tcp: reorganize retransmit code loops

Both loops are quite similar, so they can be combined
with little effort. As a result, forward_skb_hint becomes
obsolete as well.

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

3 files changed, 33 insertions, 48 deletions

diff --git a/include/linux/tcp.h b/include/linux/tcp.h
index d7637c4b2840..767290628292 100644
--- a/include/linux/tcp.h
+++ b/include/linux/tcp.h
@@ -342,7 +342,6 @@ struct tcp_sock {
         struct sk_buff* lost_skb_hint;
         struct sk_buff *scoreboard_skb_hint;
         struct sk_buff *retransmit_skb_hint;
-        struct sk_buff *forward_skb_hint;
 
         struct sk_buff_head     out_of_order_queue; /* Out of order segments go here */
 
diff --git a/include/net/tcp.h b/include/net/tcp.h
index d0e90c50722b..220f54cf42ec 100644
--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -1042,7 +1042,6 @@ static inline void tcp_clear_all_retrans_hints(struct tcp_sock *tp)
         tp->lost_skb_hint = NULL;
         tp->scoreboard_skb_hint = NULL;
         tp->retransmit_skb_hint = NULL;
-        tp->forward_skb_hint = NULL;
 }
 
 /* MD5 Signature */
diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index 9f44be633ef6..b5b4ddcdda41 100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -2032,7 +2032,9 @@ void tcp_xmit_retransmit_queue(struct sock *sk)
         const struct inet_connection_sock *icsk = inet_csk(sk);
         struct tcp_sock *tp = tcp_sk(sk);
         struct sk_buff *skb;
+        struct sk_buff *hole = NULL;
         int mib_idx;
+        int fwd_rexmitting = 0;
 
         if (!tp->lost_out)
                 tp->retransmit_high = tp->snd_una;
@@ -2049,7 +2051,8 @@ void tcp_xmit_retransmit_queue(struct sock *sk)
                 if (skb == tcp_send_head(sk))
                         break;
                 /* we could do better than to assign each time */
-                tp->retransmit_skb_hint = skb;
+                if (hole == NULL)
+                        tp->retransmit_skb_hint = skb;
 
                 /* Assume this retransmit will generate
                  * only one packet for congestion window
@@ -2060,65 +2063,49 @@ void tcp_xmit_retransmit_queue(struct sock *sk)
                  */
                 if (tcp_packets_in_flight(tp) >= tp->snd_cwnd)
                         return;
-                if (!before(TCP_SKB_CB(skb)->seq, tp->retransmit_high))
-                        break;
-                if (sacked & (TCPCB_SACKED_ACKED|TCPCB_SACKED_RETRANS))
-                        continue;
-
-                if (!(sacked & TCPCB_LOST))
-                        continue;
-
-                if (tcp_retransmit_skb(sk, skb)) {
-                        tp->retransmit_skb_hint = NULL;
-                        return;
-                }
-                if (icsk->icsk_ca_state != TCP_CA_Loss)
-                        mib_idx = LINUX_MIB_TCPFASTRETRANS;
-                else
-                        mib_idx = LINUX_MIB_TCPSLOWSTARTRETRANS;
-                NET_INC_STATS_BH(sock_net(sk), mib_idx);
-
-                if (skb == tcp_write_queue_head(sk))
-                        inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS,
-                                                  inet_csk(sk)->icsk_rto,
-                                                  TCP_RTO_MAX);
-        }
-
-        /* OK, demanded retransmission is finished. */
-        if (!tcp_can_forward_retransmit(sk))
-                return;
 
-        if (tp->forward_skb_hint)
-                skb = tp->forward_skb_hint;
-        else
-                skb = tcp_write_queue_head(sk);
+                if (fwd_rexmitting) {
+begin_fwd:
+                        if (!before(TCP_SKB_CB(skb)->seq, tcp_highest_sack_seq(tp)))
+                                break;
+                        mib_idx = LINUX_MIB_TCPFORWARDRETRANS;
 
-        tcp_for_write_queue_from(skb, sk) {
-                if (skb == tcp_send_head(sk))
-                        break;
-                tp->forward_skb_hint = skb;
+                } else if (!before(TCP_SKB_CB(skb)->seq, tp->retransmit_high)) {
+                        if (!tcp_can_forward_retransmit(sk))
+                                break;
+                        /* Backtrack if necessary to non-L'ed skb */
+                        if (hole != NULL) {
+                                skb = hole;
+                                hole = NULL;
+                        }
+                        fwd_rexmitting = 1;
+                        goto begin_fwd;
 
-                if (!before(TCP_SKB_CB(skb)->seq, tcp_highest_sack_seq(tp)))
-                        break;
+                } else if (!(sacked & TCPCB_LOST)) {
+                        if (hole == NULL && !(sacked & TCPCB_SACKED_RETRANS))
+                                hole = skb;
+                        continue;
 
-                if (tcp_packets_in_flight(tp) >= tp->snd_cwnd)
-                        break;
+                } else {
+                        if (icsk->icsk_ca_state != TCP_CA_Loss)
+                                mib_idx = LINUX_MIB_TCPFASTRETRANS;
+                        else
+                                mib_idx = LINUX_MIB_TCPSLOWSTARTRETRANS;
+                }
 
-                if (TCP_SKB_CB(skb)->sacked & TCPCB_TAGBITS)
+                if (sacked & (TCPCB_SACKED_ACKED|TCPCB_SACKED_RETRANS))
                         continue;
 
-                /* Ok, retransmit it. */
                 if (tcp_retransmit_skb(sk, skb)) {
-                        tp->forward_skb_hint = NULL;
-                        break;
+                        tp->retransmit_skb_hint = NULL;
+                        return;
                 }
+                NET_INC_STATS_BH(sock_net(sk), mib_idx);
 
                 if (skb == tcp_write_queue_head(sk))
                         inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS,
                                                   inet_csk(sk)->icsk_rto,
                                                   TCP_RTO_MAX);
-
-                NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPFORWARDRETRANS);
         }
 }