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authorIlpo Järvinen <ilpo.jarvinen@helsinki.fi>2008-04-08 01:33:07 -0400
committerDavid S. Miller <davem@davemloft.net>2008-04-08 01:33:07 -0400
commit882bebaaca4bb1484078d44ef011f918c0e1e14e (patch)
treed6542dd9fc3d941ecc5f418b66ea09e91f47b71f /net/ipv4/tcp_output.c
parentc137f3dda04b0aee1bc6889cdc69185f53df8a82 (diff)
[TCP]: tcp_simple_retransmit can cause S+L
This fixes Bugzilla #10384 tcp_simple_retransmit does L increment without any checking whatsoever for overflowing S+L when Reno is in use. The simplest scenario I can currently think of is rather complex in practice (there might be some more straightforward cases though). Ie., if mss is reduced during mtu probing, it may end up marking everything lost and if some duplicate ACKs arrived prior to that sacked_out will be non-zero as well, leading to S+L > packets_out, tcp_clean_rtx_queue on the next cumulative ACK or tcp_fastretrans_alert on the next duplicate ACK will fix the S counter. More straightforward (but questionable) solution would be to just call tcp_reset_reno_sack() in tcp_simple_retransmit but it would negatively impact the probe's retransmission, ie., the retransmissions would not occur if some duplicate ACKs had arrived. So I had to add reno sacked_out reseting to CA_Loss state when the first cumulative ACK arrives (this stale sacked_out might actually be the explanation for the reports of left_out overflows in kernel prior to 2.6.23 and S+L overflow reports of 2.6.24). However, this alone won't be enough to fix kernel before 2.6.24 because it is building on top of the commit 1b6d427bb7e ([TCP]: Reduce sacked_out with reno when purging write_queue) to keep the sacked_out from overflowing. Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@helsinki.fi> Reported-by: Alessandro Suardi <alessandro.suardi@gmail.com> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net/ipv4/tcp_output.c')
-rw-r--r--net/ipv4/tcp_output.c3
1 files changed, 3 insertions, 0 deletions
diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index 72b9350006fe..d29ef79c00ca 100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -1808,6 +1808,9 @@ void tcp_simple_retransmit(struct sock *sk)
1808 if (!lost) 1808 if (!lost)
1809 return; 1809 return;
1810 1810
1811 if (tcp_is_reno(tp))
1812 tcp_limit_reno_sacked(tp);
1813
1811 tcp_verify_left_out(tp); 1814 tcp_verify_left_out(tp);
1812 1815
1813 /* Don't muck with the congestion window here. 1816 /* Don't muck with the congestion window here.