| From: Nicolas Dichtel <nicolas.dichtel@6wind.com> |
| Date: Thu, 31 May 2018 10:59:32 +0200 |
| Subject: ip_tunnel: restore binding to ifaces with a large mtu |
| |
| commit 82612de1c98e610d194e34178bde3cca7dedce41 upstream. |
| |
| After commit f6cc9c054e77, the following conf is broken (note that the |
| default loopback mtu is 65536, ie IP_MAX_MTU + 1): |
| |
| $ ip tunnel add gre1 mode gre local 10.125.0.1 remote 10.125.0.2 dev lo |
| add tunnel "gre0" failed: Invalid argument |
| $ ip l a type dummy |
| $ ip l s dummy1 up |
| $ ip l s dummy1 mtu 65535 |
| $ ip tunnel add gre1 mode gre local 10.125.0.1 remote 10.125.0.2 dev dummy1 |
| add tunnel "gre0" failed: Invalid argument |
| |
| dev_set_mtu() doesn't allow to set a mtu which is too large. |
| First, let's cap the mtu returned by ip_tunnel_bind_dev(). Second, remove |
| the magic value 0xFFF8 and use IP_MAX_MTU instead. |
| 0xFFF8 seems to be there for ages, I don't know why this value was used. |
| |
| With a recent kernel, it's also possible to set a mtu > IP_MAX_MTU: |
| $ ip l s dummy1 mtu 66000 |
| After that patch, it's also possible to bind an ip tunnel on that kind of |
| interface. |
| |
| CC: Petr Machata <petrm@mellanox.com> |
| CC: Ido Schimmel <idosch@mellanox.com> |
| Link: https://git.kernel.org/pub/scm/linux/kernel/git/davem/netdev-vger-cvs.git/commit/?id=e5afd356a411a |
| Fixes: f6cc9c054e77 ("ip_tunnel: Emit events for post-register MTU changes") |
| Signed-off-by: Nicolas Dichtel <nicolas.dichtel@6wind.com> |
| Reviewed-by: Ido Schimmel <idosch@mellanox.com> |
| Signed-off-by: David S. Miller <davem@davemloft.net> |
| [bwh: Backported to 3.16: |
| - Drop change in ip_tunnel_create() |
| - Adjust context] |
| Signed-off-by: Ben Hutchings <ben@decadent.org.uk> |
| --- |
| --- a/net/ipv4/ip_tunnel.c |
| +++ b/net/ipv4/ip_tunnel.c |
| @@ -387,7 +387,7 @@ static int ip_tunnel_bind_dev(struct net |
| |
| if (tdev) { |
| hlen = tdev->hard_header_len + tdev->needed_headroom; |
| - mtu = tdev->mtu; |
| + mtu = min(tdev->mtu, IP_MAX_MTU); |
| } |
| dev->iflink = tunnel->parms.link; |
| |
| @@ -851,7 +851,7 @@ int ip_tunnel_change_mtu(struct net_devi |
| int t_hlen = tunnel->hlen + sizeof(struct iphdr); |
| |
| if (new_mtu < 68 || |
| - new_mtu > 0xFFF8 - dev->hard_header_len - t_hlen) |
| + new_mtu > IP_MAX_MTU - dev->hard_header_len - t_hlen) |
| return -EINVAL; |
| dev->mtu = new_mtu; |
| return 0; |
| @@ -979,7 +979,7 @@ int ip_tunnel_newlink(struct net_device |
| |
| mtu = ip_tunnel_bind_dev(dev); |
| if (tb[IFLA_MTU]) { |
| - unsigned int max = 0xfff8 - dev->hard_header_len - nt->hlen; |
| + unsigned int max = IP_MAX_MTU - dev->hard_header_len - nt->hlen; |
| |
| mtu = clamp(dev->mtu, (unsigned int)ETH_MIN_MTU, |
| (unsigned int)(max - sizeof(struct iphdr))); |