Commit 5c25f30c authored Sep 05, 2017 by Xin Long Committed by David S. Miller Sep 07, 2017

ip6_gre: update mtu properly in ip6gre_err



Now when probessing ICMPV6_PKT_TOOBIG, ip6gre_err only subtracts the
offset of gre header from mtu info. The expected mtu of gre device
should also subtract gre header. Otherwise, the next packets still
can't be sent out.

Jianlin found this issue when using the topo:
  client(ip6gre)<---->(nic1)route(nic2)<----->(ip6gre)server

and reducing nic2's mtu, then both tcp and sctp's performance with
big size data became 0.

This patch is to fix it by also subtracting grehdr (tun->tun_hlen)
from mtu info when updating gre device's mtu in ip6gre_err(). It
also needs to subtract ETH_HLEN if gre dev'type is ARPHRD_ETHER.

Reported-by: Jianlin Shi <jishi@redhat.com>
Signed-off-by: Xin Long <lucien.xin@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

parent 80532384

net/ipv6/ip6_gre.c

+3 −1

Original line number	Diff line number	Diff line
		@@ -432,7 +432,9 @@ static void ip6gre_err(struct sk_buff skb, struct inet6_skb_parm opt,
		}
		break;
		case ICMPV6_PKT_TOOBIG:
		mtu = be32_to_cpu(info) - offset;
		mtu = be32_to_cpu(info) - offset - t->tun_hlen;
		if (t->dev->type == ARPHRD_ETHER)
		mtu -= ETH_HLEN;
		if (mtu < IPV6_MIN_MTU)
		mtu = IPV6_MIN_MTU;
		t->dev->mtu = mtu;

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