From 840a3cbe89694fad75578856976f180e852e69aa Mon Sep 17 00:00:00 2001 From: Yuchung Cheng Date: Thu, 12 Jan 2017 22:11:38 -0800 Subject: tcp: remove forward retransmit feature Forward retransmit is an esoteric feature in RFC3517 (condition(3) in the NextSeg()). Basically if a packet is not considered lost by the current criteria (# of dupacks etc), but the congestion window has room for more packets, then retransmit this packet. However it actually conflicts with the rest of recovery design. For example, when reordering is detected we want to be conservative in retransmitting packets but forward-retransmit feature would break that to force more retransmission. Also the implementation is fairly complicated inside the retransmission logic inducing extra iterations in the write queue. With RACK losses are being detected timely and this heuristic is no longer necessary. There this patch removes the feature. Signed-off-by: Yuchung Cheng Signed-off-by: Neal Cardwell Acked-by: Eric Dumazet Signed-off-by: David S. Miller --- net/ipv4/tcp_input.c | 5 ----- 1 file changed, 5 deletions(-) (limited to 'net/ipv4/tcp_input.c') diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c index 9469ce384d3b..a041a92348ee 100644 --- a/net/ipv4/tcp_input.c +++ b/net/ipv4/tcp_input.c @@ -916,10 +916,6 @@ static void tcp_verify_retransmit_hint(struct tcp_sock *tp, struct sk_buff *skb) before(TCP_SKB_CB(skb)->seq, TCP_SKB_CB(tp->retransmit_skb_hint)->seq)) tp->retransmit_skb_hint = skb; - - if (!tp->lost_out || - after(TCP_SKB_CB(skb)->end_seq, tp->retransmit_high)) - tp->retransmit_high = TCP_SKB_CB(skb)->end_seq; } /* Sum the number of packets on the wire we have marked as lost. @@ -1983,7 +1979,6 @@ void tcp_enter_loss(struct sock *sk) TCP_SKB_CB(skb)->sacked &= ~TCPCB_SACKED_ACKED; TCP_SKB_CB(skb)->sacked |= TCPCB_LOST; tp->lost_out += tcp_skb_pcount(skb); - tp->retransmit_high = TCP_SKB_CB(skb)->end_seq; } } tcp_verify_left_out(tp); -- cgit v1.2.3