gen/FreeBSD/sysctl.3

   1 .\" Copyright (c) 1993
   2 .\"     The Regents of the University of California.  All rights reserved.
   3 .\"
   4 .\" Redistribution and use in source and binary forms, with or without
   5 .\" modification, are permitted provided that the following conditions
   6 .\" are met:
   7 .\" 1. Redistributions of source code must retain the above copyright
   8 .\"    notice, this list of conditions and the following disclaimer.
   9 .\" 2. Redistributions in binary form must reproduce the above copyright
  10 .\"    notice, this list of conditions and the following disclaimer in the
  11 .\"    documentation and/or other materials provided with the distribution.
  12 .\" 3. All advertising materials mentioning features or use of this software
  13 .\"    must display the following acknowledgement:
  14 .\"     This product includes software developed by the University of
  15 .\"     California, Berkeley and its contributors.
  16 .\" 4. Neither the name of the University nor the names of its contributors
  17 .\"    may be used to endorse or promote products derived from this software
  18 .\"    without specific prior written permission.
  19 .\"
  20 .\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  21 .\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  22 .\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  23 .\" ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  24 .\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  25 .\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  26 .\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  27 .\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  28 .\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  29 .\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  30 .\" SUCH DAMAGE.
  31 .\"
  32 .\"     @(#)sysctl.3    8.4 (Berkeley) 5/9/95
  33 .\" $FreeBSD: src/lib/libc/gen/sysctl.3,v 1.63 2004/07/02 23:52:10 ru Exp $
  34 .\"
  35 .Dd October 21, 2008
  36 .Dt SYSCTL 3
  37 .Os
  38 .Sh NAME
  39 .Nm sysctl ,
  40 .Nm sysctlbyname ,
  41 .Nm sysctlnametomib
  42 .Nd get or set system information
  43 .Sh LIBRARY
  44 .Lb libc
  45 .Sh SYNOPSIS
  46 .In sys/types.h
  47 .In sys/sysctl.h
  48 .Ft int
  49 .Fn sysctl "int *name" "u_int namelen" "void *oldp" "size_t *oldlenp" "void *newp" "size_t newlen"
  50 .Ft int
  51 .Fn sysctlbyname "const char *name" "void *oldp" "size_t *oldlenp" "void *newp" "size_t newlen"
  52 .Ft int
  53 .Fn sysctlnametomib "const char *name" "int *mibp" "size_t *sizep"
  54 .Sh DESCRIPTION
  55 The
  56 .Fn sysctl
  57 function retrieves system information and allows processes with
  58 appropriate privileges to set system information.
  59 The information available from
  60 .Fn sysctl
  61 consists of integers, strings, and tables.
  62 Information may be retrieved and set from the command interface
  63 using the
  64 .Xr sysctl 8
  65 utility.
  66 .Pp
  67 Unless explicitly noted below,
  68 .Fn sysctl
  69 returns a consistent snapshot of the data requested.
  70 Consistency is obtained by locking the destination
  71 buffer into memory so that the data may be copied out without blocking.
  72 Calls to
  73 .Fn sysctl
  74 are serialized to avoid deadlock.
  75 .Pp
  76 The state is described using a ``Management Information Base'' (MIB)
  77 style name, listed in
  78 .Fa name ,
  79 which is a
  80 .Fa namelen
  81 length array of integers.
  82 .Pp
  83 The
  84 .Fn sysctlbyname
  85 function accepts an ASCII representation of the name and internally
  86 looks up the integer name vector.
  87 Apart from that, it behaves the same
  88 as the standard
  89 .Fn sysctl
  90 function.
  91 For a list of ASCII representations of commonly used sysctl names, please see
  92 .Xr sysctl 1 .
  93 .Pp
  94 The information is copied into the buffer specified by
  95 .Fa oldp .
  96 The size of the buffer is given by the location specified by
  97 .Fa oldlenp
  98 before the call,
  99 and that location gives the amount of data copied after a successful call
 100 and after a call that returns with the error code
 101 .Er ENOMEM .
 102 If the amount of data available is greater
 103 than the size of the buffer supplied,
 104 the call supplies as much data as fits in the buffer provided
 105 and returns with the error code
 106 .Er ENOMEM .
 107 If the old value is not desired,
 108 .Fa oldp
 109 and
 110 .Fa oldlenp
 111 should be set to NULL.
 112 .Pp
 113 The size of the available data can be determined by calling
 114 .Fn sysctl
 115 with the
 116 .Dv NULL
 117 argument for
 118 .Fa oldp .
 119 The size of the available data will be returned in the location pointed to by
 120 .Fa oldlenp .
 121 For some operations, the amount of space may change often.
 122 For these operations,
 123 the system attempts to round up so that the returned size is
 124 large enough for a call to return the data shortly thereafter.
