1.\" 2.\" Copyright (c) 2006 Robert N. M. Watson 3.\" All rights reserved. 4.\" 5.\" Redistribution and use in source and binary forms, with or without 6.\" modification, are permitted provided that the following conditions 7.\" are met: 8.\" 1. Redistributions of source code must retain the above copyright 9.\" notice, this list of conditions and the following disclaimer. 10.\" 2. Redistributions in binary form must reproduce the above copyright 11.\" notice, this list of conditions and the following disclaimer in the 12.\" documentation and/or other materials provided with the distribution. 13.\" 14.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND 15.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 16.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 17.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE 18.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 19.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 20.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 21.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 22.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 23.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 24.\" SUCH DAMAGE. 25.\" 26.\" $FreeBSD: src/share/man/man9/sysctl.9,v 1.3 2006/04/28 23:21:36 keramida Exp $ 27.\" $DragonFly: src/share/man/man9/sysctl.9,v 1.6 2008/09/02 11:50:46 matthias Exp $ 28.\" 29.Dd September 2, 2008 30.Dt SYSCTL 9 31.Os 32.Sh NAME 33.Nm SYSCTL_DECL , 34.Nm SYSCTL_INT , 35.Nm SYSCTL_LONG , 36.Nm SYSCTL_QUAD , 37.Nm SYSCTL_NODE , 38.Nm SYSCTL_OPAQUE , 39.Nm SYSCTL_PROC , 40.Nm SYSCTL_STRING , 41.Nm SYSCTL_STRUCT , 42.Nm SYSCTL_UINT , 43.Nm SYSCTL_ULONG , 44.Nm SYSCTL_UQUAD 45.Nd Static sysctl declaration functions 46.Sh SYNOPSIS 47.In sys/types.h 48.In sys/sysctl.h 49.Fo SYSCTL_DECL 50.Fa "name" 51.Fc 52.Fo SYSCTL_INT 53.Fa "parent" 54.Fa "nbr" 55.Fa "name" 56.Fa "access" 57.Fa "ptr" 58.Fa "val" 59.Fa "descr" 60.Fc 61.Fo SYSCTL_LONG 62.Fa "parent" 63.Fa "nbr" 64.Fa "name" 65.Fa "access" 66.Fa "ptr" 67.Fa "val" 68.Fa "descr" 69.Fc 70.Fo SYSCTL_QUAD 71.Fa "parent" 72.Fa "nbr" 73.Fa "name" 74.Fa "access" 75.Fa "ptr" 76.Fa "val" 77.Fa "descr" 78.Fc 79.Fo SYSCTL_NODE 80.Fa "parent" 81.Fa "nbr" 82.Fa "name" 83.Fa "access" 84.Fa "handler" 85.Fa "descr" 86.Fc 87.Fo SYSCTL_OPAQUE 88.Fa "parent" 89.Fa "nbr" 90.Fa "name" 91.Fa "access" 92.Fa "ptr" 93.Fa "len" 94.Fa "fmt" 95.Fa "descr" 96.Fc 97.Fo SYSCTL_PROC 98.Fa "parent" 99.Fa "nbr" 100.Fa "name" 101.Fa "access" 102.Fa "ptr" 103.Fa "arg" 104.Fa "handler" 105.Fa "fmt" 106.Fa "descr" 107.Fc 108.Fo SYSCTL_STRING 109.Fa "parent" 110.Fa "nbr" 111.Fa "name" 112.Fa "access" 113.Fa "arg" 114.Fa "len" 115.Fa "descr" 116.Fc 117.Fo SYSCTL_STRUCT 118.Fa "parent" 119.Fa "nbr" 120.Fa "name" 121.Fa "access" 122.Fa "ptr" 123.Fa "type" 124.Fa "descr" 125.Fc 126.Fo SYSCTL_UINT 127.Fa "parent" 128.Fa "nbr" 129.Fa "name" 130.Fa "access" 131.Fa "ptr" 132.Fa "val" 133.Fa "descr" 134.Fc 135.Fo SYSCTL_ULONG 136.Fa "parent" 137.Fa "nbr" 138.Fa "name" 139.Fa "access" 140.Fa "ptr" 141.Fa "val" 142.Fa "descr" 143.Fc 144.Fo SYSCTL_UQUAD 145.Fa "parent" 146.Fa "nbr" 147.Fa "name" 148.Fa "access" 149.Fa "ptr" 150.Fa "val" 151.Fa "descr" 152.Fc 153.Sh DESCRIPTION 154The 155.Nm 156kernel interfaces allow code to statically declare 157.Xr sysctl 8 158MIB entries, which will be initialized when the kernel module containing the 159declaration is initialized. 160When the module is unloaded, the sysctl will be automatically destroyed. 