tcp: reinitialize MTU probing when setting MSS in a TCP repair

MTU probing initialization occurred only at connect() and at SYN or
SYN-ACK reception, but the former sets MSS to either the default or the
user set value (through TCP_MAXSEG sockopt) and the latter never happens
with repaired sockets.

The result was that, with MTU probing enabled and unless TCP_MAXSEG
sockopt was used before connect(), probing would be stuck at
tcp_base_mss value until tcp_probe_interval seconds have passed.
Signed-off-by: Douglas Caetano dos Santos <douglascs@taghos.com.br>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/ipv4/tcp.c

@@ -2381,9 +2381,10 @@ static int tcp_repair_set_window(struct tcp_sock *tp, char __user *optbuf, int l
 	return 0;
 }
 
-static int tcp_repair_options_est(struct tcp_sock *tp,
+static int tcp_repair_options_est(struct sock *sk,
 		struct tcp_repair_opt __user *optbuf, unsigned int len)
 {
+	struct tcp_sock *tp = tcp_sk(sk);
 	struct tcp_repair_opt opt;
 
 	while (len >= sizeof(opt)) {
@@ -2396,6 +2397,7 @@ static int tcp_repair_options_est(struct tcp_sock *tp,
 		switch (opt.opt_code) {
 		case TCPOPT_MSS:
 			tp->rx_opt.mss_clamp = opt.opt_val;
+			tcp_mtup_init(sk);
 			break;
 		case TCPOPT_WINDOW:
 			{
@@ -2555,7 +2557,7 @@ static int do_tcp_setsockopt(struct sock *sk, int level,
 		if (!tp->repair)
 			err = -EINVAL;
 		else if (sk->sk_state == TCP_ESTABLISHED)
-			err = tcp_repair_options_est(tp,
+			err = tcp_repair_options_est(sk,
 					(struct tcp_repair_opt __user *)optval,
 					optlen);
 		else