md_get_uint32le(9) set of functions to dissect an mbuf chain to various data types

Other Alias

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_int64, md_get_int64be, md_get_int64le, md_get_mem, md_get_mbuf, md_get_uio


options LIBMCHAIN kldload libmchain

In sys/param.h In sys/uio.h In sys/mchain.h Ft void Fn md_initm struct mdchain *mdp struct mbuf *m Ft void Fn md_done struct mdchain *mdp Ft void Fn md_append_record struct mdchain *mdp struct mbuf *top Ft int Fn md_next_record struct mdchain *mdp Ft int Fn md_get_uint8 struct mdchain *mdp uint8_t *x Ft int Fn md_get_uint16 struct mdchain *mdp uint16_t *x Ft int Fn md_get_uint16be struct mdchain *mdp uint16_t *x Ft int Fn md_get_uint16le struct mdchain *mdp uint16_t *x Ft int Fn md_get_uint32 struct mdchain *mdp uint32_t *x Ft int Fn md_get_uint32be struct mdchain *mdp uint32_t *x Ft int Fn md_get_uint32le struct mdchain *mdp uint32_t *x Ft int Fn md_get_int64 struct mdchain *mdp int64_t *x Ft int Fn md_get_int64be struct mdchain *mdp int64_t *x Ft int Fn md_get_int64le struct mdchain *mdp int64_t *x Ft int Fn md_get_mem struct mdchain *mdp caddr_t target int size int type Ft int Fn md_get_mbuf struct mdchain *mdp int size struct mbuf **m Ft int Fn md_get_uio struct mdchain *mdp struct uio *uiop int size


These functions are used to decompose mbuf chains to various data types. The Vt mdchain structure is used as a working context and should be initialized through a call of the Fn mb_initm function. It has the following fields:

(Vt struct mbuf * ) A pointer to the top of the parsed mbuf chain.
(Vt struct mbuf * ) A pointer to the currently parsed mbuf.
(Vt int ) Offset in the current mbuf.

The Fn md_done function disposes of an mbuf chain pointed to by the Fa mdp->md_top field and sets the field to NULL

The Fn md_append_record appends a new mbuf chain using m_nextpkt field to form a single linked list of mbuf chains. If the Fa mdp->md_top field is NULL then this function behaves exactly as the Fn md_initm function.

The Fn md_next_record function extracts the next mbuf chain and disposes the current one, if any. For a new mbuf chain it calls the Fn md_initm function. If there is no data left the function returns Er ENOENT .

All Fn 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.

Fn md_get_mem function copies Fa size bytes of data specified by the Fa source argument from an mbuf chain. The Fa type argument specifies the method used to perform a copy, and can be one of the following:

Use the Fn bcopy function.
Use the copyin(9) function.
Use an ``inline'' loop which does not call any function.

If Fa target is NULL an actual copy is not performed and the function just skips the given number of bytes.


All Ft 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 Fn md_done function can safely be called to destroy it.


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;


This manual page was written by An Boris Popov Aq [email protected] .