.\" $NetBSD: sysctl.3,v 1.40 1999/10/14 09:33:51 jdolecek Exp $ .\" .\" Copyright (c) 1993 .\" The Regents of the University of California. All rights reserved. .\" .\" Redistribution and use in source and binary forms, with or without .\" modification, are permitted provided that the following conditions .\" are met: .\" 1. Redistributions of source code must retain the above copyright .\" notice, this list of conditions and the following disclaimer. .\" 2. Redistributions in binary form must reproduce the above copyright .\" notice, this list of conditions and the following disclaimer in the .\" documentation and/or other materials provided with the distribution. .\" 3. All advertising materials mentioning features or use of this software .\" must display the following acknowledgement: .\" This product includes software developed by the University of .\" California, Berkeley and its contributors. .\" 4. Neither the name of the University nor the names of its contributors .\" may be used to endorse or promote products derived from this software .\" without specific prior written permission. .\" .\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND .\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE .\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE .\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE .\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL .\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS .\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) .\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT .\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY .\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF .\" SUCH DAMAGE. .\" .\" @(#)sysctl.3 8.4 (Berkeley) 5/9/95 .\" .Dd June 24, 1999 .Dt SYSCTL 3 .Os .Sh NAME .Nm sysctl .Nd get or set system information .Sh LIBRARY .Lb libc .Sh SYNOPSIS .Fd #include .Fd #include .Ft int .Fn sysctl "int *name" "u_int namelen" "void *oldp" "size_t *oldlenp" "void *newp" "size_t newlen" .Sh DESCRIPTION The .Nm function retrieves system information and allows processes with appropriate privileges to set system information. The information available from .Nm consists of integers, strings, and tables. Information may be retrieved and set from the command interface using the .Xr sysctl 8 utility. .Pp Unless explicitly noted below, .Nm returns a consistent snapshot of the data requested. Consistency is obtained by locking the destination buffer into memory so that the data may be copied out without blocking. Calls to .Nm are serialized to avoid deadlock. .Pp The state is described using a ``Management Information Base'' (MIB) style name, listed in .Fa name , which is a .Fa namelen length array of integers. .Pp The information is copied into the buffer specified by .Fa oldp . The size of the buffer is given by the location specified by .Fa oldlenp before the call, and that location gives the amount of data copied after a successful call. If the amount of data available is greater than the size of the buffer supplied, the call supplies as much data as fits in the buffer provided and returns with the error code ENOMEM. If the old value is not desired, .Fa oldp and .Fa oldlenp should be set to NULL. .Pp The size of the available data can be determined by calling .Nm with a NULL parameter for .Fa oldp . The size of the available data will be returned in the location pointed to by .Fa oldlenp . For some operations, the amount of space may change often. For these operations, the system attempts to round up so that the returned size is large enough for a call to return the data shortly thereafter. .Pp To set a new value, .Fa newp is set to point to a buffer of length .Fa newlen from which the requested value is to be taken. If a new value is not to be set, .Fa newp should be set to NULL and .Fa newlen set to 0. .Pp The top level names are defined with a CTL_ prefix in .Pa , and are as follows. The next and subsequent levels down are found in the include files listed here, and described in separate sections below. .Pp .Bl -column CTLXMACHDEPXXX "Next level namesXXXXXX" -offset indent .It Sy Pa Name Next level names Description .It CTL\_DEBUG sys/sysctl.h Debugging .It CTL\_VFS sys/mount.h Filesystem .It CTL\_HW sys/sysctl.h Generic CPU, I/O .It CTL\_KERN sys/sysctl.h High kernel limits .It