853 lines
24 KiB
Groff
853 lines
24 KiB
Groff
.\"
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.\" Copyright (c) 2006 Robert N. M. Watson
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.\" All rights reserved.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
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.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
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.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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.\" SUCH DAMAGE.
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.\"
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.\" $FreeBSD$
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.\"
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.Dd October 23, 2015
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.Dt SYSCTL 9
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.Os
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.Sh NAME
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.Nm SYSCTL_DECL ,
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.Nm SYSCTL_ADD_INT ,
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.Nm SYSCTL_ADD_LONG ,
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.Nm SYSCTL_ADD_NODE ,
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.Nm SYSCTL_ADD_OPAQUE ,
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.Nm SYSCTL_ADD_PROC ,
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.Nm SYSCTL_ADD_QUAD ,
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.Nm SYSCTL_ADD_ROOT_NODE ,
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.Nm SYSCTL_ADD_S8 ,
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.Nm SYSCTL_ADD_S16 ,
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.Nm SYSCTL_ADD_S32 ,
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.Nm SYSCTL_ADD_S64 ,
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.Nm SYSCTL_ADD_STRING ,
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.Nm SYSCTL_ADD_STRUCT ,
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.Nm SYSCTL_ADD_U8 ,
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.Nm SYSCTL_ADD_U16 ,
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.Nm SYSCTL_ADD_U32 ,
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.Nm SYSCTL_ADD_U64 ,
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.Nm SYSCTL_ADD_UAUTO ,
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.Nm SYSCTL_ADD_UINT ,
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.Nm SYSCTL_ADD_ULONG ,
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.Nm SYSCTL_ADD_UQUAD ,
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.Nm SYSCTL_CHILDREN ,
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.Nm SYSCTL_STATIC_CHILDREN ,
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.Nm SYSCTL_NODE_CHILDREN ,
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.Nm SYSCTL_PARENT ,
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.Nm SYSCTL_INT ,
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.Nm SYSCTL_LONG ,
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.Nm SYSCTL_NODE ,
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.Nm SYSCTL_OPAQUE ,
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.Nm SYSCTL_PROC ,
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.Nm SYSCTL_QUAD ,
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.Nm SYSCTL_ROOT_NODE ,
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.Nm SYSCTL_S8 ,
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.Nm SYSCTL_S16 ,
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.Nm SYSCTL_S32 ,
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.Nm SYSCTL_S64 ,
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.Nm SYSCTL_STRING ,
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.Nm SYSCTL_STRUCT ,
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.Nm SYSCTL_U8 ,
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.Nm SYSCTL_U16 ,
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.Nm SYSCTL_U32 ,
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.Nm SYSCTL_U64 ,
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.Nm SYSCTL_UINT ,
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.Nm SYSCTL_ULONG ,
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.Nm SYSCTL_UQUAD
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.Nd Dynamic and static sysctl MIB creation functions
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.Sh SYNOPSIS
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.In sys/types.h
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.In sys/sysctl.h
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.Fn SYSCTL_DECL name
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.Ft struct sysctl_oid *
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.Fo SYSCTL_ADD_INT
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.Fa "struct sysctl_ctx_list *ctx"
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.Fa "struct sysctl_oid_list *parent"
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.Fa "int number"
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.Fa "const char *name"
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.Fa "int ctlflags"
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.Fa "int *ptr"
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.Fa "int val"
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.Fa "const char *descr"
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.Fc
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.Ft struct sysctl_oid *
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.Fo SYSCTL_ADD_LONG
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.Fa "struct sysctl_ctx_list *ctx"
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.Fa "struct sysctl_oid_list *parent"
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.Fa "int number"
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.Fa "const char *name"
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.Fa "int ctlflags"
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.Fa "long *ptr"
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.Fa "const char *descr"
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.Fc
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.Ft struct sysctl_oid *
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.Fo SYSCTL_ADD_NODE
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.Fa "struct sysctl_ctx_list *ctx"
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.Fa "struct sysctl_oid_list *parent"
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.Fa "int number"
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.Fa "const char *name"
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.Fa "int ctlflags"
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.Fa "int (*handler)(SYSCTL_HANDLER_ARGS)"
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.Fa "const char *descr"
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.Fc
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.Ft struct sysctl_oid *
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.Fo SYSCTL_ADD_OPAQUE
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.Fa "struct sysctl_ctx_list *ctx"
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.Fa "struct sysctl_oid_list *parent"
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.Fa "int number"
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.Fa "const char *name"
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.Fa "int ctlflags"
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.Fa "void *ptr"
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.Fa "intptr_t len"
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.Fa "const char *format"
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.Fa "const char *descr"
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.Fc
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.Ft struct sysctl_oid *
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.Fo SYSCTL_ADD_PROC
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.Fa "struct sysctl_ctx_list *ctx"
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.Fa "struct sysctl_oid_list *parent"
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.Fa "int number"
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.Fa "const char *name"
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.Fa "int ctlflags"
