[PATCH net 3/3] sit: fix IFLA_MTU ignored on NEWLINK

[Xin Long]

Commit 128bb975dc3c ("ip6_gre: init dev->mtu and dev->hard_header_len
correctly") fixed IFLA_MTU ignored on NEWLINK for ip6_gre. The same
mtu fix is also needed for sit.

Note that dev->hard_header_len setting for sit works fine, no need to
fix it. sit is actually ipv4 tunnel, it can't call ip6_tnl_change_mtu
to set mtu.

Reported-by: Jianlin Shi <ji...@redhat.com>
Signed-off-by: Xin Long <lucien....@gmail.com>
---
 net/ipv6/sit.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/net/ipv6/sit.c b/net/ipv6/sit.c
index 3a1775a..0195598 100644
--- a/net/ipv6/sit.c
+++ b/net/ipv6/sit.c
@@ -1578,6 +1578,13 @@ static int ipip6_newlink(struct net *src_net, struct 
net_device *dev,
        if (err < 0)
                return err;
 
+       if (tb[IFLA_MTU]) {
+               u32 mtu = nla_get_u32(tb[IFLA_MTU]);
+
+               if (mtu >= IPV6_MIN_MTU && mtu <= 0xFFF8 - dev->hard_header_len)
+                       dev->mtu = mtu;
+       }
+
 #ifdef CONFIG_IPV6_SIT_6RD
        if (ipip6_netlink_6rd_parms(data, &ip6rd))
                err = ipip6_tunnel_update_6rd(nt, &ip6rd);
-- 
2.1.0