• Jarek Poplawski's avatar
    net_sched: Add qdisc __NET_XMIT_STOLEN flag · 378a2f09
    Jarek Poplawski authored
    Patrick McHardy <kaber@trash.net> noticed:
    "The other problem that affects all qdiscs supporting actions is
    TC_ACT_QUEUED/TC_ACT_STOLEN getting mapped to NET_XMIT_SUCCESS
    even though the packet is not queued, corrupting upper qdiscs'
    qlen counters."
    
    and later explained:
    "The reason why it translates it at all seems to be to not increase
    the drops counter. Within a single qdisc this could be avoided by
    other means easily, upper qdiscs would still increase the counter
    when we return anything besides NET_XMIT_SUCCESS though.
    
    This means we need a new NET_XMIT return value to indicate this to
    the upper qdiscs. So I'd suggest to introduce NET_XMIT_STOLEN,
    return that to upper qdiscs and translate it to NET_XMIT_SUCCESS
    in dev_queue_xmit, similar to NET_XMIT_BYPASS."
    
    David Miller <davem@davemloft.net> noticed:
    "Maybe these NET_XMIT_* values being passed around should be a set of
    bits. They could be composed of base meanings, combined with specific
    attributes.
    
    So you could say "NET_XMIT_DROP | __NET_XMIT_NO_DROP_COUNT"
    
    The attributes get masked out by the top-level ->enqueue() caller,
    such that the base meanings are the only thing that make their
    way up into the stack. If it's only about communication within the
    qdisc tree, let's simply code it that way."
    
    This patch is trying to realize these ideas.
    Signed-off-by: default avatarJarek Poplawski <jarkao2@gmail.com>
    Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
    378a2f09
sch_netem.c 17 KB