conn: coalesce via scatter-gather writes#51
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Pull request overview
This PR ports tailscale/tailscale#19054 to change Linux UDP GSO batching to coalesce datagrams using scatter-gather (sendmmsg(2) iovecs) instead of copying fragments into a single contiguous buffer, reducing per-packet copying.
Changes:
- Update
coalesceMessagesto append additional datagram payloads as additionalipv6.Message.Buffersentries (scatter-gather) while tracking total coalesced payload length. - Adjust message pooling cleanup to keep
Buffers[0]accessible after coalescing. - Update
Test_coalesceMessagesexpectations to validate per-iovec buffer lengths rather than a single concatenated buffer length.
Reviewed changes
Copilot reviewed 2 out of 2 changed files in this pull request and generated 3 comments.
| File | Description |
|---|---|
conn/bind_std.go |
Switch coalescing from copy-append into a single buffer to scatter-gather iovec appends for Linux WriteBatch. |
conn/bind_std_test.go |
Update coalescing tests to assert the shape/lengths of Message.Buffers after scatter-gather coalescing. |
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On Linux BindStd will now write a vector of coalesced buffers via sendmmsg(2) instead of copying fragments into a single buffer. Updates tailscale/corp#36989 Signed-off-by: Alex Valiushko <alexvaliushko@tailscale.com>
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Apr 7, 2026
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Port of tailscale/tailscale#19054
On Linux BindStd will now write a vector of
coalesced buffers via sendmmsg(2) instead of copying fragments into a single buffer.
Updates tailscale/corp#36989