network daemon cannot change link-offloading settings

[Lukas Märdian]

netplan.io is showing new autopkgtest failures in Questing VMs, when testing against Linux kernel 6.17

Interestingly, the same failure happens with both the systemd-networkd and NetworkManager daemons. Also, the issue does NOT happen inside the armhf runners (containers) that are using an old 6.8 container host kernel.

Specifically:
942s ======================================================================
942s FAIL: test_link_offloading (__main__.TestNetworkManager.test_link_offloading)
942s ----------------------------------------------------------------------
942s Traceback (most recent call last):
942s File "/tmp/autopkgtest.urTG2T/build.w51/src/tests/integration/ethernets.py", line 331, in test_link_offloading
942s self.assertIn(b'tcp-segmentation-offload: off', out)
942s ~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
942s AssertionError: b'tcp-segmentation-offload: off' not found in b'Features for eth42:\nrx-checksumming: off\ntx-checksumming: off\n\ttx-checksum-ipv4: off [fixed]\n\ttx-checksum-ip-generic: off\n\ttx-checksum-ipv6: off [fixed]\n\ttx-checksum-fcoe-crc: off [fixed]\n\ttx-checksum-sctp: off\nscatter-gather: on\n\ttx-scatter-gather: on\n\ttx-scatter-gather-fraglist: on\ntcp-segmentation-offload: on\n\ttx-tcp-segmentation: off\n\ttx-tcp-ecn-segmentation: off [requested on]\n\ttx-tcp-mangleid-segmentation: off [requested on]\n\ttx-tcp6-segmentation: off\n\ttx-tcp-accecn-segmentation: on\ngeneric-segmentation-offload: off\ngeneric-receive-offload: off\nlarge-receive-offload: off [fixed]\nrx-vlan-offload: on\ntx-vlan-offload: on\nntuple-filters: off [fixed]\nreceive-hashing: off [fixed]\nhighdma: on\nrx-vlan-filter: off [fixed]\nvlan-challenged: off [fixed]\ntx-gso-robust: off [fixed]\ntx-fcoe-segmentation: off [fixed]\ntx-gre-segmentation: on\ntx-gre-csum-segmentation: on\ntx-ipxip4-segmentation: on\ntx-ipxip6-segmentation: on\ntx-udp_tnl-segmentation: on\ntx-udp_tnl-csum-segmentation: on\ntx-gso-partial: off [fixed]\ntx-tunnel-remcsum-segmentation: off [fixed]\ntx-sctp-segmentation: on\ntx-esp-segmentation: off [fixed]\ntx-udp-segmentation: off [requested on]\ntx-gso-list: on\ntx-nocache-copy: off\nloopback: off [fixed]\nrx-fcs: off [fixed]\nrx-all: off [fixed]\ntx-vlan-stag-hw-insert: on\nrx-vlan-stag-hw-parse: on\nrx-vlan-stag-filter: off [fixed]\nl2-fwd-offload: off [fixed]\nhw-tc-offload: off [fixed]\nesp-hw-offload: off [fixed]\nesp-tx-csum-hw-offload: off [fixed]\nrx-udp_tunnel-port-offload: off [fixed]\ntls-hw-tx-offload: off [fixed]\ntls-hw-rx-offload: off [fixed]\nrx-gro-hw: off [fixed]\ntls-hw-record: off [fixed]\nrx-gro-list: off\nmacsec-hw-offload: off [fixed]\nrx-udp-gro-forwarding: off\nhsr-tag-ins-offload: off [fixed]\nhsr-tag-rm-offload: off [fixed]\nhsr-fwd-offload: off [fixed]\nhsr-dup-offload: off [fixed]\n'
942s
942s ======================================================================
942s FAIL: test_link_offloading (__main__.TestNetworkd.test_link_offloading)
942s ----------------------------------------------------------------------