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.Fa "void *arg1"
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.Fa "intptr_t arg2"
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.Fa "int (*handler) (SYSCTL_HANDLERARGS)"
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.Fa "const char *format"
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.Fa "const char *descr"
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.Fc
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.Ft struct sysctl_oid *
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.Fo SYSCTL_ADD_QUAD
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.Fa "struct sysctl_ctx_list *ctx"
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.Fa "struct sysctl_oid_list *parent"
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.Fa "int number"
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.Fa "const char *name"
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.Fa "int ctlflags"
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.Fa "int64_t *ptr"
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.Fa "const char *descr"
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.Fc
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.Ft struct sysctl_oid *
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.Fo SYSCTL_ADD_ROOT_NODE
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.Fa "struct sysctl_ctx_list *ctx"
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.Fa "int number"
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.Fa "const char *name"
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.Fa "int ctlflags"
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.Fa "int (*handler)(SYSCTL_HANDLER_ARGS)"
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.Fa "const char *descr"
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.Fc
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.Ft struct sysctl_oid *
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.Fo SYSCTL_ADD_S8
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.Fa "struct sysctl_ctx_list *ctx"
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.Fa "struct sysctl_oid_list *parent"
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.Fa "int number"
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.Fa "const char *name"
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.Fa "int ctlflags"
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.Fa "int8_t *ptr"
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.Fa "int8_t val"
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.Fa "const char *descr"
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.Fc
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.Ft struct sysctl_oid *
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.Fo SYSCTL_ADD_S16
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.Fa "struct sysctl_ctx_list *ctx"
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.Fa "struct sysctl_oid_list *parent"
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.Fa "int number"
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.Fa "const char *name"
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.Fa "int ctlflags"
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.Fa "int16_t *ptr"
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.Fa "int16_t val"
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.Fa "const char *descr"
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.Fc
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.Ft struct sysctl_oid *
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.Fo SYSCTL_ADD_S32
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.Fa "struct sysctl_ctx_list *ctx"
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.Fa "struct sysctl_oid_list *parent"
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.Fa "int number"
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.Fa "const char *name"
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.Fa "int ctlflags"
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.Fa "int32_t *ptr"
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.Fa "int32_t val"
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.Fa "const char *descr"
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.Fc
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.Ft struct sysctl_oid *
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.Fo SYSCTL_ADD_S64
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.Fa "struct sysctl_ctx_list *ctx"
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.Fa "struct sysctl_oid_list *parent"
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.Fa "int number"
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.Fa "const char *name"
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.Fa "int ctlflags"
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.Fa "int64_t *ptr"
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.Fa "int64_t val"
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.Fa "const char *descr"
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.Fc
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.Ft struct sysctl_oid *
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.Fo SYSCTL_ADD_STRING
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.Fa "struct sysctl_ctx_list *ctx"
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.Fa "struct sysctl_oid_list *parent"
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.Fa "int number"
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.Fa "const char *name"
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.Fa "int ctlflags"
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.Fa "char *ptr"
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.Fa "intptr_t len"
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.Fa "const char *descr"
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.Fc
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.Ft struct sysctl_oid *
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.Fo SYSCTL_ADD_STRUCT
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.Fa "struct sysctl_ctx_list *ctx"
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.Fa "struct sysctl_oid_list *parent"
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.Fa "int number"
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.Fa "const char *name"
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.Fa "int ctlflags"
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.Fa "void *ptr"
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.Fa struct_type
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.Fa "const char *descr"
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.Fc
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.Ft struct sysctl_oid *
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.Fo SYSCTL_ADD_U8
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.Fa "struct sysctl_ctx_list *ctx"
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.Fa "struct sysctl_oid_list *parent"
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.Fa "int number"
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.Fa "const char *name"
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.Fa "int ctlflags"
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.Fa "uint8_t *ptr"
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.Fa "uint8_t val"
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.Fa "const char *descr"
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.Fc
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.Ft struct sysctl_oid *
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.Fo SYSCTL_ADD_U16
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.Fa "struct sysctl_ctx_list *ctx"
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.Fa "struct sysctl_oid_list *parent"
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.Fa "int number"
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.Fa "const char *name"
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.Fa "int ctlflags"
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.Fa "uint16_t *ptr"
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.Fa "uint16_t val"
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.Fa "const char *descr"
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.Fc
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.Ft struct sysctl_oid *
