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Florian Westphal authored
since commit 6aafeef0 ("netfilter: push reasm skb through instead of original frag skbs") we will end up sometimes re-fragmenting skbs that we've reassembled. ipv6 defrag preserves the original skbs using the skb frag list, i.e. as long as the skb frag list is preserved there is no problem since we keep original geometry of fragments intact. However, in the rare case where the frag list is munged or skb is linearized, we might send larger fragments than what we originally received. A router in the path might then send packet-too-big errors even if sender never sent fragments exceeding the reported mtu: mtu 1500 - 1500:1400 - 1400:1280 - 1280 A R1 R2 B 1 - A sends to B, fragment size 1400 2 - R2 sends pkttoobig error for 1280 3 - A sends to B, fragment size 1280 4 - R2 sends pkttoobig error for 1280 again because it sees fragments of size 1400. make sure ip6_fragment always caps MTU at largest packet size seen when defragmented skb is forwarded. Acked-by:
Hannes Frederic Sowa <hannes@stressinduktion.org> Signed-off-by:
Florian Westphal <fw@strlen.de> Signed-off-by:
David S. Miller <davem@davemloft.net>
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