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Differential D52546

vtnet: deprecate loader tunable fixup_needs_csum
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Authored by timo.voelker_fh-muenster.de on Sep 15 2025, 10:05 AM.

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Reviewers

tuexen
kevans
markj
bryanv
jhb
vmaffione

Commits

rGa16c7286b5c4: vtnet: deprecate loader tunable fixup_needs_csum
rG28f2d9b86de5: vtnet: deprecate loader tunable fixup_needs_csum
rG5da388d93917: vtnet: deprecate loader tunable fixup_needs_csum

Summary

Deprecate loader tunable fixup_needs_csum of the vtnet interface.

If this tunable is enabled and vtnet receives a packet with VIRTIO_NET_HDR_F_NEEDS_CSUM set, vtnet computes the TCP/UDP checksum and writes it in the checksum field. This was somewhat useful in the time when vtnet pretended that such a packet has a correct checksum and set the mbuf flag CSUM_DATA_VALID. However, since D51686, this is not the case anymore.

Furthermore, the guest can avoid receiving packets with an incorrect checksum and VIRTIO_NET_HDR_F_NEEDS_CSUM set by disabling the feature VIRTIO_NET_F_GUEST_CSUM. With vtnet, this is possible by disabling RXCSUM on the interface.

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rG FreeBSD src repository

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Event Timeline

timo.voelker_fh-muenster.de created this revision.Sep 15 2025, 10:05 AM

Herald added subscribers: ziaee, imp. · View Herald TranscriptSep 15 2025, 10:05 AM

timo.voelker_fh-muenster.de requested review of this revision.Sep 15 2025, 10:05 AM

tuexen added inline comments.Sep 15 2025, 11:55 AM

share/man/man4/vtnet.4
87	I guess you want something like This tunable is deprecated and will be removed in .Fx 16 .

Addressed comment from @tuexen

timo.voelker_fh-muenster.de marked an inline comment as done.Sep 16 2025, 12:32 PM

timo.voelker_fh-muenster.de added inline comments.

share/man/man4/vtnet.4
87	Yes, that's probably better. Thanks!

tuexen accepted this revision.Sep 16 2025, 9:37 PM

This revision is now accepted and ready to land.Sep 16 2025, 9:37 PM

Closed by commit rG5da388d93917: vtnet: deprecate loader tunable fixup_needs_csum (authored by timo.voelker_fh-muenster.de, committed by tuexen). · Explain WhySep 16 2025, 9:44 PM

This revision was automatically updated to reflect the committed changes.

tuexen added a commit: rG5da388d93917: vtnet: deprecate loader tunable fixup_needs_csum.

tuexen added a commit: rG28f2d9b86de5: vtnet: deprecate loader tunable fixup_needs_csum.Sep 22 2025, 7:24 PM

tuexen added a commit: rGa16c7286b5c4: vtnet: deprecate loader tunable fixup_needs_csum.Sep 22 2025, 7:31 PM

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Diff 162211

share/man/man4/vtnet.4

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