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ip6_gre: Fix MTU setting

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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: Tom Herbert <tom@herbertland.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Tom Herbert 2016-05-09 17:12:08 -07:00 committed by David S. Miller
parent bfca2eba2a
commit db2ec95d1b
1 changed files with 13 additions and 16 deletions
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29
net/ipv6/ip6_gre.c
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@ -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);
tunnel->hlen = tunnel->tun_hlen;
t_hlen = tunnel->hlen + sizeof(struct ipv6hdr);
dev->needed_headroom = LL_MAX_HEADER + t_hlen + 4;
dev->mtu = ETH_DATA_LEN - t_hlen - 4;
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;