NAME

m_tag, m_tag_get, m_tag_free, m_tag_prepend, m_tag_unlink, m_tag_delete, m_tag_delete_chain, m_tag_find, m_tag_copy, m_tag_copy_chain — 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 *
m_tag_find(struct mbuf *m, int type);

struct m_tag *
m_tag_copy(struct m_tag *m);

int
m_tag_copy_chain(struct mbuf *to, struct mbuf *from);

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)

Unlink and free mbuf tags from the mbuf m.

m_tag_find(m, type)

Find an mbuf tag with type type in the tag chain associated with the mbuf m. 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.

CODE REFERENCES

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