Patch "vxlan: update skb dst pmtu on tx path" has been added to the 4.14-stable tree

This is a note to let you know that I've just added the patch titled

vxlan: update skb dst pmtu on tx path

to the 4.14-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
vxlan-update-skb-dst-pmtu-on-tx-path.patch
and it can be found in the queue-4.14 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Xin Long <[email protected]>
Date: Mon, 18 Dec 2017 14:20:56 +0800
Subject: vxlan: update skb dst pmtu on tx path

From: Xin Long <[email protected]>

[ Upstream commit a93bf0ff449064e6b7f44e58522e940f88c0d966 ]

Unlike ip tunnels, now vxlan doesn't do any pmtu update for upper dst pmtu, even if it doesn't match the lower dst pmtu any more.

The problem can be reproduced when reducing the vxlan lower dev's pmtu when running netperf. In jianlin's testing, the performance went to 1/7 of the previous.

This patch is to update the upper dst pmtu to match the lower dst pmtu on tx path so that packets can be sent out even when lower dev's pmtu has been changed.

It also works for metadata dst.

Note that this patch doesn't process any pmtu icmp packet. But even in the future, the support for pmtu icmp packets process of udp tunnels will also needs this.

The same thing will be done for geneve in another patch.

---
 drivers/net/vxlan.c |   14 ++++++++++++++
 1 file changed, 14 insertions(+)

@@ -2155,6 +2155,13 @@ static void vxlan_xmit_one(struct sk_buf
 		}
 
 		ndst = &rt->dst;
+		if (skb_dst(skb)) {
+			int mtu = dst_mtu(ndst) - VXLAN_HEADROOM;
+
+			skb_dst(skb)->ops->update_pmtu(skb_dst(skb), NULL,
+						       skb, mtu);
+		}
+
 		tos = ip_tunnel_ecn_encap(tos, old_iph, skb);
 		ttl = ttl ? : ip4_dst_hoplimit(&rt->dst);
 		err = vxlan_build_skb(skb, ndst, sizeof(struct iphdr),

@@ -2190,6 +2197,13 @@ static void vxlan_xmit_one(struct sk_buf
 				goto out_unlock;
 		}
 
+		if (skb_dst(skb)) {
+			int mtu = dst_mtu(ndst) - VXLAN6_HEADROOM;
+
+			skb_dst(skb)->ops->update_pmtu(skb_dst(skb), NULL,
+						       skb, mtu);
+		}
+
 		tos = ip_tunnel_ecn_encap(tos, old_iph, skb);
 		ttl = ttl ? : ip6_dst_hoplimit(ndst);
 		skb_scrub_packet(skb, xnet);

Patches currently in stable-queue which might be from [email protected] are

queue-4.14/ip_gre-remove-the-incorrect-mtu-limit-for-ipgre-tap.patch queue-4.14/ip6_gre-remove-the-incorrect-mtu-limit-for-ipgre-tap.patch queue-4.14/ip6_tunnel-allow-ip6gre-dev-mtu-to-be-set-below-1280.patch queue-4.14/vxlan-update-skb-dst-pmtu-on-tx-path.patch queue-4.14/ip6_tunnel-get-the-min-mtu-properly-in-ip6_tnl_xmit.patch queue-4.14/sctp-fix-the-issue-that-a-__u16-variable-may-overflow-in-sctp_ulpq_renege.patch