sysctl(3) - NetBSD Manual Pages

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SYSCTL(3)                 NetBSD Programmer's Manual                 SYSCTL(3)


NAME
sysctl - get or set system information
LIBRARY
Standard C Library (libc, -lc)
SYNOPSIS
#include <sys/param.h> #include <sys/sysctl.h> int sysctl(int *name, u_int namelen, void *oldp, size_t *oldlenp, void *newp, size_t newlen);
DESCRIPTION
The sysctl function retrieves system information and allows processes with appropriate privileges to set system information. The information available from sysctl consists of integers, strings, and tables. Infor- mation may be retrieved and set from the command interface using the sysctl(8) utility. Unless explicitly noted below, sysctl 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 sysctl are serialized to avoid deadlock. The state is described using a ``Management Information Base'' (MIB) style name, listed in name, which is a namelen length array of integers. The information is copied into the buffer specified by oldp. The size of the buffer is given by the location specified by 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, oldp and oldlenp should be set to NULL. The size of the available data can be determined by calling sysctl with a NULL parameter for oldp. The size of the available data will be returned in the location pointed to by 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. To set a new value, newp is set to point to a buffer of length newlen from which the requested value is to be taken. If a new value is not to be set, newp should be set to NULL and newlen set to 0. The top level names are defined with a CTL_ prefix in <sys/sysctl.h>, and are as follows. The next and subsequent levels down are found in the in- clude files listed here, and described in separate sections below. Name Next level names Description CTL_KERN sys/sysctl.h High kernel limits CTL_VM uvm/uvm_param.h Virtual memory CTL_VFS sys/mount.h Filesystem CTL_NET sys/socket.h Networking CTL_DEBUG sys/sysctl.h Debugging CTL_HW sys/sysctl.h Generic CPU, I/O CTL_MACHDEP sys/sysctl.h Machine dependent CTL_USER sys/sysctl.h User-level CTL_DDB sys/sysctl.h In-kernel debugger CTL_PROC sys/sysctl.h Per-process CTL_VENDOR ? Vendor specific For example, the following retrieves the maximum number of processes al- lowed in the system: int mib[2], maxproc; size_t len; mib[0] = CTL_KERN; mib[1] = KERN_MAXPROC; len = sizeof(maxproc); sysctl(mib, 2, &maxproc, &len, NULL, 0); To retrieve the standard search path for the system utilities: int mib[2]; size_t len; char *p; 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);
CTL_DEBUG
The debugging variables vary from system to system. A debugging variable may be added or deleted without need to recompile sysctl to know about it. Each time it runs, sysctl gets the list of debugging variables from the kernel and displays their current values. The system defines twenty (struct ctldebug) variables named debug0 through debug19. They are de- clared as separate variables so that they can be individually initialized at the location of their associated variable. The loader prevents multi- ple use of the same variable by issuing errors if a variable is initial- ized in more than one place. For example, to export the variable dospecialcheck as a debugging variable, the following declaration would be used: int dospecialcheck = 1; struct ctldebug debug5 = { "dospecialcheck", &dospecialcheck };
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 in- formation about the filesystem type given as a fourth level identifier. The remaining second level identifiers are the filesystem type number re- turned by a 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.
CTL_HW
The string and integer information available for the CTL_HW level is de- tailed below. The changeable column shows whether a process with appro- priate privilege may change the value. Second level name Type Changeable HW_MACHINE string no HW_MODEL string no HW_NCPU integer no HW_BYTEORDER integer no HW_PHYSMEM integer no HW_USERMEM integer no HW_PAGESIZE integer no HW_MACHINE_ARCH string no HW_ALIGNBYTES integer no HW_DISKNAMES string no HW_DISKSTATS struct disk_sysctl no HW_MACHINE The machine class. HW_MODEL The machine model HW_NCPU The number of cpus. HW_BYTEORDER The byteorder (4,321, or 1,234). HW_PHYSMEM The bytes of physical memory. HW_USERMEM The bytes of non-kernel memory. HW_PAGESIZE The software page size. HW_DISKNAMES The list of (space separated) disk device names on the system. HW_DISKSTATS Return statistical information on the disk devices on the system. An array of struct disk_sysctl structures is returned, whose size depends on the current number of such objects in the system. The third level name is the size of the struct disk_sysctl. HW_MACHINE_ARCH The machine cpu class. HW_ALIGNBYTES Alignment constraint for all possible data types. This shows the value ALIGNBYTES in /usr/include/machine/param.h, at the kernel compilation time.