 125 .Pp
 126 To set a new value,
 127 .Fa newp
 128 is set to point to a buffer of length
 129 .Fa newlen
 130 from which the requested value is to be taken.
 131 If a new value is not to be set,
 132 .Fa newp
 133 should be set to NULL and
 134 .Fa newlen
 135 set to 0.
 136 .Pp
 137 The
 138 .Fn sysctlnametomib
 139 function accepts an ASCII representation of the name,
 140 looks up the integer name vector,
 141 and returns the numeric representation in the mib array pointed to by
 142 .Fa mibp .
 143 The number of elements in the mib array is given by the location specified by
 144 .Fa sizep
 145 before the call,
 146 and that location gives the number of entries copied after a successful call.
 147 The resulting
 148 .Fa mib
 149 and
 150 .Fa size
 151 may be used in subsequent
 152 .Fn sysctl
 153 calls to get the data associated with the requested ASCII name.
 154 This interface is intended for use by applications that want to
 155 repeatedly request the same variable (the
 156 .Fn sysctl
 157 function runs in about a third the time as the same request made via the
 158 .Fn sysctlbyname
 159 function).
 160 The
 161 .Fn sysctlnametomib
 162 function is also useful for fetching mib prefixes and then adding
 163 a final component.
 164 For example, to fetch process information
 165 for processes with pid's less than 100:
 166 .Pp
 167 .Bd -literal -offset indent -compact
 168 int i, mib[4];
 169 size_t len;
 170 struct kinfo_proc kp;
 171
 172 /* Fill out the first three components of the mib */
 173 len = 4;
 174 sysctlnametomib("kern.proc.pid", mib, &len);
 175
 176 /* Fetch and print entries for pid's < 100 */
 177 for (i = 0; i < 100; i++) {
 178         mib[3] = i;
 179         len = sizeof(kp);
 180         if (sysctl(mib, 4, &kp, &len, NULL, 0) == -1)
 181                 perror("sysctl");
 182         else if (len > 0)
 183                 printkproc(&kp);
 184 }
 185 .Ed
 186 .Pp
 187 Note:  Implementation of
 188 .Fn printkproc
 189 -- to print whatever data deemed necessary from the large
 190 .Vt kinfo_proc
 191 structure (
 192 .In sys/sysctl.h
 193 ) -- is left as an exercise for the reader.
 194 .Pp
 195 The top level names are defined with a CTL_ prefix in
 196 .In sys/sysctl.h ,
 197 and are as follows.
 198 The next and subsequent levels down are found in the include files
 199 listed here, and described in separate sections below.
 200 .Pp
 201 .Bl -column CTLXMACHDEP "Next level names" -offset indent
 202 .It Sy "Name    Next level names        Description"
 203 .It "CTL_DEBUG  sys/sysctl.h    Debugging"
 204 .It "CTL_VFS    sys/mount.h     File system"
 205 .It "CTL_HW     sys/sysctl.h    Generic CPU, I/O"
 206 .It "CTL_KERN   sys/sysctl.h    High kernel limits"
 207 .It "CTL_MACHDEP        sys/sysctl.h    Machine dependent"
 208 .It "CTL_NET    sys/socket.h    Networking"
 209 .It "CTL_USER   sys/sysctl.h    User-level"
 210 .It "CTL_VM     sys/resources.h Virtual memory (struct loadavg)"
 211 .It "CTL_VM     sys/vmmeter.h   Virtual memory (struct vmtotal)"
 212 .El
 213 .Pp
 214 For example, the following retrieves the maximum number of processes allowed
 215 in the system:
 216 .Pp
 217 .Bd -literal -offset indent -compact
 218 int mib[2], maxproc;
 219 size_t len;
 220
 221 mib[0] = CTL_KERN;
 222 mib[1] = KERN_MAXPROC;
 223 len = sizeof(maxproc);
 224 sysctl(mib, 2, &maxproc, &len, NULL, 0);
 225 .Ed
 226 .Pp
 227 To retrieve the standard search path for the system utilities:
 228 .Pp
 229 .Bd -literal -offset indent -compact
 230 int mib[2];
 231 size_t len;
 232 char *p;
 233
 234 mib[0] = CTL_USER;
 235 mib[1] = USER_CS_PATH;
 236 sysctl(mib, 2, NULL, &len, NULL, 0);
 237 p = malloc(len);
 238 sysctl(mib, 2, p, &len, NULL, 0);
 239 .Ed
 240 .Ss CTL_DEBUG
 241 The debugging variables vary from system to system.
 242 A debugging variable may be added or deleted without need to recompile
 243 .Fn sysctl
 244 to know about it.
