tcp: Make SACK code to split only at mss boundaries

Sadly enough, this adds possible divide though we try to avoid
it by checking one mss as common case.

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 3f26599ddc88ca0074830ad18c39f9b78ee628ae..ca46eb9151f8e535f13756e48844b1580c5f0ca1 100644 (file)
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -1248,20 +1248,39 @@ static int tcp_match_skb_to_sack(struct sock *sk, struct sk_buff *skb,
 {
        int in_sack, err;
        unsigned int pkt_len;
+       unsigned int mss;
 
        in_sack = !after(start_seq, TCP_SKB_CB(skb)->seq) &&
                  !before(end_seq, TCP_SKB_CB(skb)->end_seq);
 
        if (tcp_skb_pcount(skb) > 1 && !in_sack &&
            after(TCP_SKB_CB(skb)->end_seq, start_seq)) {
-
+               mss = tcp_skb_mss(skb);
                in_sack = !after(start_seq, TCP_SKB_CB(skb)->seq);
 
-               if (!in_sack)
+               if (!in_sack) {
                        pkt_len = start_seq - TCP_SKB_CB(skb)->seq;
-               else
+                       if (pkt_len < mss)
+                               pkt_len = mss;
+               } else {
                        pkt_len = end_seq - TCP_SKB_CB(skb)->seq;
-               err = tcp_fragment(sk, skb, pkt_len, skb_shinfo(skb)->gso_size);
+                       if (pkt_len < mss)
+                               return -EINVAL;
+               }
+
+               /* Round if necessary so that SACKs cover only full MSSes
+                * and/or the remaining small portion (if present)
+                */
+               if (pkt_len > mss) {
+                       unsigned int new_len = (pkt_len / mss) * mss;
+                       if (!in_sack && new_len < pkt_len) {
+                               new_len += mss;
+                               if (new_len > skb->len)
+                                       return 0;
+                       }
+                       pkt_len = new_len;
+               }
+               err = tcp_fragment(sk, skb, pkt_len, mss);
                if (err < 0)
                        return err;
        }