• Eric Dumazet's avatar
    ipv4: IP defragmentation must be ECN aware · 6623e3b2
    Eric Dumazet authored
    RFC3168 (The Addition of Explicit Congestion Notification to IP)
    states :
    
    5.3.  Fragmentation
    
       ECN-capable packets MAY have the DF (Don't Fragment) bit set.
       Reassembly of a fragmented packet MUST NOT lose indications of
       congestion.  In other words, if any fragment of an IP packet to be
       reassembled has the CE codepoint set, then one of two actions MUST be
       taken:
    
          * Set the CE codepoint on the reassembled packet.  However, this
            MUST NOT occur if any of the other fragments contributing to
            this reassembly carries the Not-ECT codepoint.
    
          * The packet is dropped, instead of being reassembled, for any
            other reason.
    
    This patch implements this requirement for IPv4, choosing the first
    action :
    
    If one fragment had NO-ECT codepoint
            reassembled frame has NO-ECT
    ElIf one fragment had CE codepoint
            reassembled frame has CE
    Signed-off-by: default avatarEric Dumazet <eric.dumazet@gmail.com>
    Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
    6623e3b2
ip_fragment.c 19 KB