CTL\_MACHDEP sys/sysctl.h Machine dependent .It CTL\_NET sys/socket.h Networking .It CTL\_PROC sys/sysctl.h Per-process .It CTL\_USER sys/sysctl.h User-level .It CTL\_VM vm/vm_param.h Virtual memory .El .Pp For example, the following retrieves the maximum number of processes allowed in the system: .Bd -literal -offset indent -compact int mib[2], maxproc; size_t len; .sp mib[0] = CTL_KERN; mib[1] = KERN_MAXPROC; len = sizeof(maxproc); sysctl(mib, 2, &maxproc, &len, NULL, 0); .Ed .sp To retrieve the standard search path for the system utilities: .Bd -literal -offset indent -compact int mib[2]; size_t len; char *p; .sp mib[0] = CTL_USER; mib[1] = USER_CS_PATH; sysctl(mib, 2, NULL, &len, NULL, 0); p = malloc(len); sysctl(mib, 2, p, &len, NULL, 0); .Ed .Sh CTL_DEBUG The debugging variables vary from system to system. A debugging variable may be added or deleted without need to recompile .Nm to know about it. Each time it runs, .Nm gets the list of debugging variables from the kernel and displays their current values. The system defines twenty .Ns ( Va struct ctldebug ) variables named .Dv debug0 through .Dv debug19 . They are declared as separate variables so that they can be individually initialized at the location of their associated variable. The loader prevents multiple use of the same variable by issuing errors if a variable is initialized in more than one place. For example, to export the variable .Dv dospecialcheck as a debugging variable, the following declaration would be used: .Bd -literal -offset indent -compact int dospecialcheck = 1; struct ctldebug debug5 = { "dospecialcheck", &dospecialcheck }; .Ed .Sh CTL_VFS A distinguished second level name, VFS_GENERIC, is used to get general information about all filesystems. One of its third level identifiers is VFS_MAXTYPENUM that gives the highest valid filesystem type number. Its other third level identifier is VFS_CONF that returns configuration information about the filesystem type given as a fourth level identifier (see .Xr getvfsbyname 3 as an example of its use). The remaining second level identifiers are the filesystem type number returned by a .Xr statfs 2 call or from VFS_CONF. The third level identifiers available for each filesystem are given in the header file that defines the mount argument structure for that filesystem. .Sh CTL_HW The string and integer information available for the CTL_HW level is detailed below. The changeable column shows whether a process with appropriate privilege may change the value. .Bl -column "Second level nameXXXXXX" integerXXX -offset indent .It Sy Pa Second level name Type Changeable .It HW\_MACHINE string no .It HW\_MODEL string no .It HW\_NCPU integer no .It HW\_BYTEORDER integer no .It HW\_PHYSMEM integer no .It HW\_USERMEM integer no .It HW\_PAGESIZE integer no .It HW\_MACHINE\_ARCH string no .\".It HW\_DISKNAMES integer no .\".It HW\_DISKSTATS integer no .El .Pp .Bl -tag -width "123456" .It Li HW_MACHINE The machine class. .It Li HW_MODEL The machine model .It Li HW_NCPU The number of cpus. .ne 1i .It Li HW_BYTEORDER The byteorder (4,321, or 1,234). .It Li HW_PHYSMEM The bytes of physical memory. .It Li HW_USERMEM The bytes of non-kernel memory. .It Li HW_PAGESIZE The software page size. .It Li HW_MACHINE_ARCH The machine cpu class. .\".It Fa HW_DISKNAMES .\".It Fa HW_DISKSTATS .El .Sh CTL_KERN The string and integer information available for the CTL_KERN level is detailed below. The changeable column shows whether a process with appropriate privilege may change the value. The types of data currently available are process information, system vnodes, the open file entries, routing table entries, virtual memory statistics, load average history, and clock rate information. .Bl -column "KERNXCHOWNXRESTRICTEDXXX" "struct clockrateXXX" -offset indent .It Sy Pa Second level name Type Changeable .It KERN\_ARGMAX integer no .It KERN\_AUTONICETIME integer yes .It KERN\_AUTONICEVAL integer yes .It KERN\_BOOTTIME struct timeval no .It KERN\_CHOWN\_RESTRICTED integer no .It KERN\_CLOCKRATE struct clockinfo no .It KERN\_DEFCORENAME string yes .It KERN\_DOMAINNAME string yes .It KERN\_FILE struct file no .It KERN\_FSYNC integer no .It KERN\_HOSTID integer yes .It KERN\_HOSTNAME string yes .It KERN\_IOV\_MAX integer no .It KERN\_JOB\_CONTROL integer no .It KERN\_LINK\_MAX integer no .It