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.Fo SYSCTL_ADD_U32
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.Fa "struct sysctl_ctx_list *ctx"
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.Fa "struct sysctl_oid_list *parent"
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.Fa "int number"
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.Fa "const char *name"
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.Fa "int ctlflags"
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.Fa "uint32_t *ptr"
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.Fa "uint32_t val"
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.Fa "const char *descr"
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.Fc
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.Ft struct sysctl_oid *
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.Fo SYSCTL_ADD_U64
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.Fa "struct sysctl_ctx_list *ctx"
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.Fa "struct sysctl_oid_list *parent"
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.Fa "int number"
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.Fa "const char *name"
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.Fa "int ctlflags"
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.Fa "uint64_t *ptr"
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.Fa "uint64_t val"
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.Fa "const char *descr"
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.Fc
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.Ft struct sysctl_oid *
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.Fo SYSCTL_ADD_UINT
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.Fa "struct sysctl_ctx_list *ctx"
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.Fa "struct sysctl_oid_list *parent"
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.Fa "int number"
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.Fa "const char *name"
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.Fa "int ctlflags"
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.Fa "unsigned int *ptr"
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.Fa "unsigned int val"
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.Fa "const char *descr"
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.Fc
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.Ft struct sysctl_oid *
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.Fo SYSCTL_ADD_ULONG
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.Fa "struct sysctl_ctx_list *ctx"
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.Fa "struct sysctl_oid_list *parent"
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.Fa "int number"
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.Fa "const char *name"
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.Fa "int ctlflags"
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.Fa "unsigned long *ptr"
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.Fa "const char *descr"
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.Fc
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.Ft struct sysctl_oid *
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.Fo SYSCTL_ADD_UQUAD
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.Fa "struct sysctl_ctx_list *ctx"
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.Fa "struct sysctl_oid_list *parent"
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.Fa "int number"
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.Fa "const char *name"
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.Fa "int ctlflags"
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.Fa "uint64_t *ptr"
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.Fa "const char *descr"
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.Fc
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.Ft struct sysctl_oid *
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.Fo SYSCTL_ADD_UAUTO
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.Fa "struct sysctl_ctx_list *ctx"
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.Fa "struct sysctl_oid_list *parent"
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.Fa "int number"
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.Fa "const char *name"
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.Fa "int ctlflags"
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.Fa "void *ptr"
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.Fa "const char *descr"
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.Fc
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.Ft struct sysctl_oid_list *
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.Fo SYSCTL_CHILDREN
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.Fa "struct sysctl_oid *oidp"
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.Fc
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.Ft struct sysctl_oid_list *
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.Fo SYSCTL_STATIC_CHILDREN
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.Fa "struct sysctl_oid_list OID_NAME"
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.Fc
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.Ft struct sysctl_oid_list *
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.Fo SYSCTL_NODE_CHILDREN
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.Fa "parent"
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.Fa "name"
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.Fc
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.Ft struct sysctl_oid *
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.Fo SYSCTL_PARENT
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.Fa "struct sysctl_oid *oid"
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.Fc
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.Fn SYSCTL_INT parent number name ctlflags ptr val descr
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.Fn SYSCTL_LONG parent number name ctlflags ptr val descr
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.Fn SYSCTL_NODE parent number name ctlflags handler descr
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.Fn SYSCTL_OPAQUE parent number name ctlflags ptr len format descr
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.Fn SYSCTL_PROC parent number name ctlflags arg1 arg2 handler format descr
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.Fn SYSCTL_QUAD parent number name ctlflags ptr val descr
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.Fn SYSCTL_ROOT_NODE number name ctlflags handler descr
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.Fn SYSCTL_S8 parent number name ctlflags ptr val descr
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.Fn SYSCTL_S16 parent number name ctlflags ptr val descr
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.Fn SYSCTL_S32 parent number name ctlflags ptr val descr
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.Fn SYSCTL_S64 parent number name ctlflags ptr val descr
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.Fn SYSCTL_STRING parent number name ctlflags arg len descr
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.Fn SYSCTL_STRUCT parent number name ctlflags ptr struct_type descr
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.Fn SYSCTL_U8 parent number name ctlflags ptr val descr
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.Fn SYSCTL_U16 parent number name ctlflags ptr val descr
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.Fn SYSCTL_U32 parent number name ctlflags ptr val descr
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.Fn SYSCTL_U64 parent number name ctlflags ptr val descr
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.Fn SYSCTL_UINT parent number name ctlflags ptr val descr
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.Fn SYSCTL_ULONG parent number name ctlflags ptr val descr
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.Fn SYSCTL_UQUAD parent number name ctlflags ptr val descr
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.Sh DESCRIPTION
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The
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.Nm SYSCTL
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kernel interface allows dynamic or static creation of
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.Xr sysctl 8
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MIB entries.
