == 100.0
+
+
+@pytest.mark.parametrize("platform,family,expected", [
+    ("linux", None, ["ping", "-c", "3", "-W", "5", "h"]),
+    ("linux", 6, ["ping", "-c", "3", "-W", "5", "-6", "h"]),
+    ("linux", 4, ["ping", "-c", "3", "-W", "5", "-4", "h"]),
+    ("win32", None, ["ping", "-n", "3", "-w", "5000", "h"]),
+    ("win32", 6, ["ping", "-n", "3", "-w", "5000", "-6", "h"]),
+    ("darwin", None, ["ping", "-c", "3", "-W", "5", "h"]),
+    ("darwin", 4, ["ping", "-c", "3", "-W", "5000", "h"]),
+    ("darwin", 6, ["ping6", "-c", "3", "h"]),
+])
+def test_ping_command(monkeypatch, platform, family, expected):
+    monkeypatch.setattr(sys, "platform", platform)
+    assert pingutil.ping_command("h", 3, 5, family) == expected

tests/test_udp_presence.py

@@ -0,0 +1,250 @@
+"""Host-level overdue alerting driven by client-reported protocol presence."""
+import asyncio
+import time
+
+from hbd.common.proto import dicttos
+from hbd.server import hbdclass, udp
+from hbd.server.hbdclass import Connection as C
+from hbd.server.udp import handle_datagram, parse_message
+
+
+class _FakeTransport:
+    def sendto(self, data, addr):
+        pass
+
+
+def _ctx():
+    return {"config": {}, "hbdclass": hbdclass, "msg_to_websockets": None,
+            "DEBUG": 0, "verbose": False}
+
+
+def _fresh(name):
+    hbdclass.Host.hosts.pop(name, None)
+
+
+def _send(name, addr, ctx, **fields):
+    msg = parse_message(dicttos("HTB", {"name": name, "id": 0, **fields}))
+    handle_datagram(msg, (addr, 50000), _FakeTransport(), ctx)
+
+
+def _events(monkeypatch):
+    events = []
+    monkeypatch.setattr(udp, "eventlog", lambda u, level, msg, **kw: events.append((level, msg)))
+    return events
+
+
+def _dual_stack(name, ctx):
+    _fresh(name)
+    _send(name, "127.0.0.1", ctx)
+    _send(name, "::1", ctx)
+    return hbdclass.Host.hosts[name]
+
+
+def test_flags_are_stored_on_host():
+    ctx = _ctx()
+    _fresh("pres-store")
+    _send("pres-store", "127.0.0.1", ctx, p4=1, p6=0)
+    h = hbdclass.Host.hosts["pres-store"]
+    assert h.presence["IPv4"]["present"] is True
+    assert h.presence["IPv6"]["present"] is False
+
+
+def test_no_flags_leaves_presence_unknown():
+    ctx = _ctx()
+    _fresh("pres-legacy")
+    _send("pres-legacy", "127.0.0.1", ctx)
+    assert hbdclass.Host.hosts["pres-legacy"].presence == {}
+
+
+def test_absent_flag_moves_overdue_family_to_absent_and_clears_alert(monkeypatch):
+    _events(monkeypatch)
+    ctx = _ctx()
+    h = _dual_stack("pres-absent", ctx)
+    v6 = h.connections["IPv6"]
+    v6.state = C.OVERDUE
+    udp._set_connectivity_alert(h, "IPv6", "CRITICAL")
+    _send("pres-absent", "127.0.0.1", ctx, p4=1, p6=0)
+    assert v6.state == C.ABSENT
+    assert "connectivity.IPv6" not in h.alert_states
+    assert h.status() == "up"
+
+
+def test_absent_flag_does_not_touch_family_that_is_up():
+    ctx = _ctx()
+    h = _dual_stack("pres-up-stays", ctx)
+    _send("pres-up-stays", "127.0.0.1", ctx, p4=1, p6=0)
+    assert h.connections["IPv6"].state == C.UP          # traffic overrides the flag
+
+
+def test_present_again_arms_grace_timer():
+    ctx = _ctx()
+
+    async def scenario():
+        _fresh("pres-back")
+        _send("pres-back", "127.0.0.1", ctx, interval=10)
+        _send("pres-back", "::1", ctx, interval=10)
