Commit db2ec95d authored by Tom Herbert's avatar Tom Herbert Committed by David S. Miller
Browse files

ip6_gre: Fix MTU setting 



In ip6gre_tnl_link_config set t->tun_len and t->hlen correctly for the
configuration. For hard_header_len and mtu calculation include
IPv6 header and encapsulation overhead.

In ip6gre_tunnel_init_common set t->tun_len and t->hlen correctly for
the configuration. Revert to setting hard_header_len instead of
needed_headroom.

Tested:

./ip link add name tun8 type ip6gretap remote \
2401:db00:20:911a:face:0:27:0 local \
2401:db00:20:911a:face:0:25:0 ttl 225

Gives MTU of 1434. That is equal to 1500 - 40 - 14 - 4 - 8.

./ip link add name tun8 type ip6gretap remote \
2401:db00:20:911a:face:0:27:0 local \
2401:db00:20:911a:face:0:25:0 ttl 225 okey 123

Gives MTU of 1430. That is equal to 1500 - 40 - 14 - 4 - 8 - 4.

Signed-off-by: default avatarTom Herbert <tom@herbertland.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent bfca2eba

net/ipv6/ip6_gre.c

+13 −16
Original line number Diff line number Diff line
@@ -700,7 +700,7 @@ static void ip6gre_tnl_link_config(struct ip6_tnl *t, int set_mtu) 
	struct net_device *dev = t->dev;

	struct __ip6_tnl_parm *p = &t->parms;

	struct flowi6 *fl6 = &t->fl.u.ip6;

	int addend = sizeof(struct ipv6hdr) + 4;

	int t_hlen;



	if (dev->type != ARPHRD_ETHER) {

		memcpy(dev->dev_addr, &p->laddr, sizeof(struct in6_addr));
@@ -727,16 +727,11 @@ static void ip6gre_tnl_link_config(struct ip6_tnl *t, int set_mtu) 
	else

		dev->flags &= ~IFF_POINTOPOINT;



	/* Precalculate GRE options length */

	if (t->parms.o_flags&(GRE_CSUM|GRE_KEY|GRE_SEQ)) {

		if (t->parms.o_flags&GRE_CSUM)

			addend += 4;

		if (t->parms.o_flags&GRE_KEY)

			addend += 4;

		if (t->parms.o_flags&GRE_SEQ)

			addend += 4;

	}

	t->hlen = addend;

	t->tun_hlen = gre_calc_hlen(t->parms.o_flags);



	t->hlen = t->tun_hlen;



	t_hlen = t->hlen + sizeof(struct ipv6hdr);



	if (p->flags & IP6_TNL_F_CAP_XMIT) {

		int strict = (ipv6_addr_type(&p->raddr) &
@@ -750,10 +745,11 @@ static void ip6gre_tnl_link_config(struct ip6_tnl *t, int set_mtu) 
			return;



		if (rt->dst.dev) {

			dev->hard_header_len = rt->dst.dev->hard_header_len + addend;

			dev->hard_header_len = rt->dst.dev->hard_header_len +

					       t_hlen;



			if (set_mtu) {

				dev->mtu = rt->dst.dev->mtu - addend;

				dev->mtu = rt->dst.dev->mtu - t_hlen;

				if (!(t->parms.flags & IP6_TNL_F_IGN_ENCAP_LIMIT))

					dev->mtu -= 8;

				if (dev->type == ARPHRD_ETHER)
@@ -1027,11 +1023,12 @@ static int ip6gre_tunnel_init_common(struct net_device *dev) 


	tunnel->tun_hlen = gre_calc_hlen(tunnel->parms.o_flags);



	t_hlen = tunnel->hlen + sizeof(struct ipv6hdr);

	tunnel->hlen = tunnel->tun_hlen;



	dev->needed_headroom	= LL_MAX_HEADER + t_hlen + 4;

	dev->mtu		= ETH_DATA_LEN - t_hlen - 4;

	t_hlen = tunnel->hlen + sizeof(struct ipv6hdr);



	dev->hard_header_len = LL_MAX_HEADER + t_hlen;

	dev->mtu = ETH_DATA_LEN - t_hlen;

	if (!(tunnel->parms.flags & IP6_TNL_F_IGN_ENCAP_LIMIT))

		dev->mtu -= 8;

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