diff --git a/net/ipv4/ip_sockglue.c b/net/ipv4/ip_sockglue.c
index c602d985fe14..2445fedec0b8 100644
--- a/net/ipv4/ip_sockglue.c
+++ b/net/ipv4/ip_sockglue.c
@@ -575,7 +575,7 @@ static int do_ip_setsockopt(struct sock *sk, int level,
 		inet->hdrincl = val ? 1 : 0;
 		break;
 	case IP_MTU_DISCOVER:
-		if (val < 0 || val > 3)
+		if (val < IP_PMTUDISC_DONT || val > IP_PMTUDISC_PROBE)
 			goto e_inval;
 		inet->pmtudisc = val;
 		break;
diff --git a/net/ipv4/route.c b/net/ipv4/route.c
index bb4199252026..68fb22702051 100644
--- a/net/ipv4/route.c
+++ b/net/ipv4/route.c
@@ -1628,9 +1628,6 @@ unsigned short ip_rt_frag_needed(struct net *net, struct iphdr *iph,
 	__be32  daddr = iph->daddr;
 	unsigned short est_mtu = 0;
 
-	if (ipv4_config.no_pmtu_disc)
-		return 0;
-
 	for (k = 0; k < 2; k++) {
 		for (i = 0; i < 2; i++) {
 			unsigned hash = rt_hash(daddr, skeys[i], ikeys[k],
diff --git a/net/ipv6/ipv6_sockglue.c b/net/ipv6/ipv6_sockglue.c
index 39e10ac88019..68566de4bcc5 100644
--- a/net/ipv6/ipv6_sockglue.c
+++ b/net/ipv6/ipv6_sockglue.c
@@ -662,7 +662,7 @@ done:
 	case IPV6_MTU_DISCOVER:
 		if (optlen < sizeof(int))
 			goto e_inval;
-		if (val<0 || val>3)
+		if (val < IP_PMTUDISC_DONT || val > IP_PMTUDISC_PROBE)
 			goto e_inval;
 		np->pmtudisc = val;
 		retv = 0;