From db2ec95d1ba419b766aae7b1d7c0271f3c9cd9f4 Mon Sep 17 00:00:00 2001 From: Tom Herbert Date: Mon, 9 May 2016 17:12:08 -0700 Subject: [PATCH] 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: Tom Herbert Signed-off-by: David S. Miller --- net/ipv6/ip6_gre.c | 29 +++++++++++++---------------- 1 file changed, 13 insertions(+), 16 deletions(-) diff --git a/net/ipv6/ip6_gre.c b/net/ipv6/ip6_gre.c index 47b671a46dc4..6d0aa94cf59a 100644 --- a/net/ipv6/ip6_gre.c +++ b/net/ipv6/ip6_gre.c @@ -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; -- 2.20.1