CTL_KERN
The string and integer information available for the CTL_KERN level is detailed below. The changeable column shows whether a process with ap- propriate 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. Second level name Type Changeable KERN_ARGMAX integer no KERN_AUTONICETIME integer yes KERN_AUTONICEVAL integer yes KERN_BOOTTIME struct timeval no KERN_CCPU integer no KERN_CLOCKRATE struct clockinfo no KERN_CP_TIME long[] no KERN_DEFCORENAME string yes KERN_DOMAINNAME string yes KERN_FILE struct file no KERN_FSCALE integer no KERN_FSYNC integer no KERN_HOSTID integer yes KERN_HOSTNAME string yes KERN_IOV_MAX integer no KERN_JOB_CONTROL integer no KERN_LOGIN_NAME_MAX integer no KERN_LOGSIGEXIT integer yes KERN_MAPPED_FILES integer no KERN_MAXFILES integer yes KERN_MAXPARTITIONS integer no KERN_MAXPROC integer yes KERN_MAXPTYS integer yes KERN_MAXVNODES integer yes KERN_MBUF node not applicable KERN_MEMLOCK integer no KERN_MEMLOCK_RANGE integer no KERN_MEMORY_PROTECTION integer no KERN_MONOTONIC_CLOCK integer no KERN_MSGBUF char[] no KERN_MSGBUFSIZE integer no KERN_NGROUPS integer no KERN_NTPTIME struct ntptimeval no KERN_OSRELEASE string no KERN_OSREV integer no KERN_OSTYPE string no KERN_POSIX1 integer no KERN_PROC struct kinfo_proc no KERN_PROC2 struct kinfo_proc2 no KERN_PROC_ARGS string no KERN_PROF node not applicable KERN_RAWPARTITION integer no KERN_ROOT_DEVICE string no KERN_RTC_OFFSET integer no KERN_SAVED_IDS integer no KERN_SECURELVL integer raise only KERN_SYNCHRONIZED_IO integer no KERN_SYSVIPC_INFO node not applicable KERN_SYSVMSG integer no KERN_SYSVSEM integer no KERN_SYSVSHM integer no KERN_TKSTAT node not applicable KERN_VERSION string no KERN_VNODE struct vnode no KERN_ARGMAX The maximum bytes of argument to execve(2). KERN_AUTONICETIME The number of seconds of cpu-time a non-root process may accumu- late 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 process- es are immediately lowered. KERN_AUTONICEVAL The priority assigned for automatically niced processes. KERN_BOOTTIME A struct timeval structure is returned. This structure contains the time that the system was booted. KERN_CCPU The scheduler exponential decay value. KERN_CLOCKRATE A struct clockinfo structure is returned. This structure con- tains the clock, statistics clock and profiling clock frequen- cies, the number of micro-seconds per hz tick, and the clock skew rate. KERN_CP_TIME Return an array if CPUSTATES longs is returned. This array con- tains the number of clock ticks spent in different CPU states. KERN_DEFCORENAME Default template for the name of core dump files (see also PROC_PID_CORENAME in the per-process variables CTL_PROC, and core(5) for format of this template). The default value is %n.core and can be changed with the kernel configuration option options DEFCORENAME (see options(4) ). KERN_DOMAINNAME Get or set the YP domain name. KERN_FILE Return the entire file table. The returned data consists of a single struct filehead followed by an array of struct file, whose size depends on the current number of such objects in the system. KERN_FSCALE The kernel fixed-point scale factor. KERN_FSYNC Return 1 if the POSIX 1003.1b File Synchronization Option is available on this system, otherwise 0. KERN_HOSTID Get or set the host id. KERN_HOSTNAME Get or set the hostname. KERN_IOV_MAX Return the maximum number of iovec structures that a process has available for use with preadv(2), pwritev(2), readv(2), recvmsg(2), sendmsg(2) and writev(2). KERN_JOB_CONTROL Return 1 if job control is available on this system, otherwise 0. KERN_LOGIN_NAME_MAX The size of the storage required for a login name, in bytes, in- cluding the terminating NUL. KERN_LOGSIGEXIT If this flag is non-zero, the kernel will log(9) all process ex- its due to signals which create a core(5) file, and whether the coredump was created. KERN_MAPPED_FILES Returns 1 if the POSIX 1003.1b Memory Mapped Files Option is available on this system, otherwise 0. KERN_MAXFILES The maximum number of open files that may be open in the system. KERN_MAXPARTITIONS The maximum number of partitions allowed per disk. KERN_MAXPROC The maximum number of simultaneous processes the system will al- low. KERN_MAXPTYS The maximum number of pseudo terminals. This value can be both raised and lowered, though it cannot be set lower than number of currently used ptys. See also pty(4). KERN_MAXVNODES The maximum number of vnodes available on the system. This can only be raised. KERN_MBUF Return information about the mbuf control variables. the third level names for the mbuf variables are detailed below. The changeable column shows whether a process with appropriate privi- lege may change the value. Third level name Type Changeable MBUF_MSIZE integer yes MBUF_MCLBYTES integer yes MBUF_NMBCLUSTERS integer yes MBUF_MBLOWAT integer yes MBUF_MCLLOWAT integer yes The variables are as follows: MBUF_MSIZE The mbuf base size. MBUF_MCLBYTES The mbuf cluster size. MBUF_NMBCLUSTERS The limit on the number of mbuf clusters. The variable can only be increased, and only increased on machines with direct-mapped pool pages MBUF_MBLOWAT The mbuf low water mark. MBUF_MCLLOWAT The mbuf cluster low water mark. KERN_MEMLOCK Returns 1 if the POSIX 1003.1b Process Memory Locking Option is available on this system, otherwise 0. KERN_MEMLOCK_RANGE Returns 1 if the POSIX 