Commit 5a25cf1e authored by Hannes Frederic Sowa's avatar Hannes Frederic Sowa Committed by Steffen Klassert

xfrm: revert ipv4 mtu determination to dst_mtu

In commit 0ea9d5e3 ("xfrm: introduce
helper for safe determination of mtu") I switched the determination of
ipv4 mtus from dst_mtu to ip_skb_dst_mtu. This was an error because in
case of IP_PMTUDISC_PROBE we fall back to the interface mtu, which is
never correct for ipv4 ipsec.

This patch partly reverts 0ea9d5e3
("xfrm: introduce helper for safe determination of mtu").

Cc: Steffen Klassert <>
Signed-off-by: default avatarHannes Frederic Sowa <>
Signed-off-by: default avatarSteffen Klassert <>
parent 844d4874
......@@ -20,7 +20,6 @@
#include <net/route.h>
#include <net/ipv6.h>
#include <net/ip6_fib.h>
#include <net/ip6_route.h>
#include <net/flow.h>
#include <linux/interrupt.h>
......@@ -1724,15 +1723,4 @@ static inline int xfrm_mark_put(struct sk_buff *skb, const struct xfrm_mark *m)
return ret;
static inline int xfrm_skb_dst_mtu(struct sk_buff *skb)
struct sock *sk = skb->sk;
if (sk && skb->protocol == htons(ETH_P_IPV6))
return ip6_skb_dst_mtu(skb);
else if (sk && skb->protocol == htons(ETH_P_IP))
return ip_skb_dst_mtu(skb);
return dst_mtu(skb_dst(skb));
#endif /* _NET_XFRM_H */
......@@ -28,7 +28,7 @@ static int xfrm4_tunnel_check_size(struct sk_buff *skb)
if (!(ip_hdr(skb)->frag_off & htons(IP_DF)) || skb->local_df)
goto out;
mtu = xfrm_skb_dst_mtu(skb);
mtu = dst_mtu(skb_dst(skb));
if (skb->len > mtu) {
if (skb->sk)
xfrm_local_error(skb, mtu);
......@@ -140,10 +140,12 @@ static int __xfrm6_output(struct sk_buff *skb)
struct dst_entry *dst = skb_dst(skb);
struct xfrm_state *x = dst->xfrm;
int mtu = xfrm_skb_dst_mtu(skb);
int mtu;
if (mtu < IPV6_MIN_MTU)
mtu = IPV6_MIN_MTU;
if (skb->protocol == htons(ETH_P_IPV6))
mtu = ip6_skb_dst_mtu(skb);
mtu = dst_mtu(skb_dst(skb));
if (skb->len > mtu && xfrm6_local_dontfrag(skb)) {
xfrm6_local_rxpmtu(skb, mtu);
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