From mboxrd@z Thu Jan 1 00:00:00 1970 From: Yuchung Cheng Subject: [PATCH] tcp: undo_retrans counter fixes Date: Mon, 7 Feb 2011 14:57:04 -0800 Message-ID: <1297119424-19956-1-git-send-email-ycheng@google.com> Cc: ilpo.jarvinen@helsinki.fi, Yuchung Cheng To: netdev@vger.kernel.org Return-path: Received: from smtp-out.google.com ([216.239.44.51]:19973 "EHLO smtp-out.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755093Ab1BGW5j (ORCPT ); Mon, 7 Feb 2011 17:57:39 -0500 Sender: netdev-owner@vger.kernel.org List-ID: Fix a bug that undo_retrans is incorrectly decremented when undo_marker is not set or undo_retrans is already 0. This happens when sender receives more DSACK ACKs than packets retransmitted during the current undo phase. This may also happen when sender receives DSACK after the undo operation is completed or cancelled. Fix another bug that undo_retrans is incorrectly incremented when sender retransmits an skb and tcp_skb_pcount(skb) > 1 (TSO). This case is rare but not impossible. Signed-off-by: Yuchung Cheng --- net/ipv4/tcp_input.c | 5 +++-- net/ipv4/tcp_output.c | 2 +- 2 files changed, 4 insertions(+), 3 deletions(-) diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c index 2f692ce..08ea735 100644 --- a/net/ipv4/tcp_input.c +++ b/net/ipv4/tcp_input.c @@ -1222,7 +1222,7 @@ static int tcp_check_dsack(struct sock *sk, struct sk_buff *ack_skb, } /* D-SACK for already forgotten data... Do dumb counting. */ - if (dup_sack && + if (dup_sack && tp->undo_marker && tp->undo_retrans && !after(end_seq_0, prior_snd_una) && after(end_seq_0, tp->undo_marker)) tp->undo_retrans--; @@ -1299,7 +1299,8 @@ static u8 tcp_sacktag_one(struct sk_buff *skb, struct sock *sk, /* Account D-SACK for retransmitted packet. */ if (dup_sack && (sacked & TCPCB_RETRANS)) { - if (after(TCP_SKB_CB(skb)->end_seq, tp->undo_marker)) + if (tp->undo_marker && tp->undo_retrans && + after(TCP_SKB_CB(skb)->end_seq, tp->undo_marker)) tp->undo_retrans--; if (sacked & TCPCB_SACKED_ACKED) state->reord = min(fack_count, state->reord); diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c index 406f320..dfa5beb 100644 --- a/net/ipv4/tcp_output.c +++ b/net/ipv4/tcp_output.c @@ -2162,7 +2162,7 @@ int tcp_retransmit_skb(struct sock *sk, struct sk_buff *skb) if (!tp->retrans_stamp) tp->retrans_stamp = TCP_SKB_CB(skb)->when; - tp->undo_retrans++; + tp->undo_retrans += tcp_skb_pcount(skb); /* snd_nxt is stored to detect loss of retransmitted segment, * see tcp_input.c tcp_sacktag_write_queue(). -- 1.7.3.1