+        h = hbdclass.Host.hosts["pres-back"]
+        v6 = h.connections["IPv6"]
+        v6.cancel_overdue_timer()
+        v6.state = C.ABSENT
+        _send("pres-back", "127.0.0.1", ctx, interval=10, p6=1)
+        assert v6.state == C.UNKNOWN and v6.overdue_timer is not None
+        for c in h.connections.values():
+            c.cancel_overdue_timer()
+
+    asyncio.run(scenario())
+
+
+def test_one_family_overdue_is_simplex_all_overdue_is_critical(monkeypatch):
+    events = _events(monkeypatch)
+    ctx = _ctx()
+    h = _dual_stack("pres-simplex", ctx)
+    on_overdue, _ = udp._make_timer_callbacks("pres-simplex", h, ctx)
+
+    asyncio.run(on_overdue(h.connections["IPv6"]))
+    assert h.status() == "simplex"
+    assert ("INFO", "IPv6 overdue (simplex)") in events
+    assert not any(level == "CRITICAL" for level, _ in events)
+    assert "connectivity.IPv6" not in h.alert_states
+
+    asyncio.run(on_overdue(h.connections["IPv4"]))
+    assert h.status() == "overdue"
+    assert [e for e in events if e[0] == "CRITICAL"] == [("CRITICAL", "IPv4, IPv6 overdue")]
+    assert {"connectivity.IPv4", "connectivity.IPv6"} <= set(h.alert_states)
+
+
+def test_timer_expiry_on_absent_family_is_silent(monkeypatch):
+    events = _events(monkeypatch)
+    ctx = _ctx()
+    h = _dual_stack("pres-quiet", ctx)
+    _send("pres-quiet", "127.0.0.1", ctx, p4=1, p6=0)   # v6 still UP => left alone
+    events.clear()
+    on_overdue, _ = udp._make_timer_callbacks("pres-quiet", h, ctx)
+    asyncio.run(on_overdue(h.connections["IPv6"]))
+    assert h.connections["IPv6"].state == C.ABSENT
+    assert events == []
+    assert h.status() == "up"
+
+
+def test_recovery_from_simplex_is_info_only(monkeypatch):
+    events = _events(monkeypatch)
+    ctx = _ctx()
+    h = _dual_stack("pres-rec-simplex", ctx)
+    v6 = h.connections["IPv6"]
+    v6.state, v6.statetime = C.OVERDUE, time.time() - 100
+    events.clear()
+    _send("pres-rec-simplex", "::1", ctx)
+    assert v6.state == C.UP
+    assert [e[0] for e in events] == ["INFO"] and "back after" in events[0][1]
+
+
+def test_recovery_from_overdue_is_recover_and_clears_all_alerts(monkeypatch):
+    events = _events(monkeypatch)
+    ctx = _ctx()
+    h = _dual_stack("pres-rec-overdue", ctx)
+    for afam in ("IPv4", "IPv6"):
+        c = h.connections[afam]
+        c.state, c.statetime = C.OVERDUE, time.time() - 100
+        udp._set_connectivity_alert(h, afam, "CRITICAL")
+    events.clear()
+    _send("pres-rec-overdue", "127.0.0.1", ctx)
+    assert [e[0] for e in events] == ["RECOVER"]
+    assert h.status() == "simplex"
+    assert "connectivity.IPv6" not in h.alert_states     # left overdue => all cleared
+    assert "connectivity.IPv4" not in h.alert_states
+
+
+def test_restore_skips_absent_and_sets_no_alert_for_simplex():
+    ctx = _ctx()
+
+    async def scenario():
+        h = _dual_stack("pres-restore", ctx)
+        h.connections["IPv6"].state = C.OVERDUE          # v4 UP + v6 OVERDUE => simplex
+        udp.restore_connection_timers(hbdclass, ctx)
+        assert "connectivity.IPv6" not in h.alert_states
+        h.connections["IPv6"].cancel_overdue_timer()
+        h.connections["IPv6"].state = C.ABSENT
+        h.set_presence("IPv6", False, time.time())
+        udp.restore_connection_timers(hbdclass, ctx)
