tcp: undo_retrans counter fixes
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 <ycheng@google.com> Acked-by: Ilpo Järvinen <ilpo.jarvinen@helsinki.fi> Signed-off-by: David S. Miller <davem@davemloft.net>
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@ -1222,7 +1222,7 @@ static int tcp_check_dsack(struct sock *sk, struct sk_buff *ack_skb,
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}
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}
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/* D-SACK for already forgotten data... Do dumb counting. */
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/* D-SACK for already forgotten data... Do dumb counting. */
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if (dup_sack &&
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if (dup_sack && tp->undo_marker && tp->undo_retrans &&
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!after(end_seq_0, prior_snd_una) &&
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!after(end_seq_0, prior_snd_una) &&
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after(end_seq_0, tp->undo_marker))
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after(end_seq_0, tp->undo_marker))
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tp->undo_retrans--;
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tp->undo_retrans--;
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@ -1299,7 +1299,8 @@ static u8 tcp_sacktag_one(struct sk_buff *skb, struct sock *sk,
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/* Account D-SACK for retransmitted packet. */
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/* Account D-SACK for retransmitted packet. */
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if (dup_sack && (sacked & TCPCB_RETRANS)) {
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if (dup_sack && (sacked & TCPCB_RETRANS)) {
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if (after(TCP_SKB_CB(skb)->end_seq, tp->undo_marker))
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if (tp->undo_marker && tp->undo_retrans &&
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after(TCP_SKB_CB(skb)->end_seq, tp->undo_marker))
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tp->undo_retrans--;
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tp->undo_retrans--;
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if (sacked & TCPCB_SACKED_ACKED)
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if (sacked & TCPCB_SACKED_ACKED)
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state->reord = min(fack_count, state->reord);
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state->reord = min(fack_count, state->reord);
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@ -2162,7 +2162,7 @@ int tcp_retransmit_skb(struct sock *sk, struct sk_buff *skb)
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if (!tp->retrans_stamp)
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if (!tp->retrans_stamp)
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tp->retrans_stamp = TCP_SKB_CB(skb)->when;
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tp->retrans_stamp = TCP_SKB_CB(skb)->when;
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tp->undo_retrans++;
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tp->undo_retrans += tcp_skb_pcount(skb);
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/* snd_nxt is stored to detect loss of retransmitted segment,
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/* snd_nxt is stored to detect loss of retransmitted segment,
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* see tcp_input.c tcp_sacktag_write_queue().
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* see tcp_input.c tcp_sacktag_write_queue().
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