NAME
icmp —
Internet Control Message
Protocol
SYNOPSIS
#include <sys/socket.h>
#include <netinet/in.h>
int
socket(
AF_INET,
SOCK_RAW,
proto);
DESCRIPTION
ICMP is the error and control message protocol used by IP and the Internet
protocol family. It may be accessed through a “raw socket” for
network monitoring and diagnostic functions. The
proto
parameter to the socket call to create an ICMP socket is obtained from
getprotobyname(3). ICMP
sockets are connectionless, and are normally used with the
sendto(2) and
recvfrom(2) calls, though the
connect(2) call may also be
used to fix the destination for future packets (in which case the
read(2) or
recv(2) and
write(2) or
send(2) system calls may be used).
Outgoing packets automatically have an IP header prepended to them (based on the
destination address). Incoming packets are received with the IP header and
options intact.
DIAGNOSTICS
A socket operation may fail with one of the following errors returned:
-
-
- [
EISCONN
]
- 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;
-
-
- [
ENOTCONN
]
- when trying to send a datagram, but no destination address
is specified, and the socket hasn't been connected;
-
-
- [
ENOBUFS
]
- when the system runs out of memory for an internal data
structure;
-
-
- [
EADDRNOTAVAIL
]
- when an attempt is made to create a socket with a network
address for which no network interface exists.
SEE ALSO
recv(2),
send(2),
inet(4),
intro(4),
ip(4)
Internet Control Message Protocol,
RFC, 792,
September 1981.
Requirements for Internet Hosts --
Communication Layers, RFC,
1122, October 1989.
HISTORY
The
icmp protocol appeared in
4.3BSD.