[TCP]: Create tcp_sacktag_one().

Worker function that implements the main logic of
the inner-most loop of tcp_sacktag_write_queue().

Idea was originally presented by David S. Miller.

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

diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index 5e01ac2..a62e0f9 100644 (file)
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -1240,6 +1240,99 @@ static int tcp_match_skb_to_sack(struct sock *sk, struct sk_buff *skb,
        return in_sack;
 }
 
+static int tcp_sacktag_one(struct sk_buff *skb, struct tcp_sock *tp,
+                          int *reord, int dup_sack, int fack_count)
+{
+       u8 sacked = TCP_SKB_CB(skb)->sacked;
+       int flag = 0;
+
+       /* Account D-SACK for retransmitted packet. */
+       if (dup_sack && (sacked & TCPCB_RETRANS)) {
+               if (after(TCP_SKB_CB(skb)->end_seq, tp->undo_marker))
+                       tp->undo_retrans--;
+               if (!after(TCP_SKB_CB(skb)->end_seq, tp->snd_una) &&
+                   (sacked & TCPCB_SACKED_ACKED))
+                       *reord = min(fack_count, *reord);
+       }
+
+       /* Nothing to do; acked frame is about to be dropped (was ACKed). */
+       if (!after(TCP_SKB_CB(skb)->end_seq, tp->snd_una))
+               return flag;
+
+       if (!(sacked & TCPCB_SACKED_ACKED)) {
+               if (sacked & TCPCB_SACKED_RETRANS) {
+                       /* If the segment is not tagged as lost,
+                        * we do not clear RETRANS, believing
+                        * that retransmission is still in flight.
+                        */
+                       if (sacked & TCPCB_LOST) {
+                               TCP_SKB_CB(skb)->sacked &=
+                                       ~(TCPCB_LOST|TCPCB_SACKED_RETRANS);
+                               tp->lost_out -= tcp_skb_pcount(skb);
+                               tp->retrans_out -= tcp_skb_pcount(skb);
+
+                               /* clear lost hint */
+                               tp->retransmit_skb_hint = NULL;
+                       }
+               } else {
+                       if (!(sacked & TCPCB_RETRANS)) {
+                               /* New sack for not retransmitted frame,
+                                * which was in hole. It is reordering.
+                                */
+                               if (before(TCP_SKB_CB(skb)->seq,
+                                          tcp_highest_sack_seq(tp)))
+                                       *reord = min(fack_count, *reord);
+
+                               /* SACK enhanced F-RTO (RFC4138; Appendix B) */
+                               if (!after(TCP_SKB_CB(skb)->end_seq, tp->frto_highmark))
+                                       flag |= FLAG_ONLY_ORIG_SACKED;
+                       }
+
+                       if (sacked & TCPCB_LOST) {
+                               TCP_SKB_CB(skb)->sacked &= ~TCPCB_LOST;
+                               tp->lost_out -= tcp_skb_pcount(skb);
+
+                               /* clear lost hint */
+                               tp->retransmit_skb_hint = NULL;
+                       }
+               }
+
+               TCP_SKB_CB(skb)->sacked |= TCPCB_SACKED_ACKED;
+               flag |= FLAG_DATA_SACKED;
+               tp->sacked_out += tcp_skb_pcount(skb);
+
+               fack_count += tcp_skb_pcount(skb);
+
+               /* Lost marker hint past SACKed? Tweak RFC3517 cnt */
+               if (!tcp_is_fack(tp) && (tp->lost_skb_hint != NULL) &&
+                   before(TCP_SKB_CB(skb)->seq,
+                          TCP_SKB_CB(tp->lost_skb_hint)->seq))
+                       tp->lost_cnt_hint += tcp_skb_pcount(skb);
+
+               if (fack_count > tp->fackets_out)
+                       tp->fackets_out = fack_count;
+
+               if (after(TCP_SKB_CB(skb)->seq, tcp_highest_sack_seq(tp)))
+                       tp->highest_sack = skb;
+
+       } else {
+               if (dup_sack && (sacked & TCPCB_RETRANS))
+                       *reord = min(fack_count, *reord);
+       }
+
+       /* D-SACK. We can detect redundant retransmission in S|R and plain R
+        * frames and clear it. undo_retrans is decreased above, L|R frames
+        * are accounted above as well.
+        */
+       if (dup_sack && (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_RETRANS)) {
+               TCP_SKB_CB(skb)->sacked &= ~TCPCB_SACKED_RETRANS;
+               tp->retrans_out -= tcp_skb_pcount(skb);
+               tp->retransmit_skb_hint = NULL;
+       }
+
+       return flag;
+}
+
 static int
 tcp_sacktag_write_queue(struct sock *sk, struct sk_buff *ack_skb, u32 prior_snd_una)
 {
@@ -1375,7 +1468,6 @@ tcp_sacktag_write_queue(struct sock *sk, struct sk_buff *ack_skb, u32 prior_snd_
 
                tcp_for_write_queue_from(skb, sk) {
                        int in_sack = 0;
-                       u8 sacked;
 
