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Add description of M_WRITABLE macro and new M_RDONLY flag. Try my best to

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conform to line break mdoc FreeBSD standards, although I am new to this.

Reviewed by: sheldonh
This commit is contained in:
Bosko Milekic 2000-11-21 22:29:31 +00:00
parent 0959cc6680
commit 5d4050cc5d
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=69013
1 changed files with 33 additions and 11 deletions
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44
share/man/man9/mbuf.9
View file

@ -33,7 +33,7 @@
.Nd "memory management in the kernel IPC subsystem"
.\"
.Sh SYNOPSIS
.Fd #include <sys/param.h>
.Fd #include <machine/param.h>
.Fd #include <sys/mbuf.h>
.\"
.Ss Mbuf allocation macros
@ -46,6 +46,8 @@
.Fa "u_int size"
.Fa "void (*free)(void *opt_args)"
.Fa "void *opt_args"
.Fa "short flags"
.Fa "int type"
.Fc
.Fn MEXTFREE "struct mbuf *mbuf"
.Fn MEXT_ADD_REF "struct mbuf *mbuf"
@ -62,6 +64,7 @@
.Fn M_TRAILINGSPACE "struct mbuf *mbuf"
.Fn M_PREPEND "struct mbuf *mbuf" "int len" "int how"
.Fn MCHTYPE "struct mbuf *mbuf" "u_int type"
.Fn M_WRITABLE "struct mbuf *mbuf"
.\"
.Ss Mbuf allocation functions
.Ft struct mbuf *
@ -146,18 +149,19 @@ The mbuf flag bits are defined as follows:
#define M_EXT 0x0001 /* has associated external storage */
#define M_PKTHDR 0x0002 /* start of record */
#define M_EOR 0x0004 /* end of record */
#define M_PROTO1 0x0008 /* protocol-specific */
#define M_PROTO2 0x0010 /* protocol-specific */
#define M_PROTO3 0x0020 /* protocol-specific */
#define M_PROTO4 0x0040 /* protocol-specific */
#define M_PROTO5 0x0080 /* protocol-specific */
#define M_RDONLY 0x0008 /* associated data marked read-only */
#define M_PROTO1 0x0010 /* 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 */
/* mbuf pkthdr flags, also in m_flags */
#define M_BCAST 0x0100 /* send/received as link-level broadcast */
#define M_MCAST 0x0200 /* send/received as link-level multicast */
#define M_FRAG 0x0400 /* packet is fragment of larger packet */
#define M_FIRSTFRAG 0x0800 /* packet is first fragment */
#define M_LASTFRAG 0x1000 /* packet is last fragment */
#define M_BCAST 0x0200 /* send/received as link-level broadcast */
#define M_MCAST 0x0400 /* send/received as link-level multicast */
#define M_FRAG 0x0800 /* packet is fragment of larger packet */
#define M_FIRSTFRAG 0x1000 /* packet is first fragment */
#define M_LASTFRAG 0x2000 /* packet is last fragment */
.Ed
.Pp
The available mbuf types are defined as follows:
@ -303,6 +307,24 @@ The new chain pointer or
is in
.Fa mbuf
after the call.
.It Fn M_WRITABLE mbuf
This macro will evaluate true if the mbuf is not marked
.Dv M_RDONLY
and if either the mbuf does not contain external storage or,
if it does,
then if the reference count of the storage is not greater than 1.
The
.Dv M_RDONLY
flag can be set in the mbuf's
.Dv m_flags.
This can be achieved during setup of the external storage,
by passing the
.Dv M_RDONLY
bit as a
.Ar flags
argument to the
.Fn MEXTADD
macro, or can be directly set in individual mbufs.
.El
.Pp
The functions are: