tcp_sack_extend(tp->duplicate_sack, seq, end_seq);
}
+static void tcp_rcv_spurious_retrans(struct sock *sk, const struct sk_buff *skb)
+{
+ /* When the ACK path fails or drops most ACKs, the sender would
+ * timeout and spuriously retransmit the same segment repeatedly.
+ * The receiver remembers and reflects via DSACKs. Leverage the
+ * DSACK state and change the txhash to re-route speculatively.
+ */
+ if (TCP_SKB_CB(skb)->seq == tcp_sk(sk)->duplicate_sack[0].start_seq)
+ sk_rethink_txhash(sk);
+}
+
static void tcp_send_dupack(struct sock *sk, const struct sk_buff *skb)
{
struct tcp_sock *tp = tcp_sk(sk);
if (tcp_is_sack(tp) && sock_net(sk)->ipv4.sysctl_tcp_dsack) {
u32 end_seq = TCP_SKB_CB(skb)->end_seq;
+ tcp_rcv_spurious_retrans(sk, skb);
if (after(TCP_SKB_CB(skb)->end_seq, tp->rcv_nxt))
end_seq = tp->rcv_nxt;
tcp_dsack_set(sk, TCP_SKB_CB(skb)->seq, end_seq);
}
if (!after(TCP_SKB_CB(skb)->end_seq, tp->rcv_nxt)) {
+ tcp_rcv_spurious_retrans(sk, skb);
/* A retransmit, 2nd most common case. Force an immediate ack. */
NET_INC_STATS(sock_net(sk), LINUX_MIB_DELAYEDACKLOST);
tcp_dsack_set(sk, TCP_SKB_CB(skb)->seq, TCP_SKB_CB(skb)->end_seq);