                        if (skb == tcp_send_head(sk))
                                break;
@@ -1413,102 +1505,10 @@ tcp_sacktag_write_queue(struct sock *sk, struct sk_buff *ack_skb, u32 prior_snd_
                        if (unlikely(in_sack < 0))
                                break;
 
-                       if (!in_sack) {
-                               fack_count += tcp_skb_pcount(skb);
-                               continue;
-                       }
-
-                       sacked = TCP_SKB_CB(skb)->sacked;
-
-                       /* Account D-SACK for retransmitted packet. */
-                       if (dup_sack && (sacked & TCPCB_RETRANS)) {
-                               if (after(TCP_SKB_CB(skb)->end_seq, tp->undo_marker))
-                                       tp->undo_retrans--;
-                               if (!after(TCP_SKB_CB(skb)->end_seq, tp->snd_una) &&
-                                   (sacked & TCPCB_SACKED_ACKED))
-                                       reord = min(fack_count, reord);
-                       }
-
-
-                       /* Nothing to do; acked frame is about to be dropped (was ACKed). */
-                       if (!after(TCP_SKB_CB(skb)->end_seq, tp->snd_una)) {
-                               fack_count += tcp_skb_pcount(skb);
-                               continue;
-                       }
-
-                       if (!(sacked&TCPCB_SACKED_ACKED)) {
-                               if (sacked & TCPCB_SACKED_RETRANS) {
-                                       /* If the segment is not tagged as lost,
-                                        * we do not clear RETRANS, believing
-                                        * that retransmission is still in flight.
-                                        */
-                                       if (sacked & TCPCB_LOST) {
-                                               TCP_SKB_CB(skb)->sacked &= ~(TCPCB_LOST|TCPCB_SACKED_RETRANS);
-                                               tp->lost_out -= tcp_skb_pcount(skb);
-                                               tp->retrans_out -= tcp_skb_pcount(skb);
-
-                                               /* clear lost hint */
-                                               tp->retransmit_skb_hint = NULL;
-                                       }
-                               } else {
-                                       if (!(sacked & TCPCB_RETRANS)) {
-                                               /* New sack for not retransmitted frame,
-                                                * which was in hole. It is reordering.
-                                                */
-                                               if (before(TCP_SKB_CB(skb)->seq,
-                                                          tcp_highest_sack_seq(tp)))
-                                                       reord = min(fack_count, reord);
-
-                                               /* SACK enhanced F-RTO (RFC4138; Appendix B) */
-                                               if (!after(TCP_SKB_CB(skb)->end_seq, tp->frto_highmark))
-                                                       flag |= FLAG_ONLY_ORIG_SACKED;
-                                       }
-
-                                       if (sacked & TCPCB_LOST) {
-                                               TCP_SKB_CB(skb)->sacked &= ~TCPCB_LOST;
-                                               tp->lost_out -= tcp_skb_pcount(skb);
-
-                                               /* clear lost hint */
-                                               tp->retransmit_skb_hint = NULL;
-                                       }
-                               }
-
-                               TCP_SKB_CB(skb)->sacked |= TCPCB_SACKED_ACKED;
-                               flag |= FLAG_DATA_SACKED;
-                               tp->sacked_out += tcp_skb_pcount(skb);
-
-                               fack_count += tcp_skb_pcount(skb);
-
-                               /* Lost marker hint past SACKed? Tweak RFC3517 cnt */
-                               if (!tcp_is_fack(tp) && (tp->lost_skb_hint != NULL) &&
-                                   before(TCP_SKB_CB(skb)->seq,
-                                          TCP_SKB_CB(tp->lost_skb_hint)->seq))
-                                       tp->lost_cnt_hint += tcp_skb_pcount(skb);
-
-                               if (fack_count > tp->fackets_out)
-                                       tp->fackets_out = fack_count;
+                       if (in_sack)
+                               flag |= tcp_sacktag_one(skb, tp, &reord, dup_sack, fack_count);
 
-                               if (after(TCP_SKB_CB(skb)->seq, tcp_highest_sack_seq(tp)))
-                                       tp->highest_sack = skb;
-
-                       } else {
-                               if (dup_sack && (sacked&TCPCB_RETRANS))
-                                       reord = min(fack_count, reord);
-
-                               fack_count += tcp_skb_pcount(skb);
-                       }
-
-                       /* D-SACK. We can detect redundant retransmission
-                        * in S|R and plain R frames and clear it.
-                        * undo_retrans is decreased above, L|R frames
-                        * are accounted above as well.
-                        */
-                       if (dup_sack &&
-                           (TCP_SKB_CB(skb)->sacked&TCPCB_SACKED_RETRANS)) {
-                               TCP_SKB_CB(skb)->sacked &= ~TCPCB_SACKED_RETRANS;
-                               tp->retrans_out -= tcp_skb_pcount(skb);
-                               tp->retransmit_skb_hint = NULL;
-                       }
+                       fack_count += tcp_skb_pcount(skb);
                }
 
                /* SACK enhanced FRTO (RFC4138, Appendix B): Clearing correct