[Expired for systemd (Ubuntu) because there has been no activity for 60
days.]
** Changed in: systemd (Ubuntu)
Status: Incomplete => Expired
--
You received this bug notification because you are a member of Ubuntu
Touch seeded packages, which is subscribed to systemd in Ubuntu.
https://bugs.launchpad.net/bugs/1940908
Title:
resolved: closes listening socket too rapidly and sends Destination
port unreachable
Status in systemd package in Ubuntu:
Expired
Bug description:
Afffects Ubuntu 18.04 through 21.04 (fixes are in systemd v248)
With systemd v245 (and v247) and systemd-resolved we're seeing
frequent problems due to resolved rapidly closing the socket on which
it sends out a query before the server has answered. The server
answers and then resolved sends an ICMP Destination Unreachable (Port
Unreachable) response!
This breaks name lookups frequently. In our case the DNS server is
reached via a Wireguard tunnel over a satellite link and latencies can
vary.
A typical example captured via tcpdump:
07:22:03.446919 IP6 fddc:7e00:e001:ee00:fffe:f875:a4f3:42b4.45338 >
fddc:7e00:e001:ee00::1.53: 2963+ [1au] AAAA?
contile-images.services.mozilla.com. (64)
07:22:03.501089 IP6 fddc:7e00:e001:ee00::1.53 >
fddc:7e00:e001:ee00:fffe:f875:a4f3:42b4.45338: 2963 1/0/1 AAAA
2a01:7e00:e001:ee64::2278:7366 (92)
07:22:03.501152 IP6 fddc:7e00:e001:ee00:fffe:f875:a4f3:42b4 >
fddc:7e00:e001:ee00::1: ICMP6, destination unreachable, unreachable port,
fddc:7e00:e001:ee00:fffe:f875:a4f3:42b4 udp port 45338, length 148
The time difference here is only 0.054170 and there is no way to alter
the timeout in resolved.
There are recent upstream commits to fix this which ought to be
cherry-picked. See:
https://github.com/systemd/systemd/issues/17421
https://github.com/systemd/systemd/pull/17535
https://github.com/systemd/systemd/commit/e03d156f78cb5a0cac85d1e1310d89fdfa4f1b88
If I am reading the code correctly the timeout is very short:
src/resolve/resolved-dns-transaction.c:22:#define DNS_TIMEOUT_USEC
(SD_RESOLVED_QUERY_TIMEOUT_USEC / DNS_TRANSACTION_ATTEMPTS_MAX)
src/resolve/resolved-def.h:79:#define SD_RESOLVED_QUERY_TIMEOUT_USEC
(120 * USEC_PER_SEC)
src/resolve/resolved-dns-transaction.h:212:#define
DNS_TRANSACTION_ATTEMPTS_MAX 24
So in micro-seconds that is 120 /24 = 5 per query with, as inferred,
up to 24 attempts (I don't see multiple duplicate requests on the wire
so not sure DNS_TRANSACTION_ATTEMPTS_MAX affects this.
To manage notifications about this bug go to:
https://bugs.launchpad.net/ubuntu/+source/systemd/+bug/1940908/+subscriptions
--
Mailing list: https://launchpad.net/~touch-packages
Post to : touch-packages@lists.launchpad.net
Unsubscribe : https://launchpad.net/~touch-packages
More help : https://help.launchpad.net/ListHelp
