tcp: refactor tcp_retransmit_timer()

It appears linux-4.14 stable needs a backport of commit
88f8598d0a30 ("tcp: exit if nothing to retransmit on RTO timeout")

Since tcp_rtx_queue_empty() is not in pre 4.15 kernels,
let's refactor tcp_retransmit_timer() to only use tcp_rtx_queue_head()

I will provide to stable teams the squashed patches.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Willem de Bruijn <willemb@google.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Acked-by: Soheil Hassas Yeganeh <soheil@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/ipv4/tcp_timer.c b/net/ipv4/tcp_timer.c
index dd5a6317a8018a45ad609f832ced6df2937ad453..1097b438befe14ae3f375f3dbcc1f2d375a93879 100644 (file)
--- a/net/ipv4/tcp_timer.c
+++ b/net/ipv4/tcp_timer.c
@@ -434,6 +434,7 @@ void tcp_retransmit_timer(struct sock *sk)
        struct net *net = sock_net(sk);
        struct inet_connection_sock *icsk = inet_csk(sk);
        struct request_sock *req;
+       struct sk_buff *skb;
 
        req = rcu_dereference_protected(tp->fastopen_rsk,
                                        lockdep_sock_is_held(sk));
@@ -446,7 +447,12 @@ void tcp_retransmit_timer(struct sock *sk)
                 */
                return;
        }
-       if (!tp->packets_out || WARN_ON_ONCE(tcp_rtx_queue_empty(sk)))
+
+       if (!tp->packets_out)
+               return;
+
+       skb = tcp_rtx_queue_head(sk);
+       if (WARN_ON_ONCE(!skb))
                return;
 
        tp->tlp_high_seq = 0;
@@ -480,7 +486,7 @@ void tcp_retransmit_timer(struct sock *sk)
                        goto out;
                }
                tcp_enter_loss(sk);
-               tcp_retransmit_skb(sk, tcp_rtx_queue_head(sk), 1);
+               tcp_retransmit_skb(sk, skb, 1);
                __sk_dst_reset(sk);
                goto out_reset_timer;
        }