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ipv6: Use 1280 as min MTU for ipv6 forwarding
Clients will set their MTU to 1280 if they receive a ICMPV6_PKT_TOOBIG message with an MTU less than 1280. To allow encapsulating of packets over a 1280 link we should always accept packets with a size of 1280 for forwarding even if the path has a lower MTU and fragment the encapsulated packets afterwards. In case a forwarded packet is not going to be encapsulated a ICMPV6_PKT_TOOBIG msg will still be send by ip6_fragment() with the correct MTU. Signed-off-by: Ulrich Weber <uweber@astaro.com> Signed-off-by: David S. Miller <davem@davemloft.net>
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@ -402,6 +402,7 @@ int ip6_forward(struct sk_buff *skb)
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struct ipv6hdr *hdr = ipv6_hdr(skb);
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struct inet6_skb_parm *opt = IP6CB(skb);
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struct net *net = dev_net(dst->dev);
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u32 mtu;
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if (net->ipv6.devconf_all->forwarding == 0)
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goto error;
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@ -508,10 +509,14 @@ int ip6_forward(struct sk_buff *skb)
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}
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}
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if (skb->len > dst_mtu(dst)) {
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mtu = dst_mtu(dst);
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if (mtu < IPV6_MIN_MTU)
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mtu = IPV6_MIN_MTU;
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if (skb->len > mtu) {
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/* Again, force OUTPUT device used as source address */
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skb->dev = dst->dev;
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icmpv6_send(skb, ICMPV6_PKT_TOOBIG, 0, dst_mtu(dst));
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icmpv6_send(skb, ICMPV6_PKT_TOOBIG, 0, mtu);
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IP6_INC_STATS_BH(net,
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ip6_dst_idev(dst), IPSTATS_MIB_INTOOBIGERRORS);
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IP6_INC_STATS_BH(net,
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@ -621,8 +626,7 @@ static int ip6_fragment(struct sk_buff *skb, int (*output)(struct sk_buff *))
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mtu = ip6_skb_dst_mtu(skb);
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/* We must not fragment if the socket is set to force MTU discovery
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* or if the skb it not generated by a local socket. (This last
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* check should be redundant, but it's free.)
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* or if the skb it not generated by a local socket.
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*/
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if (!skb->local_df) {
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skb->dev = skb_dst(skb)->dev;
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