Revert Backoff [v3]: Revert RTO on ICMP destination unreachable

[GitHub/mt8127/android_kernel_alcatel_ttab.git] / net / ipv4 / tcp_ipv4.c

diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c
index 6ca1bc8c3025fc652e425cb82bcab49baae05618..6755e29a6dd3d7c072050b0951d84ba6d5824643 100644 (file)
--- a/net/ipv4/tcp_ipv4.c
+++ b/net/ipv4/tcp_ipv4.c
@@ -332,12 +332,15 @@ void tcp_v4_err(struct sk_buff *icmp_skb, u32 info)
 {
        struct iphdr *iph = (struct iphdr *)icmp_skb->data;
        struct tcphdr *th = (struct tcphdr *)(icmp_skb->data + (iph->ihl << 2));
+       struct inet_connection_sock *icsk;
        struct tcp_sock *tp;
        struct inet_sock *inet;
        const int type = icmp_hdr(icmp_skb)->type;
        const int code = icmp_hdr(icmp_skb)->code;
        struct sock *sk;
+       struct sk_buff *skb;
        __u32 seq;
+       __u32 remaining;
        int err;
        struct net *net = dev_net(icmp_skb->dev);
 
@@ -367,6 +370,7 @@ void tcp_v4_err(struct sk_buff *icmp_skb, u32 info)
        if (sk->sk_state == TCP_CLOSE)
                goto out;
 
+       icsk = inet_csk(sk);
        tp = tcp_sk(sk);
        seq = ntohl(th->seq);
        if (sk->sk_state != TCP_LISTEN &&
@@ -393,6 +397,39 @@ void tcp_v4_err(struct sk_buff *icmp_skb, u32 info)
                }
 
                err = icmp_err_convert[code].errno;
+               /* check if icmp_skb allows revert of backoff
+                * (see draft-zimmermann-tcp-lcd) */
+               if (code != ICMP_NET_UNREACH && code != ICMP_HOST_UNREACH)
+                       break;
+               if (seq != tp->snd_una  || !icsk->icsk_retransmits ||
+                   !icsk->icsk_backoff)
+                       break;
+
+               icsk->icsk_backoff--;
+               inet_csk(sk)->icsk_rto = __tcp_set_rto(tp) <<
+                                        icsk->icsk_backoff;
+               tcp_bound_rto(sk);
+
+               skb = tcp_write_queue_head(sk);
+               BUG_ON(!skb);
+
+               remaining = icsk->icsk_rto - min(icsk->icsk_rto,
+                               tcp_time_stamp - TCP_SKB_CB(skb)->when);
+
+               if (remaining) {
+                       inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS,
+                                                 remaining, TCP_RTO_MAX);
+               } else if (sock_owned_by_user(sk)) {
+                       /* RTO revert clocked out retransmission,
+                        * but socket is locked. Will defer. */
+                       inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS,
+                                                 HZ/20, TCP_RTO_MAX);
+               } else {
+                       /* RTO revert clocked out retransmission.
+                        * Will retransmit now */
+                       tcp_retransmit_timer(sk);
+               }
+
                break;
        case ICMP_TIME_EXCEEDED:
                err = EHOSTUNREACH;