mdchain9
Set of functions to dissect an mbuf chain to various data types
Part of md_append_record(9).
Usage
options LIBMCHAIN
kldload
libmchain
void
void
void
int
int
int
int
int
int
int
int
int
int
int
int
int
int
Overview
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);
History
- FreeBSD 16.0-CURRENT (2026-10-27) to FreeBSD 13.3-RELEASE: the text shown here
- FreeBSD 13.2-RELEASE to FreeBSD 13.0-RELEASE
- FreeBSD 12.4-RELEASE
- FreeBSD 12.3-RELEASE
- FreeBSD 12.2-RELEASE
- FreeBSD 12.1-RELEASE
- FreeBSD 12.0-RELEASE
- FreeBSD 11.4-RELEASE
- FreeBSD 11.3-RELEASE
- FreeBSD 11.2-RELEASE
- FreeBSD 11.1-RELEASE
- FreeBSD 11.0-RELEASE
- FreeBSD 10.4-RELEASE
- FreeBSD 10.3-RELEASE
- FreeBSD 10.2-RELEASE
- FreeBSD 10.1-RELEASE
- FreeBSD 10.0-RELEASE
- FreeBSD 9.3-RELEASE
- FreeBSD 9.2-RELEASE
- FreeBSD 9.1-RELEASE
- FreeBSD 9.0-RELEASE
- FreeBSD 8.4-RELEASE
- FreeBSD 8.3-RELEASE
- FreeBSD 8.2-RELEASE
- FreeBSD 8.1-RELEASE
- FreeBSD 8.0-RELEASE
- FreeBSD 7.4-RELEASE
- FreeBSD 7.3-RELEASE
- FreeBSD 7.2-RELEASE
- FreeBSD 7.1-RELEASE
- FreeBSD 7.0-RELEASE
- FreeBSD 6.4-RELEASE
- FreeBSD 6.3-RELEASE to FreeBSD 6.0-RELEASE
- FreeBSD 5.5-RELEASE to FreeBSD 5.0-RELEASE