• Jon Maloy's avatar
    tipc: fix bug in multicast congestion handling · 908344cd
    Jon Maloy authored
    One aim of commit 50100a5e ("tipc:
    use pseudo message to wake up sockets after link congestion") was
    to handle link congestion abatement in a uniform way for both unicast
    and multicast transmit. However, the latter doesn't work correctly,
    and has been broken since the referenced commit was applied.
    
    If a user now sends a burst of multicast messages that is big
    enough to cause broadcast link congestion, it will be put to sleep,
    and not be waked up when the congestion abates as it should be.
    
    This has two reasons. First, the flag that is used, TIPC_WAKEUP_USERS,
    is set correctly, but in the wrong field. Instead of setting it in the
    'action_flags' field of the arrival node struct, it is by mistake set
    in the dummy node struct that is owned by the broadcast link, where it
    will never tested for. Second, we cannot use the same flag for waking
    up unicast and multicast users, since the function tipc_node_unlock()
    needs to pick the wakeup pseudo messages to deliver from different
    queues. It must hence be able to distinguish between the two cases.
    
    This commit solves this problem by adding a new flag
    TIPC_WAKEUP_BCAST_USERS, and a new function tipc_bclink_wakeup_user().
    The latter is to be called by tipc_node_unlock() when the named flag,
    now set in the correct field, is encountered.
    
    v2: using explicit 'unsigned int' declaration instead of 'uint', as
    per comment from David Miller.
    Signed-off-by: default avatarJon Maloy <jon.maloy@ericsson.com>
    Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
    908344cd
node.c 15.6 KB