KERN\_LOGIN\_NAME\_MAX integer no .It KERN\_MAPPED\_FILES integer no .It KERN\_MAXFILES integer yes .It KERN\_MAXPARTITIONS integer no .It KERN\_MAXPROC integer yes .It KERN\_MAXVNODES integer yes .It KERN\_MAX\_CANON integer no .It KERN\_MAX\_INPUT integer no .It KERN\_MEMLOCK integer no .It KERN\_MEMLOCK\_RANGE integer no .It KERN\_MEMORY\_PROTECTION integer no .It KERN\_MSGBUFSIZE integer no .It KERN\_NAME\_MAX integer no .It KERN\_NGROUPS integer no .It KERN\_NO\_TRUNC integer no .It KERN\_OSRELEASE string no .It KERN\_OSREV integer no .It KERN\_OSTYPE string no .It KERN\_PATH\_MAX integer no .It KERN\_PIPE\_BUF integer no .It KERN\_POSIX1 integer no .It KERN\_PROC struct proc no .It KERN\_PROF node not applicable .It KERN\_RAWPARTITION integer no .It KERN\_SAVED\_IDS integer no .It KERN\_SECURELVL integer raise only .It KERN\_SYNCHRONIZED\_IO integer no .It KERN\_SYSVMSG integer no .It KERN\_SYSVSEM integer no .It KERN\_SYSVSHM integer no .It KERN\_VDISABLE integer no .It KERN\_VERSION string no .It KERN\_VNODE struct vnode no .El .ne 1i .Pp .Bl -tag -width "123456" .It Li KERN_ARGMAX The maximum bytes of argument to .Xr execve 2 . .It Li KERN_AUTONICETIME The number of seconds of cpu-time a non-root process may accumulate before having its priority lowered from the default to the value of KERN_AUTONICEVAL. If set to 0, automatic lowering of priority is not performed, and if set to -1 all non-root processes are immediately lowered. .It Li KERN_AUTONICEVAL The priority assigned for automatically niced processes. .It Li KERN_BOOTTIME A .Va struct timeval structure is returned. This structure contains the time that the system was booted. .It Li KERN_CHOWN_RESTRICTED Return 1 if appropriate privileges are required for the .Xr chown 2 system call, otherwise 0. .It Li KERN_CLOCKRATE A .Va struct clockinfo structure is returned. This structure contains the clock, statistics clock and profiling clock frequencies, the number of micro-seconds per hz tick, and the clock skew rate. .It Li KERN_DEFCORENAME Default template for the name of core dump files (see also PROC_PID_CORENAME in the per-process variables CTL_PROC, and .Xr core 5 for format of this template). The default value is .Nm %n.core and can be changed with the kernel configuration option .Cd options DEFCORENAME (see .Xr options 4 ). .It Li KERN_DOMAINNAME Get or set the YP domain name. .It Li KERN_FILE Return the entire file table. The returned data consists of a single .Va struct filehead followed by an array of .Va struct file , whose size depends on the current number of such objects in the system. .It Li KERN_FSYNC Return 1 if the POSIX 1003.1b File Synchronization Option is available on this system, otherwise 0. .It Li KERN_HOSTID Get or set the host id. .It Li KERN_HOSTNAME Get or set the hostname. .It Li KERN_IOV_MAX Return the maximum number of .Va iovec structures that a process has available for use with .Xr preadv 2 , .Xr pwritev 2 , .Xr readv 2 , .Xr recvmsg 2 , .Xr sendmsg 2 and .Xr writev 2 . .It Li KERN_JOB_CONTROL Return 1 if job control is available on this system, otherwise 0. .It Li KERN_LINK_MAX The maximum file link count. .It Li KERN_LOGIN_NAME_MAX The size of the storage required for a login name, in bytes, including the terminating NUL. .It Li KERN_MAPPED_FILES Returns 1 if the POSIX 1003.1b Memory Mapped Files Option is available on this system, otherwise 0. .It Li KERN_MAXFILES The maximum number of open files that may be open in the system. .It Li KERN_MAXPARTITIONS The maximum number of partitions allowed per disk. .It Li KERN_MAXPROC The maximum number of simultaneous processes the system will allow. .It Li KERN_MAXVNODES The maximum number of vnodes available on the system. .It Li KERN_MAX_CANON The maximum number of bytes in terminal canonical input line. .It Li KERN_MAX_INPUT The minimum maximum number of bytes for which space is available in a terminal input queue. .It Li KERN_MEMLOCK Returns 1 if the POSIX 1003.1b Process Memory Locking Option is available on this system, otherwise 0. .It Li KERN_MEMLOCK_RANGE Returns 1 if the POSIX 1003.1b Range Memory Locking Option is available on this system, otherwise 0. .It Li KERN_MEMORY_PROTECTION Returns 1 if the POSIX 1003.1b Memory Protection Option is available on this system, otherwise 0. .It Li KERN_MSGBUFSIZE The maximum number