220 lines
5.6 KiB
Groff
220 lines
5.6 KiB
Groff
.\" -*- nroff -*-
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.\"
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.\" Copyright (c) 2001 Boris Popov
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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 DEVELOPERS ``AS IS'' AND ANY EXPRESS OR
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.\" IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
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.\" OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
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.\" IN NO EVENT SHALL THE DEVELOPERS BE LIABLE FOR ANY DIRECT, INDIRECT,
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.\" INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
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.\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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.\" DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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.\" THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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.\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
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.\" THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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.\"
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.\" $FreeBSD$
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.\"
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.Dd February 20, 2001
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.Dt MBCHAIN 9
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.Os
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.Sh NAME
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.Nm mbchain ,
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.Nm mb_init ,
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.Nm mb_initm ,
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.Nm mb_done ,
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.Nm mb_detach ,
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.Nm mb_fixhdr ,
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.Nm mb_reserve ,
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.Nm mb_put_uint8 ,
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.Nm mb_put_uint16be ,
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.Nm mb_put_uint16le ,
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.Nm mb_put_uint32be ,
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.Nm mb_put_uint32le ,
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.Nm mb_put_int64be ,
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.Nm mb_put_int64le ,
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.Nm mb_put_mem ,
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.Nm mb_put_mbuf ,
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.Nm mb_put_uio
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.Nd "set of functions to build an mbuf chain from various data types"
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.Sh SYNOPSIS
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.Cd options LIBMCHAIN
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.Li kldload libmchain
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.Pp
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.Fd #include <sys/param.h>
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.Fd #include <sys/mchain.h>
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.Ft int
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.Fn mb_init "struct mbchain *mbp"
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.Ft void
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.Fn mb_initm "struct mbchain *mbp" "struct mbuf *m"
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.Ft void
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.Fn mb_done "struct mbchain *mbp"
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.Ft struct mbuf *
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.Fn mb_detach "struct mbchain *mbp"
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.Ft int
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.Fn mb_fixhdr "struct mbchain *mbp"
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.Ft caddr_t
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.Fn mb_reserve "struct mbchain *mbp" "int size"
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.Ft int
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.Fn mb_put_uint8 "struct mbchain *mbp" "u_int8_t x"
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.Ft int
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.Fn mb_put_uint16be "struct mbchain *mbp" "u_int16_t x"
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.Ft int
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.Fn mb_put_uint16le "struct mbchain *mbp" "u_int16_t x"
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.Ft int
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.Fn mb_put_uint32be "struct mbchain *mbp" "u_int32_t x"
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.Ft int
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.Fn mb_put_uint32le "struct mbchain *mbp" "u_int32_t x"
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.Ft int
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.Fn mb_put_int64be "struct mbchain *mbp" "int64_t x"
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.Ft int
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.Fn mb_put_int64le "struct mbchain *mbp" "int64_t x"
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.Ft int
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.Fn mb_put_mem "struct mbchain *mbp" "c_caddr_t source" "int size" "int type"
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.Ft int
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.Fn mb_put_mbuf "struct mbchain *mbp" "struct mbuf *m"
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.Ft int
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.Fn mb_put_uio "struct mbchain *mbp" "struct uio *uiop" "int size"
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.Sh DESCRIPTION
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These functions are used to compose mbuf chains from various data types.
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The
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.Vt mbchain
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structure is used as a working context and should be initialized with a call
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to either
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.Fn mb_init
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or
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.Fn mb_initm .
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It has the following fields:
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.Bl -tag -width "mb_count"
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.It Va "mb_top"
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.Vt ( "struct mbuf *" )
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a pointer to the top of constructed mbuf chain
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.It Va mb_cur
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.Vt ( "struct mbuf *" )
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a pointer to the currently filled mbuf
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.It Va mb_mleft
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.Vt ( int )
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number of bytes left in the current mbuf
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.It Va mb_count
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.Vt ( int )
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total number of bytes placed in the mbuf chain
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.It Va mb_copy
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.Vt ( "mb_copy_t *" )
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user-defined function to perform a copy into mbuf;
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useful if any unusual
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data conversion is necessesary
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.It Va mb_udata
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.Vt ( "void *" )
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user-supplied data which can be used in the
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.Va mb_copy
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function
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.El
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.Pp
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.Fn mb_done
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function disposes an mbuf chain pointed to by
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.Fa mbp->mb_top
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field and sets
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the field to
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.Dv NULL .
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.Pp
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.Fn mb_detach
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function returns the value of
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.Fa mbp->mb_top
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field and sets its value to
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.Dv NULL .
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.Pp
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.Fn mb_fixhdr
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recalculates the length of an mbuf chain and updates the
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.Va m_pkthdr.len
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field of the first mbuf in the chain.
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.Pp
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.Fn mb_reserve
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ensures that the object of the length specified by the
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.Fa size
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argument will fit in the current mbuf (mbuf allocation is performed if
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necessary), and advances all pointers as if the real data was placed.
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Returned
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value will point to the beginning of the reserved space.
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Note that the size
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of the object should not exceed
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.Dv MLEN
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bytes.
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.Pp
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All
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.Fn mb_put_*
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functions perform an actual copy of the data into mbuf chain.
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Functions which have
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.Cm le
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or
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.Cm be
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suffixes will perform conversion to the little\- or big\-endian data formats.
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.Pp
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.Fn mb_put_mem
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function copies
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.Fa size
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bytes of data specified by the
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.Fa source
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argument to an mbuf chain.
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The
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.Fa type
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argument specifies the method used to perform a copy,
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and can be one of the following:
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.Bl -tag -width "MB_MINLINE"
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.It Dv MB_MSYSTEM
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use
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.Fn bcopy
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function
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.It Dv MB_MUSER
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use
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.Xr copyin 9
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function
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.It Dv MB_MINLINE
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use an
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.Dq inline
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loop which does not call any function
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.It Dv MB_MZERO
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do not copy any data, but just fill the destination with zero bytes
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.It Dv MB_MCUSTOM
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call function specified by the
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.Fa mbp->mb_copy
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field
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.El
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.Sh RETURN VALUES
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All
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.Ft int
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functions return zero if successful,
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otherwise error code is returned.
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.Pp
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.Em Note :
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after failure of any function, an mbuf chain is left in the broken state,
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and only
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.Fn mb_done
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function can safely be called to destroy it.
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.Sh EXAMPLES
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.Bd -literal
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struct mbchain *mbp;
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struct mbuf *m;
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mb_init(mbp);
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mb_put_uint8(mbp, 33);
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mb_put_uint16le(mbp, length);
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m = m_copym(mbp->mb_top, 0, M_COPYALL, M_TRYWAIT);
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send(m);
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mb_done(mbp);
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.Ed
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.Sh SEE ALSO
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.Xr mbuf 9 ,
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.Xr mdchain 9
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.Sh AUTHORS
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This manual page was written by
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.An Boris Popov Aq bp@FreeBSD.org .
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