net: Do delayed neigh confirmation.

When a dst_confirm() happens, mark the confirmation as pending in the
dst.  Then on the next packet out, when we have the neigh in-hand, do
the update.

This removes the dependency in dst_confirm() of dst's having an
attached neigh.

While we're here, remove the explicit 'dst' NULL check, all except 2
or 3 call sites ensure it's not NULL.  So just fix those cases up.

Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 13 insertions, 6 deletions

diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index 8416f8a68e65..ca0d0e7c9778 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -740,13 +740,13 @@ void tcp_update_metrics(struct sock *sk)
         if (sysctl_tcp_nometrics_save)
                 return;
 
-        dst_confirm(dst);
-
         if (dst && (dst->flags & DST_HOST)) {
                 const struct inet_connection_sock *icsk = inet_csk(sk);
                 int m;
                 unsigned long rtt;
 
+                dst_confirm(dst);
+
                 if (icsk->icsk_backoff || !tp->srtt) {
                         /* This session failed to estimate rtt. Why?
                          * Probably, no packets returned in time.
@@ -3869,9 +3869,11 @@ static int tcp_ack(struct sock *sk, const struct sk_buff *skb, int flag)
                         tcp_cong_avoid(sk, ack, prior_in_flight);
         }
 
-        if ((flag & FLAG_FORWARD_PROGRESS) || !(flag & FLAG_NOT_DUP))
-                dst_confirm(__sk_dst_get(sk));
-
+        if ((flag & FLAG_FORWARD_PROGRESS) || !(flag & FLAG_NOT_DUP)) {
+                struct dst_entry *dst = __sk_dst_get(sk);
+                if (dst)
+                        dst_confirm(dst);
+        }
         return 1;
 
 no_queue:
@@ -6140,9 +6142,14 @@ int tcp_rcv_state_process(struct sock *sk, struct sk_buff *skb,
 
                 case TCP_FIN_WAIT1:
                         if (tp->snd_una == tp->write_seq) {
+                                struct dst_entry *dst;
+
                                 tcp_set_state(sk, TCP_FIN_WAIT2);
                                 sk->sk_shutdown |= SEND_SHUTDOWN;
-                                dst_confirm(__sk_dst_get(sk));
+
+                                dst = __sk_dst_get(sk);
+                                if (dst)
+                                        dst_confirm(dst);
 
                                 if (!sock_flag(sk, SOCK_DEAD))
                                         /* Wake up lingering close() */