of characters that the kernel message buffer can hold. .It Li KERN_NAME_MAX The maximum number of bytes in a file name. .It Li KERN_NGROUPS The maximum number of supplemental groups. .It Li KERN_NO_TRUNC Return 1 if file names longer than KERN_NAME_MAX are truncated. .It Li KERN_OSRELEASE The system release string. .It Li KERN_OSREV The system revision string. .It Li KERN_OSTYPE The system type string. .It Li KERN_PATH_MAX The maximum number of bytes in a pathname. .It Li KERN_PIPE_BUF The maximum number of bytes which will be written atomically to a pipe. .It Li KERN_POSIX1 The version of ISO/IEC 9945 (POSIX 1003.1) with which the system attempts to comply. .It Li KERN_PROC Return the entire process table, or a subset of it. An array of .Va struct kinfo_proc structures is returned, whose size depends on the current number of such objects in the system. The third and fourth level names are as follows: .Bl -column "Third level nameXXXXXX" "Fourth level is:XXXXXX" -offset indent .It Pa Third level name Fourth level is: .It KERN\_PROC\_ALL None .It KERN\_PROC\_PID A process ID .It KERN\_PROC\_PGRP A process group .It KERN\_PROC\_TTY A tty device .It KERN\_PROC\_UID A user ID .It KERN\_PROC\_RUID A real user ID .El .It Li KERN_PROF Return profiling information about the kernel. If the kernel is not compiled for profiling, attempts to retrieve any of the KERN_PROF values will fail with EOPNOTSUPP. The third level names for the string and integer profiling information is detailed below. The changeable column shows whether a process with appropriate privilege may change the value. .Bl -column "GPROFXGMONPARAMXXX" "struct gmonparamXXX" -offset indent .It Sy Pa Third level name Type Changeable .It GPROF\_STATE integer yes .It GPROF\_COUNT u_short[\|] yes .It GPROF\_FROMS u_short[\|] yes .It GPROF\_TOS struct tostruct yes .It GPROF\_GMONPARAM struct gmonparam no .El .Pp The variables are as follows: .Bl -tag -width "123456" .It Li GPROF_STATE Returns GMON_PROF_ON or GMON_PROF_OFF to show that profiling is running or stopped. .It Li GPROF_COUNT Array of statistical program counter counts. .It Li GPROF_FROMS Array indexed by program counter of call-from points. .It Li GPROF_TOS Array of .Va struct tostruct describing destination of calls and their counts. .It Li GPROF_GMONPARAM Structure giving the sizes of the above arrays. .El .It Li KERN_RAWPARTITION The raw partition of a disk (a == 0). .It Li KERN_SAVED_IDS Returns 1 if saved set-group and saved set-user ID is available. .It Li KERN_SECURELVL The system security level. This level may be raised by processes with appropriate privilege. It may only be lowered by process 1. .It Li KERN_SYNCHRONIZED_IO Returns 1 if the POSIX 1003.1b Synchronized I/O Option is available on this system, otherwise 0. .It Li KERN_SYSVMSG Returns 1 if System V style message queue functionality is available on this system, otherwise 0. .It Li KERN_SYSVSEM Returns 1 if System V style semaphore functionality is available on this system, otherwise 0. .It Li KERN_SYSVSHM Returns 1 if System V style share memory functionality is available on this system, otherwise 0. .It Li KERN_VDISABLE Returns the terminal character disabling value. .It Li KERN_VERSION The system version string. .It Li KERN_VNODE Return the entire vnode table. Note, the vnode table is not necessarily a consistent snapshot of the system. The returned data consists of an array whose size depends on the current number of such objects in the system. Each element of the array contains the kernel address of a vnode .Va struct vnode * followed by the vnode itself .Va struct vnode . .El .Sh CTL_MACHDEP The set of variables defined is architecture dependent. Most architectures define at least the following variables. .Bl -column "CONSOLE_DEVICEXXX" "integerXXX" -offset indent .It Sy Pa Second level name Type Changeable .It Li CPU_CONSDEV dev_t no .El .Sh CTL_NET The string and integer information available for the CTL_NET level is detailed below. The changeable column shows whether a process with appropriate privilege may change the value. .Bl -column "Second level nameXXXXXX" "routing messagesXXX" -offset indent .It Sy Pa Second level name Type Changeable .It PF\_ROUTE routing messages no .It PF\_INET internet values yes .El .Pp .Bl -tag -width "123456" .It Li PF_ROUTE Return the entire routing