M_TAG(9)

NAME
m_tag, m_tag_get, m_tag_free, m_tag_prepend, m_tag_unlink, m_tag_delete, m_tag_delete_chain, m_tag_delete_nonpersistent, m_tag_find, m_tag_copy, m_tag_copy_chain, m_tag_init, m_tag_first, m_tag_next - mbuf tagging interfaces

SYNOPSIS
#include <sys/mbuf.h>
struct m_tag *
m_tag_get(int type, int len, int wait);
void
m_tag_free(struct m_tag *t);
void
m_tag_prepend(struct mbuf *m, struct m_tag *t);
void
m_tag_unlink(struct mbuf *m, struct m_tag *t);
void
m_tag_delete(struct mbuf *m, struct m_tag *t);
void
m_tag_delete_chain(struct mbuf *m, struct m_tag *t);
void
m_tag_delete_nonpersistent(struct mbuf *);
struct m_tag *
m_tag_find(struct mbuf *m, int type, struct m_tag *t);
struct m_tag *
m_tag_copy(struct m_tag *m);
int
m_tag_copy_chain(struct mbuf *to, struct mbuf *from);
void
m_tag_init(struct mbuf *m);
struct m_tag *
m_tag_first(struct mbuf *m);
struct m_tag *
m_tag_next(struct mbuf *m, struct m_tag *t);

DESCRIPTION
The m_tag interface is used to “tag” mbufs.

FUNCTIONS

m_tag_get(type, len, wait)
    Allocate an mbuf tag. type is one of the PACKET_TAG_ macros. len is the size of the data associated with the tag, in bytes. wait is either M_WAITOK or M_NOWAIT.

m_tag_free(t)
    Free the mbuf tag t.

m_tag_prepend(m, t)
    Prepend the mbuf tag t to the mbuf m. t will become the first tag of the mbuf m. When m is freed, t will also be freed.

m_tag_unlink(m, t)
    Unlink the mbuf tag t from the mbuf m.

m_tag_delete(m, t)
    The same as m_tag_unlink() followed by m_tag_free().

m_tag_delete_chain(m, t)
    Unlink and free mbuf tags beginning with the mbuf tag t from the mbuf m. If t is NULL, m_tag_delete_chain() unlinks and frees all mbuf tags associated with the mbuf m.

m_tag_delete_nonpersistent(m)
    Unlink and free all non persistent tags associated with the mbuf m.

m_tag_find(m, type, t)
    Find an mbuf tag with type type after the mbuf tag t in the tag chain associated with the mbuf m. If t is NULL, search from the first mbuf tag. If an mbuf tag is found, return a pointer to it. Otherwise return NULL.

m_tag_copy(t)
    Copy an mbuf tag t. Return a new mbuf tag on success. Otherwise return NULL.

m_tag_copy_chain(to, from)
    Copy all mbuf tags associated with the mbuf from to the mbuf to. If to already has any mbuf tags, they will be unlinked and freed beforehand. Return 1 on success. Otherwise return 0.

m_tag_init(m)
    Initialize mbuf tag chain of the mbuf m.

m_tag_first(m)
    Return the first mbuf tag associated with the mbuf m. Return NULL if no mbuf tags are found.

m_tag_next(m, t)
    Return the next mbuf tag after t associated with the mbuf m. Return NULL if t is the last tag in the chain.

CODE REFERENCES
This section describes places within the NetBSD source tree where actual code implementing the mbuf tagging interfaces can be found. All pathnames are relative to /usr/src.

The mbuf tagging interfaces are implemented within the file sys/kern/uipc_mbuf2.c.

The PACKET_TAG_ macros are defined in the file sys/sys/mbuf.h.

SEE ALSO
intro(9), malloc(9), mbuf(9)

BUGS
The semantics of the term "persistent tag" are vague.