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Merge branch 'tunnel-mtus'
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Nicolas Dichtel says:

====================
ip[6] tunnels: fix mtu calculations

The first patch restores the possibility to bind an ip4 tunnel to an
interface whith a large mtu.
The second patch was spotted after the first fix. I also target it to net
because it fixes the max mtu value that can be used for ipv6 tunnels.

v2: remove the 0xfff8 in ip_tunnel_newlink()
====================

Signed-off-by: David S. Miller <davem@davemloft.net>
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@davem330
davem330 committed Jun 1, 2018
2 parents ccfde6e + f7ff1fd commit 8a11801
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Showing 3 changed files with 15 additions and 9 deletions.
8 changes: 4 additions & 4 deletions net/ipv4/ip_tunnel.c
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Original file line number Diff line number Diff line change
Expand Up @@ -328,7 +328,7 @@ 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->needed_headroom = t_hlen + hlen;
Expand Down Expand Up @@ -362,7 +362,7 @@ static struct ip_tunnel *ip_tunnel_create(struct net *net,
nt = netdev_priv(dev);
t_hlen = nt->hlen + sizeof(struct iphdr);
dev->min_mtu = ETH_MIN_MTU;
dev->max_mtu = 0xFFF8 - dev->hard_header_len - t_hlen;
dev->max_mtu = IP_MAX_MTU - dev->hard_header_len - t_hlen;
ip_tunnel_add(itn, nt);
return nt;

Expand Down Expand Up @@ -930,7 +930,7 @@ int __ip_tunnel_change_mtu(struct net_device *dev, int new_mtu, bool strict)
{
struct ip_tunnel *tunnel = netdev_priv(dev);
int t_hlen = tunnel->hlen + sizeof(struct iphdr);
int max_mtu = 0xFFF8 - dev->hard_header_len - t_hlen;
int max_mtu = IP_MAX_MTU - dev->hard_header_len - t_hlen;

if (new_mtu < ETH_MIN_MTU)
return -EINVAL;
Expand Down Expand Up @@ -1107,7 +1107,7 @@ 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)));
Expand Down
11 changes: 8 additions & 3 deletions net/ipv6/ip6_tunnel.c
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Original file line number Diff line number Diff line change
Expand Up @@ -1692,8 +1692,13 @@ int ip6_tnl_change_mtu(struct net_device *dev, int new_mtu)
if (new_mtu < ETH_MIN_MTU)
return -EINVAL;
}
if (new_mtu > 0xFFF8 - dev->hard_header_len)
return -EINVAL;
if (tnl->parms.proto == IPPROTO_IPV6 || tnl->parms.proto == 0) {
if (new_mtu > IP6_MAX_MTU - dev->hard_header_len)
return -EINVAL;
} else {
if (new_mtu > IP_MAX_MTU - dev->hard_header_len)
return -EINVAL;
}
dev->mtu = new_mtu;
return 0;
}
Expand Down Expand Up @@ -1841,7 +1846,7 @@ ip6_tnl_dev_init_gen(struct net_device *dev)
if (!(t->parms.flags & IP6_TNL_F_IGN_ENCAP_LIMIT))
dev->mtu -= 8;
dev->min_mtu = ETH_MIN_MTU;
dev->max_mtu = 0xFFF8 - dev->hard_header_len;
dev->max_mtu = IP6_MAX_MTU - dev->hard_header_len;

return 0;

Expand Down
5 changes: 3 additions & 2 deletions net/ipv6/sit.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -1371,7 +1371,7 @@ static void ipip6_tunnel_setup(struct net_device *dev)
dev->hard_header_len = LL_MAX_HEADER + t_hlen;
dev->mtu = ETH_DATA_LEN - t_hlen;
dev->min_mtu = IPV6_MIN_MTU;
dev->max_mtu = 0xFFF8 - t_hlen;
dev->max_mtu = IP6_MAX_MTU - t_hlen;
dev->flags = IFF_NOARP;
netif_keep_dst(dev);
dev->addr_len = 4;
Expand Down Expand Up @@ -1583,7 +1583,8 @@ static int ipip6_newlink(struct net *src_net, struct net_device *dev,
if (tb[IFLA_MTU]) {
u32 mtu = nla_get_u32(tb[IFLA_MTU]);

if (mtu >= IPV6_MIN_MTU && mtu <= 0xFFF8 - dev->hard_header_len)
if (mtu >= IPV6_MIN_MTU &&
mtu <= IP6_MAX_MTU - dev->hard_header_len)
dev->mtu = mtu;
}

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