 245 Each time it runs,
 246 .Fn sysctl
 247 gets the list of debugging variables from the kernel and
 248 displays their current values.
 249 The system defines twenty
 250 .Pq Vt "struct ctldebug"
 251 variables named
 252 .Va debug0
 253 through
 254 .Va debug19 .
 255 They are declared as separate variables so that they can be
 256 individually initialized at the location of their associated variable.
 257 The loader prevents multiple use of the same variable by issuing errors
 258 if a variable is initialized in more than one place.
 259 For example, to export the variable
 260 .Va dospecialcheck
 261 as a debugging variable, the following declaration would be used:
 262 .Pp
 263 .Bd -literal -offset indent -compact
 264 int dospecialcheck = 1;
 265 struct ctldebug debug5 = { "dospecialcheck", &dospecialcheck };
 266 .Ed
 267 .Ss CTL_VFS
 268 A distinguished second level name, VFS_GENERIC,
 269 is used to get general information about all file systems.
 270 One of its third level identifiers is VFS_MAXTYPENUM
 271 that gives the highest valid file system type number.
 272 Its other third level identifier is VFS_CONF that
 273 returns configuration information about the file system
 274 type given as a fourth level identifier (see
 275 .Xr getvfsbyname 3
 276 as an example of its use).
 277 The remaining second level identifiers are the
 278 file system type number returned by a
 279 .Xr statfs 2
 280 call or from VFS_CONF.
 281 The third level identifiers available for each file system
 282 are given in the header file that defines the mount
 283 argument structure for that file system.
 284 .Ss CTL_HW
 285 The string and integer information available for the CTL_HW level
 286 is detailed below.
 287 The changeable column shows whether a process with appropriate
 288 privilege may change the value.
 289 .Bl -column "Second level nameXXXXXX" integerXXX -offset indent
 290 .It Sy "Second level name       Type    Changeable"
 291 .It "HW_MACHINE string  no"
 292 .It "HW_MODEL   string  no"
 293 .It "HW_NCPU    integer no (DEPRECATED)"
 294 .It "HW_BYTEORDER       integer no"
 295 .It "HW_PHYSMEM integer no"
 296 .It "HW_MEMSIZE integer no"
 297 .It "HW_USERMEM integer no"
 298 .It "HW_PAGESIZE        integer no"
 299 .It "HW_FLOATINGPOINT   integer no"
 300 .It "HW_MACHINE_ARCH    string  no"
 301 .\".It "HW_DISKNAMES    integer no"
 302 .\".It "HW_DISKSTATS    integer no"
 303 .El
 304 .Pp
 305 .Bl -tag -width 6n
 306 .It Li HW_MACHINE
 307 The machine class.
 308 .It Li HW_MODEL
 309 The machine model
 310 .It Li HW_NCPU (DEPRECATED)
 311 The number of cpus.  It is recommended that you use "hw.physicalcpu" "hw.physicalcpu_max" "hw.logicalcpu" or "hw.logicalcpu_max" instead.
 312 .It Li "hw.physicalcpu"
 313 The number of physical processors available in the current power management mode.
 314 .It Li "hw.physicalcpu_max"
 315 The maximum number of physical processors that could be available this boot.
 316 .It Li "hw.logicalcpu"
 317 The number of logical processors available in the current power management mode.
 318 .It Li "hw.logicalcpu_max"
 319 The maximum number of logical processors that could be available this boot.
 320 .It Li HW_BYTEORDER
 321 The byteorder (4,321, or 1,234).
 322 .It Li HW_PHYSMEM
 323 The bytes of physical memory represented by a 32-bit integer (for backward compatibility). Use HW_MEMSIZE instead.
 324 .It Li HW_MEMSIZE
 325 The bytes of physical memory represented by a 64-bit integer.
 326 .It Li HW_USERMEM
 327 The bytes of non-kernel memory.
 328 .It Li HW_PAGESIZE
 329 The software page size.
 330 .It Li HW_FLOATINGPOINT
 331 Nonzero if the floating point support is in hardware.
 332 .It Li HW_MACHINE_ARCH
 333 The machine dependent architecture type.
 334 .\".It Fa HW_DISKNAMES
 335 .\".It Fa HW_DISKSTATS
 336 .El
 337 .Ss CTL_KERN
 338 The string and integer information available for the CTL_KERN level
 339 is detailed below.
 340 The changeable column shows whether a process with appropriate
 341 privilege may change the value.
 342 The types of data currently available are process information,
 343 system vnodes, the open file entries, routing table entries,
 344 virtual memory statistics, load average history, and clock rate
 345 information.