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All static sysctls are automatically destroyed when the module which
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they are part of is unloaded.
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Most top level categories are created statically and are available to
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all kernel code and its modules.
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.Sh DESCRIPTION OF ARGUMENTS
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.Bl -tag -width ctlflags
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.It Fa ctx
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Pointer to sysctl context or NULL, if no context.
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See
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.Xr sysctl_ctx_init 9
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for how to create a new sysctl context.
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Programmers are strongly advised to use contexts to organize the
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dynamic OIDs which they create because when a context is destroyed all
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belonging sysctls are destroyed as well.
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This makes the sysctl cleanup code much simpler.
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Else deletion of all created OIDs is required at module unload.
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.It Fa parent
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A pointer to a
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.Li struct sysctl_oid_list ,
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which is the head of the parent's list of children.
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This pointer is retrieved using the
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.Fn SYSCTL_STATIC_CHILDREN
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macro for static sysctls and the
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.Fn SYSCTL_CHILDREN
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macro for dynamic sysctls.
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The
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.Fn SYSCTL_PARENT
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macro can be used to get the parent of an OID.
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The macro returns NULL if there is no parent.
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.It Fa number
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The OID number that will be assigned to this OID.
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In almost all cases this should be set to
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.Dv OID_AUTO ,
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which will result in the assignment of the next available OID number.
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.It Fa name
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The name of the OID.
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The newly created OID will contain a copy of the name.
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.It Fa ctlflags
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A bit mask of sysctl control flags.
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See the section below describing all the control flags.
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.It Fa arg1
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First callback argument for procedure sysctls.
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.It Fa arg2
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Second callback argument for procedure sysctls.
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.It Fa len
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The length of the data pointed to by the
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.Fa ptr
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argument.
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For string type OIDs a length of zero means that
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.Xr strlen 3
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will be used to get the length of the string at each access to the OID.
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.It Fa ptr
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Pointer to sysctl variable or string data.
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For sysctl values the pointer can be SYSCTL_NULL_XXX_PTR which means the OID is read-only and the returned value should be taken from the
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.Fa val
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argument.
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.It Fa val
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If the
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.Fa ptr
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argument is SYSCTL_NULL_XXX_PTR, gives the constant value returned by this OID.
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Else this argument is not used.
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.It Fa struct_type
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Name of structure type.
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.It Fa handler
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A pointer to the function
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that is responsible for handling read and write requests
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to this OID.
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There are several standard handlers
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that support operations on nodes,
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integers, strings and opaque objects.
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It is possible to define custom handlers using the
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.Fn SYSCTL_PROC
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macro or the
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.Fn SYSCTL_ADD_PROC
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function.
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.It Fa format
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A pointer to a string
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which specifies the format of the OID in a symbolic way.
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This format is used as a hint by
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.Xr sysctl 8
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to apply proper data formatting for display purposes.
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.Pp
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Current formats:
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.Bl -tag -width "S,TYPE" -compact -offset indent
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.It Cm N
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node
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.It Cm A
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.Li "char *"
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.It Cm I
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.Li "int"
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.It Cm IK Ns Op Ar n
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temperature in Kelvin, multiplied by an optional single digit
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power of ten scaling factor: 1 (default) gives deciKelvin, 0 gives Kelvin, 3
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gives milliKelvin
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.It Cm IU
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.Li "unsigned int"
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.It Cm L
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.Li "long"
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.It Cm LU
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.Li "unsigned long"
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.It Cm Q
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.Li "quad_t"
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.It Cm QU
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.Li "u_quad_t"
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.It Cm "S,TYPE"
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.Li "struct TYPE"
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structures
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.El
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.It Fa descr
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A pointer to a textual description of the OID.
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.El
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.Sh CREATING ROOT NODES
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Sysctl MIBs or OIDs are created in a hierarchical tree.
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The nodes at the bottom of the tree are called root nodes, and have no
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parent OID.
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To create bottom tree nodes the
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.Fn SYSCTL_ROOT_NODE
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macro or the
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.Fn SYSCTL_ADD_ROOT_NODE
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function needs to be used.
