** Description changed: [impact] if the 'disable_ipv6' procfs setting is disabled, and networkd is configured with ipv6 networking, networkd will not enable ipv6 via the procfs setting unless the interface mtu is also set to a custom value, that doesn't match the current interface mtu. [test case] create networkd config similar to: [Match] MACAddress=52:54:00:0c:09:77 Name=ens3 [Network] DHCP=ipv4 LinkLocalAddressing=ipv6 Address=2001:db8::100/64 manually disable ipv6 for the interface: ubuntu@lp1859862-b:~$ echo 1 | sudo tee /proc/sys/net/ipv6/conf/ens3/disable_ipv6 1 the interface should not contain any ipv6 addresses: ubuntu@lp1859862-b:~$ ip -6 a show ens3 ubuntu@lp1859862-b:~$ restart networkd; it should enable ipv6 as ipv6 addresses are configured, but it does not: ubuntu@lp1859862-b:~$ sudo systemctl restart systemd-networkd ubuntu@lp1859862-b:~$ ip -6 a show ens3 ubuntu@lp1859862-b:~$ Note that with the mtu set, it will successfully re-enable ipv6; modify the networkd config to set the mtu by adding this: [Link] MTUBytes=1400 + + (be sure to set the MTU config to something other than its current mtu) verify ipv6 is still disabled and has no addresses, then restart and check again: ubuntu@lp1859862-b:~$ cat /proc/sys/net/ipv6/conf/ens3/disable_ipv6 1 ubuntu@lp1859862-b:~$ ip -6 a show ens3 ubuntu@lp1859862-b:~$ sudo systemctl restart systemd-networkd ubuntu@lp1859862-b:~$ cat /proc/sys/net/ipv6/conf/ens3/disable_ipv6 0 ubuntu@lp1859862-b:~$ ip -6 a show ens3 2: ens3: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1400 state UP qlen 1000 inet6 2001:db8::100/64 scope global valid_lft forever preferred_lft forever inet6 fe80::5054:ff:fe0c:977/64 scope link valid_lft forever preferred_lft forever That should be the behavior even if MTUBytes is not set. [regression potential] as this adjusts when the procfs 'disable_ipv6' setting is changed, the regression potential could cause failure to properly set/create ipv6 addresses, or to leave ipv6 disabled entirely. [scope] This is needed in Bionic and Eoan. the commit to fix this is 482efedc081b0c4bf2e77a3dee6b979d9c9a5765 which is included starting in v243, so it is included already in Focal. Ignoring Disco, as it is EOL next week. This problem was introduced by commit 44b598a1c9d11c23420a5ef45ff11bcb0ed195eb, which was included starting in v239, but also backported to Bionic in bug 1850704. [other info] for Eoan, this bug has always existed since release, but for Bionic, this is a regression introduced by bug 1850704. However, manual disabling of ipv6 is very unusual, so this bug is unlikely to have an impact to many systems.
-- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1859862 Title: networkd doesn't re-enable ipv6 unless mtu is set To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/systemd/+bug/1859862/+subscriptions -- ubuntu-bugs mailing list [email protected] https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