+        assert h.connections["IPv6"].state == C.ABSENT
+        for c in h.connections.values():
+            c.cancel_overdue_timer()
+
+    asyncio.run(scenario())
+
+
+def _past_drop(conn):
+    conn.state, conn.statetime = C.OVERDUE, time.time() - (udp.DROPOVERDUE + 10)
+
+
+def test_restore_past_drop_window_keeps_alert_single_family():
+    ctx = _ctx()
+
+    async def scenario():
+        _fresh("pres-drop-single")
+        _send("pres-drop-single", "127.0.0.1", ctx)
+        h = hbdclass.Host.hosts["pres-drop-single"]
+        _past_drop(h.connections["IPv4"])
+        udp.restore_connection_timers(hbdclass, ctx)
+        assert h.connections["IPv4"].state == C.UNKNOWN
+        assert "connectivity.IPv4" in h.alert_states
+
+    asyncio.run(scenario())
+
+
+def test_restore_past_drop_window_keeps_alerts_dual_family():
+    ctx = _ctx()
+
+    async def scenario():
+        h = _dual_stack("pres-drop-dual", ctx)
+        for c in h.connections.values():
+            _past_drop(c)
+        udp.restore_connection_timers(hbdclass, ctx)
+        assert {"connectivity.IPv4", "connectivity.IPv6"} <= set(h.alert_states)
+
+    asyncio.run(scenario())
+
+
+def test_v4_only_host_overdue_is_single_critical(monkeypatch):
+    events = _events(monkeypatch)
+    ctx = _ctx()
+    _fresh("pres-v4only")
+    _send("pres-v4only", "127.0.0.1", ctx)
+    h = hbdclass.Host.hosts["pres-v4only"]
+    on_overdue, _ = udp._make_timer_callbacks("pres-v4only", h, ctx)
+    asyncio.run(on_overdue(h.connections["IPv4"]))
+    assert [e for e in events if e[0] == "CRITICAL"] == [("CRITICAL", "IPv4 overdue")]
+    assert "connectivity.IPv4" in h.alert_states
+    asyncio.run(on_overdue(h.connections["IPv4"]))
+    assert len([e for e in events if e[0] == "CRITICAL"]) == 1
+
+
+def test_all_families_absent_v4_only_host_still_alerts_when_it_dies(monkeypatch):
+    events = _events(monkeypatch)
+    ctx = _ctx()
+    _fresh("pres-allabsent")
+    _send("pres-allabsent", "127.0.0.1", ctx, p4=0)
+    h = hbdclass.Host.hosts["pres-allabsent"]
+    on_overdue, _ = udp._make_timer_callbacks("pres-allabsent", h, ctx)
+    asyncio.run(on_overdue(h.connections["IPv4"]))
+    assert [e for e in events if e[0] == "CRITICAL"] == [("CRITICAL", "IPv4 overdue")]
+    assert h.connections["IPv4"].state == C.OVERDUE
+    assert h.status() == "overdue"
+    assert "connectivity.IPv4" in h.alert_states
+
+
+def test_last_present_family_is_not_parked_when_other_is_absent(monkeypatch):
+    events = _events(monkeypatch)
+    ctx = _ctx()
+    h = _dual_stack("pres-lastfam", ctx)
+    _send("pres-lastfam", "127.0.0.1", ctx, p4=0, p6=0)
+    events.clear()
+    on_overdue, _ = udp._make_timer_callbacks("pres-lastfam", h, ctx)
+    asyncio.run(on_overdue(h.connections["IPv4"]))
+    assert h.connections["IPv4"].state == C.ABSENT
+    assert not any(level == "CRITICAL" for level, _ in events)
+    assert h.status() == "up"
+    asyncio.run(on_overdue(h.connections["IPv6"]))
+    assert [e for e in events if e[0] == "CRITICAL"] == [("CRITICAL", "IPv6 overdue")]
+    assert h.connections["IPv6"].state == C.OVERDUE
+    assert h.status() == "overdue"

tests/test_udp_rtt_history.py

@@ -0,0 +1,153 @@
+"""Tests for RTT history capture in udp.py's handle_datagram."""
