SYSCTL(3N)SYSCTL(3N)NAMEsysctl - get or set system information
SYNOPSIS
#include <sys/sysctl.h>
#include <sys/socket.h>
sysctl(int *name, u_int namelen, void *oldp, size_t *oldlenp,
void *newp, size_t newlen)
DESCRIPTION
The sysctl function retrieves system information. The information
available from sysctl consists of integers, strings, and tables, and is a
small subset of that available from the function of the same name in
4.4BSD-Lite.
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.
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
include files listed here, and described in separate sections below.
Name Next level names Description
CTL_NET sys/socket.h Networking
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SYSCTL(3N)SYSCTL(3N)
CTL_NET
The string and integer information available for the CTL_NET level is
detailed below.
Second level name Type
PF_ROUTE routing messages
PF_INET internet values
PF_ROUTE
Return the entire routing table or a subset of it. The data is
returned as a sequence of routing messages. See route(7p) 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 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:
Fifth level name Sixth level is: Table
NET_RT_FLAGS rtflags Routing
NET_RT_DUMP None Routing (by flags)
NET_RT_IFLIST None Interface list
PF_INET
Get or set various global information about IP (version 4) and
related transport protocols. 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
ip forwarding integer
ip redirect integer
udp checksum integer
The variables are as follows:
ip.forwarding
Indicates whether IPv4 forwarding is enabled for the host, meaning
that the host is acting as an IPv4 router. A value of 1 means that
the system will forward IPv4 packets, a value of 0 means it will
not. A privileged user may modify this value.
ip.redirect
Indicates whether ICMP redirects may be sent by the host. A value of
1 means that ICMP redirects may be sent, a value of 0 means they
will not. This option is ignored unless the host is routing IPv4
packets, and should normally be enabled on all systems. A privileged
user may modify this value.
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SYSCTL(3N)SYSCTL(3N)
udp.checksum
Returns 1 when UDP checksums are being computed and checked. The
value is always 1. It cannot be modified.
PF_INET6
Get or set various global information about IP (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
ipv6 forwarding integer
The variables are as follows:
ipv6.forwarding
Indicates whether IPv6 forwarding is enabled for the host, meaning
that the host is acting as an IPv6 router. A value of 1 means that
the system will forward IPv6 packets, a value of 0 means it will
not. A privileged user may modify this value.
SEE ALSO
The set of metrics available from sysctl(3N) is very limited in the
context of all metrics available from IRIX.
For uniform access to the widest possible collection of metrics, the
Performance Co-Pilot (PCP) APIs provide an alternative to sysctl(3N) that
includes a number additional features (e.g. distributed operation and
archive creation and replay).
The PCP APIs are fully documented in the Performance Co-Pilot
Programmer's Guide (avaliable from http://techpubs.sgi.com) and source
code for many example applications using the APIs are included in the
open source release of PCP available from
http://oss.sgi.com/projects/pcp).
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