[TCP]: Earlier SACK block verification & simplify access to them

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

2 files changed, 52 insertions, 35 deletions

diff --git a/include/linux/tcp.h b/include/linux/tcp.h
index 34acee662230..794497c7d755 100644
--- a/include/linux/tcp.h
+++ b/include/linux/tcp.h
@@ -330,7 +330,7 @@ struct tcp_sock {
         struct tcp_sack_block duplicate_sack[1]; /* D-SACK block */
         struct tcp_sack_block selective_acks[4]; /* The SACKS themselves*/
 
-        struct tcp_sack_block_wire recv_sack_cache[4];
+        struct tcp_sack_block recv_sack_cache[4];
 
         struct sk_buff *highest_sack;   /* highest skb with SACK received
                                          * (validity guaranteed only if
diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index a62e0f90f566..a287747e9dd6 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -1340,9 +1340,11 @@ 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 = (skb_transport_header(ack_skb) +
                               TCP_SKB_CB(ack_skb)->sacked);
-        struct tcp_sack_block_wire *sp = (struct tcp_sack_block_wire *)(ptr+2);
+        struct tcp_sack_block_wire *sp_wire = (struct tcp_sack_block_wire *)(ptr+2);
+        struct tcp_sack_block sp[4];
         struct sk_buff *cached_skb;
         int num_sacks = (ptr[1] - TCPOLEN_SACK_BASE)>>3;
+        int used_sacks;
         int reord = tp->packets_out;
         int flag = 0;
         int found_dup_sack = 0;
@@ -1357,7 +1359,7 @@ tcp_sacktag_write_queue(struct sock *sk, struct sk_buff *ack_skb, u32 prior_snd_
                 tp->highest_sack = tcp_write_queue_head(sk);
         }
 
-        found_dup_sack = tcp_check_dsack(tp, ack_skb, sp,
+        found_dup_sack = tcp_check_dsack(tp, ack_skb, sp_wire,
                                          num_sacks, prior_snd_una);
         if (found_dup_sack)
                 flag |= FLAG_DSACKING_ACK;
@@ -1372,14 +1374,49 @@ tcp_sacktag_write_queue(struct sock *sk, struct sk_buff *ack_skb, u32 prior_snd_
         if (!tp->packets_out)
                 goto out;
 
+        used_sacks = 0;
+        first_sack_index = 0;
+        for (i = 0; i < num_sacks; i++) {
+                int dup_sack = !i && found_dup_sack;
+
+                sp[used_sacks].start_seq = ntohl(get_unaligned(&sp_wire[i].start_seq));
+                sp[used_sacks].end_seq = ntohl(get_unaligned(&sp_wire[i].end_seq));
+
+                if (!tcp_is_sackblock_valid(tp, dup_sack,
+                                            sp[used_sacks].start_seq,
+                                            sp[used_sacks].end_seq)) {
+                        if (dup_sack) {
+                                if (!tp->undo_marker)
+                                        NET_INC_STATS_BH(LINUX_MIB_TCPDSACKIGNOREDNOUNDO);
+                                else
+                                        NET_INC_STATS_BH(LINUX_MIB_TCPDSACKIGNOREDOLD);
+                        } else {
+                                /* Don't count olds caused by ACK reordering */
+                                if ((TCP_SKB_CB(ack_skb)->ack_seq != tp->snd_una) &&
+                                    !after(sp[used_sacks].end_seq, tp->snd_una))
+                                        continue;
+                                NET_INC_STATS_BH(LINUX_MIB_TCPSACKDISCARD);
+                        }
+                        if (i == 0)
+                                first_sack_index = -1;
+                        continue;
+                }
+
+                /* Ignore very old stuff early */
+                if (!after(sp[used_sacks].end_seq, prior_snd_una))
+                        continue;
+
+                used_sacks++;
+        }
+
         /* 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 */
         force_one_sack = 1;
-        for (i = 0; i < num_sacks; i++) {
-                __be32 start_seq = sp[i].start_seq;
-                __be32 end_seq = sp[i].end_seq;
+        for (i = 0; i < used_sacks; i++) {
+                u32 start_seq = sp[i].start_seq;
+                u32 end_seq = sp[i].end_seq;
 
                 if (i == 0) {
                         if (tp->recv_sack_cache[i].start_seq != start_seq)
@@ -1398,19 +1435,17 @@ tcp_sacktag_write_queue(struct sock *sk, struct sk_buff *ack_skb, u32 prior_snd_
                 tp->recv_sack_cache[i].end_seq = 0;
         }
 
-        first_sack_index = 0;
         if (force_one_sack)
-                num_sacks = 1;
+                used_sacks = 1;
         else {
                 int j;
                 tp->fastpath_skb_hint = NULL;
 
                 /* order SACK blocks to allow in order walk of the retrans queue */
-                for (i = num_sacks-1; i > 0; i--) {
+                for (i = used_sacks - 1; i > 0; i--) {
                         for (j = 0; j < i; j++){
-                                if (after(ntohl(sp[j].start_seq),
-                                          ntohl(sp[j+1].start_seq))){
-                                        struct tcp_sack_block_wire tmp;
+                                if (after(sp[j].start_seq, sp[j+1].start_seq)) {
+                                        struct tcp_sack_block tmp;
 
                                         tmp = sp[j];
                                         sp[j] = sp[j+1];
@@ -1433,32 +1468,14 @@ tcp_sacktag_write_queue(struct sock *sk, struct sk_buff *ack_skb, u32 prior_snd_
                 cached_fack_count = 0;
         }
 
-        for (i = 0; i < num_sacks; i++) {
+        for (i = 0; i < used_sacks; i++) {
                 struct sk_buff *skb;
-                __u32 start_seq = ntohl(sp->start_seq);
-                __u32 end_seq = ntohl(sp->end_seq);
+                u32 start_seq = sp[i].start_seq;
+                u32 end_seq = sp[i].end_seq;
                 int fack_count;
                 int dup_sack = (found_dup_sack && (i == first_sack_index));
                 int next_dup = (found_dup_sack && (i+1 == first_sack_index));
 
-                sp++;
-
-                if (!tcp_is_sackblock_valid(tp, dup_sack, start_seq, end_seq)) {
-                        if (dup_sack) {
-                                if (!tp->undo_marker)
-                                        NET_INC_STATS_BH(LINUX_MIB_TCPDSACKIGNOREDNOUNDO);
-                                else
-                                        NET_INC_STATS_BH(LINUX_MIB_TCPDSACKIGNOREDOLD);
-                        } else {
-                                /* Don't count olds caused by ACK reordering */
-                                if ((TCP_SKB_CB(ack_skb)->ack_seq != tp->snd_una) &&
-                                    !after(end_seq, tp->snd_una))
-                                        continue;
-                                NET_INC_STATS_BH(LINUX_MIB_TCPSACKDISCARD);
-                        }
-                        continue;
-                }
-
                 skb = cached_skb;
                 fack_count = cached_fack_count;
 
@@ -1489,8 +1506,8 @@ tcp_sacktag_write_queue(struct sock *sk, struct sk_buff *ack_skb, u32 prior_snd_
 
                         /* Due to sorting DSACK may reside within this SACK block! */
                         if (next_dup) {
-                                u32 dup_start = ntohl(sp->start_seq);
-                                u32 dup_end = ntohl(sp->end_seq);
+                                u32 dup_start = sp[i+1].start_seq;
+                                u32 dup_end = sp[i+1].end_seq;
 
                                 if (before(TCP_SKB_CB(skb)->seq, dup_end)) {
                                         in_sack = tcp_match_skb_to_sack(sk, skb, dup_start, dup_end);