+import time
+
+from hbd.common.proto import dicttos
+from hbd.server import hbdclass
+from hbd.server.udp import handle_datagram, parse_message
+
+
+class _FakeTransport:
+    def __init__(self):
+        self.sent = []
+
+    def sendto(self, data, addr):
+        self.sent.append((data, addr))
+
+
+def _htb(name, rtt=None, interval=0, boot=0):
+    d = {"name": name, "interval": interval, "id": 0}
+    if rtt is not None:
+        d["rtt"] = rtt
+    if boot:
+        d["boot"] = boot
+    return parse_message(dicttos("HTB", d))
+
+
+def _base_ctx():
+    return {
+        "config": {},
+        "hbdclass": hbdclass,
+        "msg_to_websockets": None,
+        "DEBUG": 0,
+        "verbose": False,
+    }
+
+
+def test_handle_datagram_records_rtt_history_for_new_connection():
+    hbdclass.Host.hosts.pop("rtt-hist-host", None)
+    handle_datagram(_htb("rtt-hist-host", rtt=42.5), ("127.0.0.1", 50000),
+                    _FakeTransport(), _base_ctx())
+
+    host = hbdclass.Host.hosts["rtt-hist-host"]
+    samples = host.plugin_data.get("rtt_ipv4")
+    assert samples is not None
+    assert len(samples) == 1
+    ts, data = samples[0]
+    assert data == {"rtt": 42.5}
+    assert isinstance(ts, float)
+
+
+def test_handle_datagram_appends_rtt_history_across_heartbeats():
+    hbdclass.Host.hosts.pop("rtt-hist-host2", None)
+    transport = _FakeTransport()
+    ctx = _base_ctx()
+    handle_datagram(_htb("rtt-hist-host2", rtt=10.0), ("127.0.0.1", 50000), transport, ctx)
+    handle_datagram(_htb("rtt-hist-host2", rtt=20.0), ("127.0.0.1", 50000), transport, ctx)
+
+    host = hbdclass.Host.hosts["rtt-hist-host2"]
+    samples = host.plugin_data["rtt_ipv4"]
+    assert [d["rtt"] for _, d in samples] == [10.0, 20.0]
+
+
+def test_handle_datagram_skips_rtt_history_when_rtt_missing():
+    hbdclass.Host.hosts.pop("rtt-hist-host3", None)
+    handle_datagram(_htb("rtt-hist-host3", rtt=None), ("127.0.0.1", 50000),
+                    _FakeTransport(), _base_ctx())
+
+    host = hbdclass.Host.hosts["rtt-hist-host3"]
+    assert "rtt_ipv4" not in host.plugin_data
+
+
+def test_request_update_fires_on_recovery_even_with_rtt_history():
+    """Regression for Finding 1: rtt_* keys must not permanently disable the
+    request_update gate. A connection recovering from a non-UP state must
+    still be asked to resend real plugin data, even though rtt_ipv4 already
+    holds samples from before the drop.
+    """
+    hbdclass.Host.hosts.pop("rtt-hist-host4", None)
+    transport = _FakeTransport()
+    ctx = _base_ctx()
+
+    # First heartbeat: brand-new host, no plugin data at all yet.