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By default all static sysctl node OIDs are global and need a
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.Fn SYSCTL_DECL
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statement prior to their
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.Fn SYSCTL_NODE
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definition statement, typically in a so-called header file.
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.Sh CREATING SYSCTL STRINGS
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Zero terminated character strings sysctls are created either using the
|
|
.Fn SYSCTL_STRING
|
|
macro or the
|
|
.Fn SYSCTL_ADD_STRING
|
|
function.
|
|
If the
|
|
.Fa len
|
|
argument in zero, the string length is computed at every access to the OID using
|
|
.Xr strlen 3 .
|
|
.Sh CREATING OPAQUE SYSCTLS
|
|
The
|
|
.Fn SYSCTL_OPAQUE
|
|
or
|
|
.Fn SYSCTL_STRUCT
|
|
macros or the
|
|
.Fn SYSCTL_ADD_OPAQUE
|
|
or
|
|
.Fn SYSCTL_ADD_STRUCT
|
|
functions create an OID that handle any chunk of data
|
|
of the size specified by the
|
|
.Fa len
|
|
argument and data pointed to by the
|
|
.Fa ptr
|
|
argument.
|
|
When using the structure version the type is encoded as part of the
|
|
created sysctl.
|
|
.Sh CREATING CUSTOM SYSCTLS
|
|
The
|
|
.Fn SYSCTL_PROC
|
|
macro and the
|
|
.Fn SYSCTL_ADD_PROC
|
|
function
|
|
create OIDs with the specified
|
|
.Pa handler
|
|
function.
|
|
The handler is responsible for handling all read and write requests to
|
|
the OID.
|
|
This OID type is especially useful if the kernel data is not easily
|
|
accessible, or needs to be processed before exporting.
|
|
.Sh CREATING A STATIC SYSCTL
|
|
Static sysctls are declared using one of the
|
|
.Fn SYSCTL_INT ,
|
|
.Fn SYSCTL_LONG ,
|
|
.Fn SYSCTL_NODE ,
|
|
.Fn SYSCTL_OPAQUE ,
|
|
.Fn SYSCTL_PROC ,
|
|
.Fn SYSCTL_QUAD ,
|
|
.Fn SYSCTL_ROOT_NODE ,
|
|
.Fn SYSCTL_S8 ,
|
|
.Fn SYSCTL_S16 ,
|
|
.Fn SYSCTL_S32 ,
|
|
.Fn SYSCTL_S64 ,
|
|
.Fn SYSCTL_STRING ,
|
|
.Fn SYSCTL_STRUCT ,
|
|
.Fn SYSCTL_U8 ,
|
|
.Fn SYSCTL_U16 ,
|
|
.Fn SYSCTL_U32 ,
|
|
.Fn SYSCTL_U64 ,
|
|
.Fn SYSCTL_UINT ,
|
|
.Fn SYSCTL_ULONG
|
|
or
|
|
.Fn SYSCTL_UQUAD
|
|
macros.
|
|
.Sh CREATING A DYNAMIC SYSCTL
|
|
Dynamic nodes are created using one of the
|
|
.Fn SYSCTL_ADD_INT ,
|
|
.Fn SYSCTL_ADD_LONG ,
|
|
.Fn SYSCTL_ADD_NODE ,
|
|
.Fn SYSCTL_ADD_OPAQUE ,
|
|
.Fn SYSCTL_ADD_PROC ,
|
|
.Fn SYSCTL_ADD_QUAD ,
|
|
.Fn SYSCTL_ADD_ROOT_NODE ,
|
|
.Fn SYSCTL_ADD_S8 ,
|
|
.Fn SYSCTL_ADD_S16 ,
|
|
.Fn SYSCTL_ADD_S32 ,
|
|
.Fn SYSCTL_ADD_S64 ,
|
|
.Fn SYSCTL_ADD_STRING ,
|
|
.Fn SYSCTL_ADD_STRUCT ,
|
|
.Fn SYSCTL_ADD_U8 ,
|
|
.Fn SYSCTL_ADD_U16 ,
|
|
.Fn SYSCTL_ADD_U32 ,
|
|
.Fn SYSCTL_ADD_U64 ,
|
|
.Fn SYSCTL_ADD_UAUTO ,
|
|
.Fn SYSCTL_ADD_UINT ,
|
|
.Fn SYSCTL_ADD_ULONG ,
|
|
or
|
|
.Fn SYSCTL_UQUAD
|
|
functions.
