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Message-Id: <20200102220451.037924125@linuxfoundation.org>
Date:   Thu,  2 Jan 2020 23:08:06 +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, Guillaume Nault <gnault@...hat.com>,
        David Ahern <dsahern@...il.com>,
        Hangbin Liu <liuhangbin@...il.com>,
        "David S. Miller" <davem@...emloft.net>
Subject: [PATCH 4.14 84/91] vti: do not confirm neighbor when do pmtu update

From: Hangbin Liu <liuhangbin@...il.com>

[ Upstream commit 8247a79efa2f28b44329f363272550c1738377de ]

When do IPv6 tunnel PMTU update and calls __ip6_rt_update_pmtu() in the end,
we should not call dst_confirm_neigh() as there is no two-way communication.

Although vti and vti6 are immune to this problem because they are IFF_NOARP
interfaces, as Guillaume pointed. There is still no sense to confirm neighbour
here.

v5: Update commit description.
v4: No change.
v3: Do not remove dst_confirm_neigh, but add a new bool parameter in
    dst_ops.update_pmtu to control whether we should do neighbor confirm.
    Also split the big patch to small ones for each area.
v2: Remove dst_confirm_neigh in __ip6_rt_update_pmtu.

Reviewed-by: Guillaume Nault <gnault@...hat.com>
Acked-by: David Ahern <dsahern@...il.com>
Signed-off-by: Hangbin Liu <liuhangbin@...il.com>
Signed-off-by: David S. Miller <davem@...emloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 net/ipv4/ip_vti.c  |    2 +-
 net/ipv6/ip6_vti.c |    2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

--- a/net/ipv4/ip_vti.c
+++ b/net/ipv4/ip_vti.c
@@ -244,7 +244,7 @@ static netdev_tx_t vti_xmit(struct sk_bu
 
 	mtu = dst_mtu(dst);
 	if (skb->len > mtu) {
-		skb_dst_update_pmtu(skb, mtu);
+		skb_dst_update_pmtu_no_confirm(skb, mtu);
 		if (skb->protocol == htons(ETH_P_IP)) {
 			icmp_send(skb, ICMP_DEST_UNREACH, ICMP_FRAG_NEEDED,
 				  htonl(mtu));
--- a/net/ipv6/ip6_vti.c
+++ b/net/ipv6/ip6_vti.c
@@ -483,7 +483,7 @@ vti6_xmit(struct sk_buff *skb, struct ne
 
 	mtu = dst_mtu(dst);
 	if (skb->len > mtu) {
-		skb_dst_update_pmtu(skb, mtu);
+		skb_dst_update_pmtu_no_confirm(skb, mtu);
 
 		if (skb->protocol == htons(ETH_P_IPV6)) {
 			if (mtu < IPV6_MIN_MTU)