+    handle_datagram(_htb("rtt-hist-host4", rtt=15.0), ("127.0.0.1", 50000), transport, ctx)
+    host = hbdclass.Host.hosts["rtt-hist-host4"]
+    assert host.plugin_data.get("rtt_ipv4")  # rtt history now non-empty
+
+    # Simulate a recovery: connection was dropped (e.g. OVERDUE->UP after a
+    # missed heartbeat) and is about to come back UP on the next heartbeat.
+    conn = host.connections["IPv4"]
+    conn.state = hbdclass.Connection.DOWN
+
+    transport.sent.clear()
+    handle_datagram(_htb("rtt-hist-host4", rtt=16.0), ("127.0.0.1", 50000), transport, ctx)
+
+    ack_data, _ = transport.sent[0]
+    ack = parse_message(ack_data)
+    assert ack.get("request_update")
+
+
+def test_ordinary_recovery_preserves_real_plugin_data_and_rtt_history():
+    """An ordinary reconnect (no boot flag) — e.g. OVERDUE->UP after a
+    transient network blip — must NOT wipe already-collected real plugin
+    data (e.g. cpu_monitor, os_info) or rtt_* history. Only an actual
+    client reboot invalidates that data (see the boot-flag test below).
+    """
+    hbdclass.Host.hosts.pop("rtt-hist-host5", None)
+    transport = _FakeTransport()
+    ctx = _base_ctx()
+
+    for rtt in (10.0, 11.0, 12.0):
+        handle_datagram(_htb("rtt-hist-host5", rtt=rtt), ("127.0.0.1", 50000), transport, ctx)
+
+    host = hbdclass.Host.hosts["rtt-hist-host5"]
+    assert len(host.plugin_data["rtt_ipv4"]) == 3
+
+    # Simulate a drop, and pretend the client had previously sent real
+    # plugin data (collected before the connection went down).
+    conn = host.connections["IPv4"]
+    conn.state = hbdclass.Connection.DOWN
+    host.add_plugin_data("os_info", {"os": "linux"}, timestamp=time.time())
+    assert "os_info" in host.plugin_data
+
+    # Ordinary recovery heartbeat — no boot flag.
+    handle_datagram(_htb("rtt-hist-host5", rtt=13.0), ("127.0.0.1", 50000), transport, ctx)
+
+    assert "os_info" in host.plugin_data
+    assert len(host.plugin_data["rtt_ipv4"]) == 4
+
+
+def test_boot_recovery_clears_real_plugin_data_but_preserves_rtt_history():
+    """A recovery heartbeat carrying the boot flag (client process actually
+    restarted) must still wipe stale real plugin data, while rtt_* history
+    (still a valid measurement, unaffected by a client reboot) survives.
+    """
+    hbdclass.Host.hosts.pop("rtt-hist-host6", None)
+    transport = _FakeTransport()
+    ctx = _base_ctx()
+
+    for rtt in (10.0, 11.0, 12.0):
+        handle_datagram(_htb("rtt-hist-host6", rtt=rtt), ("127.0.0.1", 50000), transport, ctx)
+
+    host = hbdclass.Host.hosts["rtt-hist-host6"]
+    assert len(host.plugin_data["rtt_ipv4"]) == 3
+
+    conn = host.connections["IPv4"]
+    conn.state = hbdclass.Connection.DOWN
+    host.add_plugin_data("os_info", {"os": "linux"}, timestamp=time.time())
+    assert "os_info" in host.plugin_data
+
+    # Recovery heartbeat with boot=1 — client process actually restarted.
+    handle_datagram(_htb("rtt-hist-host6", rtt=13.0, boot=1), ("127.0.0.1", 50000), transport, ctx)
+
+    assert "os_info" not in host.plugin_data
+    assert len(host.plugin_data["rtt_ipv4"]) == 4