geneve, vxlan: Don't set exceptions if skb->len < mtu

We shouldn't abuse exceptions: if the destination MTU is already higher
than what we're transmitting, no exception should be created.

Fixes: 52a589d51f10 ("geneve: update skb dst pmtu on tx path")
Fixes: a93bf0ff4490 ("vxlan: update skb dst pmtu on tx path")
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
Reviewed-by: Sabrina Dubroca <sd@queasysnail.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/drivers/net/geneve.c b/drivers/net/geneve.c
index 61c4bfbeb41c043ef0a0f24ce242c960eaa03db1..493cd382b8aa0f187fcaf1dc520da765f9595fe0 100644 (file)
--- a/drivers/net/geneve.c
+++ b/drivers/net/geneve.c
@@ -830,8 +830,8 @@ static int geneve_xmit_skb(struct sk_buff *skb, struct net_device *dev,
        if (IS_ERR(rt))
                return PTR_ERR(rt);
 
-       skb_dst_update_pmtu(skb, dst_mtu(&rt->dst) -
-                                GENEVE_IPV4_HLEN - info->options_len);
+       skb_tunnel_check_pmtu(skb, &rt->dst,
+                             GENEVE_IPV4_HLEN + info->options_len);
 
        sport = udp_flow_src_port(geneve->net, skb, 1, USHRT_MAX, true);
        if (geneve->collect_md) {
@@ -872,8 +872,7 @@ static int geneve6_xmit_skb(struct sk_buff *skb, struct net_device *dev,
        if (IS_ERR(dst))
                return PTR_ERR(dst);
 
-       skb_dst_update_pmtu(skb, dst_mtu(dst) -
-                                GENEVE_IPV6_HLEN - info->options_len);
+       skb_tunnel_check_pmtu(skb, dst, GENEVE_IPV6_HLEN + info->options_len);
 
        sport = udp_flow_src_port(geneve->net, skb, 1, USHRT_MAX, true);
        if (geneve->collect_md) {

diff --git a/drivers/net/vxlan.c b/drivers/net/vxlan.c
index 22e0ce592e07468599feb4f867e865de7aa7409c..27bd586b94b0a01f1f99e0c01d8df85c1757b960 100644 (file)
--- a/drivers/net/vxlan.c
+++ b/drivers/net/vxlan.c
@@ -2194,7 +2194,7 @@ static void vxlan_xmit_one(struct sk_buff *skb, struct net_device *dev,
                }
 
                ndst = &rt->dst;
-               skb_dst_update_pmtu(skb, dst_mtu(ndst) - VXLAN_HEADROOM);
+               skb_tunnel_check_pmtu(skb, ndst, VXLAN_HEADROOM);
 
                tos = ip_tunnel_ecn_encap(tos, old_iph, skb);
                ttl = ttl ? : ip4_dst_hoplimit(&rt->dst);
@@ -2231,7 +2231,7 @@ static void vxlan_xmit_one(struct sk_buff *skb, struct net_device *dev,
                                goto out_unlock;
                }
 
-               skb_dst_update_pmtu(skb, dst_mtu(ndst) - VXLAN6_HEADROOM);
+               skb_tunnel_check_pmtu(skb, ndst, VXLAN6_HEADROOM);
 
                tos = ip_tunnel_ecn_encap(tos, old_iph, skb);
                ttl = ttl ? : ip6_dst_hoplimit(ndst);

diff --git a/include/net/dst.h b/include/net/dst.h
index 7f735e76ca7391f07de28b33a2cf63eabda475bf..6cf0870414c783720026a151ba94307a2bb4ad30 100644 (file)
--- a/include/net/dst.h
+++ b/include/net/dst.h
@@ -527,4 +527,14 @@ static inline void skb_dst_update_pmtu(struct sk_buff *skb, u32 mtu)
                dst->ops->update_pmtu(dst, NULL, skb, mtu);
 }
 
+static inline void skb_tunnel_check_pmtu(struct sk_buff *skb,
+                                        struct dst_entry *encap_dst,
+                                        int headroom)
+{
+       u32 encap_mtu = dst_mtu(encap_dst);
+
+       if (skb->len > encap_mtu - headroom)
+               skb_dst_update_pmtu(skb, encap_mtu - headroom);
+}
+
 #endif /* _NET_DST_H */