refactor

hbd/dns.py

@@ -0,0 +1,91 @@
+"""DNS update helper and thread for heartbeat daemon."""
+from __future__ import annotations
+import threading
+import subprocess
+from subprocess import Popen, PIPE, STDOUT
+from typing import Optional
+
+
+def create_nsupdate_payload(hostname: str, newip: str, dyndomain: str, dnsttl: str = "5") -> str:
+    D = {"domain": dyndomain, "fqdn": f"{hostname}.dy.{dyndomain}", "dnsttl": dnsttl, "newip": newip, "ts": __import__("time").strftime("%Y-%m-%d.%H:%M:%S", __import__("time").gmtime())}
+    if ":" in newip:
+        nsup = (
+            """update delete %(fqdn)s AAAA
+update add %(fqdn)s %(dnsttl)s AAAA %(newip)s
+update delete %(fqdn)s TXT
+update add %(fqdn)s %(dnsttl)s TXT "Created: %(ts)s"
+send
+answer
+
+""" % D
+        )
+    else:
+        nsup = (
+            """update delete %(fqdn)s A
+update add %(fqdn)s %(dnsttl)s A %(newip)s
+update delete %(fqdn)s TXT
+update add %(fqdn)s %(dnsttl)s TXT "Created: %(ts)s"
+send
+answer
+
+""" % D
+        )
+    return nsup
+
+
+def nsupdate(hostname: str, newip: str, dyndomain: str, nsupdate_bin: str = "/usr/local/bin/nsupdate", rndc_key: str = "/etc/dhcpc/rndc-key") -> Optional[str]:
+    """Perform DNS update via nsupdate command.
+
+    Returns None on success, else returns combined stdout/stderr as a string.
+    """
+    nsup = create_nsupdate_payload(hostname, newip, dyndomain)
+    cmd = [nsupdate_bin, "-k", rndc_key, "-v"]
+    try:
+        p = Popen(cmd, shell=False, bufsize=0, stdin=PIPE, stdout=PIPE, stderr=STDOUT)
+    except OSError as e:
+        return f"nsupdate: execution failed: {e}"
+    except Exception as e:
+        return f"nsupdate: some error occured: {e}"
+
+    (output, err) = p.communicate(nsup.encode())
+    out = output.decode() if output else ""
+    if out.find("status: NOERROR") >= 0:
+        return None
+    return out
+
+
+def dnsupdatethread(hbdclass, cfg: dict, log: Optional[callable] = None, email: Optional[callable] = None):
+    """Thread target: process dns update queue from hbdclass.Host.dnsQ.
+
+    hbdclass: module with Host class that exposes dnsQ queue
+    cfg: configuration mapping with 'dyndomains' and 'nsupdate_bin'
+    log: callable(host, message)
+    email: callable(subject, message)
+    """
+    while True:
+        name, addr = hbdclass.Host.dnsQ.get()
+        m = f"changed address to {addr}"
+        for dyndomain in cfg.get("dyndomains", []):
+            err = nsupdate(name, addr, dyndomain, nsupdate_bin=cfg.get("nsupdate_bin", "/usr/local/bin/nsupdate"))
+            if err:
+                m += f", DNS update failed: {err}"
+                if email:
+                    try:
+                        email("error: nsupdate failed", f"{name}.dy.{dyndomain}: {m}")
+                    except Exception:
+                        pass
+            else:
+                m += ", DNS updated."
+        hbdclass.Host.dnsQ.task_done()
+        if log:
+            try:
+                log(name, m)
+            except Exception:
+                pass
+
+
+def start_dns_thread(hbdclass, cfg: dict, log: Optional[callable] = None, email: Optional[callable] = None) -> threading.Thread:
+    t = threading.Thread(target=dnsupdatethread, args=(hbdclass, cfg, log, email))
+    t.daemon = True
+    t.start()
+    return t