table or a subset of it. The data is returned as a sequence of routing messages (see .Xr route 4 for the header file, format and meaning). The length of each message is contained in the message header. .Pp The third level name is a protocol number, which is currently always 0. The fourth level name is an address family, which may be set to 0 to select all address families. The fifth and sixth level names are as follows: .Bl -column "Fifth level nameXXXXXX" "Sixth level is:XXX" -offset indent .It Pa Fifth level name Sixth level is: .It NET\_RT\_FLAGS rtflags .It NET\_RT\_DUMP None .It NET\_RT\_IFLIST None .El .It Li PF_INET Get or set various global information about the internet protocols. The third level name is the protocol. The fourth level name is the variable name. The currently defined protocols and names are: .Bl -column "Protocol name" "Variable nameXX" "integer" "yes" -offset indent .It Pa Protocol name Variable name Type Changeable .It ip forwarding integer yes .It ip redirect integer yes .It ip ttl integer yes .It ip forwsrcrt integer yes .It ip directed-broadcast integer yes .It ip allowsrcrt integer yes .It ip subnetsarelocal integer yes .It ip mtudisc integer yes .It ip anonportmin integer yes .It ip anonportmax integer yes .It ip mtudisctimeout integer yes .It icmp maskrepl integer yes .It tcp rfc1323 integer yes .It tcp sendspace integer yes .It tcp recvspace integer yes .It tcp mssdflt integer yes .It tcp syn_cache_limit integer yes .It tcp syn_bucket_limit integer yes .It tcp syn_cache_interval integer yes .It tcp init_win integer yes .It tcp mss_ifmtu integer yes .It tcp sack integer yes .It tcp win_scale integer yes .It tcp timestamps integer yes .It tcp compat_42 integer yes .It tcp cwm integer yes .It tcp cwm_burstsize integer yes .It tcp ack_on_push integer yes .It tcp keepidle integer yes .It tcp keepintvl integer yes .It tcp keepcnt integer yes .It tcp slowhz integer no .It tcp newreno integer yes .It tcp log_refused integer yes .It udp checksum integer yes .It udp sendspace integer yes .It udp recvspace integer yes .El .Pp The variables are as follows: .Bl -tag -width "123456" .It Li ip.forwarding Returns 1 when IP forwarding is enabled for the host, meaning that the host is acting as a router. .It Li ip.redirect Returns 1 when ICMP redirects may be sent by the host. This option is ignored unless the host is routing IP packets, and should normally be enabled on all systems. .It Li ip.ttl The maximum time-to-live (hop count) value for an IP packet sourced by the system. This value applies to normal transport protocols, not to ICMP. .It Li ip.forwsrcrt Returns 1 when forwarding of source-routed packets is enabled for the host. This value may only be changed if the kernel security level is less than 1. .It Li ip.directed-broadcast Returns 1 if directed broadcast behavior is enabled for the host. .It Li ip.allowsrcrt Returns 1 if the host accepts source routed packets. .It Li ip.subnetsarelocal Returns 1 if subnets are to be considered local addresses. .It Li ip.mtudisc Returns 1 if Path MTU Discovery is enabled. .It Li ip.anonportmin The lowest port number to use for TCP and UDP ephemeral port allocation. This cannot be set to less that 1024 or greater than 65535. .It Li ip.anonportmax The highest port number to use for TCP and UDP ephemeral port allocation. This cannot be set to less that 1024 or greater than 65535, and must be greater than .Li ip.anonportmin . .It Li ip.mtudisctimeout Returns the number of seconds in which a route added by the Path MTU Discovery engine will time out. When the route times out, the Path MTU Discovery engine will attempt to probe a larger path MTU. .It Li icmp.maskrepl Returns 1 if ICMP network mask requests are to be answered. .It Li tcp.rfc1323 Returns 1 if RFC1323 extensions to TCP are enabled. .It Li tcp.sendspace Returns the default TCP send buffer size. .It Li tcp.recvspace Returns the default TCP receive buffer size. .It Li tcp.mssdflt Returns the default maximum segment size both advertsized to the peer and to use when the peer does not advertize a maximum segment size to us during connection setup. Do not change this value unless you really know what you are doing. .It Li tcp.syn_cache_limit Returns the maximum number of entries allowed in the TCP compressed state engine. .It Li tcp.syn_bucket_limit