 346 .Bl -column "KERNXMAXFILESPERPROCXXX" "struct clockrateXXX" -offset indent
 347 .It Sy "Second level name       Type    Changeable"
 348 .It "KERN_ARGMAX        integer no"
 349 .It "KERN_BOOTFILE      string  yes"
 350 .It "KERN_BOOTTIME      struct timeval  no"
 351 .It "KERN_CLOCKRATE     struct clockinfo        no"
 352 .It "KERN_FILE  struct file     no"
 353 .It "KERN_HOSTID        integer yes"
 354 .It "KERN_HOSTNAME      string  yes"
 355 .It "KERN_JOB_CONTROL   integer no"
 356 .It "KERN_MAXFILES      integer yes"
 357 .It "KERN_MAXFILESPERPROC       integer yes"
 358 .It "KERN_MAXPROC       integer no"
 359 .It "KERN_MAXPROCPERUID integer yes"
 360 .It "KERN_MAXVNODES     integer yes"
 361 .It "KERN_NGROUPS       integer no"
 362 .It "KERN_NISDOMAINNAME string  yes"
 363 .It "KERN_OSRELDATE     integer no"
 364 .It "KERN_OSRELEASE     string  no"
 365 .It "KERN_OSREV integer no"
 366 .It "KERN_OSTYPE        string  no"
 367 .It "KERN_POSIX1        integer no"
 368 .It "KERN_PROC  struct kinfo_proc       no"
 369 .It "KERN_PROF  node    not applicable"
 370 .It "KERN_QUANTUM       integer yes"
 371 .It "KERN_SAVED_IDS     integer no"
 372 .It "KERN_SECURELVL     integer raise only"
 373 .It "KERN_UPDATEINTERVAL        integer no"
 374 .It "KERN_VERSION       string  no"
 375 .It "KERN_VNODE struct vnode    no"
 376 .El
 377 .Pp
 378 .Bl -tag -width 6n
 379 .It Li KERN_ARGMAX
 380 The maximum bytes of argument to
 381 .Xr execve 2 .
 382 .It Li KERN_BOOTFILE
 383 The full pathname of the file from which the kernel was loaded.
 384 .It Li KERN_BOOTTIME
 385 A
 386 .Va struct timeval
 387 structure is returned.
 388 This structure contains the time that the system was booted.
 389 .It Li KERN_CLOCKRATE
 390 A
 391 .Va struct clockinfo
 392 structure is returned.
 393 This structure contains the clock, statistics clock and profiling clock
 394 frequencies, the number of micro-seconds per hz tick and the skew rate.
 395 .It Li KERN_FILE
 396 Return the entire file table.
 397 The returned data consists of a single
 398 .Va struct filehead
 399 followed by an array of
 400 .Va struct file ,
 401 whose size depends on the current number of such objects in the system.
 402 .It Li KERN_HOSTID
 403 Get or set the host id.
 404 .It Li KERN_HOSTNAME
 405 Get or set the hostname.
 406 .It Li KERN_JOB_CONTROL
 407 Return 1 if job control is available on this system, otherwise 0.
 408 .It Li KERN_MAXFILES
 409 The maximum number of files that may be open in the system.
 410 .It Li KERN_MAXFILESPERPROC
 411 The maximum number of files that may be open for a single process.
 412 This limit only applies to processes with an effective uid of nonzero
 413 at the time of the open request.
 414 Files that have already been opened are not affected if the limit
 415 or the effective uid is changed.
 416 .It Li KERN_MAXPROC
 417 The maximum number of concurrent processes the system will allow.
 418 .It Li KERN_MAXPROCPERUID
 419 The maximum number of concurrent processes the system will allow
 420 for a single effective uid.
 421 This limit only applies to processes with an effective uid of nonzero
 422 at the time of a fork request.
 423 Processes that have already been started are not affected if the limit
 424 is changed.
 425 .It Li KERN_MAXVNODES
 426 The maximum number of vnodes available on the system.
 427 .It Li KERN_NGROUPS
 428 The maximum number of supplemental groups.
 429 .It Li KERN_NISDOMAINNAME
 430 The name of the current YP/NIS domain.
 431 .It Li KERN_OSRELDATE
 432 The kernel release version in the format
 433 .Ar M Ns Ar mm Ns Ar R Ns Ar xx ,
 434 where
 435 .Ar M
 436 is the major version,
 437 .Ar mm
 438 is the two digit minor version,
 439 .Ar R
 440 is 0 if release branch, otherwise 1,
 441 and
 442 .Ar xx
 443 is updated when the available APIs change.
 444 .Pp
 445 The userland release version is available from
 446 .In osreldate.h ;
 447 parse this file if you need to get the release version of
 448 the currently installed userland.
