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

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[ Upstream commit 82a40777de12728dedf4075453b694f0d1baee80 ]

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: c9fefa08190f ("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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Xin Long 2018-08-05 22:46:07 +08:00 committed by Greg Kroah-Hartman
parent 59f9f2c76f
commit b3fb939872
1 changed files with 2 additions and 6 deletions
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8
net/ipv6/ip6_tunnel.c
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@ -1134,12 +1134,8 @@ route_lookup:
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)) {