1003.1b Range Memory Locking Option is available on this system, otherwise 0. KERN_MEMORY_PROTECTION Returns 1 if the POSIX 1003.1b Memory Protection Option is avail- able on this system, otherwise 0. KERN_MONOTONIC_CLOCK Returns the standard version the implementation of the POSIX 1003.1b Monotonic Clock Option conforms to, otherwise 0. KERN_MSGBUF The kernel message buffer, rotated so that the head of the circu- lar kernel message buffer is returned at the start of the buffer specified by oldp. The returned data may contain NUL bytes. KERN_MSGBUFSIZE The maximum number of characters that the kernel message buffer can hold. KERN_NGROUPS The maximum number of supplemental groups. KERN_NO_TRUNC Return 1 if file names longer than KERN_NAME_MAX are truncated. KERN_NTPTIME A struct ntptimeval structure is returned. This structure con- tains data used by the ntpd(8) program. KERN_OSRELEASE The system release string. KERN_OSREV The system revision string. KERN_OSTYPE The system type string. KERN_PATH_MAX The maximum number of bytes in a pathname. KERN_POSIX1 The version of ISO/IEC 9945 (POSIX 1003.1) with which the system attempts to comply. KERN_PROC Return the entire process table, or a subset of it. An array of 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: Third level name Fourth level is: KERN_PROC_ALL None KERN_PROC_PID A process ID KERN_PROC_PGRP A process group KERN_PROC_SESSION A session ID KERN_PROC_TTY A tty device KERN_PROC_UID A user ID KERN_PROC_RUID A real user ID KERN_PROC_GID A group ID KERN_PROC_RGID A real group ID KERN_PROC2 As for KERN_PROC, but an array of struct kinfo_proc2 structures are returned. The fifth level name is the size of the struct kinfo_proc2 and the sixth level name is the number of structures to return. KERN_PROC_ARGS Return the argv or environment strings (or the number thereof) of a process. Multiple strings are returned separated by NUL char- acters. The third level name is the process ID. The fourth lev- el name is as follows: KERN_PROC_ARGV The argv strings KERN_PROC_NARGV The number of argv strings KERN_PROC_ENV The environ strings KERN_PROC_NENV The number of environ strings 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 de- tailed below. The changeable column shows whether a process with appropriate privilege may change the value. Third level name Type Changeable GPROF_STATE integer yes GPROF_COUNT u_short[] yes GPROF_FROMS u_short[] yes GPROF_TOS struct tostruct yes GPROF_GMONPARAM struct gmonparam no The variables are as follows: GPROF_STATE Returns GMON_PROF_ON or GMON_PROF_OFF to show that pro- filing is running or stopped. GPROF_COUNT Array of statistical program counter counts. GPROF_FROMS Array indexed by program counter of call-from points. GPROF_TOS Array of struct tostruct describing destination of calls and their counts. GPROF_GMONPARAM Structure giving the sizes of the above arrays. KERN_RAWPARTITION The raw partition of a disk (a == 0). KERN_ROOT_DEVICE The name of the root device. KERN_RTC_OFFSET Return the offset of real time clock from UTC in minutes. KERN_SAVED_IDS Returns 1 if saved set-group and saved set-user ID is available. KERN_SECURELVL The system security level. This level may be raised by processes with appropriate privilege. It may only be lowered by process 1. KERN_SYNCHRONIZED_IO Returns 1 if the POSIX 1003.1b Synchronized I/O Option is avail- able on this system, otherwise 0. KERN_SYSVIPC_INFO Return System V style IPC configuration and run-time information. The third level name selects the System V style IPC facility. Third level name Type KERN_SYSVIPC_MSG_INFO struct msg_sysctl_info KERN_SYSVIPC_SEM_INFO struct sem_sysctl_info KERN_SYSVIPC_SHM_INFO struct shm_sysctl_info KERN_SYSVIPC_MSG_INFO Return information on the System V style message facili- ty. The msg_sysctl_info structure is defined in <sys/msg.h>. KERN_SYSVIPC_SEM_INFO Return information on the System V style semaphore facil- ity. The sem_sysctl_info structure is defined in <sys/sem.h>. KERN_SYSVIPC_SHM_INFO Return information on the System V style shared memory facility. The shm_sysctl_info structure is defined in <sys/shm.h>. KERN_SYSVMSG Returns 1 if System V style message queue functionality is avail- able on this system, otherwise 0. KERN_SYSVSEM Returns 1 if System V style semaphore functionality is available on this system, otherwise 0. KERN_SYSVSHM Returns 1 if System V style share memory functionality is avail- able on this system, otherwise 0. KERN_TKSTAT Return information about the number of characters sent and re- ceived on ttys. The third level names for the tty statistic variables are detailed below. The changeable column shows whether a process with appropriate privilege may change the val- ue. Third level name Type Changeable KERN_TKSTAT_NIN quad no KERN_TKSTAT_NOUT quad no KERN_TKSTAT_CANCC quad no KERN_TKSTAT_RAWCC quad no The variables are as follows: KERN_TKSTAT_NIN The total number of input characters. KERN_TKSTAT_NOUT The total number of output characters. KERN_TKSTAT_CANCC The number of canonical input characters. KERN_TKSTAT_RAWCC The number of raw input characters. KERN_VERSION The system version string. KERN_VNODE Return the entire vnode table. Note, the vnode table is not nec- essarily 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 struct vnode * followed by the vn- ode itself struct vnode.