942s Traceback (most recent call last):
942s File "/tmp/autopkgtest.urTG2T/build.w51/src/tests/integration/ethernets.py", line 331, in test_link_offloading
942s self.assertIn(b'tcp-segmentation-offload: off', out)
942s ~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
942s AssertionError: b'tcp-segmentation-offload: off' not found in b'Features for eth42:\nrx-checksumming: off\ntx-checksumming: off\n\ttx-checksum-ipv4: off [fixed]\n\ttx-checksum-ip-generic: off\n\ttx-checksum-ipv6: off [fixed]\n\ttx-checksum-fcoe-crc: off [fixed]\n\ttx-checksum-sctp: off\nscatter-gather: on\n\ttx-scatter-gather: on\n\ttx-scatter-gather-fraglist: on\ntcp-segmentation-offload: on\n\ttx-tcp-segmentation: off\n\ttx-tcp-ecn-segmentation: off [requested on]\n\ttx-tcp-mangleid-segmentation: off [requested on]\n\ttx-tcp6-segmentation: off\n\ttx-tcp-accecn-segmentation: on\ngeneric-segmentation-offload: off\ngeneric-receive-offload: off\nlarge-receive-offload: off [fixed]\nrx-vlan-offload: on\ntx-vlan-offload: on\nntuple-filters: off [fixed]\nreceive-hashing: off [fixed]\nhighdma: on\nrx-vlan-filter: off [fixed]\nvlan-challenged: off [fixed]\ntx-gso-robust: off [fixed]\ntx-fcoe-segmentation: off [fixed]\ntx-gre-segmentation: on\ntx-gre-csum-segmentation: on\ntx-ipxip4-segmentation: on\ntx-ipxip6-segmentation: on\ntx-udp_tnl-segmentation: on\ntx-udp_tnl-csum-segmentation: on\ntx-gso-partial: off [fixed]\ntx-tunnel-remcsum-segmentation: off [fixed]\ntx-sctp-segmentation: on\ntx-esp-segmentation: off [fixed]\ntx-udp-segmentation: off [requested on]\ntx-gso-list: on\ntx-nocache-copy: off\nloopback: off [fixed]\nrx-fcs: off [fixed]\nrx-all: off [fixed]\ntx-vlan-stag-hw-insert: on\nrx-vlan-stag-hw-parse: on\nrx-vlan-stag-filter: off [fixed]\nl2-fwd-offload: off [fixed]\nhw-tc-offload: off [fixed]\nesp-hw-offload: off [fixed]\nesp-tx-csum-hw-offload: off [fixed]\nrx-udp_tunnel-port-offload: off [fixed]\ntls-hw-tx-offload: off [fixed]\ntls-hw-rx-offload: off [fixed]\nrx-gro-hw: off [fixed]\ntls-hw-record: off [fixed]\nrx-gro-list: off\nmacsec-hw-offload: off [fixed]\nrx-udp-gro-forwarding: off\nhsr-tag-ins-offload: off [fixed]\nhsr-tag-rm-offload: off [fixed]\nhsr-fwd-offload: off [fixed]\nhsr-dup-offload: off [fixed]\n'

[Lukas Märdian (slyon)]

Note: Original discussion about this issue from July 2025 is in bug #2115790

[Lukas Märdian (slyon)]

This is likely not a Netplan issue, nor a networking daemon, as we're seeing the same failure on systemd-networkd and NetworkManager. And test are working fine in the armhf container environment, using an older kernel.

[Lukas Märdian (slyon)]

This might also be related to udev, as it was in the past: https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=1071220

This could mean "netplan apply" needs to execute "udevadm trigger --action=add --subsystem-match=net" (instead of "--action=move", or maybe both... but it's unlikely). See: https://github.com/canonical/netplan/pull/479

[Nick Rosbrook (enr0n)]

Not sure where to look exactly on the udev side of things. Is there a manual reproducer you could give me to investigate? Or do you think it's just on the kernel side?