NAME¶
mdchain
,
md_initm
,
md_done
,
md_append_record
,
md_next_record
,
md_get_uint8
,
md_get_uint16
,
md_get_uint16be
,
md_get_uint16le
,
md_get_uint32
,
md_get_uint32be
,
md_get_uint32le
,
md_get_int64
,
md_get_int64be
,
md_get_int64le
,
md_get_mem
,
md_get_mbuf
,
md_get_uio
—
set of functions to dissect an mbuf chain to various
data types
SYNOPSIS¶
options LIBMCHAIN
kldload
libmchain
#include
<sys/param.h>
#include
<sys/uio.h>
#include
<sys/mchain.h>
void
md_initm
(
struct
mdchain *mdp,
struct mbuf *m);
void
md_done
(
struct
mdchain *mdp);
void
md_append_record
(
struct
mdchain *mdp,
struct mbuf
*top);
int
md_next_record
(
struct
mdchain *mdp);
int
md_get_uint8
(
struct
mdchain *mdp,
uint8_t *x);
int
md_get_uint16
(
struct
mdchain *mdp,
uint16_t *x);
int
md_get_uint16be
(
struct
mdchain *mdp,
uint16_t *x);
int
md_get_uint16le
(
struct
mdchain *mdp,
uint16_t *x);
int
md_get_uint32
(
struct
mdchain *mdp,
uint32_t *x);
int
md_get_uint32be
(
struct
mdchain *mdp,
uint32_t *x);
int
md_get_uint32le
(
struct
mdchain *mdp,
uint32_t *x);
int
md_get_int64
(
struct
mdchain *mdp,
int64_t *x);
int
md_get_int64be
(
struct
mdchain *mdp,
int64_t *x);
int
md_get_int64le
(
struct
mdchain *mdp,
int64_t *x);
int
md_get_mem
(
struct
mdchain *mdp,
caddr_t target,
int size,
int type);
int
md_get_mbuf
(
struct
mdchain *mdp,
int size,
struct mbuf
**m);
int
md_get_uio
(
struct
mdchain *mdp,
struct uio
*uiop,
int
size);
DESCRIPTION¶
These functions are used to decompose mbuf chains to various data types. The
mdchain structure is used as a working
context and should be initialized through a call of the
mb_initm
() function. It has the following
fields:
- md_top
- (struct mbuf *) A pointer to the top of
the parsed mbuf chain.
- md_cur
- (struct mbuf *) A pointer to the
currently parsed mbuf.
- md_pas
- (int) Offset in the current mbuf.
The
md_done
() function disposes of an mbuf
chain pointed to by the
mdp->md_top field
and sets the field to
NULL
.
The
md_append_record
() appends a new mbuf
chain using
m_nextpkt field to form a single
linked list of mbuf chains. If the
mdp->md_top field is
NULL
, then this function behaves exactly as
the
md_initm
() function.
The
md_next_record
() function extracts the
next mbuf chain and disposes the current one, if any. For a new mbuf chain it
calls the
md_initm
() function. If there is
no data left the function returns
ENOENT
.
All
md_get_*
() functions perform an actual
copy of the data from an mbuf chain. Functions which have
le
or
be
suffixes will perform conversion to the little- or big-endian data formats.
md_get_mem
() function copies
size bytes of data specified by the
source argument from an mbuf chain. The
type argument specifies the method used to
perform a copy, and can be one of the following:
MB_MSYSTEM
- Use the
bcopy
() function.
MB_MUSER
- Use the copyin(9) function.
MB_MINLINE
- Use an “inline” loop which does not call any function.
If
target is
NULL
, an actual copy is not performed and
the function just skips the given number of bytes.
RETURN VALUES¶
All
int functions return zero if successful,
otherwise an error code is returned.
Note: after failure of any function, an mbuf chain
is left in the broken state and only the
md_done
() function can safely be called to
destroy it.
EXAMPLES¶
struct mdchain *mdp;
struct mbuf *m;
uint16_t length;
uint8_t byte;
receive(so, &m);
md_initm(mdp, m);
if (md_get_uint8(mdp, &byte) != 0 ||
md_get_uint16le(mdp, &length) != 0)
error = EBADRPC;
mb_done(mdp);
SEE ALSO¶
mbchain(9),
mbuf(9)
AUTHORS¶
This manual page was written by
Boris Popov
⟨bp@FreeBSD.org⟩.