diff --git a/include/net/ip.h b/include/net/ip.h
index 0278d63c1527..52abfc00b5e3 100644
--- a/include/net/ip.h
+++ b/include/net/ip.h
@@ -30,6 +30,7 @@
 #include <net/flow.h>
 #include <net/flow_dissector.h>
 #include <net/netns/hash.h>
+#include <net/lwtunnel.h>
 
 #define IPV4_MAX_PMTU		65535U		/* RFC 2675, Section 5.1 */
 #define IPV4_MIN_MTU		68			/* RFC 791 */
@@ -448,22 +449,25 @@ static inline unsigned int ip_dst_mtu_maybe_forward(const struct dst_entry *dst,
 
 	/* 'forwarding = true' case should always honour route mtu */
 	mtu = dst_metric_raw(dst, RTAX_MTU);
-	if (mtu)
-		return mtu;
+	if (!mtu)
+		mtu = min(READ_ONCE(dst->dev->mtu), IP_MAX_MTU);
 
-	return min(READ_ONCE(dst->dev->mtu), IP_MAX_MTU);
+	return mtu - lwtunnel_headroom(dst->lwtstate, mtu);
 }
 
 static inline unsigned int ip_skb_dst_mtu(struct sock *sk,
 					  const struct sk_buff *skb)
 {
+	unsigned int mtu;
+
 	if (!sk || !sk_fullsock(sk) || ip_sk_use_pmtu(sk)) {
 		bool forwarding = IPCB(skb)->flags & IPSKB_FORWARDED;
 
 		return ip_dst_mtu_maybe_forward(skb_dst(skb), forwarding);
 	}
 
-	return min(READ_ONCE(skb_dst(skb)->dev->mtu), IP_MAX_MTU);
+	mtu = min(READ_ONCE(skb_dst(skb)->dev->mtu), IP_MAX_MTU);
+	return mtu - lwtunnel_headroom(skb_dst(skb)->lwtstate, mtu);
 }
 
 struct dst_metrics *ip_fib_metrics_init(struct net *net, struct nlattr *fc_mx,
diff --git a/include/net/ip6_route.h b/include/net/ip6_route.h
index 2d0d91070268..40602def3fe7 100644
--- a/include/net/ip6_route.h
+++ b/include/net/ip6_route.h
@@ -263,11 +263,18 @@ int ip6_fragment(struct net *net, struct sock *sk, struct sk_buff *skb,
 
 static inline int ip6_skb_dst_mtu(struct sk_buff *skb)
 {
+	int mtu;
+
 	struct ipv6_pinfo *np = skb->sk && !dev_recursion_level() ?
 				inet6_sk(skb->sk) : NULL;
 
-	return (np && np->pmtudisc >= IPV6_PMTUDISC_PROBE) ?
-	       skb_dst(skb)->dev->mtu : dst_mtu(skb_dst(skb));
+	if (np && np->pmtudisc >= IPV6_PMTUDISC_PROBE) {
+		mtu = READ_ONCE(skb_dst(skb)->dev->mtu);
+		mtu -= lwtunnel_headroom(skb_dst(skb)->lwtstate, mtu);
+	} else
+		mtu = dst_mtu(skb_dst(skb));
+
+	return mtu;
 }
 
 static inline bool ip6_sk_accept_pmtu(const struct sock *sk)
@@ -315,7 +322,7 @@ static inline unsigned int ip6_dst_mtu_forward(const struct dst_entry *dst)
 	if (dst_metric_locked(dst, RTAX_MTU)) {
 		mtu = dst_metric_raw(dst, RTAX_MTU);
 		if (mtu)
-			return mtu;
+			goto out;
 	}
 
 	mtu = IPV6_MIN_MTU;
@@ -325,7 +332,8 @@ static inline unsigned int ip6_dst_mtu_forward(const struct dst_entry *dst)
 		mtu = idev->cnf.mtu6;
 	rcu_read_unlock();
 
-	return mtu;
+out:
+	return mtu - lwtunnel_headroom(dst->lwtstate, mtu);
 }
 
 u32 ip6_mtu_from_fib6(const struct fib6_result *res,
diff --git a/net/ipv4/route.c b/net/ipv4/route.c
index 3ff702380b62..0e976848d4bb 100644
--- a/net/ipv4/route.c
+++ b/net/ipv4/route.c
@@ -1321,7 +1321,7 @@ static unsigned int ipv4_mtu(const struct dst_entry *dst)
 		mtu = dst_metric_raw(dst, RTAX_MTU);
 
 	if (mtu)
-		return mtu;
+		goto out;
 
 	mtu = READ_ONCE(dst->dev->mtu);
 
@@ -1330,6 +1330,7 @@ static unsigned int ipv4_mtu(const struct dst_entry *dst)
 			mtu = 576;
 	}
 
+out:
 	mtu = min_t(unsigned int, mtu, IP_MAX_MTU);
 
 	return mtu - lwtunnel_headroom(dst->lwtstate, mtu);