CTL_MACHDEP
The set of variables defined is architecture dependent. Most architec- tures define at least the following variables. Second level name Type Changeable CPU_CONSDEV dev_t no
CTL_NET
The string and integer information available for the CTL_NET level is de- tailed below. The changeable column shows whether a process with appro- priate privilege may change the value. Second level name Type Changeable PF_ROUTE routing messages no PF_INET IPv4 values yes PF_INET6 IPv6 values yes PF_KEY IPsec key management valuesyes PF_ROUTE Return the entire routing table or a subset of it. The data is returned as a sequence of routing messages (see route(4) for the header file, format and meaning). The length of each message is contained in the message header. The third level name is a protocol number, which is currently al- ways 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: Fifth level name Sixth level is: NET_RT_FLAGS rtflags NET_RT_DUMP None NET_RT_IFLIST None PF_INET Get or set various global information about the IPv4 (Internet Protocol version 4). The third level name is the protocol. The fourth level name is the variable name. The currently defined protocols and names are: Protocol name Variable name Type Changeable ip forwarding integer yes ip redirect integer yes ip ttl integer yes ip forwsrcrt integer yes ip directed-broadcast integer yes ip allowsrcrt integer yes ip subnetsarelocal integer yes ip mtudisc integer yes ip anonportmin integer yes ip anonportmax integer yes ip mtudisctimeout integer yes ip gifttl integer yes ip grettl integer yes ip lowportmin integer yes ip lowportmax integer yes ip maxfragpacket integer yes icmp maskrepl integer yes icmp errppslimit integer yes icmp rediraccept integer yes icmp redirtimeout integer yes tcp rfc1323 integer yes tcp sendspace integer yes tcp recvspace integer yes tcp mssdflt integer yes tcp syn_cache_limit integer yes tcp syn_bucket_limit integer yes tcp syn_cache_interval integer yes tcp init_win integer yes tcp mss_ifmtu integer yes tcp sack integer yes tcp win_scale integer yes tcp timestamps integer yes tcp compat_42 integer yes tcp cwm integer yes tcp cwm_burstsize integer yes tcp ack_on_push integer yes tcp keepidle integer yes tcp keepintvl integer yes tcp keepcnt integer yes tcp slowhz integer no tcp newreno integer yes tcp log_refused integer yes tcp rstppslimit integer yes udp checksum integer yes udp sendspace integer yes udp recvspace integer yes The variables are as follows: ip.forwarding Returns 1 when IP forwarding is enabled for the host, meaning that the host is acting as a router. 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. ip.ttl The maximum time-to-live (hop count) value for an IP packet sourced by the system. This value applies to nor- mal transport protocols, not to ICMP. ip.forwsrcrt Returns 1 when forwarding of source-routed packets is en- abled for the host. This value may only be changed if the kernel security level is less than 1. ip.directed-broadcast Returns 1 if directed broadcast behavior is enabled for the host. ip.allowsrcrt Returns 1 if the host accepts source routed packets. ip.subnetsarelocal Returns 1 if subnets are to be considered local address- es. ip.mtudisc Returns 1 if Path MTU Discovery is enabled. ip.anonportmin The lowest port number to use for TCP and UDP ephemeral port allocation. This cannot be set to less than 1024 or greater than 65535. ip.anonportmax The highest port number to use for TCP and UDP ephemeral port allocation. This cannot be set to less than 1024 or greater than 65535, and must be greater than ip.anonportmin. 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 at- tempt to probe a larger path MTU. ip.gifttl The maximum time-to-live (hop count) value for an IPv4 packet generated by gif(4) tunnel interface. ip.grettl The maximum time-to-live (hop count) value for an IPv4 packet generated by gre(4) tunnel interface. ip.lowportmin The lowest port number to use for TCP and UDP reserved port allocation. This cannot be set to less than 0 or greater than 1024, and must be smaller than ip.lowportmax. ip.lowportmax The highest port number to use for TCP and UDP reserved port allocation. This cannot be set to less than 0 or greater than 1024, and must be greater than ip.lowportmin. ip.maxfragpackets The maximum number of fragmented packets the node will accept. 0 means that the node will not accept any frag- mented packets. -1 means that the node will accept as many fragmented packets as it receives. The flag is pro- vided basically for avoiding possible DoS attacks. icmp.maskrepl Returns 1 if ICMP network mask requests are to be an- swered. icmp.errppslimit The variable specifies the maximum number of outgoing ICMP error messages, per second. ICMP error messages that exceeded the value are subject to rate limitation and will not go out from the node. Negative value dis- ables rate limitation. icmp.rediraccept If set to non-zero, the host will accept ICMP redirect packets. Note that routers will never accept ICMP redi- rect packets, and the variable is meaningful on IP hosts only. icmp.redirtimeout The variable specifies lifetime of routing entries gener- ated by incoming ICMP redirect. This defaults to 600 seconds. tcp.rfc1323 Returns 1 if RFC1323 extensions to TCP are enabled. tcp.sendspace Returns the default TCP send buffer size. tcp.recvspace Returns the default TCP receive buffer size. 