From: Hangbin Liu liuhangbin@gmail.com
commit 9992a078b1771da354ac1f9737e1e639b687caa2 upstream.
Commit 28e104d00281 ("net: ip_tunnel: fix mtu calculation") removed dev->hard_header_len subtraction when calculate MTU for tunnel devices as there is an overhead for device that has header_ops.
But there are ETHER tunnel devices, like gre_tap or erspan, which don't have header_ops but set dev->hard_header_len during setup. This makes pkts greater than (MTU - ETH_HLEN) could not be xmited. Fix it by subtracting the ETHER tunnel devices' dev->hard_header_len for MTU calculation.
Fixes: 28e104d00281 ("net: ip_tunnel: fix mtu calculation") Reported-by: Jianlin Shi jishi@redhat.com Signed-off-by: Hangbin Liu liuhangbin@gmail.com Signed-off-by: David S. Miller davem@davemloft.net Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- net/ipv4/ip_tunnel.c | 18 +++++++++++++++--- 1 file changed, 15 insertions(+), 3 deletions(-)
--- a/net/ipv4/ip_tunnel.c +++ b/net/ipv4/ip_tunnel.c @@ -317,7 +317,7 @@ static int ip_tunnel_bind_dev(struct net }
dev->needed_headroom = t_hlen + hlen; - mtu -= t_hlen; + mtu -= t_hlen + (dev->type == ARPHRD_ETHER ? dev->hard_header_len : 0);
if (mtu < IPV4_MIN_MTU) mtu = IPV4_MIN_MTU; @@ -348,6 +348,9 @@ static struct ip_tunnel *ip_tunnel_creat t_hlen = nt->hlen + sizeof(struct iphdr); dev->min_mtu = ETH_MIN_MTU; dev->max_mtu = IP_MAX_MTU - t_hlen; + if (dev->type == ARPHRD_ETHER) + dev->max_mtu -= dev->hard_header_len; + ip_tunnel_add(itn, nt); return nt;
@@ -495,11 +498,14 @@ static int tnl_update_pmtu(struct net_de
tunnel_hlen = md ? tunnel_hlen : tunnel->hlen; pkt_size = skb->len - tunnel_hlen; + pkt_size -= dev->type == ARPHRD_ETHER ? dev->hard_header_len : 0;
- if (df) + if (df) { mtu = dst_mtu(&rt->dst) - (sizeof(struct iphdr) + tunnel_hlen); - else + mtu -= dev->type == ARPHRD_ETHER ? dev->hard_header_len : 0; + } else { mtu = skb_valid_dst(skb) ? dst_mtu(skb_dst(skb)) : dev->mtu; + }
if (skb_valid_dst(skb)) skb_dst_update_pmtu_no_confirm(skb, mtu); @@ -965,6 +971,9 @@ int __ip_tunnel_change_mtu(struct net_de int t_hlen = tunnel->hlen + sizeof(struct iphdr); int max_mtu = IP_MAX_MTU - t_hlen;
+ if (dev->type == ARPHRD_ETHER) + max_mtu -= dev->hard_header_len; + if (new_mtu < ETH_MIN_MTU) return -EINVAL;
@@ -1142,6 +1151,9 @@ int ip_tunnel_newlink(struct net_device if (tb[IFLA_MTU]) { unsigned int max = IP_MAX_MTU - (nt->hlen + sizeof(struct iphdr));
+ if (dev->type == ARPHRD_ETHER) + max -= dev->hard_header_len; + mtu = clamp(dev->mtu, (unsigned int)ETH_MIN_MTU, max); }