From 83ca28befc43e93849e79c564cda10e39d983e75 Mon Sep 17 00:00:00 2001 From: Herbert Xu Date: Thu, 22 Sep 2005 23:32:56 -0700 Subject: [PATCH] [TCP]: Adjust Reno SACK estimate in tcp_fragment Since the introduction of TSO pcount a year ago, it has been possible for tcp_fragment() to cause packets_out to decrease. Prior to that, tcp_retrans_try_collapse() was the only way for that to happen on the retransmission path. When this happens with Reno, it is possible for sasked_out to become invalid because it is only an estimate and not tied to any particular packet on the retransmission queue. Therefore we need to adjust sacked_out as well as left_out in the Reno case. The following patch does exactly that. This bug is pretty difficult to trigger in practice though since you need a SACKless peer with a retransmission that occurs just as the cached MTU value expires. Signed-off-by: Herbert Xu Signed-off-by: David S. Miller --- net/ipv4/tcp_output.c | 9 +++++++++ 1 file changed, 9 insertions(+) diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c index 5dd6dd7d09..d6e3d269e9 100644 --- a/net/ipv4/tcp_output.c +++ b/net/ipv4/tcp_output.c @@ -509,7 +509,16 @@ int tcp_fragment(struct sock *sk, struct sk_buff *skb, u32 len, unsigned int mss tp->lost_out -= diff; tp->left_out -= diff; } + if (diff > 0) { + /* Adjust Reno SACK estimate. */ + if (!tp->rx_opt.sack_ok) { + tp->sacked_out -= diff; + if ((int)tp->sacked_out < 0) + tp->sacked_out = 0; + tcp_sync_left_out(tp); + } + tp->fackets_out -= diff; if ((int)tp->fackets_out < 0) tp->fackets_out = 0; -- 2.39.5