Returns the maximum number of entries allowed per hash bucket in the TCP compressed state engine. .It Li tcp.syn_cache_interval Returns the TCP compressed state engine's timer interval. .It Li tcp.init_win Returns a value indicating the TCP initial congestion window. If this value is 0, an auto-tuning algorithm designed to use an initial window of approximately 4K bytes is in use. Otherwise, this value indicates a fixed number of packets. .It Li tcp.mss_ifmtu Returns 1 if TCP calculates the outgoing maximum segment size based on the MTU of the appropriate interface. Otherwise, it is calculated based on the greater of the MTU of the interface, and the largest (non-loopback) interface MTU on the system. .It Li tcp.sack Returns a value which determines the level of Selective Acknowledgement supported by TCP. If 2, we will transmit and receive SACK options. If 1, we will transmit SACK options, but ignore any SACK options received. If 0, SACK is disabled. .It Li tcp.win_scale If rfc1323 is enabled, a value of 1 indicates RFC1323 window scale options, for increasing the TCP window size, are enabled. .It Li tcp.timestamps If rfc1323 is enabled, a value of 1 indicates RFC1323 time stamp options, used for measuring TCP round trip times, are enabled. .It Li tcp.compat_42 Returns 1 if work-arounds for bugs in the 4.2BSD TCP implementation are enabled. Use of this option is not recommended, although it may be required in order to communicate with extremely old TCP implementations. .It Li tcp.cwm Returns 1 if use of the Hughes/Touch/Heidemann Congestion Window Monitoring algorithm is enabled. This algorithm prevents line-rate bursts of packets that could otherwise occur when data begins flowing on an idle TCP connection. These line-rate bursts can contribute to network and router congestion. This can be particularly useful on World Wide Web servers which support HTTP/1.1, which has lingering connections. .It Li tcp.cwm_burstsize Returns the Congestion Window Monitoring allowed burst size, in terms of packet count. .It Li tcp.ack_on_push Returns 1 if TCP is to immediately transmit an ACK upon reception of a packet with PUSH set. This can avoid losing a round trip time in some rare situations, but has the caveat of potentially defeating TCP's delayed ACK algorithm. Use of this option is generally not recommended, but the variable exists in case your configuration really needs it. .It Li tcp.keepidle Time a connection must be idle before keepalives are sent (if keepalives are enabled for the connection). See also tcp.slowhz. .It Li tcp.keepintvl Time after a keepalive probe is sent until, in the absence of any response, another probe is sent. See also tcp.slowhz. .It Li tcp.keepcnt Number of keepalive probes sent before declaring a connection dead. If set to zero, there is no limit; keepalives will be sent until some kind of response is received from the peer. .It Li tcp.slowhz The units for tcp.keepidle and tcp.keepintvl; those variables are in ticks of a clock that ticks tcp.slowhz times per second. (That is, their values must be divided by the tcp.slowhz value to get times in seconds.) .It Li tcp.newreno Returns 1 if the use of J. Hoe's NewReno congestion control algorithm is enabled. This algorithm improves the start-up behavior of TCP connections. .It Li tcp.log_refused When set to 1, all refused TCP connections to the host are logged. .It Li udp.checksum Returns 1 when UDP checksums are being computed and checked. Disabling UDP checksums is strongly discouraged. .It Li udp.sendspace Returns the default UDP send buffer size. .It Li udp.recvspace Returns the default UDP receive buffer size. .El .Pp For variables net.*.ipsec, please refer to .Xr ipsec 4 . .El .Sh CTL_PROC The string and integer information available for the CTL_PROC is detailed below. The changeable column shows whether a process with appropriate privilege may change the value. These values are per-process, and as such may change from one process to another. When a process is created, the default values are inherited from its parent. When a set-user-ID or set-group-ID binary is executed, the value of PROC_PID_CORENAME is reset to the system default value. The second level name is either the magic value PROC_CURPROC, which points to the current process, or the PID of the target process. .Bl -column "USER_COLL_WEIGHTS_MAXXXX" "integerXXX" "yes" -offset indent .It Sy Pa Third level name Type Changeable .It PROC\_PID\_CORENAME string yes .It PROC\_PID\_LIMIT node not applicable .El .Bl -tag -width "123456" .Pp .It Li PROC_PID_CORENAME The template used for the core dump file name (see .Xr core 5 for details). The base name must either be .Nm core or end with the suffix ``.core'' (the super-user may set arbitrary names). By default it points to KERN_DEFCORENAME. .It Li PROC_PID_LIMIT Return resources limits, as defined for the .Xr getrlimit 2 and .Xr setrlimit 2 system calls. The fourth level name is one of: .Bl -tag -width PROC_PID_LIMIT_MEMLOCKAA .It Li PROC_PID_LIMIT_CPU The maximum amount of cpu time (in seconds) to be used by each process. .It Li PROC_PID_LIMIT_FSIZE The largest size (in bytes) file that may be created. .It Li PROC_PID_LIMIT_DATA The maximum size (in bytes) of the data segment for a process; this defines how far a program may extend its break with the .Xr sbrk 2 system call. .It Li PROC_PID_LIMIT_STACK The maximum size (in bytes) of the stack segment for a process; this defines how far a program's stack segment may be extended. Stack extension is performed automatically by the system. .It Li PROC_PID_LIMIT_CORE The largest size (in bytes) .Pa core file that may be created. .It Li PROC_PID_LIMIT_RSS The maximum size (in bytes) to which a process's resident set size may grow. This imposes a limit on the amount of physical memory to be given to a process; if memory is tight, the system will prefer to take memory from processes that are exceeding their declared resident set size. .It Li PROC_PID_LIMIT_MEMLOCK The maximum size (in bytes) which a process may lock into memory using the .Xr mlock 2 function. .It Li PROC_PID_LIMIT_NPROC The maximum number of simultaneous processes for this user id. .It Li PROC_PID_LIMIT_NOFILE The maximum number of open files for this process. .El .Pp The fifth level name is one of PROC_PID_LIMIT_TYPE_SOFT or PROC_PID_LIMIT_TYPE_HARD, to select respectively the soft or hard limit. Both are of type integer. .El .Pp .Sh CTL_USER The string and integer information available for the CTL_USER level is detailed below. The changeable column shows whether a process with appropriate privilege may change the value. .Bl -column "USER_COLL_WEIGHTS_MAXXXX" "integerXXX" -offset indent .It Sy Pa Second level name Type Changeable .It USER\_BC\_BASE\_MAX integer no .It USER\_BC\_DIM\_MAX integer no .It USER\_BC\_SCALE\_MAX integer no .It USER\_BC\_STRING\_MAX integer no .It USER\_COLL\_WEIGHTS\_MAX integer no .It USER\_CS\_PATH string no .It USER\_EXPR\_NEST\_MAX integer no .It USER\_LINE\_MAX integer no .It USER\_POSIX2\_CHAR\_TERM integer no .It USER\_POSIX2\_C\_BIND integer no .It USER\_POSIX2\_C\_DEV integer no .It USER\_POSIX2\_FORT\_DEV integer no .It USER\_POSIX2\_FORT\_RUN integer no .It USER\_POSIX2\_LOCALEDEF integer no .It USER\_POSIX2\_SW\_DEV integer no .It USER\_POSIX2\_UPE integer no .It USER\_POSIX2\_VERSION integer no .It USER\_RE\_DUP\_MAX integer no .It USER\_STREAM\_MAX integer no .It USER\_TZNAME\_MAX integer no .El .Bl -tag -width "123456" .Pp .It Li USER_BC_BASE_MAX The maximum ibase/obase values in the .Xr bc 1 utility. .It Li USER_BC_DIM_MAX The maximum array size in the .Xr bc 1 utility. .It Li USER_BC_SCALE_MAX The maximum scale value in the .Xr bc 1 utility. .It Li USER_BC_STRING_MAX The maximum string length in the .Xr bc 1 utility. .It Li USER_COLL_WEIGHTS_MAX The maximum number of weights that can be assigned to any entry of the LC_COLLATE order keyword in the locale definition file. .It Li USER_CS_PATH Return a value for the .Ev PATH environment variable that finds all the standard utilities. .It Li USER_EXPR_NEST_MAX The maximum number of expressions that can be nested within parenthesis by the .Xr expr 1 utility. .It Li USER_LINE_MAX The maximum length in bytes of a text-processing utility's input line. .It Li USER_POSIX2_CHAR_TERM Return 1 if the system supports at least one terminal type capable of all operations described in POSIX 1003.2, otherwise 0. .It Li USER_POSIX2_C_BIND Return 1 if the system's C-language development facilities support the C-Language Bindings Option, otherwise 0. .It Li USER_POSIX2_C_DEV Return 1 if the system supports the C-Language Development Utilities Option, otherwise 0. .It Li