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Man Pages


Manual Reference Pages  -  DRBR_FREE (9)

NAME

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

CONTENTS

Synopsis
Description
Return Values
History

SYNOPSIS


.In sys/param.h
.In net/if.h
.In net/if_var.h void drbr_free struct buf_ring *br struct malloc_type *type int drbr_enqueue struct ifnet *ifp struct buf_ring *br struct mbuf *m struct mbuf * drbr_dequeue struct ifnet *ifp struct buf_ring *br struct mbuf * drbr_dequeue_cond struct ifnet *ifp struct buf_ring *br int (*func) (struct mbuf *, void *) void *arg void drbr_flush struct ifnet *ifp struct buf_ring *br int drbr_empty struct ifnet *ifp struct buf_ring *br int drbr_inuse struct ifnet *ifp struct buf_ring *br

DESCRIPTION

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.

RETURN VALUES

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.

HISTORY

These functions were introduced in
.Fx 8.0 .
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