tcp: keepalive cleanups

Introduce keepalive_probes(tp) helper, and use it, like 
keepalive_time_when(tp) and keepalive_intvl_when(tp)

Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index 9114524..59f69a6 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -2336,13 +2336,13 @@
 		val = !!(tp->nonagle&TCP_NAGLE_CORK);
 		break;
 	case TCP_KEEPIDLE:
-		val = (tp->keepalive_time ? : sysctl_tcp_keepalive_time) / HZ;
+		val = keepalive_time_when(tp) / HZ;
 		break;
 	case TCP_KEEPINTVL:
-		val = (tp->keepalive_intvl ? : sysctl_tcp_keepalive_intvl) / HZ;
+		val = keepalive_intvl_when(tp) / HZ;
 		break;
 	case TCP_KEEPCNT:
-		val = tp->keepalive_probes ? : sysctl_tcp_keepalive_probes;
+		val = keepalive_probes(tp);
 		break;
 	case TCP_SYNCNT:
 		val = icsk->icsk_syn_retries ? : sysctl_tcp_syn_retries;