• Michal Kubecek's avatar
    net: ipv4: do not handle duplicate fragments as overlapping · ade44640
    Michal Kubecek authored
    Since commit 7969e5c4 ("ip: discard IPv4 datagrams with overlapping
    segments.") IPv4 reassembly code drops the whole queue whenever an
    overlapping fragment is received. However, the test is written in a way
    which detects duplicate fragments as overlapping so that in environments
    with many duplicate packets, fragmented packets may be undeliverable.
    
    Add an extra test and for (potentially) duplicate fragment, only drop the
    new fragment rather than the whole queue. Only starting offset and length
    are checked, not the contents of the fragments as that would be too
    expensive. For similar reason, linear list ("run") of a rbtree node is not
    iterated, we only check if the new fragment is a subset of the interval
    covered by existing consecutive fragments.
    
    v2: instead of an exact check iterating through linear list of an rbtree
    node, only check if the new fragment is subset of the "run" (suggested
    by Eric Dumazet)
    
    Fixes: 7969e5c4 ("ip: discard IPv4 datagrams with overlapping segments.")
    Signed-off-by: default avatarMichal Kubecek <mkubecek@suse.cz>
    Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
    ade44640
ip_fragment.c 24.5 KB