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. tcp.syn_cache_limit Returns the maximum number of entries allowed in the TCP compressed state engine. tcp.syn_bucket_limit Returns the maximum number of entries allowed per hash bucket in the TCP compressed state engine. tcp.syn_cache_interval Returns the TCP compressed state engine's timer interval. tcp.init_win Returns a value indicating the TCP initial congestion window. If this value is 0, an auto-tuning algorithm de- signed to use an initial window of approximately 4K bytes is in use. Otherwise, this value indicates a fixed num- ber of packets. tcp.mss_ifmtu Returns 1 if TCP calculates the outgoing maximum segment size based on the MTU of the appropriate interface. Oth- erwise, it is calculated based on the greater of the MTU of the interface, and the largest (non-loopback) inter- face MTU on the system. tcp.sack TCP Selective ACKnowledgement (RFC 2018) is not imple- mented in NetBSD at this time. Changing this value will have no effect. tcp.win_scale If rfc1323 is enabled, a value of 1 indicates RFC1323 window scale options, for increasing the TCP window size, are enabled. tcp.timestamps If rfc1323 is enabled, a value of 1 indicates RFC1323 time stamp options, used for measuring TCP round trip times, are enabled. tcp.compat_42 Returns 1 if work-arounds for bugs in the 4.2BSD TCP im- plementation are enabled. Use of this option is not rec- ommended, although it may be required in order to commu- nicate with extremely old TCP implementations. 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. tcp.cwm_burstsize Returns the Congestion Window Monitoring allowed burst size, in terms of packet count. 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 los- ing a round trip time in some rare situations, but has the caveat of potentially defeating TCP's delayed ACK al- gorithm. Use of this option is generally not recommend- ed, but the variable exists in case your configuration really needs it. tcp.keepidle Time a connection must be idle before keepalives are sent (if keepalives are enabled for the connection). See also tcp.slowhz. tcp.keepintvl Time after a keepalive probe is sent until, in the ab- sence of any response, another probe is sent. See also tcp.slowhz. tcp.keepcnt Number of keepalive probes sent before declaring a con- nection dead. If set to zero, there is no limit; keepalives will be sent until some kind of response is received from the peer. tcp.slowhz The units for tcp.keepidle and tcp.keepintvl; those vari- ables 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.) tcp.newreno Returns 1 if the use of J. Hoe's NewReno congestion con- trol algorithm is enabled. This algorithm improves the start-up behavior of TCP connections. tcp.log_refused Returns 1 if refused TCP connections to the host will be logged. tcp.rstppslimit The variable specifies the maximum number of outgoing TCP RST packets, per second. TCP RST packet that exceeded the value are subject to rate limitation and will not go out from the node. Negative value disables rate limita- tion. udp.checksum Returns 1 when UDP checksums are being computed and checked. Disabling UDP checksums is strongly discour- aged. udp.sendspace Returns the default UDP send buffer size. udp.recvspace Returns the default UDP receive buffer size. For variables net.*.ipsec, please refer to ipsec(4). PF_INET6 Get or set various global information about the IPv6 (Internet Protocol version 6). The third level name is the protocol. The fourth level name is the variable name. The currently defined protocols and names are: Protocol name Variable name Type Changeable ip6 forwarding integer yes ip6 redirect integer yes ip6 hlim integer yes ip6 maxfragpackets integer yes ip6 accept_rtadv integer yes ip6 keepfaith integer yes ip6 log_interval integer yes ip6 hdrnestlimit integer yes ip6 dad_count integer yes ip6 auto_flowlabel integer yes ip6 defmcasthlim integer yes ip6 gif_hlim integer yes ip6 kame_version string no ip6 use_deprecated integer yes ip6 rr_prune integer yes ip6 v6only integer yes ip6 anonportmin integer yes ip6 anonportmax integer yes ip6 lowportmin integer yes ip6 lowportmax integer yes icmp6 rediraccept integer yes icmp6 redirtimeout integer yes icmp6 nd6_prune integer yes icmp6 nd6_delay integer yes icmp6 nd6_umaxtries integer yes icmp6 nd6_mmaxtries integer yes icmp6 nd6_useloopback integer yes icmp6 nodeinfo integer yes icmp6 errppslimit integer yes icmp6 nd6_maxnudhint integer yes icmp6 mtudisc_hiwat integer yes icmp6 mtudisc_lowat integer yes icmp6 nd6_debug integer yes udp6 sendspace integer yes udp6 recvspace integer yes The variables are as follows: ip6.forwarding Returns 1 when IPv6 forwarding is enabled for the node, meaning that the node is acting as a router. Returns 0 when IPv6 forwarding is disabled for the node, meaning that the node is acting as a host. IPv6 specification defines node behavior for ``router'' case and ``host'' case quite differently, and changing this variable during operation may cause serious trouble. It is recommended to configure the variable at bootstrap time, and boot- strap time only. ip6.redirect Returns 1 when ICMPv6 redirects may be sent by the node. This option is ignored unless the node is routing IP packets, and should normally be enabled on all systems. ip6.hlim The default hop limit value for an IPv6 unicast packet sourced by the node. This value applies to all the transport protocols on top of IPv6. There are APIs to override the value, as documented in ip6(4). ip6.maxfragpackets The maximum number of fragmented packets the node will accept. 