USER_POSIX2_FORT_DEV Return 1 if the system supports the FORTRAN Development Utilities Option, otherwise 0. .It Li USER_POSIX2_FORT_RUN Return 1 if the system supports the FORTRAN Runtime Utilities Option, otherwise 0. .It Li USER_POSIX2_LOCALEDEF Return 1 if the system supports the creation of locales, otherwise 0. .It Li USER_POSIX2_SW_DEV Return 1 if the system supports the Software Development Utilities Option, otherwise 0. .It Li USER_POSIX2_UPE Return 1 if the system supports the User Portability Utilities Option, otherwise 0. .It Li USER_POSIX2_VERSION The version of POSIX 1003.2 with which the system attempts to comply. .It Li USER_RE_DUP_MAX The maximum number of repeated occurrences of a regular expression permitted when using interval notation. .ne 1i .It Li USER_STREAM_MAX The minimum maximum number of streams that a process may have open at any one time. .It Li USER_TZNAME_MAX The minimum maximum number of types supported for the name of a timezone. .El .Sh CTL_VM The string and integer information available for the CTL_VM level is detailed below. The changeable column shows whether a process with appropriate privilege may change the value. .Bl -column "Second level nameXXXXXX" "struct loadavgXXX" -offset indent .It Sy Pa Second level name Type Changeable .It VM\_LOADAVG struct loadavg no .It VM\_METER struct vmtotal no .El .Pp .Bl -tag -width "123456" .It Li VM_LOADAVG Return the load average history. The returned data consists of a .Va struct loadavg . .It Li VM_METER Return the system wide virtual memory statistics. The returned data consists of a .Va struct vmtotal . .El .Sh CTL_DDB The integer information available for the CTL_DDB level is detailed below. The changeable column shows whether a process with appropriate privilege may change the value. .Bl -column "DBCTL_TABSTOPSXXX" "integerXXX" -offset indent .It Sy Pa Second level name Type Changeable .It DBCTL\_RADIX integer yes .It DBCTL\_MAXOFF integer yes .It DBCTL\_LINES integer yes .It DBCTL\_TABSTOPS integer yes .It DBCTL\_ONPANIC integer yes .It DBCTL\_FROMCONSOLE integer yes .El .Pp .Bl -tag -width "123456" .It Li DBCTL_RADIX The input and output radix. .It Li DBCTL_MAXOFF The maximum symbol offset. .It Li DBCTL_LINES Number of display lines. .It Li DBCTL_TABSTOPS Tab width. .It Li DBCTL_ONPANIC If non-zero, DDB will be entered when the kernel panics. .It Li DBCTL_FROMCONSOLE If not zero, DDB may be entered by sending a break on a serial console or by a special key sequence on a graphics console. .El .Pp These MIB nodes are also available as variables from within the DDB. See .Xr ddb 4 for more details. .Sh RETURN VALUES If the call to .Nm is successful, the number of bytes copied out is returned. Otherwise \-1 is returned and .Va errno is set appropriately. .Sh ERRORS The following errors may be reported: .Bl -tag -width Er .It Bq Er EFAULT The buffer .Fa name , .Fa oldp , .Fa newp , or length pointer .Fa oldlenp contains an invalid address. .It Bq Er EINVAL The .Fa name array is less than two or greater than CTL_MAXNAME. .It Bq Er EINVAL A non-null .Fa newp is given and its specified length in .Fa newlen is too large or too small. .It Bq Er ENOMEM The length pointed to by .Fa oldlenp is too short to hold the requested value. .It Bq Er ENOTDIR The .Fa name array specifies an intermediate rather than terminal name. .It Bq Er EOPNOTSUPP The .Fa name array specifies a value that is unknown. .It Bq Er EPERM An attempt is made to set a read-only value. .It Bq Er EPERM A process without appropriate privilege attempts to set a value. .It Bq Er EPERM An attempt to change a value protected by the current kernel security level is made. .El .Sh FILES .Bl -tag -width -compact .It Pa definitions for top level identifiers, second level kernel and hardware identifiers, and user level identifiers .It Pa definitions for second level network identifiers .It Pa definitions for third level profiling identifiers .It Pa definitions for second level virtual memory identifiers .It Pa definitions for third level Internet identifiers and fourth level IP identifiers .It Pa definitions for fourth level ICMP identifiers .It Pa definitions for fourth level TCP identifiers .It Pa definitions for fourth level UDP identifiers .El .Sh SEE ALSO .Xr sysctl 8 , .Xr ipsec 4 .Sh HISTORY The .Nm function first appeared in .Bx 4.4 .