• Neil Horman's avatar
    net: Generalize socket rx gap / receive queue overflow cmsg · 3b885787
    Neil Horman authored
    Create a new socket level option to report number of queue overflows
    
    Recently I augmented the AF_PACKET protocol to report the number of frames lost
    on the socket receive queue between any two enqueued frames.  This value was
    exported via a SOL_PACKET level cmsg.  AFter I completed that work it was
    requested that this feature be generalized so that any datagram oriented socket
    could make use of this option.  As such I've created this patch, It creates a
    new SOL_SOCKET level option called SO_RXQ_OVFL, which when enabled exports a
    SOL_SOCKET level cmsg that reports the nubmer of times the sk_receive_queue
    overflowed between any two given frames.  It also augments the AF_PACKET
    protocol to take advantage of this new feature (as it previously did not touch
    sk->sk_drops, which this patch uses to record the overflow count).  Tested
    successfully by me.
    
    Notes:
    
    1) Unlike my previous patch, this patch simply records the sk_drops value, which
    is not a number of drops between packets, but rather a total number of drops.
    Deltas must be computed in user space.
    
    2) While this patch currently works with datagram oriented protocols, it will
    also be accepted by non-datagram oriented protocols. I'm not sure if thats
    agreeable to everyone, but my argument in favor of doing so is that, for those
    protocols which aren't applicable to this option, sk_drops will always be zero,
    and reporting no drops on a receive queue that isn't used for those
    non-participating protocols seems reasonable to me.  This also saves us having
    to code in a per-protocol opt in mechanism.
    
    3) This applies cleanly to net-next assuming that commit
    97775007 (my af packet cmsg patch) is reverted
    Signed-off-by: default avatarNeil Horman <nhorman@tuxdriver.com>
    Signed-off-by: default avatarEric Dumazet <eric.dumazet@gmail.com>
    Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
    3b885787
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