 449 .It Li KERN_OSRELEASE
 450 The system release string.
 451 .It Li KERN_OSREV
 452 The system revision string.
 453 .It Li KERN_OSTYPE
 454 The system type string.
 455 .It Li KERN_POSIX1
 456 The version of
 457 .St -p1003.1
 458 with which the system
 459 attempts to comply.
 460 .It Li KERN_PROC
 461 Return the entire process table, or a subset of it.
 462 An array of
 463 .Va struct kinfo_proc
 464 structures is returned,
 465 whose size depends on the current number of such objects in the system.
 466 The third and fourth level names are as follows:
 467 .Bl -column "Third level nameXXXXXX" "Fourth level is:XXXXXX" -offset indent
 468 .It "Third level name   Fourth level is:"
 469 .It "KERN_PROC_ALL      None"
 470 .It "KERN_PROC_PID      A process ID"
 471 .It "KERN_PROC_PGRP     A process group"
 472 .It "KERN_PROC_TTY      A tty device"
 473 .It "KERN_PROC_UID      A user ID"
 474 .It "KERN_PROC_RUID     A real user ID"
 475 .El
 476 .It Li KERN_PROF
 477 Return profiling information about the kernel.
 478 If the kernel is not compiled for profiling,
 479 attempts to retrieve any of the KERN_PROF values will
 480 fail with
 481 .Er ENOENT .
 482 The third level names for the string and integer profiling information
 483 is detailed below.
 484 The changeable column shows whether a process with appropriate
 485 privilege may change the value.
 486 .Bl -column "GPROFXGMONPARAMXXX" "struct gmonparamXXX" -offset indent
 487 .It Sy "Third level name        Type    Changeable"
 488 .It "GPROF_STATE        integer yes"
 489 .It "GPROF_COUNT        u_short[\|]     yes"
 490 .It "GPROF_FROMS        u_short[\|]     yes"
 491 .It "GPROF_TOS  struct tostruct yes"
 492 .It "GPROF_GMONPARAM    struct gmonparam        no"
 493 .El
 494 .Pp
 495 The variables are as follows:
 496 .Bl -tag -width 6n
 497 .It Li GPROF_STATE
 498 Returns GMON_PROF_ON or GMON_PROF_OFF to show that profiling
 499 is running or stopped.
 500 .It Li GPROF_COUNT
 501 Array of statistical program counter counts.
 502 .It Li GPROF_FROMS
 503 Array indexed by program counter of call-from points.
 504 .It Li GPROF_TOS
 505 Array of
 506 .Va struct tostruct
 507 describing destination of calls and their counts.
 508 .It Li GPROF_GMONPARAM
 509 Structure giving the sizes of the above arrays.
 510 .El
 511 .It Li KERN_QUANTUM
 512 The maximum period of time, in microseconds, for which a process is allowed
 513 to run without being preempted if other processes are in the run queue.
 514 .It Li KERN_SAVED_IDS
 515 Returns 1 if saved set-group and saved set-user ID is available.
 516 .It Li KERN_SECURELVL
 517 The system security level.
 518 This level may be raised by processes with appropriate privilege.
 519 It may not be lowered.
 520 .It Li KERN_VERSION
 521 The system version string.
 522 .It Li KERN_VNODE
 523 Return the entire vnode table.
 524 Note, the vnode table is not necessarily a consistent snapshot of
 525 the system.
 526 The returned data consists of an array whose size depends on the
 527 current number of such objects in the system.
 528 Each element of the array contains the kernel address of a vnode
 529 .Va struct vnode *
 530 followed by the vnode itself
 531 .Va struct vnode .
 532 .El
 533 .Ss CTL_MACHDEP
 534 The set of variables defined is architecture dependent.
 535 The following variables are defined for the i386 architecture.
 536 .Bl -column "CONSOLE_DEVICEXXX" "struct bootinfoXXX" -offset indent
 537 .It Sy "Second level name       Type    Changeable"
 538 .It Li "CPU_CONSDEV     dev_t   no"
 539 .It Li "CPU_ADJKERNTZ   int     yes"
 540 .It Li "CPU_DISRTCSET   int     yes"
 541 .It Li "CPU_BOOTINFO    struct bootinfo no"
 542 .It Li "CPU_WALLCLOCK   int     yes"
 543 .El
 544 .Ss CTL_NET
 545 The string and integer information available for the CTL_NET level
 546 is detailed below.
 547 The changeable column shows whether a process with appropriate
 548 privilege may change the value.
 549 .Bl -column "Second level nameXXXXXX" "routing messagesXXX" -offset indent
 550 .It Sy "Second level name       Type    Changeable"
 551 .It "PF_ROUTE   routing messages        no"
 552 .It "PF_INET    IPv4 values     yes"
 553 .It "PF_INET6   IPv6 values     yes"
 554 .El
 555 .Pp
 556 .Bl -tag -width 6n
 557 .It Li PF_ROUTE
 558 Return the entire routing table or a subset of it.
 559 The data is returned as a sequence of routing messages (see
 560 .Xr route 4
 561 for the header file, format and meaning).
