Commit 582442d6 authored Oct 03, 2013 by Oussama Ghorbel Committed by David S. Miller Oct 07, 2013

ipv6: Allow the MTU of ipip6 tunnel to be set below 1280

The (inner) MTU of a ipip6 (IPv4-in-IPv6) tunnel cannot be set below 1280, which is the minimum MTU in IPv6.
However, there should be no IPv6 on the tunnel interface at all, so the IPv6 rules should not apply.
More info at https://bugzilla.kernel.org/show_bug.cgi?id=15530



This patch allows to check the minimum MTU for ipv6 tunnel according to these rules:
-In case the tunnel is configured with ipip6 mode the minimum MTU is 68.
-In case the tunnel is configured with ip6ip6 or any mode the minimum MTU is 1280.

Signed-off-by: Oussama Ghorbel <ou.ghorbel@gmail.com>
Acked-by: Hannes Frederic Sowa <hannes@stressinduktion.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

parent 3573540c

net/ipv6/ip6_tunnel.c

+10 −2

Original line number	Diff line number	Diff line
		@@ -1430,9 +1430,17 @@ ip6_tnl_ioctl(struct net_device dev, struct ifreq ifr, int cmd)
		static int
		ip6_tnl_change_mtu(struct net_device *dev, int new_mtu)
		{
		if (new_mtu < IPV6_MIN_MTU) {
		struct ip6_tnl *tnl = netdev_priv(dev);

		if (tnl->parms.proto == IPPROTO_IPIP) {
		if (new_mtu < 68)
		return -EINVAL;
		} else {
		if (new_mtu < IPV6_MIN_MTU)
		return -EINVAL;
		}
		if (new_mtu > 0xFFF8 - dev->hard_header_len)
		return -EINVAL;
		dev->mtu = new_mtu;
		return 0;
		}

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