161.Pp 162Sysctl nodes are created in a hierarchical tree, with all static nodes being 163represented by named C data structures; in order to create a new node under 164an existing node in the tree, the structure representing the desired parent 165node must be declared in the current context using 166.Fn SYSCTL_DECL . 167.Pp 168New nodes are declared using one of 169.Nm SYSCTL_INT , 170.Nm SYSCTL_LONG , 171.Nm SYSCTL_QUAD , 172.Nm SYSCTL_NODE , 173.Nm SYSCTL_OPAQUE , 174.Nm SYSCTL_PROC , 175.Nm SYSCTL_STRING , 176.Nm SYSCTL_STRUCT , 177.Nm SYSCTL_UINT , 178.Nm SYSCTL_ULONG , 179and 180.Nm SYSCTL_UQUAD . 181Each macro accepts a parent name, as declared using 182.Nm SYSCTL_DECL , 183an OID number, typically 184.Dv OID_AUTO , 185a node name, a set of control and access flags, and a description. 186Depending on the macro, a pointer to a variable supporting the MIB entry, a 187size, a value, and a function pointer implementing the MIB entry may also be 188present. 189.Pp 190For most of the above macros, declaring a type as part of the access flags is 191not necessary -- however, when declaring a sysctl implemented by a function, 192including a type in the access mask is required: 193.Bl -tag -width CTLTYPE_STRING 194.It Dv CTLTYPE_NODE 195This is a node intended to be a parent for other nodes. 196.It Dv CTLTYPE_INT 197This is a signed integer. 198.It Dv CTLTYPE_STRING 199This is a nul-terminated string stored in a character array. 200.It Dv CTLTYPE_QUAD 201This is a 64-bit signed integer. 202.It Dv CTLTYPE_OPAQUE 203This is an opaque data structure. 204.It Dv CTLTYPE_STRUCT 205Alias for 206.Dv CTLTYPE_OPAQUE . 207.It Dv CTLTYPE_UINT 208This is an unsigned integer. 209.It Dv CTLTYPE_LONG 210This is a signed long. 211.It Dv CTLTYPE_ULONG 212This is an unsigned long. 213.It Dv CTLTYPE_UQUAD 214This is a 64-bit unsigned integer. 215.El 216.Pp 217All sysctl types except for new node declarations require one or more flags 218to be set indicating the read and write disposition of the sysctl: 219.Bl -tag -width CTLFLAG_ANYBODY 220.It Dv CTLFLAG_RD 221This is a read-only sysctl. 222.It Dv CTLFLAG_WR 223This is a writable sysctl. 224.It Dv CTLFLAG_RW 225This sysctl is readable and writable. 226.It Dv CTLFLAG_ANYBODY 227Any user or process can write to this sysctl. 228.It Dv CTLFLAG_NOLOCK 229Don't lock. 230.It Dv CTLFLAG_SECURE 231This sysctl can be written to only if the effective securelevel of the 232process is <= 0. 233.It Dv CTLFLAG_PRISON 234This sysctl can be written to by processes in 235.Xr jail 2 . 236.\".It Dv CTLFLAG_SKIP 237.\"When iterating the sysctl name space, do not list this sysctl. 238.El 239.Pp 240When creating new sysctls, careful attention should be paid to the security 241implications of the monitoring or management interface being created. 242Most sysctls present in the kernel are read-only or writable only by the 243superuser. 244Sysctls exporting extensive information on system data structures and 245operation, especially those implemented using procedures, will wish to 246implement access control to limit the undesired exposure of information about 247other processes, network connections, etc. 248.Pp 249The following top level sysctl name spaces are commonly used: 250.Bl -tag -width ".Va machdep" 251.It Va compat 252Compatibility layer information. 253.It Va debug 254Debugging information. 255Various name spaces exist under 256.Va debug . 257.It Va hw 258Hardware and device driver information. 259.It Va lwkt 260Information about the 261.Xr lwkt 9 262subsystem. 263.It Va kern 264Kernel behavior tuning; generally deprecated in favor of more specific 265name spaces. 266.It Va machdep 267Machine-dependent configuration parameters. 