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Document the MEXTADD macro.

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MFC after:	2 weeks
This commit is contained in:
Dag-Erling Smørgrav 2010-08-07 13:26:08 +00:00
parent 1757d9699d
commit c3a2dbe9e5
1 changed files with 55 additions and 2 deletions
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57
share/man/man9/mbuf.9
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@ -24,7 +24,7 @@
.\"
.\" $FreeBSD$
.\"
.Dd March 25, 2008
.Dd August 7, 2010
.Dt MBUF 9
.Os
.\"
@ -211,7 +211,7 @@ flag bits are defined as follows:
#define M_EOR 0x0004 /* end of record */
#define M_RDONLY 0x0008 /* associated data marked read-only */
#define M_PROTO1 0x0010 /* protocol-specific */
#define M_PROTO2 0x0020 /* protocol-specific */
#define M_PROTO2 0x0020 /* protocol-specific */
#define M_PROTO3 0x0040 /* protocol-specific */
#define M_PROTO4 0x0080 /* protocol-specific */
#define M_PROTO5 0x0100 /* protocol-specific */
@ -238,6 +238,22 @@ types are defined as follows:
#define MT_OOBDATA 15 /* expedited data */
.Ed
.Pp
The available external buffer types are defined as follows:
.Bd -literal
/* external buffer types */
#define EXT_CLUSTER 1 /* mbuf cluster */
#define EXT_SFBUF 2 /* sendfile(2)'s sf_bufs */
#define EXT_JUMBOP 3 /* jumbo cluster 4096 bytes */
#define EXT_JUMBO9 4 /* jumbo cluster 9216 bytes */
#define EXT_JUMBO16 5 /* jumbo cluster 16184 bytes */
#define EXT_PACKET 6 /* mbuf+cluster from packet zone */
#define EXT_MBUF 7 /* external mbuf reference (M_IOVEC) */
#define EXT_NET_DRV 100 /* custom ext_buf provided by net driver(s) */
#define EXT_MOD_TYPE 200 /* custom module's ext_buf type */
#define EXT_DISPOSABLE 300 /* can throw this buffer away w/page flipping */
#define EXT_EXTREF 400 /* has externally maintained ref_cnt ptr */
.Ed
.Pp
If the
.Dv M_PKTHDR
flag is set, a
@ -383,6 +399,43 @@ and internal data.
See
.Fn MGET
for details.
.It Fn MEXTADD mbuf buf size free opt_arg1 opt_arg2 flags type
Associate externally managed data with
.Fa mbuf .
Any internal data contained in the mbuf will be discarded, and the
.Dv M_EXT flag will be set.
The
.Fa buf
and
.Fa size
arguments are the address and length, respectively, of the data.
The
.Fa free
argument points to a function which will be called to free the data
when the mbuf is freed; it is only used if
.Fa type
is
.Dv EXT_EXTREF .
The
.Fa opt_arg1
and
.Fa opt_arg2
arguments will be passed unmodified to
.Fa free .
The
.Fa flags
argument specifies additional
.Vt mbuf
flags; it is not necessary to specify
.Dv M_EXT .
Finally, the
.Fa type
argument specifies the type of external data, which controls how it
will be disposed of when the
.Vt mbuf
is freed.
In most cases, the correct value is
.Dv EXT_EXTREF .
.It Fn MCLGET mbuf how
Allocate and attach an
.Vt mbuf cluster