tcp: fix SYN-data space mis-accounting

[cascardo/linux.git] / net / ipv4 / tcp_output.c

diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index fd0cea1..e2b4461 100644 (file)
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -1351,8 +1351,8 @@ int tcp_trim_head(struct sock *sk, struct sk_buff *skb, u32 len)
        return 0;
 }
 
-/* Calculate MSS. Not accounting for SACKs here.  */
-int tcp_mtu_to_mss(struct sock *sk, int pmtu)
+/* Calculate MSS not accounting any TCP options.  */
+static inline int __tcp_mtu_to_mss(struct sock *sk, int pmtu)
 {
        const struct tcp_sock *tp = tcp_sk(sk);
        const struct inet_connection_sock *icsk = inet_csk(sk);
@@ -1381,13 +1381,17 @@ int tcp_mtu_to_mss(struct sock *sk, int pmtu)
        /* Then reserve room for full set of TCP options and 8 bytes of data */
        if (mss_now < 48)
                mss_now = 48;
-
-       /* Now subtract TCP options size, not including SACKs */
-       mss_now -= tp->tcp_header_len - sizeof(struct tcphdr);
-
        return mss_now;
 }
 
+/* Calculate MSS. Not accounting for SACKs here.  */
+int tcp_mtu_to_mss(struct sock *sk, int pmtu)
+{
+       /* Subtract TCP options size, not including SACKs */
+       return __tcp_mtu_to_mss(sk, pmtu) -
+              (tcp_sk(sk)->tcp_header_len - sizeof(struct tcphdr));
+}
+
 /* Inverse of above */
 int tcp_mss_to_mtu(struct sock *sk, int mss)
 {
@@ -2930,7 +2934,7 @@ static int tcp_send_syn_data(struct sock *sk, struct sk_buff *syn)
         */
        if (tp->rx_opt.user_mss && tp->rx_opt.user_mss < tp->rx_opt.mss_clamp)
                tp->rx_opt.mss_clamp = tp->rx_opt.user_mss;
-       space = tcp_mtu_to_mss(sk, inet_csk(sk)->icsk_pmtu_cookie) -
+       space = __tcp_mtu_to_mss(sk, inet_csk(sk)->icsk_pmtu_cookie) -
                MAX_TCP_OPTION_SPACE;
 
        syn_data = skb_copy_expand(syn, skb_headroom(syn), space,