 562 The length of each message is contained in the message header.
 563 .Pp
 564 The third level name is a protocol number, which is currently always 0.
 565 The fourth level name is an address family, which may be set to 0 to
 566 select all address families.
 567 The fifth and sixth level names are as follows:
 568 .Bl -column "Fifth level nameXXXXXX" "Sixth level is:XXX" -offset indent
 569 .It Sy "Fifth level name        Sixth level is:"
 570 .It "NET_RT_FLAGS       rtflags"
 571 .It "NET_RT_DUMP        None"
 572 .It "NET_RT_IFLIST      0 or if_index"
 573 .It "NET_RT_IFMALIST    0 or if_index"
 574 .El
 575 .Pp
 576 The
 577 .Dv NET_RT_IFMALIST
 578 name returns information about multicast group memberships on all interfaces
 579 if 0 is specified, or for the interface specified by
 580 .Va if_index .
 581 .It Li PF_INET
 582 Get or set various global information about the IPv4
 583 (Internet Protocol version 4).
 584 The third level name is the protocol.
 585 The fourth level name is the variable name.
 586 The currently defined protocols and names are:
 587 .Bl -column ProtocolXX VariableXX TypeXX ChangeableXX
 588 .It Sy "Protocol        Variable        Type    Changeable"
 589 .It "icmp       bmcastecho      integer yes"
 590 .It "icmp       maskrepl        integer yes"
 591 .It "ip forwarding      integer yes"
 592 .It "ip redirect        integer yes"
 593 .It "ip ttl     integer yes"
 594 .It "udp        checksum        integer yes"
 595 .El
 596 .Pp
 597 The variables are as follows:
 598 .Bl -tag -width 6n
 599 .It Li icmp.bmcastecho
 600 Returns 1 if an ICMP echo request to a broadcast or multicast address is
 601 to be answered.
 602 .It Li icmp.maskrepl
 603 Returns 1 if ICMP network mask requests are to be answered.
 604 .It Li ip.forwarding
 605 Returns 1 when IP forwarding is enabled for the host,
 606 meaning that the host is acting as a router.
 607 .It Li ip.redirect
 608 Returns 1 when ICMP redirects may be sent by the host.
 609 This option is ignored unless the host is routing IP packets,
 610 and should normally be enabled on all systems.
 611 .It Li ip.ttl
 612 The maximum time-to-live (hop count) value for an IP packet sourced by
 613 the system.
 614 This value applies to normal transport protocols, not to ICMP.
 615 .It Li udp.checksum
 616 Returns 1 when UDP checksums are being computed and checked.
 617 Disabling UDP checksums is strongly discouraged.
 618 .Pp
 619 For variables net.inet.*.ipsec, please refer to
 620 .Xr ipsec 4 .
 621 .El
 622 .It Li PF_INET6
 623 Get or set various global information about the IPv6
 624 (Internet Protocol version 6).
 625 The third level name is the protocol.
 626 The fourth level name is the variable name.
 627 .Pp
 628 For variables net.inet6.* please refer to
 629 .Xr inet6 4 .
 630 For variables net.inet6.*.ipsec6, please refer to
 631 .Xr ipsec 4 .
 632 .El
 633 .Ss CTL_USER
 634 The string and integer information available for the CTL_USER level
 635 is detailed below.
 636 The changeable column shows whether a process with appropriate
 637 privilege may change the value.
 638 .Bl -column "USER_COLL_WEIGHTS_MAXXXX" "integerXXX" -offset indent
 639 .It Sy "Second level name       Type    Changeable"
 640 .It "USER_BC_BASE_MAX   integer no"
 641 .It "USER_BC_DIM_MAX    integer no"
 642 .It "USER_BC_SCALE_MAX  integer no"
 643 .It "USER_BC_STRING_MAX integer no"
 644 .It "USER_COLL_WEIGHTS_MAX      integer no"
 645 .It "USER_CS_PATH       string  no"
 646 .It "USER_EXPR_NEST_MAX integer no"
 647 .It "USER_LINE_MAX      integer no"
 648 .It "USER_POSIX2_CHAR_TERM      integer no"
 649 .It "USER_POSIX2_C_BIND integer no"
 650 .It "USER_POSIX2_C_DEV  integer no"
 651 .It "USER_POSIX2_FORT_DEV       integer no"
 652 .It "USER_POSIX2_FORT_RUN       integer no"
 653 .It "USER_POSIX2_LOCALEDEF      integer no"
 654 .It "USER_POSIX2_SW_DEV integer no"
 655 .It "USER_POSIX2_UPE    integer no"
 656 .It "USER_POSIX2_VERSION        integer no"
 657 .It "USER_RE_DUP_MAX    integer no"
 658 .It "USER_STREAM_MAX    integer no"
 659 .It "USER_TZNAME_MAX    integer no"
 660 .El
 661 .Bl -tag -width 6n
 662 .Pp
 663 .It Li USER_BC_BASE_MAX
 664 The maximum ibase/obase values in the
 665 .Xr bc 1
 666 utility.