268.It Va net 269Network subsystem. 270Various protocols have name spaces under 271.Va net . 272.It Va sysctl 273Reserved name space for the implementation of sysctl. 274.It Va user 275Configuration settings relating to user application behavior. 276Generally, configuring applications using kernel sysctls is discouraged. 277.It Va vfs 278Virtual file system configuration and information. 279.It Va vm 280Virtual memory subsystem configuration and information. 281.El 282.Sh EXAMPLES 283Sample use of 284.Nm SYSCTL_DECL 285to declare the "machdep" sysctl tree for use by new nodes: 286.Bd -literal -offset indent 287SYSCTL_DECL(_machdep); 288.Ed 289.Pp 290Examples of integer, opaque, string, and procedure sysctls follow: 291.Bd -literal -offset indent 292/* 293 * Example of a constant integer value. Notice that the control 294 * flags are CTLFLAG_RD, the variable pointer is NULL, and the 295 * value is declared. 296 */ 297SYSCTL_INT(_debug_sizeof, OID_AUTO, bio, CTLFLAG_RD, NULL, 298 sizeof(struct bio), "sizeof(struct bio)"); 299 300/* 301 * Example of a variable integer value. Notice that the control 302 * flags are CTLFLAG_RW, the variable pointer is set, and the 303 * value is 0. 304 */ 305static int doingcache = 1; /* 1 => enable the cache */ 306SYSCTL_INT(_debug, OID_AUTO, vfscache, CTLFLAG_RW, &doingcache, 0, 307 "Enable name cache"); 308 309/* 310 * Example of a variable string value. Notice that the control 311 * flags are CTLFLAG_RW, that the variable pointer and string 312 * size are set. Unlike newer sysctls, this older sysctl uses a 313 * static oid number. 314 */ 315char kernelname[MAXPATHLEN] = "/boot/kernel"; /* XXX bloat */ 316SYSCTL_STRING(_kern, KERN_BOOTFILE, bootfile, CTLFLAG_RW, 317 kernelname, sizeof(kernelname), "Name of kernel file booted"); 318 319/* 320 * Example of an opaque data type exported by sysctl. Notice that 321 * the variable pointer and size are provided, as well as a format 322 * string for sysctl(8). 323 */ 324static l_fp pps_freq; /* scaled frequence offset (ns/s) */ 325SYSCTL_OPAQUE(_kern_ntp_pll, OID_AUTO, pps_freq, CTLFLAG_RD, 326 &pps_freq, sizeof(pps_freq), "I", ""); 327 328/* 329 * Example of a procedure based sysctl exporting string 330 * information. Notice that the data type is declared, the NULL 331 * variable pointer and 0 size, the function pointer, and the 332 * format string for sysctl(8). 333 */ 334SYSCTL_PROC(_kern, OID_AUTO, msgbuf, CTLTYPE_STRING | CTLFLAG_RD, 335 0, 0, sysctl_kern_msgbuf, "A", "Contents of kernel message buffer"); 336.Ed 337.Pp 338When adding, modifying, or removing sysctl names, it is important to be 339aware that these interfaces may be used by users, libraries, applications, 340or documentation (such as published books), and are implicitly published 341application interfaces. 342As with other application interfaces, caution must be taken not to break 343existing applications, and to think about future use of new name spaces so as 344to avoid the need to rename or remove interfaces that might be depended on in 345the future. 346.Sh SEE ALSO 347.Xr sysctl 8 , 348.Xr sysctl_add_oid 9 , 349.Xr sysctl_ctx_free 9 , 350.Xr sysctl_ctx_init 9 , 351.Xr sysctl_remove_oid 9 352.Sh HISTORY 353.Xr sysctl 8 354first appeared in 355.Bx 4.4 . 356.Sh AUTHORS 357.An -nosplit 358The sysctl implementation originally found in 359.Bx 360has been extensively rewritten by 361.An Poul-Henning Kamp 362in order to add support for name lookups, name space iteration, and dynamic 363addition of MIB nodes. 364.Pp 365This man page was written by 366.An Robert N. M. Watson . 367