148 lines
4.2 KiB
Groff
148 lines
4.2 KiB
Groff
.\" Copyright (c) 2009 Bitgravity Inc
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.\" Written by: Kip Macy <kmacy@@FreeBSD.org>
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.\" All rights reserved.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
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.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
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.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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.\" SUCH DAMAGE.
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.\"
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.\" $FreeBSD$
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.\"
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.Dd January 30, 2012
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.Dt DRBR 9
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.Os
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.Sh NAME
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.Nm drbr ,
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.Nm drbr_free ,
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.Nm drbr_enqueue ,
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.Nm drbr_dequeue ,
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.Nm drbr_dequeue_cond ,
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.Nm drbr_flush ,
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.Nm drbr_empty ,
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.Nm drbr_inuse ,
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.Nm drbr_stats_update ,
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.Nd network driver interface to buf_ring
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.Sh SYNOPSIS
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.In sys/param.h
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.In net/if.h
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.In net/if_var.h
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.Ft void
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.Fn drbr_free "struct buf_ring *br" "struct malloc_type *type"
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.Ft int
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.Fn drbr_enqueue "struct ifnet *ifp" "struct buf_ring *br" "struct mbuf *m"
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.Ft struct mbuf *
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.Fn drbr_dequeue "struct ifnet *ifp" "struct buf_ring *br"
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.Ft struct mbuf *
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.Fn drbr_dequeue_cond "struct ifnet *ifp" "struct buf_ring *br" "int (*func) (struct mbuf *, void *)" "void *arg"
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.Ft void
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.Fn drbr_flush "struct ifnet *ifp" "struct buf_ring *br"
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.Ft int
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.Fn drbr_empty "struct ifnet *ifp" "struct buf_ring *br"
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.Ft int
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.Fn drbr_inuse "struct ifnet *ifp" "struct buf_ring *br"
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.Ft void
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.Fn drbr_stats_update "struct ifnet *ifp" "int len" "int mflags"
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.Sh DESCRIPTION
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The
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.Nm
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functions provide an API to network drivers for using
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.Xr buf_ring 9
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for enqueueing and dequeueing packets.
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This is meant as a replacement for the IFQ interface for packet queuing.
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It allows a packet to be enqueued with a single atomic and packet
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dequeue to be done without any per-packet atomics as it is protected
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by the driver's tx queue lock.
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If
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.Dv INVARIANTS
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is enabled,
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.Fn drbr_dequeue
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will assert that the tx queue lock is held when it is called.
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.Pp
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The
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.Fn drbr_free
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function frees all the enqueued mbufs and then frees the buf_ring.
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.Pp
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The
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.Fn drbr_enqueue
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function is used to enqueue an mbuf to a buf_ring, falling back to the
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ifnet's IFQ if
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.Xr ALTQ 4
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is enabled.
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.Pp
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The
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.Fn drbr_dequeue
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function is used to dequeue an mbuf from a buf_ring or, if
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.Xr ALTQ 4
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is enabled, from the ifnet's IFQ.
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.Pp
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The
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.Fn drbr_dequeue_cond
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function is used to conditionally dequeue an mbuf from a buf_ring based
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on whether
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.Fa func
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returns
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.Dv TRUE
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or
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.Dv FALSE .
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.Pp
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The
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.Fn drbr_flush
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function frees all mbufs enqueued in the buf_ring and the ifnet's IFQ.
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.Pp
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The
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.Fn drbr_empty
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function returns
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.Dv TRUE
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if there are no mbufs enqueued,
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.Dv FALSE
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otherwise.
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.Pp
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The
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.Fn drbr_inuse
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function returns the number of mbufs enqueued.
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Note to users that this is intrinsically racy as there is no guarantee that
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there will not be more mbufs when
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.Fn drbr_dequeue
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is actually called.
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Provided the tx queue lock is held there will not be less.
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.Pp
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The
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.Fn drbr_stats_update
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function updates the number of bytes and the number of multicast packets sent.
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.Sh RETURN VALUES
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The
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.Fn drbr_enqueue
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function returns
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.Er ENOBUFS
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if there are no slots available in the buf_ring and
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.Dv 0
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on success.
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.Pp
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The
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.Fn drbr_dequeue
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and
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.Fn drbr_dequeue_cond
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functions return an mbuf on success and
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.Dv NULL
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if the buf_ring is empty.
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.Sh HISTORY
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These functions were introduced in
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.Fx 8.0 .
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