For testing with the latest upstream, can you try the systemd from this ppa: https://launchpad.net/~ddstreet/+archive/ubuntu/systemd-upstream
You should only use that for testing, please - remove it and revert the packages back to the official versions once you've tested. Also, strictly as a workaround, you could try setting the mtu with a link file, like: [Match] Name=ens4 [Link] MTUBytes=1460 see 'man systemd.link' for more details, and of course that doesn't actually fix the problem, just tries to work around it by setting your link mtu before running dhcp, so your 'original' link mtu == dhcp mtu. -- 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/1874661 Title: networkd sometimes doesn't set mtu received by dhcp Status in systemd package in Ubuntu: Confirmed Bug description: I'm running ubuntu-minimal-1910-eoan on google compute engine with systemd 242-7ubuntu3.7. GCE has mtu 1460, set by dhcp. After having networking issues, I figured out that the mtu on the interface was sometimes incorrectly set to 1500. I manually changed it to 1420 to have a working system again and enabled debugging for systemd-networkd. Log (filtered for ens4, some columns removed for better readability): 09:51:00 ens4: New device has no master, continuing without 09:51:00 ens4: Flags change: +UP +LOWER_UP +RUNNING +MULTICAST +BROADCAST 09:51:00 ens4: Link 2 added 09:51:00 ens4: udev initialized link 09:51:00 ens4: Saved original MTU: 1420 09:51:00 ens4: Adding address: fe80::4001:aff:fea4:2/64 (valid forever) 09:51:00 ens4: Gained IPv6LL 09:51:00 ens4: Adding address: 10.164.0.2/32 (valid for 15h 15s) 09:51:00 ens4: Adding route: dst: ff00::/8, src: n/a, gw: n/a, prefsrc: n/a 09:51:00 ens4: Adding route: dst: fe80::4001:aff:fea4:2/128, src: n/a, gw: n/a, prefsrc: n/a 09:51:00 ens4: Adding route: dst: fe80::/64, src: n/a, gw: n/a, prefsrc: n/a 09:51:00 ens4: Adding route: dst: 10.164.0.2/32, src: n/a, gw: n/a, prefsrc: 10.164.0.2 09:51:00 ens4: Adding route: dst: 10.164.0.1/32, src: n/a, gw: n/a, prefsrc: 10.164.0.2 09:51:00 ens4: Adding route: dst: n/a, src: n/a, gw: 10.164.0.1, prefsrc: 10.164.0.2 09:51:00 ens4: Link state is up-to-date 09:51:00 ens4: found matching network '/run/systemd/network/10-netplan-ens4.network' 09:51:00 Setting '/proc/sys/net/ipv6/conf/ens4/proxy_ndp' to '0' 09:51:00 Setting '/proc/sys/net/ipv6/conf/ens4/use_tempaddr' to '0' 09:51:00 Setting '/proc/sys/net/ipv6/conf/ens4/accept_ra' to '0' 09:51:00 ens4: Started LLDP. 09:51:00 ens4: Setting address genmode for link 09:51:00 ens4: Setting address genmode done. 09:51:00 ens4: Removing address 10.164.0.2 09:51:00 ens4: Acquiring DHCPv4 lease 09:51:00 ens4: Discovering IPv6 routers 09:51:00 ens4: Removing address: 10.164.0.2/32 (valid for 15h 15s) 09:51:00 ens4: Removing route: dst: 10.164.0.2/32, src: n/a, gw: n/a, prefsrc: 10.164.0.2 09:51:00 ens4: DHCPv4 address 10.164.0.2/32 via 10.164.0.1 09:51:00 ens4: Setting MTU: 1460 09:51:00 Setting '/proc/sys/net/ipv6/conf/ens4/disable_ipv6' to '0' 09:51:00 ens4: IPv6 successfully enabled 09:51:00 ens4: Setting MTU done. 09:51:00 ens4: Updating address: 10.164.0.2/32 (valid for 1d) 09:51:00 ens4: Adding route: dst: 10.164.0.2/32, src: n/a, gw: n/a, prefsrc: 10.164.0.2 09:51:00 ens4: Configuring route: dst: 10.164.0.1/32, src: n/a, gw: n/a, prefsrc: 10.164.0.2 09:51:00 ens4: Configuring route: dst: n/a, src: n/a, gw: 10.164.0.1, prefsrc: 10.164.0.2 09:51:00 ens4: Updating route: dst: 10.164.0.1/32, src: n/a, gw: n/a, prefsrc: 10.164.0.2 09:51:00 ens4: Updating route: dst: n/a, src: n/a, gw: 10.164.0.1, prefsrc: 10.164.0.2 09:51:00 ens4: Configured 21:50:59 ens4: DHCP lease lost 21:50:59 ens4: Removing address 10.164.0.2 21:50:59 ens4: Setting MTU: 1420 21:50:59 Setting '/proc/sys/net/ipv6/conf/ens4/disable_ipv6' to '0' 21:50:59 ens4: IPv6 successfully enabled 21:50:59 ens4: DHCPv4 address 10.164.0.2/32 via 10.164.0.1 21:50:59 ens4: Removing route: dst: 10.164.0.1/32, src: n/a, gw: n/a, prefsrc: 10.164.0.2 21:50:59 ens4: Removing route: dst: n/a, src: n/a, gw: 10.164.0.1, prefsrc: 10.164.0.2 21:50:59 ens4: Removing address: 10.164.0.2/32 (valid for 12h 1s) 21:50:59 ens4: Removing route: dst: 10.164.0.2/32, src: n/a, gw: n/a, prefsrc: 10.164.0.2 21:50:59 ens4: Setting MTU done. 21:50:59 ens4: Adding address: 10.164.0.2/32 (valid for 1d) 21:50:59 ens4: Adding route: dst: 10.164.0.2/32, src: n/a, gw: n/a, prefsrc: 10.164.0.2 21:50:59 ens4: Configuring route: dst: 10.164.0.1/32, src: n/a, gw: n/a, prefsrc: 10.164.0.2 21:50:59 ens4: Configuring route: dst: n/a, src: n/a, gw: 10.164.0.1, prefsrc: 10.164.0.2 21:50:59 ens4: Updating route: dst: 10.164.0.1/32, src: n/a, gw: n/a, prefsrc: 10.164.0.2 21:50:59 ens4: Updating route: dst: n/a, src: n/a, gw: 10.164.0.1, prefsrc: 10.164.0.2 21:50:59 ens4: Configured On dhcp renew (09:51:00), mtu got properly changed to 1460. On next dhcp renew (21:50:59) it got changed back to previous value 1420. In all cases, /run/systemd/netif/leases/2 correctly contained MTU=1460. There have been some changes to mtu handling in the past, I assume this is a regression, potentially from https://github.com/systemd/systemd/issues/12552 or https://github.com/systemd/systemd/issues/6593. To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/systemd/+bug/1874661/+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
