Manual Pages  — DRBR

#include <sys/param.h>

#include <net/if.h>

#include <net/if_var.h>

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.