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| author | Jeremy Kerr <jk@codeconstruct.com.au> | 2026-03-24 15:19:56 +0800 |
|---|---|---|
| committer | Jakub Kicinski <kuba@kernel.org> | 2026-03-26 18:47:29 -0700 |
| commit | e1877cf6231152ff4686bd9900a6a88ffdd90f84 (patch) | |
| tree | e59160a7e8e5357756e8e9c02fa89bc75471078f /net/mctp/test | |
| parent | 2b8e147c006ef2b40863be1911e29dd5731c205d (diff) | |
| download | lwn-e1877cf6231152ff4686bd9900a6a88ffdd90f84.tar.gz lwn-e1877cf6231152ff4686bd9900a6a88ffdd90f84.zip | |
net: mctp: avoid copy in fragmentation loop for near-MTU messages
Currently, we incorrectly send messages that are within 4 bytes (a
struct mctp_hdr) smaller than the MTU through mctp_do_fragment_route().
This has no effect on the actual fragmentation, as we will still send as
one packet, but unnecessarily copies the original skb into a new
single-fragment skb.
Instead of having the MTU comparisons in both mctp_local_output() and
mctp_do_fragment_route(), feed all local messages through the latter,
and add the single-packet optimisation there.
This means we can coalesce the routing path of mctp_local_output, so our
out_release path is now solely for errors, so rename the label
accordingly.
Include a check in the route tests for the single-packet case too.
Reported-by: yuanzhaoming <yuanzm2@lenovo.com>
Closes: https://github.com/openbmc/linux/commit/269936db5eb3962fe290b1dc4dbf1859cd5a04dd#r175836230
Signed-off-by: Jeremy Kerr <jk@codeconstruct.com.au>
Reviewed-by: Simon Horman <horms@kernel.org>
Link: https://patch.msgid.link/20260324-dev-mtu-copy-v1-1-7af6bd7027d3@codeconstruct.com.au
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Diffstat (limited to 'net/mctp/test')
| -rw-r--r-- | net/mctp/test/route-test.c | 4 |
1 files changed, 4 insertions, 0 deletions
diff --git a/net/mctp/test/route-test.c b/net/mctp/test/route-test.c index 75ea96c10e49..61c989c43ec0 100644 --- a/net/mctp/test/route-test.c +++ b/net/mctp/test/route-test.c @@ -63,6 +63,10 @@ static void mctp_test_fragment(struct kunit *test) if (!skb2) break; + /* avoid copying single-skb messages */ + if (first && last) + KUNIT_EXPECT_PTR_EQ(test, skb, skb2); + hdr2 = mctp_hdr(skb2); tag_mask = MCTP_HDR_TAG_MASK | MCTP_HDR_FLAG_TO; |