Manual page for ICMP(4P)
icmp - Internet Control Message Protocol
s = socket(AF_INET, SOCK_RAW, proto);
is the error and control message protocol used
by the Internet protocol family.
It is used by the kernel to handle and report errors
in protocol processing.
It may also be accessed
through a ``raw socket'' for network monitoring
and diagnostic functions.
The protocol number for
used in the
parameter to the socket call,
can be obtained from
sockets are connectionless,
and are normally used with the
calls, though the
call may also be used to fix the destination for future
packets (in which case the
system calls may be used).
Outgoing packets automatically have an Internet Protocol (IP)
header prepended to them.
Incoming packets are provided to the holder of a raw
socket with the
header and options intact.
is an unreliable datagram protocol layered above
It is used internally by the protcol code
for various purposes including routing,
and congestion control.
Receipt of an
``redirect'' message will add a new entry in
the routing table,
or modify an existing one.
messages are routinely sent by the protocol code.
messages may be reflected back to users
of higher-level protocols such as
as error returns from system calls.
A copy of all
message received by the system
is provided using the
A socket operation may fail with one of the following errors returned:
when trying to establish a connection on a socket which
already has one, or when trying to send a datagram with the destination
address specified and the socket is already connected;
when trying to send a datagram, but
no destination address is specified, and the socket hasn't been
when the system runs out of memory for
an internal data structure;
when an attempt is made to create a
socket with a network address for which no network interface
Internet Control Message Protocol -- DARPA Internet Program Protocol Specification,
792, Network Information Center,
International, Menlo Park, Calif.,
September 1981. (Sun 800-1064-01)
``echo'' messages which are source routed
are not sent back using inverted source routes,
but rather go back through the normal routing mechanisms.
Created by unroff & hp-tools.
© by Hans-Peter Bischof. All Rights Reserved (1997).
Last modified 21/April/97