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authorNicolas Dichtel <nicolas.dichtel@6wind.com>2018-05-31 10:59:32 +0200
committerBen Hutchings <ben@decadent.org.uk>2018-10-21 08:46:22 +0100
commit95bd9e47cd54136c0eed9f2176243f0160db7754 (patch)
treea5947500d00fb35e8a3a67d3a9f7689ec66fe00a
parent19d751c873288da008fe4bef536ef0c4b5d21504 (diff)
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>
-rw-r--r--net/ipv4/ip_tunnel.c6
1 files changed, 3 insertions, 3 deletions
diff --git a/net/ipv4/ip_tunnel.c b/net/ipv4/ip_tunnel.c
index 1e6b8734dcf2..32f685b35302 100644
--- a/net/ipv4/ip_tunnel.c
+++ b/net/ipv4/ip_tunnel.c
@@ -387,7 +387,7 @@ static int ip_tunnel_bind_dev(struct net_device *dev)
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_device *dev, int new_mtu)
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 *dev, struct nlattr *tb[],
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)));