[PATCH 4.14 163/496] ip_gre: fix IFLA_MTU ignored on NEWLINK

From: Greg Kroah-Hartman
Date: Mon May 28 2018 - 06:48:43 EST


4.14-stable review patch. If anyone has any objections, please let me know.

------------------

From: Xin Long <lucien.xin@xxxxxxxxx>

[ Upstream commit ffc2b6ee417435605ee8bb1eb4c8f02e9ff4b4a5 ]

It's safe to remove the setting of dev's needed_headroom and mtu in
__gre_tunnel_init, as discussed in [1], ip_tunnel_newlink can do it
properly.

Now Eric noticed that it could cover the mtu value set in do_setlink
when creating a ip_gre dev. It makes IFLA_MTU param not take effect.

So this patch is to remove them to make IFLA_MTU work, as in other
ipv4 tunnels.

[1]: https://patchwork.ozlabs.org/patch/823504/

Fixes: c54419321455 ("GRE: Refactor GRE tunneling code.")
Reported-by: Eric Garver <e@xxxxxxx>
Signed-off-by: Xin Long <lucien.xin@xxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Sasha Levin <alexander.levin@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
net/ipv4/ip_gre.c | 5 -----
1 file changed, 5 deletions(-)

--- a/net/ipv4/ip_gre.c
+++ b/net/ipv4/ip_gre.c
@@ -951,9 +951,6 @@ static void __gre_tunnel_init(struct net

t_hlen = tunnel->hlen + sizeof(struct iphdr);

- dev->needed_headroom = LL_MAX_HEADER + t_hlen + 4;
- dev->mtu = ETH_DATA_LEN - t_hlen - 4;
-
dev->features |= GRE_FEATURES;
dev->hw_features |= GRE_FEATURES;

@@ -1253,8 +1250,6 @@ static int erspan_tunnel_init(struct net
sizeof(struct erspanhdr);
t_hlen = tunnel->hlen + sizeof(struct iphdr);

- dev->needed_headroom = LL_MAX_HEADER + t_hlen + 4;
- dev->mtu = ETH_DATA_LEN - t_hlen - 4;
dev->features |= GRE_FEATURES;
dev->hw_features |= GRE_FEATURES;
dev->priv_flags |= IFF_LIVE_ADDR_CHANGE;