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[2a01:cb05:8529:0:c08f:cfaf:4969:c46f]) by smtp.gmail.com with ESMTPSA id u8sm6671660wmm.15.2019.12.19.09.47.21 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 19 Dec 2019 09:47:21 -0800 (PST) Date: Thu, 19 Dec 2019 18:47:20 +0100 From: Guillaume Nault To: Hangbin Liu Cc: netdev@vger.kernel.org, Julian Anastasov , Marcelo Ricardo Leitner , David Ahern , Eric Dumazet , David Miller , Pablo Neira , Stephen Hemminger , Alexey Kodanev Subject: Re: [PATCH net-next 5/8] tunnel: do not confirm neighbor when do pmtu update Message-ID: <20191219174720.GA14566@linux.home> References: <20191203021137.26809-1-liuhangbin@gmail.com> <20191218115313.19352-1-liuhangbin@gmail.com> <20191218115313.19352-6-liuhangbin@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20191218115313.19352-6-liuhangbin@gmail.com> Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On Wed, Dec 18, 2019 at 07:53:10PM +0800, Hangbin Liu wrote: > 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 ipv4 tunnel is not affected as __ip_rt_update_pmtu() does not call > dst_confirm_neigh(), we still not do neigh confirm to keep consistency with > IPv6 code. > This is a bit confusing. IPv4 tunnels (e.g. gretap) are affected, as show by your reproducer. Quoting patch 0: """ The reason is when we ping6 remote via gretap, we will call like gre_tap_xmit() - ip_tunnel_xmit() - tnl_update_pmtu() - skb_dst_update_pmtu() - ip6_rt_update_pmtu() - __ip6_rt_update_pmtu() - dst_confirm_neigh() - ip6_confirm_neigh() - __ipv6_confirm_neigh() - n->confirmed = now """ IPv4 is not affected if it's on the overlay, but that's not what is this patch cares about. Unless I've misunderstood this paragraph, I think that you can just delete it. > Signed-off-by: Hangbin Liu > --- > net/ipv4/ip_tunnel.c | 2 +- > net/ipv6/ip6_tunnel.c | 4 ++-- > 2 files changed, 3 insertions(+), 3 deletions(-) > > diff --git a/net/ipv4/ip_tunnel.c b/net/ipv4/ip_tunnel.c > index 38c02bb62e2c..0fe2a5d3e258 100644 > --- a/net/ipv4/ip_tunnel.c > +++ b/net/ipv4/ip_tunnel.c > @@ -505,7 +505,7 @@ static int tnl_update_pmtu(struct net_device *dev, struct sk_buff *skb, > mtu = skb_valid_dst(skb) ? dst_mtu(skb_dst(skb)) : dev->mtu; > > if (skb_valid_dst(skb)) > - skb_dst_update_pmtu(skb, mtu); > + skb_dst_update_pmtu_no_confirm(skb, mtu); > Fixes: 0dec879f636f ("net: use dst_confirm_neigh for UDP, RAW, ICMP, L2TP")