drbr, drbr_free, drbr_enqueue, drbr_dequeue, drbr_dequeue_cond, drbr_flush, drbr_empty, drbr_inuse, —

       The  drbr functions provide an API to network drivers for using buf_ring(9) for enqueueing and dequeueing
       packets.  This is meant as a replacement for the IFQ interface for packet queuing.  It allows a packet to
       be enqueued with a single atomic and packet dequeue to be done without any per-packet atomics  as  it  is
       protected  by  the driver's tx queue lock.  If INVARIANTS is enabled, drbr_dequeue() will assert that the
       tx queue lock is held when it is called.

       The drbr_free() function frees all the enqueued mbufs and then frees the buf_ring.

       The drbr_enqueue() function is used to enqueue an mbuf to a buf_ring, falling back to the ifnet's IFQ  if
       ALTQ(4) is enabled.

       The  drbr_dequeue()  function  is used to dequeue an mbuf from a buf_ring or, if ALTQ(4) is enabled, from
       the ifnet's IFQ.

       The drbr_dequeue_cond() function is used to conditionally dequeue  an  mbuf  from  a  buf_ring  based  on
       whether func returns TRUE or FALSE.

       The drbr_flush() function frees all mbufs enqueued in the buf_ring and the ifnet's IFQ.

       The drbr_empty() function returns TRUE if there are no mbufs enqueued, FALSE otherwise.

       The drbr_inuse() function returns the number of mbufs enqueued.  Note to users that this is intrinsically
       racy  as  there is no guarantee that there will not be more mbufs when drbr_dequeue() is actually called.
       Provided the tx queue lock is held there will not be less.

       These functions were introduced in FreeBSD 8.0.

Debian                                         September 27, 2012                                        DRBR(9)

       drbr,  drbr_free,  drbr_enqueue,  drbr_dequeue,  drbr_dequeue_cond, drbr_flush, drbr_empty, drbr_inuse, —
       network driver interface to buf_ring

       The drbr_enqueue() function returns ENOBUFS if there are no slots available in  the  buf_ring  and  0  on
       success.

       The  drbr_dequeue()  and drbr_dequeue_cond() functions return an mbuf on success and NULL if the buf_ring
       is empty.

#include<sys/param.h>#include<net/if.h>#include<net/if_var.h>voiddrbr_free(structbuf_ring*br, structmalloc_type*type);

       intdrbr_enqueue(structifnet*ifp, structbuf_ring*br, structmbuf*m);

       structmbuf*drbr_dequeue(structifnet*ifp, structbuf_ring*br);

       structmbuf*drbr_dequeue_cond(structifnet*ifp,  structbuf_ring*br,  int(*func)(structmbuf*,void*),
           void*arg);

       voiddrbr_flush(structifnet*ifp, structbuf_ring*br);

       intdrbr_empty(structifnet*ifp, structbuf_ring*br);

       intdrbr_inuse(structifnet*ifp, structbuf_ring*br);