tcp: add tcp_can_forward_retransmit

Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@helsinki.fi>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 28 insertions, 18 deletions

diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index cfae61b40c44..957c4e3d2176 100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -1992,6 +1992,33 @@ int tcp_retransmit_skb(struct sock *sk, struct sk_buff *skb)
         return err;
 }
 
+static int tcp_can_forward_retransmit(struct sock *sk)
+{
+        const struct inet_connection_sock *icsk = inet_csk(sk);
+        struct tcp_sock *tp = tcp_sk(sk);
+
+        /* Forward retransmissions are possible only during Recovery. */
+        if (icsk->icsk_ca_state != TCP_CA_Recovery)
+                return 0;
+
+        /* No forward retransmissions in Reno are possible. */
+        if (tcp_is_reno(tp))
+                return 0;
+
+        /* Yeah, we have to make difficult choice between forward transmission
+         * and retransmission... Both ways have their merits...
+         *
+         * For now we do not retransmit anything, while we have some new
+         * segments to send. In the other cases, follow rule 3 for
+         * NextSeg() specified in RFC3517.
+         */
+
+        if (tcp_may_send_now(sk))
+                return 0;
+
+        return 1;
+}
+
 /* This gets called after a retransmit timeout, and the initially
  * retransmitted data is acknowledged.  It tries to continue
  * resending the rest of the retransmit queue, until either
@@ -2057,24 +2084,7 @@ void tcp_xmit_retransmit_queue(struct sock *sk)
         }
 
         /* OK, demanded retransmission is finished. */
-
-        /* Forward retransmissions are possible only during Recovery. */
-        if (icsk->icsk_ca_state != TCP_CA_Recovery)
-                return;
-
-        /* No forward retransmissions in Reno are possible. */
-        if (tcp_is_reno(tp))
-                return;
-
-        /* Yeah, we have to make difficult choice between forward transmission
-         * and retransmission... Both ways have their merits...
-         *
-         * For now we do not retransmit anything, while we have some new
-         * segments to send. In the other cases, follow rule 3 for
-         * NextSeg() specified in RFC3517.
-         */
-
-        if (tcp_may_send_now(sk))
+        if (!tcp_can_forward_retransmit(sk))
                 return;
 
         /* If nothing is SACKed, highest_sack in the loop won't be valid */