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ip6_tunnel: use the right value for ipv4 min mtu check in ip6_tnl_xmit 

According to RFC791, 68 bytes is the minimum size of IPv4 datagram every
device must be able to forward without further fragmentation while 576
bytes is the minimum size of IPv4 datagram every device has to be able
to receive, so in ip6_tnl_xmit(), 68(IPV4_MIN_MTU) should be the right
value for the ipv4 min mtu check in ip6_tnl_xmit.

While at it, change to use max() instead of if statement.

Fixes: c9fefa0819 ("ip6_tunnel: get the min mtu properly in ip6_tnl_xmit")
Reported-by: Sabrina Dubroca <sd@queasysnail.net>
Signed-off-by: Xin Long <lucien.xin@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Xin Long 2018-08-05 22:46:07 +08:00 committed by David S. Miller
parent e70a3aad44
commit 82a40777de
1 changed files with 2 additions and 6 deletions
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8
net/ipv6/ip6_tunnel.c
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@ -1133,12 +1133,8 @@ int ip6_tnl_xmit(struct sk_buff *skb, struct net_device *dev, __u8 dsfield,
max_headroom += 8;
mtu -= 8;
}
if (skb->protocol == htons(ETH_P_IPV6)) {
if (mtu < IPV6_MIN_MTU)
mtu = IPV6_MIN_MTU;
} else if (mtu < 576) {
mtu = 576;
}
mtu = max(mtu, skb->protocol == htons(ETH_P_IPV6) ?
IPV6_MIN_MTU : IPV4_MIN_MTU);
skb_dst_update_pmtu(skb, mtu);
if (skb->len - t->tun_hlen - eth_hlen > mtu && !skb_is_gso(skb)) {