• Daniel Borkmann's avatar
    packet: nlmon: virtual netlink monitoring device for packet sockets · e4fc408e
    Daniel Borkmann authored
    Currently, there is no good possibility to debug netlink traffic that
    is being exchanged between kernel and user space. Therefore, this patch
    implements a netlink virtual device, so that netlink messages will be
    made visible to PF_PACKET sockets. Once there was an approach with a
    similar idea [1], but it got forgotten somehow.
    
    I think it makes most sense to accept the "overhead" of an extra netlink
    net device over implementing the same functionality from PF_PACKET
    sockets once again into netlink sockets. We have BPF filters that can
    already be easily applied which even have netlink extensions, we have
    RX_RING zero-copy between kernel- and user space that can be reused,
    and much more features. So instead of re-implementing all of this, we
    simply pass the skb to a given PF_PACKET socket for further analysis.
    
    Another nice benefit that comes from that is that no code needs to be
    changed in user space packet analyzers (maybe adding a dissector, but
    not more), thus out of the box, we can already capture pcap files of
    netlink traffic to debug/troubleshoot netlink problems.
    
    Also thanks goes to Thomas Graf, Flavio Leitner, Jesper Dangaard Brouer.
    
     [1] http://marc.info/?l=linux-netdev&m=113813401516110
    
    Signed-off-by: default avatarDaniel Borkmann <dborkman@redhat.com>
    Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
    e4fc408e