Merge branch 'Support-PMTU-discovery-with-bridged-UDP-tunnels'

Stefano Brivio says:

====================
Support PMTU discovery with bridged UDP tunnels

Currently, PMTU discovery for UDP tunnels only works if packets are
routed to the encapsulating interfaces, not bridged.

This results from the fact that we generally don't have valid routes
to the senders we can use to relay ICMP and ICMPv6 errors, and makes
PMTU discovery completely non-functional for VXLAN and GENEVE ports of
both regular bridges and Open vSwitch instances.

If the sender is local, and packets are forwarded to the port by a
regular bridge, all it takes is to generate a corresponding route
exception on the encapsulating device. The bridge then finds the route
exception carrying the PMTU value estimate as it forwards frames, and
relays ICMP messages back to the socket of the local sender. Patch 1/6
fixes this case.

If the sender resides on another node, we actually need to reply to
IP and IPv6 packets ourselves and send these ICMP or ICMPv6 errors
back, using the same encapsulating device. Patch 2/6, based on an
original idea by Florian Westphal, adds the needed functionality,
while patches 3/6 and 4/6 add matching support for VXLAN and GENEVE.

Finally, 5/6 and 6/6 introduce selftests for all combinations of
inner and outer IP versions, covering both VXLAN and GENEVE, with
both regular bridges and Open vSwitch instances.

v2: Add helper to check for any bridge port, skip oif check for PMTU
    routes for bridge ports only, split IPv4 and IPv6 helpers and
    functions (all suggested by David Ahern)
====================

Signed-off-by: David S. Miller <davem@davemloft.net>

3 files changed, 7 insertions, 10 deletions

diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index 88d40b9abaa1..90444622b703 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -4840,6 +4840,11 @@ static inline bool netif_is_ovs_port(const struct net_device *dev)
 	return dev->priv_flags & IFF_OVS_DATAPATH;
 }
 
+static inline bool netif_is_any_bridge_port(const struct net_device *dev)
+{
+	return netif_is_bridge_port(dev) || netif_is_ovs_port(dev);
+}
+
 static inline bool netif_is_team_master(const struct net_device *dev)
 {
 	return dev->priv_flags & IFF_TEAM;
diff --git a/include/net/dst.h b/include/net/dst.h
index 852d8fb36ab7..6ae2e625050d 100644
--- a/include/net/dst.h
+++ b/include/net/dst.h
@@ -535,14 +535,4 @@ static inline void skb_dst_update_pmtu_no_confirm(struct sk_buff *skb, u32 mtu)
 		dst->ops->update_pmtu(dst, NULL, skb, mtu, false);
 }
 
-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_no_confirm(skb, encap_mtu - headroom);
-}
-
 #endif /* _NET_DST_H */
diff --git a/include/net/ip_tunnels.h b/include/net/ip_tunnels.h
index 36025dea7612..02ccd32542d0 100644
--- a/include/net/ip_tunnels.h
+++ b/include/net/ip_tunnels.h
@@ -420,6 +420,8 @@ void iptunnel_xmit(struct sock *sk, struct rtable *rt, struct sk_buff *skb,
 		   u8 tos, u8 ttl, __be16 df, bool xnet);
 struct metadata_dst *iptunnel_metadata_reply(struct metadata_dst *md,
 					     gfp_t flags);
+int skb_tunnel_check_pmtu(struct sk_buff *skb, struct dst_entry *encap_dst,
+			  int headroom, bool reply);
 
 int iptunnel_handle_offloads(struct sk_buff *skb, int gso_type_mask);