drbr_empty (9)

Leading comments

Copyright (c) 2009 Bitgravity Inc
Written by: Kip Macy <kmacy@@FreeBSD.org>
All rights reserved.

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modification, are permitted provided that the following conditions
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   notice, this list of conditions and the following disclaimer.
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   notice, this list of conditions and the following dis...

(The comments found at the beginning of the groff file "man9/drbr_empty.9freebsd".)

NAME

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

SYNOPSIS

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

DESCRIPTION

The ifconfig functions provide an API to network drivers for using buf_ring9 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, Fn drbr_dequeue will assert that the tx queue lock is held when it is called.

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

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

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

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

The Fn 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 Fn drbr_dequeue is actually called. Provided the tx queue lock is held there will not be less.

RETURN VALUES

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

The Fn drbr_dequeue and Fn 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 .