0 means that the node will not accept any frag- mented packets. -1 means that the node will accept as many fragmented packets as it receives. The flag is pro- vided basically for avoiding possible DoS attacks. ip6.accept_rtadv If set to non-zero, the node will accept ICMPv6 router advertisement packets and autoconfigures address prefixes and default routers. The node must be a host (not a router) for the option to be meaningful. ip6.keepfaith If set to non-zero, it enables ``FAITH'' TCP relay IPv6-to-IPv4 translator code in the kernel. Refer faith(4) and faithd(8) for detail. ip6.log_interval The variable controls amount of logs generated by IPv6 packet forwarding engine, by seting interval between log output (in seconds). ip6.hdrnestlimit The number of IPv6 extension headers permitted on incom- ing IPv6 packets. If set to 0, the node will accept as many extension headers as possible. ip6.dad_count The variable cofigures number of IPv6 DAD (duplicated address detection) probe packets. The packets will be generated when IPv6 interface addresses are configured. ip6.auto_flowlabel On connected transport protocol packets, fill IPv6 flowlabel field to help intermediate routers to identify packet flows. ip6.defmcasthlim The default hop limit value for an IPv6 multicast packet sourced by the node. This value applies to all the transport protocols on top of IPv6. There are APIs to override the value, as documented in ip6(4). ip6.gif_hlim The maximum hop limit value for an IPv6 packet generated by gif(4) tunnel interface. ip6.kame_version The string identifies the version of KAME IPv6 stack im- plemented in the kernel. ip6.use_deprecated The variable controls use of deprecated address, speci- fied in RFC2462 5.5.4. ip6.rr_prune The variable specifies interval between IPv6 router renumbering prefix babysitting, in seconds. ip6.v6only The variable specifies initial value for IPV6_V6ONLY socket option for AF_INET6 socket. Please refer to ip6(4) for detail. ip6.anonportmin The lowest port number to use for TCP and UDP ephemeral port allocation. This cannot be set to less than 1024 or greater than 65535. ip6.anonportmax The highest port number to use for TCP and UDP ephemeral port allocation. This cannot be set to less than 1024 or greater than 65535, and must be greater than ip6.anonportmin. ip6.lowportmin The lowest port number to use for TCP and UDP reserved port allocation. This cannot be set to less than 0 or greater than 1024, and must be smaller than ip6.lowportmax. ip6.lowportmax The highest port number to use for TCP and UDP reserved port allocation. This cannot be set to less than 0 or greater than 1024, and must be greater than ip6.lowportmin. icmp6.rediraccept If set to non-zero, the host will accept ICMPv6 redirect packets. Note that IPv6 routers will never accept ICMPv6 redirect packets, and the variable is meaningful on IPv6 hosts (non-router) only. icmp6.redirtimeout The variable specifies lifetime of routing entries gener- ated by incoming ICMPv6 redirect. icmp6.nd6_prune The variable specifies interval between IPv6 neighbor cache babysitting, in seconds. icmp6.nd6_delay The variable specifies DELAY_FIRST_PROBE_TIME timing con- stant in IPv6 neighbor discovery specification (RFC2461), in seconds. icmp6.nd6_umaxtries The variable specifies MAX_UNICAST_SOLICIT constant in IPv6 neighbor discovery specification (RFC2461). icmp6.nd6_mmaxtries The variable specifies MAX_MULTICAST_SOLICIT constant in IPv6 neighbor discovery specification (RFC2461). icmp6.nd6_useloopback If set to non-zero, kernel IPv6 stack will use loopback interface for local traffic. icmp6.nodeinfo The variable enables responses to ICMPv6 node information queries. If you set the variable to 0, reponses will not be generated for ICMPv6 node information queries. Since node information queries can have a security impact, it is possible to fine tune which responses should be an- swered. Two separate bits can be set. 1 Respond to ICMPv6 FQDN queries, e.g. ping6 -w. 2 Respond to ICMPv6 node addresses queries, e.g. ping6 -a. icmp6.errppslimit The variable specifies the maximum number of outgoing ICMPv6 error messages, per second. ICMPv6 error messages that exceeded the value are subject to rate limitation and will not go out from the node. Negative value dis- ables rate limitation. icmp6.nd6_maxnudhint IPv6 neighbor discovery permits upper layer protocols to supply reachability hints, to avoid unnecessary neighbor discovery exchanges. The variable defines the number of consecutive hints the neighbor discovery layer will take. For example, by setting the variable to 3, neighbor dis- covery layer will take 3 consecutive hints in maximum. After receiving 3 hints, neighbor discovery layer will perform normal neighbor discovery process. icmp6.mtudisc_hiwat icmp6.mtudisc_lowat The variables define the maximum number of routing table entries, created due to path MTU discovery (prevents denial-of-service attacks with ICMPv6 too big messages). When IPv6 path MTU discovery happens, we keep path MTU information into the routing table. If the number of routing table entries exceed the value, the kernel will not attempt to keep the path MTU information. icmp6.mtudisc_hiwat is used when we have verified ICMPv6 too big messages. icmp6.mtudisc_lowat is used when we have unverified ICMPv6 too big messages. Verification is performed by using address/port pairs kept in connected pcbs. Negative value disables the upper limit. icmp6.nd6_debug If set to non-zero, kernel IPv6 neighbor discovery code will generate debugging messages. The debug outputs are useful to diagnose IPv6 interoperability issues. The flag must be set to 0 for normal operation. We reuse net.*.tcp for TCP over IPv6, and therefore we do not have variables net.*.tcp6. Variables net.inet6.udp6 have identi- cal meaning to net.inet.udp. Please refer to PF_INET section above. For variables net.