|
|
See
|
|
.Xr sysctl_remove_oid 9
|
|
or
|
|
.Xr sysctl_ctx_free 9
|
|
for more information on how to destroy a dynamically created OID.
|
|
.Sh CONTROL FLAGS
|
|
For most of the above functions and macros, declaring a type as part
|
|
of the access flags is not necessary \[em] however, when declaring a
|
|
sysctl implemented by a function, including a type in the access mask
|
|
is required:
|
|
.Bl -tag -width ".Dv CTLTYPE_NOFETCH"
|
|
.It Dv CTLTYPE_NODE
|
|
This is a node intended to be a parent for other nodes.
|
|
.It Dv CTLTYPE_INT
|
|
This is a signed integer.
|
|
.It Dv CTLTYPE_STRING
|
|
This is a nul-terminated string stored in a character array.
|
|
.It Dv CTLTYPE_S8
|
|
This is an 8-bit signed integer.
|
|
.It Dv CTLTYPE_S16
|
|
This is a 16-bit signed integer.
|
|
.It Dv CTLTYPE_S32
|
|
This is a 32-bit signed integer.
|
|
.It Dv CTLTYPE_S64
|
|
This is a 64-bit signed integer.
|
|
.It Dv CTLTYPE_OPAQUE
|
|
This is an opaque data structure.
|
|
.It Dv CTLTYPE_STRUCT
|
|
Alias for
|
|
.Dv CTLTYPE_OPAQUE .
|
|
.It Dv CTLTYPE_U8
|
|
This is an 8-bit unsigned integer.
|
|
.It Dv CTLTYPE_U16
|
|
This is a 16-bit unsigned integer.
|
|
.It Dv CTLTYPE_U32
|
|
This is a 32-bit unsigned integer.
|
|
.It Dv CTLTYPE_U64
|
|
This is a 64-bit unsigned integer.
|
|
.It Dv CTLTYPE_UINT
|
|
This is an unsigned integer.
|
|
.It Dv CTLTYPE_LONG
|
|
This is a signed long.
|
|
.It Dv CTLTYPE_ULONG
|
|
This is an unsigned long.
|
|
.El
|
|
.Pp
|
|
All sysctl types except for new node declarations require one of the following
|
|
flags to be set indicating the read and write disposition of the sysctl:
|
|
.Bl -tag -width ".Dv CTLFLAG_ANYBODY"
|
|
.It Dv CTLFLAG_RD
|
|
This is a read-only sysctl.
|
|
.It Dv CTLFLAG_RDTUN
|
|
This is a read-only sysctl and tunable which is tried fetched once
|
|
from the system environment early during module load or system boot.
|
|
.It Dv CTLFLAG_WR
|
|
This is a writable sysctl.
|
|
.It Dv CTLFLAG_RW
|
|
This sysctl is readable and writable.
|
|
.It Dv CTLFLAG_RWTUN
|
|
This is a readable and writeable sysctl and tunable which is tried
|
|
fetched once from the system environment early during module load or
|
|
system boot.
|
|
.It Dv CTLFLAG_NOFETCH
|
|
In case the node is marked as a tunable using the CTLFLAG_[XX]TUN,
|
|
this flag will prevent fetching the initial value from the system
|
|
environment. Typically this flag should only be used for very early
|
|
low level system setup code, and not by common drivers and modules.
|
|
.El
|
|
.Pp
|
|
Additionally, any of the following optional flags may also be specified:
|
|
.Bl -tag -width ".Dv CTLFLAG_ANYBODY"
|
|
.It Dv CTLFLAG_ANYBODY
|
|
Any user or process can write to this sysctl.
|
|
.It Dv CTLFLAG_SECURE
|
|
This sysctl can be written to only if the effective securelevel of the
|
|
process is \[<=] 0.
|
|
.It Dv CTLFLAG_PRISON
|
|
This sysctl can be written to by processes in
|
|
.Xr jail 2 .
|
|
.It Dv CTLFLAG_SKIP
|
|
When iterating the sysctl name space, do not list this sysctl.
|
|
.It Dv CTLFLAG_TUN
|
|
Advisory flag that a system tunable also exists for this variable.
|
|
The initial sysctl value is tried fetched once from the system
|
|
environment early during module load or system boot.
|
|
.It Dv CTLFLAG_DYN
|
|
Dynamically created OIDs automatically get this flag set.
|
|
.It Dv CTLFLAG_VNET
|
|
OID references a VIMAGE-enabled variable.
