tcp: make mtu probe failure to not break gso'ed skbs unnecessarily

I noticed that since skb->len has nothing to do with actual segment
length with gso, we need to figure it out separately, reuse
a function from the recent shifting stuff (generalize it).

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 33902f6..21c6701 100644 (file)
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -1445,14 +1445,9 @@ static int tcp_shifted_skb(struct sock *sk, struct sk_buff *prev,
 /* I wish gso_size would have a bit more sane initialization than
  * something-or-zero which complicates things
  */
-static int tcp_shift_mss(struct sk_buff *skb)
+static int tcp_skb_seglen(struct sk_buff *skb)
 {
-       int mss = tcp_skb_mss(skb);
-
-       if (!mss)
-               mss = skb->len;
-
-       return mss;
+       return tcp_skb_pcount(skb) == 1 ? skb->len : tcp_skb_mss(skb);
 }
 
 /* Shifting pages past head area doesn't work */
@@ -1503,12 +1498,12 @@ static struct sk_buff *tcp_shift_skb_data(struct sock *sk, struct sk_buff *skb,
        if (in_sack) {
                len = skb->len;
                pcount = tcp_skb_pcount(skb);
-               mss = tcp_shift_mss(skb);
+               mss = tcp_skb_seglen(skb);
 
                /* TODO: Fix DSACKs to not fragment already SACKed and we can
                 * drop this restriction as unnecessary
                 */
-               if (mss != tcp_shift_mss(prev))
+               if (mss != tcp_skb_seglen(prev))
                        goto fallback;
        } else {
                if (!after(TCP_SKB_CB(skb)->end_seq, start_seq))
@@ -1549,7 +1544,7 @@ static struct sk_buff *tcp_shift_skb_data(struct sock *sk, struct sk_buff *skb,
                /* TODO: Fix DSACKs to not fragment already SACKed and we can
                 * drop this restriction as unnecessary
                 */
-               if (mss != tcp_shift_mss(prev))
+               if (mss != tcp_skb_seglen(prev))
                        goto fallback;
 
                if (len == mss) {
@@ -1578,7 +1573,7 @@ static struct sk_buff *tcp_shift_skb_data(struct sock *sk, struct sk_buff *skb,
        if (!skb_can_shift(skb) ||
            (skb == tcp_send_head(sk)) ||
            ((TCP_SKB_CB(skb)->sacked & TCPCB_TAGBITS) != TCPCB_SACKED_ACKED) ||
-           (mss != tcp_shift_mss(skb)))
+           (mss != tcp_skb_seglen(skb)))
                goto out;
 
        len = skb->len;
@@ -2853,7 +2848,7 @@ void tcp_simple_retransmit(struct sock *sk)
        tcp_for_write_queue(skb, sk) {
                if (skb == tcp_send_head(sk))
                        break;
-               if (skb->len > mss &&
+               if (tcp_skb_seglen(skb) > mss &&
                    !(TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_ACKED)) {
                        if (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_RETRANS) {
                                TCP_SKB_CB(skb)->sacked &= ~TCPCB_SACKED_RETRANS;