[PATCH] tcp: fix TSO sizing bugs

MSS changes can be lost since we preemptively initialize the tso_segs count
for an SKB before we %100 commit to sending it out.

So, by the time we send it out, the tso_size information can be stale due
to PMTU events.  This mucks up all of the logic in our send engine, and can
even result in the BUG() triggering in tcp_tso_should_defer().

Another problem we have is that we're storing the tp->mss_cache, not the
SACK block normalized MSS, as the tso_size.  That's wrong too.

Signed-off-by: David S. Miller <davem@davemloft.net>
Cc: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index e3f8ea1..e118b4b 100644 (file)
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -403,11 +403,9 @@ static void tcp_queue_skb(struct sock *sk, struct sk_buff *skb)
                sk->sk_send_head = skb;
 }
 
-static void tcp_set_skb_tso_segs(struct sock *sk, struct sk_buff *skb)
+static void tcp_set_skb_tso_segs(struct sock *sk, struct sk_buff *skb, unsigned int mss_now)
 {
-       struct tcp_sock *tp = tcp_sk(sk);
-
-       if (skb->len <= tp->mss_cache ||
+       if (skb->len <= mss_now ||
            !(sk->sk_route_caps & NETIF_F_TSO)) {
                /* Avoid the costly divide in the normal
                 * non-TSO case.
@@ -417,10 +415,10 @@ static void tcp_set_skb_tso_segs(struct sock *sk, struct sk_buff *skb)
        } else {
                unsigned int factor;
 
-               factor = skb->len + (tp->mss_cache - 1);
-               factor /= tp->mss_cache;
+               factor = skb->len + (mss_now - 1);
+               factor /= mss_now;
                skb_shinfo(skb)->tso_segs = factor;
-               skb_shinfo(skb)->tso_size = tp->mss_cache;
+               skb_shinfo(skb)->tso_size = mss_now;
        }
 }
 
@@ -429,7 +427,7 @@ static void tcp_set_skb_tso_segs(struct sock *sk, struct sk_buff *skb)
  * packet to the list.  This won't be called frequently, I hope. 
  * Remember, these are still headerless SKBs at this point.
  */
-static int tcp_fragment(struct sock *sk, struct sk_buff *skb, u32 len)
+static int tcp_fragment(struct sock *sk, struct sk_buff *skb, u32 len, unsigned int mss_now)
 {
        struct tcp_sock *tp = tcp_sk(sk);
        struct sk_buff *buff;
@@ -492,8 +490,8 @@ static int tcp_fragment(struct sock *sk, struct sk_buff *skb, u32 len)
        }
 
        /* Fix up tso_factor for both original and new SKB.  */
-       tcp_set_skb_tso_segs(sk, skb);
-       tcp_set_skb_tso_segs(sk, buff);
+       tcp_set_skb_tso_segs(sk, skb, mss_now);
+       tcp_set_skb_tso_segs(sk, buff, mss_now);
 
        if (TCP_SKB_CB(skb)->sacked & TCPCB_LOST) {
                tp->lost_out += tcp_skb_pcount(skb);
@@ -569,7 +567,7 @@ int tcp_trim_head(struct sock *sk, struct sk_buff *skb, u32 len)
         * factor and mss.
         */
        if (tcp_skb_pcount(skb) > 1)
-               tcp_set_skb_tso_segs(sk, skb);
+               tcp_set_skb_tso_segs(sk, skb, tcp_current_mss(sk, 1));
 
        return 0;
 }
@@ -734,12 +732,14 @@ static inline unsigned int tcp_cwnd_test(struct tcp_sock *tp, struct sk_buff *sk
 /* This must be invoked the first time we consider transmitting
  * SKB onto the wire.
  */
-static inline int tcp_init_tso_segs(struct sock *sk, struct sk_buff *skb)
+static inline int tcp_init_tso_segs(struct sock *sk, struct sk_buff *skb, unsigned int mss_now)
 {
        int tso_segs = tcp_skb_pcount(skb);
 
-       if (!tso_segs) {
-               tcp_set_skb_tso_segs(sk, skb);
+       if (!tso_segs ||
+           (tso_segs > 1 &&
+            skb_shinfo(skb)->tso_size != mss_now)) {
+               tcp_set_skb_tso_segs(sk, skb, mss_now);
                tso_segs = tcp_skb_pcount(skb);
        }
        return tso_segs;
@@ -817,7 +817,7 @@ static unsigned int tcp_snd_test(struct sock *sk, struct sk_buff *skb,
        struct tcp_sock *tp = tcp_sk(sk);
        unsigned int cwnd_quota;
 