|
|
.El
|
|
.Sh EXAMPLES
|
|
Sample use of
|
|
.Fn SYSCTL_DECL
|
|
to declare the
|
|
.Va security
|
|
sysctl tree for use by new nodes:
|
|
.Bd -literal -offset indent
|
|
SYSCTL_DECL(_security);
|
|
.Ed
|
|
.Pp
|
|
Examples of integer, opaque, string, and procedure sysctls follow:
|
|
.Bd -literal -offset indent
|
|
/*
|
|
* Example of a constant integer value. Notice that the control
|
|
* flags are CTLFLAG_RD, the variable pointer is SYSCTL_NULL_INT_PTR,
|
|
* and the value is declared.
|
|
*/
|
|
SYSCTL_INT(_debug_sizeof, OID_AUTO, bio, CTLFLAG_RD, SYSCTL_NULL_INT_PTR,
|
|
sizeof(struct bio), "sizeof(struct bio)");
|
|
|
|
/*
|
|
* Example of a variable integer value. Notice that the control
|
|
* flags are CTLFLAG_RW, the variable pointer is set, and the
|
|
* value is 0.
|
|
*/
|
|
static int doingcache = 1; /* 1 => enable the cache */
|
|
SYSCTL_INT(_debug, OID_AUTO, vfscache, CTLFLAG_RW, &doingcache, 0,
|
|
"Enable name cache");
|
|
|
|
/*
|
|
* Example of a variable string value. Notice that the control
|
|
* flags are CTLFLAG_RW, that the variable pointer and string
|
|
* size are set. Unlike newer sysctls, this older sysctl uses a
|
|
* static oid number.
|
|
*/
|
|
char kernelname[MAXPATHLEN] = "/kernel"; /* XXX bloat */
|
|
SYSCTL_STRING(_kern, KERN_BOOTFILE, bootfile, CTLFLAG_RW,
|
|
kernelname, sizeof(kernelname), "Name of kernel file booted");
|
|
|
|
/*
|
|
* Example of an opaque data type exported by sysctl. Notice that
|
|
* the variable pointer and size are provided, as well as a format
|
|
* string for sysctl(8).
|
|
*/
|
|
static l_fp pps_freq; /* scaled frequency offset (ns/s) */
|
|
SYSCTL_OPAQUE(_kern_ntp_pll, OID_AUTO, pps_freq, CTLFLAG_RD,
|
|
&pps_freq, sizeof(pps_freq), "I", "");
|
|
|
|
/*
|
|
* Example of a procedure based sysctl exporting string
|
|
* information. Notice that the data type is declared, the NULL
|
|
* variable pointer and 0 size, the function pointer, and the
|
|
* format string for sysctl(8).
|
|
*/
|
|
SYSCTL_PROC(_kern_timecounter, OID_AUTO, hardware, CTLTYPE_STRING |
|
|
CTLFLAG_RW, NULL, 0, sysctl_kern_timecounter_hardware, "A",
|
|
"");
|
|
.Ed
|
|
.Pp
|
|
The following is an example of
|
|
how to create a new top-level category
|
|
and how to hook up another subtree to an existing static node.
|
|
This example does not use contexts,
|
|
which results in tedious management of all intermediate oids,
|
|
as they need to be freed later on:
|
|
.Bd -literal -offset indent
|
|
#include <sys/sysctl.h>
|
|
...
|
|
/*
|
|
* Need to preserve pointers to newly created subtrees,
|
|
* to be able to free them later:
|
|
*/
|
|
static struct sysctl_oid *root1;
|
|
static struct sysctl_oid *root2;
|
|
static struct sysctl_oid *oidp;
|
|
static int a_int;
|
|
static char *string = "dynamic sysctl";
|
|
...
|
|
|
|
root1 = SYSCTL_ADD_ROOT_NODE(NULL,
|
|
OID_AUTO, "newtree", CTLFLAG_RW, 0, "new top level tree");
|
|
oidp = SYSCTL_ADD_INT(NULL, SYSCTL_CHILDREN(root1),
|
|
OID_AUTO, "newint", CTLFLAG_RW, &a_int, 0, "new int leaf");
|
|
...
|
|
root2 = SYSCTL_ADD_NODE(NULL, SYSCTL_STATIC_CHILDREN(_debug),
|
|
OID_AUTO, "newtree", CTLFLAG_RW, 0, "new tree under debug");
|
|
oidp = SYSCTL_ADD_STRING(NULL, SYSCTL_CHILDREN(root2),
|
|
OID_AUTO, "newstring", CTLFLAG_RD, string, 0, "new string leaf");
|
|
.Ed
|
|
.Pp
|
|
This example creates the following subtrees:
|
|
.Bd -literal -offset indent
|
|
debug.newtree.newstring
|
|
newtree.newint
|
|
.Ed
|
|
.Pp
|
|
.Em "Care should be taken to free all OIDs once they are no longer needed!"