 667 .It Li USER_BC_DIM_MAX
 668 The maximum array size in the
 669 .Xr bc 1
 670 utility.
 671 .It Li USER_BC_SCALE_MAX
 672 The maximum scale value in the
 673 .Xr bc 1
 674 utility.
 675 .It Li USER_BC_STRING_MAX
 676 The maximum string length in the
 677 .Xr bc 1
 678 utility.
 679 .It Li USER_COLL_WEIGHTS_MAX
 680 The maximum number of weights that can be assigned to any entry of
 681 the LC_COLLATE order keyword in the locale definition file.
 682 .It Li USER_CS_PATH
 683 Return a value for the
 684 .Ev PATH
 685 environment variable that finds all the standard utilities.
 686 .It Li USER_EXPR_NEST_MAX
 687 The maximum number of expressions that can be nested within
 688 parenthesis by the
 689 .Xr expr 1
 690 utility.
 691 .It Li USER_LINE_MAX
 692 The maximum length in bytes of a text-processing utility's input
 693 line.
 694 .It Li USER_POSIX2_CHAR_TERM
 695 Return 1 if the system supports at least one terminal type capable of
 696 all operations described in
 697 .St -p1003.2 ,
 698 otherwise 0.
 699 .It Li USER_POSIX2_C_BIND
 700 Return 1 if the system's C-language development facilities support the
 701 C-Language Bindings Option, otherwise 0.
 702 .It Li USER_POSIX2_C_DEV
 703 Return 1 if the system supports the C-Language Development Utilities Option,
 704 otherwise 0.
 705 .It Li USER_POSIX2_FORT_DEV
 706 Return 1 if the system supports the FORTRAN Development Utilities Option,
 707 otherwise 0.
 708 .It Li USER_POSIX2_FORT_RUN
 709 Return 1 if the system supports the FORTRAN Runtime Utilities Option,
 710 otherwise 0.
 711 .It Li USER_POSIX2_LOCALEDEF
 712 Return 1 if the system supports the creation of locales, otherwise 0.
 713 .It Li USER_POSIX2_SW_DEV
 714 Return 1 if the system supports the Software Development Utilities Option,
 715 otherwise 0.
 716 .It Li USER_POSIX2_UPE
 717 Return 1 if the system supports the User Portability Utilities Option,
 718 otherwise 0.
 719 .It Li USER_POSIX2_VERSION
 720 The version of
 721 .St -p1003.2
 722 with which the system attempts to comply.
 723 .It Li USER_RE_DUP_MAX
 724 The maximum number of repeated occurrences of a regular expression
 725 permitted when using interval notation.
 726 .It Li USER_STREAM_MAX
 727 The minimum maximum number of streams that a process may have open
 728 at any one time.
 729 .It Li USER_TZNAME_MAX
 730 The minimum maximum number of types supported for the name of a
 731 timezone.
 732 .El
 733 .Ss CTL_VM
 734 The string and integer information available for the CTL_VM level
 735 is detailed below.
 736 The changeable column shows whether a process with appropriate
 737 privilege may change the value.
 738 .Bl -column "Second level nameXXXXXX" "struct loadavgXXX" -offset indent
 739 .It Sy "Second level name       Type    Changeable"
 740 .It "VM_LOADAVG struct loadavg  no"
 741 .It "VM_PAGEOUT_ALGORITHM       integer yes"
 742 .It "VM_SWAPPING_ENABLED        integer maybe"
 743 .It "VM_V_CACHE_MAX     integer yes"
 744 .It "VM_V_CACHE_MIN     integer yes"
 745 .It "VM_V_FREE_MIN      integer yes"
 746 .It "VM_V_FREE_RESERVED integer yes"
 747 .It "VM_V_FREE_TARGET   integer yes"
 748 .It "VM_V_INACTIVE_TARGET       integer yes"
 749 .It "VM_V_PAGEOUT_FREE_MIN      integer yes"
 750 .El
 751 .Pp
 752 .Bl -tag -width 6n
 753 .It Li VM_LOADAVG
 754 Return the load average history.
 755 The returned data consists of a
 756 .Va struct loadavg .
