Commit 82a40777 authored Aug 05, 2018 by Xin Long Committed by David S. Miller Aug 05, 2018

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: c9fefa08 ("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>

parent e70a3aad

net/ipv6/ip6_tunnel.c

+2 −6

Original line number	Diff line number	Diff line
		@@ -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);

		skb_dst_update_pmtu(skb, mtu);
		if (skb->len - t->tun_hlen - eth_hlen > mtu && !skb_is_gso(skb)) {

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