1 files changed, 60 insertions, 45 deletions

diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index c26076fb890e..c6109895bb5e 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -936,28 +936,58 @@ tcp_sacktag_write_queue(struct sock *sk, struct sk_buff *ack_skb, u32 prior_snd_
         struct tcp_sock *tp = tcp_sk(sk);
         unsigned char *ptr = ack_skb->h.raw + TCP_SKB_CB(ack_skb)->sacked;
         struct tcp_sack_block_wire *sp = (struct tcp_sack_block_wire *)(ptr+2);
+        struct sk_buff *cached_skb;
         int num_sacks = (ptr[1] - TCPOLEN_SACK_BASE)>>3;
         int reord = tp->packets_out;
         int prior_fackets;
         u32 lost_retrans = 0;
         int flag = 0;
         int dup_sack = 0;
+        int cached_fack_count;
         int i;
+        int first_sack_index;
 
         if (!tp->sacked_out)
                 tp->fackets_out = 0;
         prior_fackets = tp->fackets_out;
 
+        /* Check for D-SACK. */
+        if (before(ntohl(sp[0].start_seq), TCP_SKB_CB(ack_skb)->ack_seq)) {
+                dup_sack = 1;
+                tp->rx_opt.sack_ok |= 4;
+                NET_INC_STATS_BH(LINUX_MIB_TCPDSACKRECV);
+        } else if (num_sacks > 1 &&
+                        !after(ntohl(sp[0].end_seq), ntohl(sp[1].end_seq)) &&
+                        !before(ntohl(sp[0].start_seq), ntohl(sp[1].start_seq))) {
+                dup_sack = 1;
+                tp->rx_opt.sack_ok |= 4;
+                NET_INC_STATS_BH(LINUX_MIB_TCPDSACKOFORECV);
+        }
+
+        /* D-SACK for already forgotten data...
+         * Do dumb counting. */
+        if (dup_sack &&
+                        !after(ntohl(sp[0].end_seq), prior_snd_una) &&
+                        after(ntohl(sp[0].end_seq), tp->undo_marker))
+                tp->undo_retrans--;
+
+        /* Eliminate too old ACKs, but take into
+         * account more or less fresh ones, they can
+         * contain valid SACK info.
+         */
+        if (before(TCP_SKB_CB(ack_skb)->ack_seq, prior_snd_una - tp->max_window))
+                return 0;
+
         /* SACK fastpath:
          * if the only SACK change is the increase of the end_seq of
          * the first block then only apply that SACK block
          * and use retrans queue hinting otherwise slowpath */
         flag = 1;
-        for (i = 0; i< num_sacks; i++) {
-                __u32 start_seq = ntohl(sp[i].start_seq);
-                __u32 end_seq =  ntohl(sp[i].end_seq);
+        for (i = 0; i < num_sacks; i++) {
+                __be32 start_seq = sp[i].start_seq;
+                __be32 end_seq = sp[i].end_seq;
 
-                if (i == 0){
+                if (i == 0) {
                         if (tp->recv_sack_cache[i].start_seq != start_seq)
                                 flag = 0;
                 } else {
@@ -967,39 +997,14 @@ tcp_sacktag_write_queue(struct sock *sk, struct sk_buff *ack_skb, u32 prior_snd_
                 }
                 tp->recv_sack_cache[i].start_seq = start_seq;
                 tp->recv_sack_cache[i].end_seq = end_seq;
-
-                /* Check for D-SACK. */
-                if (i == 0) {
-                        u32 ack = TCP_SKB_CB(ack_skb)->ack_seq;
-
-                        if (before(start_seq, ack)) {
-                                dup_sack = 1;
-                                tp->rx_opt.sack_ok |= 4;
-                                NET_INC_STATS_BH(LINUX_MIB_TCPDSACKRECV);
-                        } else if (num_sacks > 1 &&
-                                   !after(end_seq, ntohl(sp[1].end_seq)) &&
-                                   !before(start_seq, ntohl(sp[1].start_seq))) {
-                                dup_sack = 1;
-                                tp->rx_opt.sack_ok |= 4;
-                                NET_INC_STATS_BH(LINUX_MIB_TCPDSACKOFORECV);
-                        }
-
-                        /* D-SACK for already forgotten data...
-                         * Do dumb counting. */
-                        if (dup_sack &&
-                            !after(end_seq, prior_snd_una) &&
-                            after(end_seq, tp->undo_marker))
-                                tp->undo_retrans--;
-
-                        /* Eliminate too old ACKs, but take into
-                         * account more or less fresh ones, they can
-                         * contain valid SACK info.
-                         */
-                        if (before(ack, prior_snd_una - tp->max_window))
-                                return 0;
-                }
+        }
+        /* Clear the rest of the cache sack blocks so they won't match mistakenly. */
+        for (; i < ARRAY_SIZE(tp->recv_sack_cache); i++) {
+                tp->recv_sack_cache[i].start_seq = 0;
+                tp->recv_sack_cache[i].end_seq = 0;
         }
 
+        first_sack_index = 0;
         if (flag)
                 num_sacks = 1;
         else {
@@ -1016,6 +1021,10 @@ tcp_sacktag_write_queue(struct sock *sk, struct sk_buff *ack_skb, u32 prior_snd_
                                         tmp = sp[j];
                                         sp[j] = sp[j+1];
                                         sp[j+1] = tmp;
+
+                                        /* Track where the first SACK block goes to */
+                                        if (j == first_sack_index)
+                                                first_sack_index = j+1;
                                 }
 
                         }
@@ -1025,20 +1034,22 @@ tcp_sacktag_write_queue(struct sock *sk, struct sk_buff *ack_skb, u32 prior_snd_
         /* clear flag as used for different purpose in following code */
         flag = 0;
 
+        /* Use SACK fastpath hint if valid */
+        cached_skb = tp->fastpath_skb_hint;
+        cached_fack_count = tp->fastpath_cnt_hint;
+        if (!cached_skb) {
+                cached_skb = sk->sk_write_queue.next;
+                cached_fack_count = 0;
+        }
+
         for (i=0; i<num_sacks; i++, sp++) {
                 struct sk_buff *skb;
                 __u32 start_seq = ntohl(sp->start_seq);
                 __u32 end_seq = ntohl(sp->end_seq);
                 int fack_count;
 
-                /* Use SACK fastpath hint if valid */
-                if (tp->fastpath_skb_hint) {
-                        skb = tp->fastpath_skb_hint;
-                        fack_count = tp->fastpath_cnt_hint;
-                } else {
-                        skb = sk->sk_write_queue.next;
-                        fack_count = 0;
-                }
+                skb = cached_skb;
+                fack_count = cached_fack_count;
 
                 /* Event "B" in the comment above. */
                 if (after(end_seq, tp->high_seq))
@@ -1048,8 +1059,12 @@ tcp_sacktag_write_queue(struct sock *sk, struct sk_buff *ack_skb, u32 prior_snd_
                         int in_sack, pcount;
                         u8 sacked;
 
-                        tp->fastpath_skb_hint = skb;
-                        tp->fastpath_cnt_hint = fack_count;
+                        cached_skb = skb;
+                        cached_fack_count = fack_count;
+                        if (i == first_sack_index) {
+                                tp->fastpath_skb_hint = skb;
+                                tp->fastpath_cnt_hint = fack_count;
+                        }
 
                         /* The retransmission queue is always in order, so
                          * we can short-circuit the walk early.