*.ipsec6, please refer to ipsec(4). PF_KEY Get or set various global information about the IPsec key manage- ment. The third level name is the variable name. The currently defined variable and names are: Variable name Type Changeable debug integer yes spi_try integer yes spi_min_value integer yes spi_max_value integer yes random_int integer yes larval_lifetime integer yes blockacq_count integer yes blockacq_lifetime integer yes esp_keymin integer yes esp_auth integer yes ah_keymin integer yes The variables are as follows: debug Turn on debugging message from within the kernel. The value is a bitmap, as defined in /usr/include/netkey/key_debug.h. spi_try The number of times the kernel will try to obtain an unique SPI when it generates it from random number gener- ator. spi_min_value Minimum SPI value when generating it within the kernel. spi_max_value Maximum SPI value when generating it within the kernel. random_int Interval to stir pseudo-random number generator, in sec- onds. Pseudo-random number generator is used only as a last resort when random number source (/dev/urandom) is not available. It should not really be used, and if it were used, kernel will warn about it. larval_lifetime Lifetime for LARVAL SAD entries, in seconds. blockacq_count Number of ACQUIRE PF_KEY messages to be blocked after an ACQUIRE message. It avoids flood of ACQUIRE PF_KEY from being sent from the kernel to the key management daemon. blockacq_lifetime Lifetime of ACQUIRE PF_KEY message. esp_keymin Minimum ESP key length, in bits. The value is used when the kernel creates proposal payload on ACQUIRE PF_KEY message. esp_auth Whether ESP authentication should be used or not. Non- zero value indicates that ESP authentication should be used. The value is used when the kernel creates proposal payload on ACQUIRE PF_KEY message. ah_keymin Minimum AH key length, in bits, The value is used when the kernel creates proposal payload on ACQUIRE PF_KEY message.
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. Third level name Type Changeable PROC_PID_CORENAME string yes PROC_PID_LIMIT node not applicable PROC_PID_CORENAME The template used for the core dump file name (see core(5) for details). The base name must either be core or end with the suf- fix ``.core'' (the super-user may set arbitrary names). By de- fault it points to KERN_DEFCORENAME. PROC_PID_LIMIT Return resources limits, as defined for the getrlimit(2) and setrlimit(2) system calls. The fourth level name is one of: PROC_PID_LIMIT_CPU The maximum amount of cpu time (in sec- onds) to be used by each process. PROC_PID_LIMIT_FSIZE The largest size (in bytes) file that may be created. 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 sbrk(2) system call. PROC_PID_LIMIT_STACK The maximum size (in bytes) of the stack segment for a process; this de- fines how far a program's stack segment may be extended. Stack extension is performed automatically by the system. PROC_PID_LIMIT_CORE The largest size (in bytes) core file that may be created. 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 pro- cess; if memory is tight, the system will prefer to take memory from pro- cesses that are exceeding their de- clared resident set size. PROC_PID_LIMIT_MEMLOCK The maximum size (in bytes) which a process may lock into memory using the mlock(2) function. PROC_PID_LIMIT_NPROC The maximum number of simultaneous pro- cesses for this user id. PROC_PID_LIMIT_NOFILE The maximum number of open files for this process. 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.
CTL_USER
The string and integer information available for the CTL_USER level is detailed below. The changeable column shows whether a process with ap- propriate privilege may change the value. Second level name Type Changeable USER_BC_BASE_MAX integer no USER_BC_DIM_MAX integer no USER_BC_SCALE_MAX integer no USER_BC_STRING_MAX integer no USER_COLL_WEIGHTS_MAX integer no USER_CS_PATH string no USER_EXPR_NEST_MAX integer no USER_LINE_MAX integer no USER_POSIX2_CHAR_TERM integer no USER_POSIX2_C_BIND integer no USER_POSIX2_C_DEV integer no USER_POSIX2_FORT_DEV integer no USER_POSIX2_FORT_RUN integer no USER_POSIX2_LOCALEDEF integer no USER_POSIX2_SW_DEV integer no USER_POSIX2_UPE integer no USER_POSIX2_VERSION integer no USER_RE_DUP_MAX integer no USER_STREAM_MAX integer no USER_TZNAME_MAX integer no USER_BC_BASE_MAX The maximum ibase/obase values in the bc(1) utility. USER_BC_DIM_MAX The maximum array size in the bc(1) utility. USER_BC_SCALE_MAX The maximum scale value in the bc(1) utility. USER_BC_STRING_MAX The maximum string length in the bc(1) utility. 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. USER_CS_PATH Return a value for the PATH environment variable that finds all the standard utilities. USER_EXPR_NEST_MAX The maximum number of expressions that can be nested within parenthesis by the expr(1) utility. USER_LINE_MAX The maximum length in bytes of a text-processing utility's input line. USER_POSIX2_CHAR_TERM Return 1 if the system supports at least one terminal type capa- ble of all operations described in POSIX 1003.2, otherwise 0. USER_POSIX2_C_BIND Return 1 if the system's C-language development facilities sup- port the C-Language Bindings Option, otherwise 0. USER_POSIX2_C_DEV Return 1 if the system supports the C-Language Development Utili- ties Option, otherwise 0. USER_POSIX2_FORT_DEV Return 1 if the system supports the FORTRAN Development Utilities Option, otherwise 0. USER_POSIX2_FORT_RUN Return 1 if the system supports the FORTRAN Runtime Utilities Op- tion, otherwise 0. USER_POSIX2_LOCALEDEF Return 1 if the system supports the creation of locales, other- wise 0. USER_POSIX2_SW_DEV Return 1 if the system supports the Software Development Utili- ties Option, otherwise 0. USER_POSIX2_UPE Return 1 if the system supports the User Portability Utilities Option, otherwise 0. USER_POSIX2_VERSION The version of POSIX 1003.2 with which the system attempts to comply. USER_RE_DUP_MAX The maximum number of repeated occurrences of a regular expres- sion permitted when using interval notation. USER_STREAM_MAX The minimum maximum number of streams that a process may have open at any one time. USER_TZNAME_MAX The minimum maximum number of types supported for the name of a timezone.
