4.9-stable review patch. If anyone has any objections, please let me know.
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From: Xin Long lucien.xin@gmail.com
[ 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 --- net/ipv6/ip6_tunnel.c | 8 ++------ 1 file changed, 2 insertions(+), 6 deletions(-)
--- a/net/ipv6/ip6_tunnel.c +++ b/net/ipv6/ip6_tunnel.c @@ -1133,12 +1133,8 @@ 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);
if (skb_dst(skb) && !t->parms.collect_md) skb_dst(skb)->ops->update_pmtu(skb_dst(skb), NULL, skb, mtu);