|
|
.Sh SYSCTL NAMING
|
|
When adding, modifying, or removing sysctl names, it is important to be
|
|
aware that these interfaces may be used by users, libraries, applications,
|
|
or documentation (such as published books), and are implicitly published application interfaces.
|
|
As with other application interfaces, caution must be taken not to break
|
|
existing applications, and to think about future use of new name spaces so as
|
|
to avoid the need to rename or remove interfaces that might be depended on in
|
|
the future.
|
|
.Pp
|
|
The semantics chosen for a new sysctl should be as clear as possible,
|
|
and the name of the sysctl must closely reflect its semantics.
|
|
Therefore the sysctl name deserves a fair amount of consideration.
|
|
It should be short but yet representative of the sysctl meaning.
|
|
If the name consists of several words, they should be separated by
|
|
underscore characters, as in
|
|
.Va compute_summary_at_mount .
|
|
Underscore characters may be omitted only if the name consists of not more
|
|
than two words, each being not longer than four characters, as in
|
|
.Va bootfile .
|
|
For boolean sysctls, negative logic should be totally avoided.
|
|
That is, do not use names like
|
|
.Va no_foobar
|
|
or
|
|
.Va foobar_disable .
|
|
They are confusing and lead to configuration errors.
|
|
Use positive logic instead:
|
|
.Va foobar ,
|
|
.Va foobar_enable .
|
|
.Pp
|
|
A temporary sysctl node OID that should not be relied upon must be designated
|
|
as such by a leading underscore character in its name. For example:
|
|
.Va _dirty_hack .
|
|
.Sh SEE ALSO
|
|
.Xr sysctl 3 ,
|
|
.Xr sysctl 8 ,
|
|
.Xr sysctl_add_oid 9 ,
|
|
.Xr sysctl_ctx_free 9 ,
|
|
.Xr sysctl_ctx_init 9 ,
|
|
.Xr sysctl_remove_oid 9
|
|
.Sh HISTORY
|
|
The
|
|
.Xr sysctl 8
|
|
utility first appeared in
|
|
.Bx 4.4 .
|
|
.Sh AUTHORS
|
|
.An -nosplit
|
|
The
|
|
.Nm sysctl
|
|
implementation originally found in
|
|
.Bx
|
|
has been extensively rewritten by
|
|
.An Poul-Henning Kamp
|
|
in order to add support for name lookups, name space iteration, and dynamic
|
|
addition of MIB nodes.
|
|
.Pp
|
|
This man page was written by
|
|
.An Robert N. M. Watson .
|
|
.Sh SECURITY CONSIDERATIONS
|
|
When creating new sysctls, careful attention should be paid to the security
|
|
implications of the monitoring or management interface being created.
|
|
Most sysctls present in the kernel are read-only or writable only by the
|
|
superuser.
|
|
Sysctls exporting extensive information on system data structures and
|
|
operation, especially those implemented using procedures, will wish to
|
|
implement access control to limit the undesired exposure of information about
|
|
other processes, network connections, etc.
|
|
.Pp
|
|
The following top level sysctl name spaces are commonly used:
|
|
.Bl -tag -width ".Va regression"
|
|
.It Va compat
|
|
Compatibility layer information.
|
|
.It Va debug
|
|
Debugging information.
|
|
Various name spaces exist under
|
|
.Va debug .
|
|
.It Va hw
|
|
Hardware and device driver information.
|
|
.It Va kern
|
|
Kernel behavior tuning; generally deprecated in favor of more specific
|
|
name spaces.
|
|
.It Va machdep
|
|
Machine-dependent configuration parameters.
|
|
.It Va net
|
|
Network subsystem.
|
|
Various protocols have name spaces under
|
|
.Va net .
|
|
.It Va regression
|
|
Regression test configuration and information.
|
|
.It Va security
|
|
Security and security-policy configuration and information.
|
|
.It Va sysctl
|
|
Reserved name space for the implementation of sysctl.
|
|
.It Va user
|
|
Configuration settings relating to user application behavior.
|
|
Generally, configuring applications using kernel sysctls is discouraged.
|
|
.It Va vfs
|
|
Virtual file system configuration and information.
|
|
.It Va vm
|
|
Virtual memory subsystem configuration and information.
|
|
.El
|