-       tcp_init_tso_segs(sk, skb);
+       tcp_init_tso_segs(sk, skb, cur_mss);
 
        if (!tcp_nagle_test(tp, skb, cur_mss, nonagle))
                return 0;
@@ -854,7 +854,7 @@ int tcp_may_send_now(struct sock *sk, struct tcp_sock *tp)
  * know that all the data is in scatter-gather pages, and that the
  * packet has never been sent out before (and thus is not cloned).
  */
-static int tso_fragment(struct sock *sk, struct sk_buff *skb, unsigned int len)
+static int tso_fragment(struct sock *sk, struct sk_buff *skb, unsigned int len, unsigned int mss_now)
 {
        struct sk_buff *buff;
        int nlen = skb->len - len;
@@ -887,8 +887,8 @@ static int tso_fragment(struct sock *sk, struct sk_buff *skb, unsigned int len)
        skb_split(skb, buff, len);
 
        /* Fix up tso_factor for both original and new SKB.  */
-       tcp_set_skb_tso_segs(sk, skb);
-       tcp_set_skb_tso_segs(sk, buff);
+       tcp_set_skb_tso_segs(sk, skb, mss_now);
+       tcp_set_skb_tso_segs(sk, buff, mss_now);
 
        /* Link BUFF into the send queue. */
        skb_header_release(buff);
@@ -976,7 +976,7 @@ static int tcp_write_xmit(struct sock *sk, unsigned int mss_now, int nonagle)
        if (unlikely(!skb))
                return 0;
 
-       tso_segs = tcp_init_tso_segs(sk, skb);
+       tso_segs = tcp_init_tso_segs(sk, skb, mss_now);
        cwnd_quota = tcp_cwnd_test(tp, skb);
        if (unlikely(!cwnd_quota))
                goto out;
@@ -1006,11 +1006,11 @@ static int tcp_write_xmit(struct sock *sk, unsigned int mss_now, int nonagle)
                                        limit = skb->len - trim;
                        }
                        if (skb->len > limit) {
-                               if (tso_fragment(sk, skb, limit))
+                               if (tso_fragment(sk, skb, limit, mss_now))
                                        break;
                        }
                } else if (unlikely(skb->len > mss_now)) {
-                       if (unlikely(tcp_fragment(sk, skb,  mss_now)))
+                       if (unlikely(tcp_fragment(sk, skb,  mss_now, mss_now)))
                                break;
                }
 
@@ -1039,7 +1039,7 @@ static int tcp_write_xmit(struct sock *sk, unsigned int mss_now, int nonagle)
                skb = sk->sk_send_head;
                if (!skb)
                        break;
-               tso_segs = tcp_init_tso_segs(sk, skb);
+               tso_segs = tcp_init_tso_segs(sk, skb, mss_now);
        }
 
        if (likely(sent_pkts)) {
@@ -1076,7 +1076,7 @@ void tcp_push_one(struct sock *sk, unsigned int mss_now)
 
        BUG_ON(!skb || skb->len < mss_now);
 
-       tso_segs = tcp_init_tso_segs(sk, skb);
+       tso_segs = tcp_init_tso_segs(sk, skb, mss_now);
        cwnd_quota = tcp_snd_test(sk, skb, mss_now, TCP_NAGLE_PUSH);
 
        if (likely(cwnd_quota)) {
@@ -1093,11 +1093,11 @@ void tcp_push_one(struct sock *sk, unsigned int mss_now)
                                        limit = skb->len - trim;
                        }
                        if (skb->len > limit) {
-                               if (unlikely(tso_fragment(sk, skb, limit)))
+                               if (unlikely(tso_fragment(sk, skb, limit, mss_now)))
                                        return;
                        }
                } else if (unlikely(skb->len > mss_now)) {
-                       if (unlikely(tcp_fragment(sk, skb, mss_now)))
+                       if (unlikely(tcp_fragment(sk, skb, mss_now, mss_now)))
                                return;
                }
 
@@ -1388,7 +1388,7 @@ int tcp_retransmit_skb(struct sock *sk, struct sk_buff *skb)
                int old_factor = tcp_skb_pcount(skb);
                int new_factor;
 
-               if (tcp_fragment(sk, skb, cur_mss))
+               if (tcp_fragment(sk, skb, cur_mss, cur_mss))
                        return -ENOMEM; /* We'll try again later. */
 
                /* New SKB created, account for it. */
@@ -1991,7 +1991,7 @@ int tcp_write_wakeup(struct sock *sk)
                            skb->len > mss) {
                                seg_size = min(seg_size, mss);
                                TCP_SKB_CB(skb)->flags |= TCPCB_FLAG_PSH;
-                               if (tcp_fragment(sk, skb, seg_size))
+                               if (tcp_fragment(sk, skb, seg_size, mss))
                                        return -1;
                                /* SWS override triggered forced fragmentation.
                                 * Disable TSO, the connection is too sick. */
@@ -2000,7 +2000,7 @@ int tcp_write_wakeup(struct sock *sk)
                                        sk->sk_route_caps &= ~NETIF_F_TSO;
                                }
                        } else if (!tcp_skb_pcount(skb))
-                               tcp_set_skb_tso_segs(sk, skb);
+                               tcp_set_skb_tso_segs(sk, skb, mss);
 
                        TCP_SKB_CB(skb)->flags |= TCPCB_FLAG_PSH;
                        TCP_SKB_CB(skb)->when = tcp_time_stamp;