49c137f7be
- Wrong integer type was specified. - Wrong or missing "access" specifier. The "access" specifier sometimes included the SYSCTL type, which it should not, except for procedural SYSCTL nodes. - Logical OR where binary OR was expected. - Properly assert the "access" argument passed to all SYSCTL macros, using the CTASSERT macro. This applies to both static- and dynamically created SYSCTLs. - Properly assert the the data type for both static and dynamic SYSCTLs. In the case of static SYSCTLs we only assert that the data pointed to by the SYSCTL data pointer has the correct size, hence there is no easy way to assert types in the C language outside a C-function. - Rewrote some code which doesn't pass a constant "access" specifier when creating dynamic SYSCTL nodes, which is now a requirement. - Updated "EXAMPLES" section in SYSCTL manual page. MFC after: 3 days Sponsored by: Mellanox Technologies
715 lines
20 KiB
Groff
715 lines
20 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 20, 2014
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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_STRING ,
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.Nm SYSCTL_ADD_STRUCT ,
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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_STRING ,
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.Nm SYSCTL_STRUCT ,
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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 "intptr_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_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 "quad_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_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_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 "intptr_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_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 "u_quad_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_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_ROOT_NODE number name ctlflags handler 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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Currently used format names are:
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.Dq N
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for node,
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.Dq A
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for
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.Li "char *" ,
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.Dq I
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for
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.Li "int" ,
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.Dq IU
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for
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.Li "unsigned int" ,
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.Dq L
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for
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.Li "long" ,
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.Dq LU
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for
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.Li "unsigned long" ,
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.Dq Q
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for
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.Li "quad_t" ,
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.Dq QU
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for
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.Li "u_quad_t"
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and
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.Dq S,TYPE
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for
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.Li "struct TYPE"
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structures.
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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
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.Fn SYSCTL_STRING
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macro or the
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.Fn SYSCTL_ADD_STRING
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function.
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If the
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.Fa len
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argument in zero, the string length is computed at every access to the OID using
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.Xr strlen 3 .
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.Sh CREATING OPAQUE SYSCTLS
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|
The
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.Fn SYSCTL_OPAQUE
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or
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.Fn SYSCTL_STRUCT
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|
macros or the
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.Fn SYSCTL_ADD_OPAQUE
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|
or
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.Fn SYSCTL_ADD_STRUCT
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functions create an OID that handle any chunk of data
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of the size specified by the
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.Fa len
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argument and data pointed to by the
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.Fa ptr
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argument.
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|
When using the structure version the type is encoded as part of the
|
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created sysctl.
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|
.Sh CREATING CUSTOM SYSCTLS
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The
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.Fn SYSCTL_PROC
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macro and the
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.Fn SYSCTL_ADD_PROC
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|
function
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create OIDs with the specified
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|
.Pa handler
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|
function.
|
|
The handler is responsible for handling all read and write requests to
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|
the OID.
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|
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
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|
Static sysctls are declared using one of the
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|
.Fn SYSCTL_INT ,
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|
.Fn SYSCTL_LONG ,
|
|
.Fn SYSCTL_NODE ,
|
|
.Fn SYSCTL_OPAQUE ,
|
|
.Fn SYSCTL_PROC ,
|
|
.Fn SYSCTL_QUAD ,
|
|
.Fn SYSCTL_ROOT_NODE ,
|
|
.Fn SYSCTL_STRING ,
|
|
.Fn SYSCTL_STRUCT ,
|
|
.Fn SYSCTL_UINT ,
|
|
.Fn SYSCTL_ULONG
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|
or
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|
.Fn SYSCTL_UQUAD
|
|
macros.
|
|
.Sh CREATING A DYNAMIC SYSCTL
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|
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_STRING ,
|
|
.Fn SYSCTL_ADD_STRUCT ,
|
|
.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_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_UINT
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|
This is an unsigned integer.
|
|
.It Dv CTLTYPE_LONG
|
|
This is a signed long.
|
|
.It Dv CTLTYPE_ULONG
|
|
This is an unsigned long.
|
|
.It Dv CTLTYPE_U64
|
|
This is a 64-bit unsigned integer.
|
|
.El
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|
.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 enviroment 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 enviroment 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
|
|
enviroment 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 frequence 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
|