tcp: fix bogus RTT on special retransmission
RTT may be bogus with tall loss probe (TLP) when a packet is retransmitted and latter (s)acked without TCPCB_SACKED_RETRANS flag. For example, TLP calls __tcp_retransmit_skb() instead of tcp_retransmit_skb(). The skb timestamps are updated but the sacked flag is not marked with TCPCB_SACKED_RETRANS. As a result we'll get bogus RTT in tcp_clean_rtx_queue() or in tcp_sacktag_one() on spurious retransmission. The fix is to apply the sticky flag TCP_EVER_RETRANS to enforce Karn's check on RTT sampling. However this will disable F-RTO if timeout occurs after TLP, by resetting undo_marker in tcp_enter_loss(). We relax this check to only if any pending retransmists are still in-flight. Signed-off-by: Yuchung Cheng <ycheng@google.com> Acked-by: Eric Dumazet <edumazet@google.com> Acked-by: Neal Cardwell <ncardwell@google.com> Acked-by: Nandita Dukkipati <nanditad@google.com> Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
parent
de39d7a4f3
commit
c84a57113f
|
@ -1945,8 +1945,9 @@ void tcp_enter_loss(struct sock *sk, int how)
|
|||
if (skb == tcp_send_head(sk))
|
||||
break;
|
||||
|
||||
if (TCP_SKB_CB(skb)->sacked & TCPCB_RETRANS)
|
||||
if (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_RETRANS)
|
||||
tp->undo_marker = 0;
|
||||
|
||||
TCP_SKB_CB(skb)->sacked &= (~TCPCB_TAGBITS)|TCPCB_SACKED_ACKED;
|
||||
if (!(TCP_SKB_CB(skb)->sacked&TCPCB_SACKED_ACKED) || how) {
|
||||
TCP_SKB_CB(skb)->sacked &= ~TCPCB_SACKED_ACKED;
|
||||
|
|
|
@ -2337,6 +2337,7 @@ int __tcp_retransmit_skb(struct sock *sk, struct sk_buff *skb)
|
|||
struct tcp_sock *tp = tcp_sk(sk);
|
||||
struct inet_connection_sock *icsk = inet_csk(sk);
|
||||
unsigned int cur_mss;
|
||||
int err;
|
||||
|
||||
/* Inconslusive MTU probe */
|
||||
if (icsk->icsk_mtup.probe_size) {
|
||||
|
@ -2400,11 +2401,15 @@ int __tcp_retransmit_skb(struct sock *sk, struct sk_buff *skb)
|
|||
skb_headroom(skb) >= 0xFFFF)) {
|
||||
struct sk_buff *nskb = __pskb_copy(skb, MAX_TCP_HEADER,
|
||||
GFP_ATOMIC);
|
||||
return nskb ? tcp_transmit_skb(sk, nskb, 0, GFP_ATOMIC) :
|
||||
-ENOBUFS;
|
||||
err = nskb ? tcp_transmit_skb(sk, nskb, 0, GFP_ATOMIC) :
|
||||
-ENOBUFS;
|
||||
} else {
|
||||
return tcp_transmit_skb(sk, skb, 1, GFP_ATOMIC);
|
||||
err = tcp_transmit_skb(sk, skb, 1, GFP_ATOMIC);
|
||||
}
|
||||
|
||||
if (likely(!err))
|
||||
TCP_SKB_CB(skb)->sacked |= TCPCB_EVER_RETRANS;
|
||||
return err;
|
||||
}
|
||||
|
||||
int tcp_retransmit_skb(struct sock *sk, struct sk_buff *skb)
|
||||
|
|
Loading…
Reference in a new issue