 757 .It Li VM_PAGEOUT_ALGORITHM
 758 0 if the statistics-based page management algorithm is in use
 759 or 1 if the near-LRU algorithm is in use.
 760 .It Li VM_SWAPPING_ENABLED
 761 1 if process swapping is enabled or 0 if disabled.
 762 This variable is
 763 permanently set to 0 if the kernel was built with swapping disabled.
 764 .It Li VM_V_CACHE_MAX
 765 Maximum desired size of the cache queue.
 766 .It Li VM_V_CACHE_MIN
 767 Minimum desired size of the cache queue.
 768 If the cache queue size
 769 falls very far below this value, the pageout daemon is awakened.
 770 .It Li VM_V_FREE_MIN
 771 Minimum amount of memory (cache memory plus free memory)
 772 required to be available before a process waiting on memory will be
 773 awakened.
 774 .It Li VM_V_FREE_RESERVED
 775 Processes will awaken the pageout daemon and wait for memory if the
 776 number of free and cached pages drops below this value.
 777 .It Li VM_V_FREE_TARGET
 778 The total amount of free memory (including cache memory) that the
 779 pageout daemon tries to maintain.
 780 .It Li VM_V_INACTIVE_TARGET
 781 The desired number of inactive pages that the pageout daemon should
 782 achieve when it runs.
 783 Inactive pages can be quickly inserted into
 784 process address space when needed.
 785 .It Li VM_V_PAGEOUT_FREE_MIN
 786 If the amount of free and cache memory falls below this value, the
 787 pageout daemon will enter "memory conserving mode" to avoid deadlock.
 788 .El
 789 .Sh RETURN VALUES
 790 .Rv -std
 791 .Sh ERRORS
 792 The following errors may be reported:
 793 .Bl -tag -width Er
 794 .It Bq Er EFAULT
 795 The buffer
 796 .Fa name ,
 797 .Fa oldp ,
 798 .Fa newp ,
 799 or length pointer
 800 .Fa oldlenp
 801 contains an invalid address.
 802 .It Bq Er EINVAL
 803 The
 804 .Fa name
 805 array is less than two or greater than CTL_MAXNAME.
 806 .It Bq Er EINVAL
 807 A non-null
 808 .Fa newp
 809 is given and its specified length in
 810 .Fa newlen
 811 is too large or too small.
 812 .It Bq Er ENOMEM
 813 The length pointed to by
 814 .Fa oldlenp
 815 is too short to hold the requested value.
 816 .It Bq Er ENOMEM
 817 The smaller of either the length pointed to by
 818 .Fa oldlenp
 819 or the estimated size of the returned data exceeds the
 820 system limit on locked memory.
 821 .It Bq Er ENOMEM
 822 Locking the buffer
 823 .Fa oldp ,
 824 or a portion of the buffer if the estimated size of the data
 825 to be returned is smaller,
 826 would cause the process to exceed its per-process locked memory limit.
 827 .It Bq Er ENOTDIR
 828 The
 829 .Fa name
 830 array specifies an intermediate rather than terminal name.
 831 .It Bq Er EISDIR
 832 The
 833 .Fa name
 834 array specifies a terminal name, but the actual name is not terminal.
 835 .It Bq Er ENOENT
 836 The
 837 .Fa name
 838 array specifies a value that is unknown.
 839 .It Bq Er EPERM
 840 An attempt is made to set a read-only value.
 841 .It Bq Er EPERM
 842 A process without appropriate privilege attempts to set a value.
 843 .El
 844 .Sh FILES
 845 .Bl -tag -width <netinet/icmpXvar.h> -compact
 846 .It In sys/sysctl.h
 847 definitions for top level identifiers, second level kernel and hardware
 848 identifiers, and user level identifiers
 849 .It In sys/socket.h
 850 definitions for second level network identifiers
 851 .It In sys/gmon.h
 852 definitions for third level profiling identifiers
 853 .It In mach/vm_param.h
 854 definitions for second level virtual memory identifiers
 855 .It In netinet/in.h
 856 definitions for third level IPv4/IPv6 identifiers and
 857 fourth level IPv4/v6 identifiers
 858 .It In netinet/icmp_var.h
 859 definitions for fourth level ICMP identifiers
 860 .It In netinet/icmp6.h
 861 definitions for fourth level ICMPv6 identifiers
 862 .It In netinet/udp_var.h
 863 definitions for fourth level UDP identifiers
 864 .El
 865 .Sh SEE ALSO
 866 .Xr sysctl 1 ,
 867 .Xr sysconf 3 ,
 868 .Xr sysctl 8
 869 .Sh HISTORY
 870 The
 871 .Fn sysctl
 872 function first appeared in
 873 .Bx 4.4 .