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author | Neal Cardwell <ncardwell@google.com> | 2012-01-28 17:29:46 (GMT) |
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committer | David S. Miller <davem@davemloft.net> | 2012-01-30 17:42:58 (GMT) |
commit | 5b35e1e6e9ca651e6b291c96d1106043c9af314a (patch) | |
tree | d18caadee5e93dc45d0c5fa2c530537cfa14586c /net/unix | |
parent | 4acb41903b2f99f3dffd4c3df9acc84ca5942cb2 (diff) | |
download | linux-5b35e1e6e9ca651e6b291c96d1106043c9af314a.tar.xz |
tcp: fix tcp_trim_head() to adjust segment count with skb MSS
This commit fixes tcp_trim_head() to recalculate the number of
segments in the skb with the skb's existing MSS, so trimming the head
causes the skb segment count to be monotonically non-increasing - it
should stay the same or go down, but not increase.
Previously tcp_trim_head() used the current MSS of the connection. But
if there was a decrease in MSS between original transmission and ACK
(e.g. due to PMTUD), this could cause tcp_trim_head() to
counter-intuitively increase the segment count when trimming bytes off
the head of an skb. This violated assumptions in tcp_tso_acked() that
tcp_trim_head() only decreases the packet count, so that packets_acked
in tcp_tso_acked() could underflow, leading tcp_clean_rtx_queue() to
pass u32 pkts_acked values as large as 0xffffffff to
ca_ops->pkts_acked().
As an aside, if tcp_trim_head() had really wanted the skb to reflect
the current MSS, it should have called tcp_set_skb_tso_segs()
unconditionally, since a decrease in MSS would mean that a
single-packet skb should now be sliced into multiple segments.
Signed-off-by: Neal Cardwell <ncardwell@google.com>
Acked-by: Nandita Dukkipati <nanditad@google.com>
Acked-by: Ilpo Järvinen <ilpo.jarvinen@helsinki.fi>
Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net/unix')
0 files changed, 0 insertions, 0 deletions