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