[Bug 1811149] [NEW] 23 wireguard peers hang systemd-networkd

[Leonid Evdokimov]

Public bug reported:

I'm running Ubuntu 18.04.1 LTS with systemd=237-3ubuntu10.9.

I have a Wireguard-based VPN server that has several peers. As soon as
number of peers is 22 or lower, everything works okay. As soon as I add
the 23rd peer, restart of `systemd-networkd` service fails with timeout
while systemd-networkd hogs CPU.

Moreover, if I reboot the box while wireguard configuration is "broken",
systemd-networkd fails to apply network settings on boot and the box is
no longer accessible over the network.

Configuration is structured in a following way (keys are fake):

==> wg0.netdev
[NetDev]
Name=wg0
Kind=wireguard
Description=Wireguard VPN server
[WireGuard]
ListenPort=4500
PrivateKey=kNl7tkhCM1Crj8RhUIn8xvwcg+UoOkw26kQjQEtZk1k=
[WireGuardPeer]
PublicKey=AfM1AN4IIUe5AVypFg2pcNrQmqOtZQIJLgusbkDYXkI=
AllowedIPs=fd6f:b446:a2ca:0400:cb6f:b446:a2ca:bd0b/128
AllowedIPs=fd6f:b446:a2ca:cb6f:b446:a2ca::/96
# and 22 more [WireGuardPeer] like that

==> wg0.network
Name=wg0
[Network]
Address=fd6f:b446:a2ca:0400::1/64
[Route]
Destination=fd6f:b446:a2ca:cb6f:b446:a2ca::/96
# and 22 more [Route] sections like that

syslog logs are attached both for "good" and "bad" cases, sample of
strace logs is also attached for "bad" case.

I'm filling the issue here as the aforementioned systemd version is
already out of scope of upstream bug tracker per
https://github.com/systemd/systemd/blob/master/docs/CONTRIBUTING.md
#filing-issues

** Affects: systemd (Ubuntu)
     Importance: Undecided
         Status: New


** Tags: networkd systemd-networkd wireguard

** Attachment added: "Archive with syslog & strace logs"
   https://bugs.launchpad.net/bugs/1811149/+attachment/5228066/+files/systemd-networkd-wireguard-many-peers.tar.gz

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https://bugs.launchpad.net/bugs/1811149

Title:
  23 wireguard peers hang systemd-networkd

Status in systemd package in Ubuntu:
  New

Bug description:
  I'm running Ubuntu 18.04.1 LTS with systemd=237-3ubuntu10.9.

  I have a Wireguard-based VPN server that has several peers. As soon as
  number of peers is 22 or lower, everything works okay. As soon as I
  add the 23rd peer, restart of `systemd-networkd` service fails with
  timeout while systemd-networkd hogs CPU.

  Moreover, if I reboot the box while wireguard configuration is
  "broken", systemd-networkd fails to apply network settings on boot and
  the box is no longer accessible over the network.

  Configuration is structured in a following way (keys are fake):

  ==> wg0.netdev
  [NetDev]
  Name=wg0
  Kind=wireguard
  Description=Wireguard VPN server
  [WireGuard]
  ListenPort=4500
  PrivateKey=kNl7tkhCM1Crj8RhUIn8xvwcg+UoOkw26kQjQEtZk1k=
  [WireGuardPeer]
  PublicKey=AfM1AN4IIUe5AVypFg2pcNrQmqOtZQIJLgusbkDYXkI=
  AllowedIPs=fd6f:b446:a2ca:0400:cb6f:b446:a2ca:bd0b/128
  AllowedIPs=fd6f:b446:a2ca:cb6f:b446:a2ca::/96
  # and 22 more [WireGuardPeer] like that

  ==> wg0.network
  Name=wg0
  [Network]
  Address=fd6f:b446:a2ca:0400::1/64
  [Route]
  Destination=fd6f:b446:a2ca:cb6f:b446:a2ca::/96
  # and 22 more [Route] sections like that

  syslog logs are attached both for "good" and "bad" cases, sample of
  strace logs is also attached for "bad" case.

  I'm filling the issue here as the aforementioned systemd version is
  already out of scope of upstream bug tracker per
  https://github.com/systemd/systemd/blob/master/docs/CONTRIBUTING.md
  #filing-issues

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