CTL_VM
The string and integer information available for the CTL_VM level is de- tailed below. The changeable column shows whether a process with appro- priate privilege may change the value. Second level name Type Changeable VM_ANONMAX int yes VM_ANONMIN int yes VM_EXECMAX int yes VM_EXECMIN int yes VM_FILEMAX int yes VM_FILEMIN int yes VM_LOADAVG struct loadavg no VM_MAXSLP int no VM_METER struct vmtotal no VM_NKMEMPAGES int no VM_USPACE int no VM_UVMEXP struct uvmexp no VM_UVMEXP2 struct uvmexp_sysctl no VM_ANONMAX The percentage of physical memory which will be reclaimed from other types of memory usage to store anonymous application data. VM_ANONMIN The percentage of physical memory which will be always be avail- able for anonymous application data. VM_EXECMAX The percentage of physical memory which will be reclaimed from other types of memory usage to store cached executable data. VM_EXECMIN The percentage of physical memory which will be always be avail- able for cached executable data. VM_FILEMAX The percentage of physical memory which will be reclaimed from other types of memory usage to store cached file data. VM_FILEMIN The percentage of physical memory which will be always be avail- able for cached file data. VM_LOADAVG Return the load average history. The returned data consists of a struct loadavg. VM_MAXSLP The value of the maxslp kernel global variable. VM_METER Return system wide virtual memory statistics. The returned data consists of a struct vmtotal. VM_USPACE The number of bytes allocated for each kernel stack. VM_UVMEXP Return system wide virtual memory statistics. The returned data consists of a struct uvmexp. VM_UVMEXP2 Return system wide virtual memory statistics. The returned data consists of a struct uvmexp_sysctl.
CTL_DDB
The integer information available for the CTL_DDB level is detailed be- low. The changeable column shows whether a process with appropriate privilege may change the value. Second level name Type Changeable DBCTL_RADIX integer yes DBCTL_MAXOFF integer yes DBCTL_LINES integer yes DBCTL_TABSTOPS integer yes DBCTL_ONPANIC integer yes DBCTL_FROMCONSOLE integer yes DBCTL_RADIX The input and output radix. DBCTL_MAXOFF The maximum symbol offset. DBCTL_LINES Number of display lines. DBCTL_TABSTOPS Tab width. DBCTL_ONPANIC If non-zero, DDB will be entered when the kernel panics. 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. These MIB nodes are also available as variables from within the DDB. See ddb(4) for more details.
CTL_VENDOR
The "vendor" toplevel name is reserved to be used by vendors who wish to have their own private MIB tree. Intended use is to store values under ``vendor.<yourname>.*''.
RETURN VALUES
If the call to sysctl is successful, the number of bytes copied out is returned. Otherwise -1 is returned and errno is set appropriately.
FILES
<sys/sysctl.h> definitions for top level identifiers, second lev- el kernel and hardware identifiers, and user level identifiers <sys/socket.h> definitions for second level network identifiers <sys/gmon.h> definitions for third level profiling identifiers <uvm/uvm_param.h> definitions for second level virtual memory iden- tifiers <netinet/in.h> definitions for third level IPv4/v6 identifiers and fourth level IPv4/v6 identifiers <netinet/icmp_var.h> definitions for fourth level ICMP identifiers <netinet/icmp6.h> definitions for fourth level ICMPv6 identifiers <netinet/tcp_var.h> definitions for fourth level TCP identifiers <netinet/udp_var.h> definitions for fourth level UDP identifiers <netinet6/udp6_var.h> definitions for fourth level IPv6 UDP identifiers <netinet6/ipsec.h> definitions for fourth level IPsec identifiers <netkey/key_var.h> definitions for third level PF_KEY identifiers
ERRORS
The following errors may be reported: [EFAULT] The buffer name, oldp, newp, or length pointer oldlenp con- tains an invalid address. [EINVAL] The name array is less than two or greater than CTL_MAX- NAME. [EINVAL] A non-null newp is given and its specified length in newlen is too large or too small. [ENOMEM] The length pointed to by oldlenp is too short to hold the requested value. [ENOTDIR] The name array specifies an intermediate rather than termi- nal name. [EOPNOTSUPP] The name array specifies a value that is unknown. [EPERM] An attempt is made to set a read-only value. [EPERM] A process without appropriate privilege attempts to set a value. [EPERM] An attempt to change a value protected by the current ker- nel security level is made.
SEE ALSO
ipsec(4), sysctl(8)
HISTORY
The sysctl function first appeared in 4.4BSD. NetBSD 1.6 June 24, 1999 24
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