[TCP]: tcp_write_timeout.c cleanup

Before submiting a patch to change a divide to a right shift, I felt
necessary to create a helper function tcp_mtu_probing() to reduce length of
lines exceeding 100 chars in tcp_write_timeout().
Signed-off-by: Eric Dumazet <dada1@cosmosbay.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/ipv4/tcp_timer.c

@@ -114,33 +114,40 @@ static int tcp_orphan_retries(struct sock *sk, int alive)
 	return retries;
 }
 
-/* A write timeout has occurred. Process the after effects. */
-static int tcp_write_timeout(struct sock *sk)
+static void tcp_mtu_probing(struct inet_connection_sock *icsk, struct sock *sk)
 {
-	struct inet_connection_sock *icsk = inet_csk(sk);
-	struct tcp_sock *tp = tcp_sk(sk);
-	int retry_until;
 	int mss;
 
-	if ((1 << sk->sk_state) & (TCPF_SYN_SENT | TCPF_SYN_RECV)) {
-		if (icsk->icsk_retransmits)
-			dst_negative_advice(&sk->sk_dst_cache);
-		retry_until = icsk->icsk_syn_retries ? : sysctl_tcp_syn_retries;
-	} else {
-		if (icsk->icsk_retransmits >= sysctl_tcp_retries1) {
 	/* Black hole detection */
 	if (sysctl_tcp_mtu_probing) {
 		if (!icsk->icsk_mtup.enabled) {
 			icsk->icsk_mtup.enabled = 1;
 			tcp_sync_mss(sk, icsk->icsk_pmtu_cookie);
 		} else {
-					mss = min(sysctl_tcp_base_mss,
-						  tcp_mtu_to_mss(sk, icsk->icsk_mtup.search_low)/2);
+			struct tcp_sock *tp = tcp_sk(sk);
+			mss = tcp_mtu_to_mss(sk, icsk->icsk_mtup.search_low)/2;
+			mss = min(sysctl_tcp_base_mss, mss);
 			mss = max(mss, 68 - tp->tcp_header_len);
 			icsk->icsk_mtup.search_low = tcp_mss_to_mtu(sk, mss);
 			tcp_sync_mss(sk, icsk->icsk_pmtu_cookie);
 		}
 	}
+}
+
+/* A write timeout has occurred. Process the after effects. */
+static int tcp_write_timeout(struct sock *sk)
+{
+	struct inet_connection_sock *icsk = inet_csk(sk);
+	int retry_until;
+
+	if ((1 << sk->sk_state) & (TCPF_SYN_SENT | TCPF_SYN_RECV)) {
+		if (icsk->icsk_retransmits)
+			dst_negative_advice(&sk->sk_dst_cache);
+		retry_until = icsk->icsk_syn_retries ? : sysctl_tcp_syn_retries;
+	} else {
+		if (icsk->icsk_retransmits >= sysctl_tcp_retries1) {
+			/* Black hole detection */
+			tcp_mtu_probing(icsk, sk);
 
 			dst_negative_advice(&sk->sk_dst_cache);
 		}