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    SubjectRe: macvtap performs IP defragmentation, causing MTU problems for virtual machines
    Date
    On onsdag 4 oktober 2023 10:00:37 CEST Florian Westphal wrote:
    > Can you submit this formally, with proper changelog and Signed-off-by?
    > See scripts/checkpatch.pl in the kernel tree.
    Sure, i can give it a shot. How do i properly credit you if i submit your
    patch with some small changes of my own?

    > You could also mention in changelog that this is ipv4 only because
    > ipv6 already considers the interface index during reassembly.
    Interesting. I've been trying to understand the code and it seems like
    ipv6 does defragmentation per-interface, while ipv4 does it "per-vrf"
    (correct me if i'm wrong). Is there any reason for this difference?

    I also did some more testing with the diff from my previous mail. It
    looks like the problem remains for interfaces under vrfs. I think simply
    doing the bcast/mcast check first fixes that though, something like this:
    if (skb->pkt_type == PACKET_BROADCAST || skb->pkt_type == PACKET_MULTICAST) {
    if (dev)
    return dev->ifindex;
    }

    return l3mdev_master_ifindex_rcu(dev);
    Does that look reasonable?
    The idea being that bcast/mcast packets are always defragmented
    per-interface, and unicast packets always "per-vrf".

    Thanks,
    Henrik


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