Patch 2: fixes to fack_counts and enhancement of SACK fast path

-Tom

---
diff -ur linux-2.6.22.6-rbtree-davem-fixed/include/net/tcp.h 
linux-2.6.22.6-rbtree-tomq/include/net/tcp.h
--- linux-2.6.22.6-rbtree-davem-fixed/include/net/tcp.h 2007-09-19 
17:36:07.000000000 -0700
+++ linux-2.6.22.6-rbtree-tomq/include/net/tcp.h        2007-09-19 
12:22:06.000000000 -0700
@@ -1213,6 +1213,11 @@
        sk->sk_send_head = tcp_write_queue_next(sk, skb);
        if (sk->sk_send_head == (struct sk_buff *)&sk->sk_write_queue)
                sk->sk_send_head = NULL;
+       else
+               /* update fack_count of send_head. Since we've sent skb already,
+                * its packet count must be set by now. */
+               TCP_SKB_CB(sk->sk_send_head)->fack_count =
+                       TCP_SKB_CB(skb)->fack_count + tcp_skb_pcount(skb);
        /* Don't override Nagle indefinately with F-RTO */
        if (tp->frto_counter == 2)
                tp->frto_counter = 3;
@@ -1310,19 +1315,22 @@
 /* An insert into the middle of the write queue causes the fack
  * counts in subsequent packets to become invalid, fix them up.
  */
-static inline void tcp_reset_fack_counts(struct sock *sk, struct sk_buff 
*first)
+static inline void tcp_reset_fack_counts(struct sock *sk, struct sk_buff *skb)
 {
-       struct sk_buff *prev = first->prev;
+       struct sk_buff *prev = skb->prev;
        unsigned int fc = 0;
 
        if (prev != (struct sk_buff *) &sk->sk_write_queue)
                fc = TCP_SKB_CB(prev)->fack_count + tcp_skb_pcount(prev);
 
-       while (first != (struct sk_buff *)&sk->sk_write_queue) {
-               TCP_SKB_CB(first)->fack_count = fc;
+       while (skb != (struct sk_buff *)&sk->sk_write_queue) {
+               if (TCP_SKB_CB(skb)->fack_count == fc || !tcp_skb_pcount(skb))
+                       break;
 
-               fc += tcp_skb_pcount(first);
-               first = first->next;
+               TCP_SKB_CB(skb)->fack_count = fc;
+
+               fc += tcp_skb_pcount(skb);
+               skb = skb->next;
        }
 }
 
diff -ur linux-2.6.22.6-rbtree-davem-fixed/net/ipv4/tcp_input.c 
linux-2.6.22.6-rbtree-tomq/net/ipv4/tcp_input.c
--- linux-2.6.22.6-rbtree-davem-fixed/net/ipv4/tcp_input.c      2007-09-13 
18:23:16.000000000 -0700
+++ linux-2.6.22.6-rbtree-tomq/net/ipv4/tcp_input.c     2007-09-19 
12:27:42.000000000 -0700
@@ -956,6 +956,7 @@
        int fack_count_base;
        int i;
        int first_sack_index;
+       u32 prev_end_seq = 0;
 
        if (!tp->sacked_out)
                tp->fackets_out = 0;
@@ -1000,6 +1001,7 @@
                if (i == 0) {
                        if (tp->recv_sack_cache[i].start_seq != start_seq)
                                flag = 0;
+                       prev_end_seq = ntohl(tp->recv_sack_cache[i].end_seq);
                } else {
                        if ((tp->recv_sack_cache[i].start_seq != start_seq) ||
                            (tp->recv_sack_cache[i].end_seq != end_seq))
@@ -1016,9 +1018,16 @@
 
        first_sack_index = 0;
        if (flag)
+               /* all that has changed is end of first SACK block. So all we
+                * need to do is tag those skbs that were'nt tagged last time. 
*/
                num_sacks = 1;
        else {
                int j;
+               
+               /* more than just end of first SACK block has changed; 
invalidate
+                * prev_end_seq */
+
+               prev_end_seq = 0;
 
                /* order SACK blocks to allow in order walk of the retrans 
queue */
                for (i = num_sacks-1; i > 0; i--) {
@@ -1051,6 +1060,8 @@
                int fack_count;
                int dup_sack = (found_dup_sack && (i == first_sack_index));
 
+               if (prev_end_seq) start_seq = prev_end_seq;
+
                skb = tcp_write_queue_find(sk, start_seq);
                if (!skb)
                        continue;
-
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