From c24f691b56107feeba076616982093ee2d3c8fb5 Mon Sep 17 00:00:00 2001 From: Yuchung Cheng Date: Mon, 7 Feb 2011 12:57:04 +0000 Subject: [PATCH] tcp: undo_retrans counter fixes MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit 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 Acked-by: Ilpo Järvinen Signed-off-by: David S. Miller --- 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 eb7f82ebf4a3..65f6c0406245 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 406f320336e6..dfa5beb0c1c8 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(). -- 2.20.1