From mboxrd@z Thu Jan  1 00:00:00 1970
From: Michael Tremer <michael.tremer@ipfire.org>
To: development@lists.ipfire.org
Subject: Re: [PATCH 1/3] unbound-dhcp-leases-bridge : fix bug 12694 - DHCP
 hosts not reliably propagated to DNS
Date: Mon, 28 Mar 2022 18:00:30 +0100
Message-ID: <6CBBDF3C-A821-4ED3-B056-11EEAF13ACA0@ipfire.org>
In-Reply-To: <20220322034756.36327-1-ajrh@ajrh.net>
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Hello Anthony,

Thank you very much for submitting this patch and welcome to the list.

I understand that it is easier to track any changes in the directory, but I d=
on=E2=80=99t quite understand why the logic had to be changed that the change=
s will be applied at the end only.

Is this just to avoid that multiple updates happen one after the other or wha=
t are you trying to achieve?

-Michael

> On 22 Mar 2022, at 03:47, Anthony Heading <ajrh(a)ajrh.net> wrote:
>=20
> Switch from inotify watching individual files to monitoring the
> containing directories, as because dhcpd renames its leases file into a
> backup, monitoring the single inode does not work well.  Additionally,
> python appears to have a bug with replacing expired inotify watches on
> single files.
> ---
> unbound-dhcp-leases-bridge | 47 +++++++++++++++++++++++++-------------
> 1 file changed, 31 insertions(+), 16 deletions(-)
>=20
> diff --git unbound-dhcp-leases-bridge unbound-dhcp-leases-bridge
> index a2df5f1..6e22066 100644
> --- unbound-dhcp-leases-bridge
> +++ unbound-dhcp-leases-bridge
> @@ -72,6 +72,15 @@ class UnboundDHCPLeasesBridge(object):
> 		self.fix_leases_file =3D fix_leases_file
> 		self.hosts_file =3D hosts_file
>=20
> +		# base mask for a completed file change
> +		mask =3D inotify.constants.IN_CLOSE_WRITE | inotify.constants.IN_MOVED_TO
> +		# IN_MODIFY since dhcpd appends lease updates to an open file
> +		self.watches =3D {
> +		    self.leases_file: mask | inotify.constants.IN_MODIFY,
> +		    self.fix_leases_file: mask,
> +		    self.hosts_file: mask
> +		}
> +
> 		self.unbound =3D UnboundConfigWriter(unbound_leases_file)
> 		self.running =3D False
>=20
> @@ -80,36 +89,42 @@ class UnboundDHCPLeasesBridge(object):
> 		self.running =3D True
>=20
> 		# Initial setup
> -		self.hosts =3D self.read_static_hosts()
> -		self.update_dhcp_leases()
> +		update_hosts =3D True
> +		update_leases =3D True
> +
> +		i =3D inotify.adapters.Inotify()
>=20
> -		i =3D inotify.adapters.Inotify([
> -			self.leases_file,
> -			self.fix_leases_file,
> -			self.hosts_file,
> -		])
> +		for f in self.watches:
> +			i.add_watch(os.path.dirname(f), self.watches[f])
>=20
> 		for event in i.event_gen():
> 			# End if we are requested to terminate
> 			if not self.running:
> 				break
>=20
> +			# Make pending updates once inotify queue is empty
> 			if event is None:
> +				if update_hosts:
> +					self.hosts =3D self.read_static_hosts()
> +					update_hosts =3D False
> +				if update_leases:
> +					self.update_dhcp_leases()
> +					update_leases =3D False
> 				continue
>=20
> 			header, type_names, watch_path, filename =3D event
>=20
> -			# Update leases after leases file has been modified
> -			if "IN_MODIFY" in type_names:
> -				# Reload hosts
> -				if watch_path =3D=3D self.hosts_file:
> -					self.hosts =3D self.read_static_hosts()
> +			file =3D os.path.join(watch_path, filename)
> +
> +			if not file in self.watches:
> +				continue
> +
> +			log.debug("Inotify %s: %s", file, " ".join(type_names))
>=20
> -				self.update_dhcp_leases()
> +			update_leases =3D True
>=20
> -			# If the file is deleted, we re-add the watcher
> -			if "IN_IGNORED" in type_names:
> -				i.add_watch(watch_path)
> +			if file =3D=3D self.hosts_file:
> +				update_hosts =3D True
>=20
> 		log.info("Unbound DHCP Leases Bridge terminated")
>=20
> --=20
> 2.34.1
>=20


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