linux-kernel - [PATCH 4.14 032/115] vxlan: update skb dst pmtu on tx path

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Date:   Fri,  2 Mar 2018 09:50:35 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Xin Long <lucien.xin@...il.com>,
        "David S. Miller" <davem@...emloft.net>,
        Sasha Levin <alexander.levin@...izon.com>
Subject: [PATCH 4.14 032/115] vxlan: update skb dst pmtu on tx path

4.14-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Xin Long <lucien.xin@...il.com>

[ 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.

Signed-off-by: Xin Long <lucien.xin@...il.com>
Signed-off-by: David S. Miller <davem@...emloft.net>
Signed-off-by: Sasha Levin <alexander.levin@...izon.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 drivers/net/vxlan.c |   14 ++++++++++++++
 1 file changed, 14 insertions(+)

--- a/drivers/net/vxlan.c
+++ b/drivers/net/vxlan.c
@@ -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);