ICMP(4P) Protocols ICMP(4P)

NAME

icmp, ICMP - Internet Control Message Protocol

SYNOPSIS

#include <sys/socket.h>
#include <netinet/in.h>
#include <netinet/ip_icmp.h>
s = socket(AF_INET, SOCK_RAW, proto);
t = t_open("/dev/icmp", O_RDWR);

DESCRIPTION

ICMP 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 by programs using the socket
interface or the Transport Level Interface (TLI) for network monitoring
and diagnostic functions. When used with the socket interface, a "raw
socket" type is used. The protocol number for ICMP, used in the proto
parameter to the socket call, can be obtained from
getprotobyname(3SOCKET). ICMP file descriptors and sockets are
connectionless, and are normally used with the t_sndudata / t_rcvudata
and the sendto() / recvfrom() calls. In order to send ICMP packets, a
process needs the PRIV_NET_ICMPACCESS privilege. (See privileges(7) for
more information on privileges.)


Outgoing packets automatically have an Internet Protocol (IP) header
prepended to them. Incoming packets are provided to the user with the IP
header and options intact.


ICMP is an datagram protocol layered above IP. It is used internally by
the protocol code for various purposes including routing, fault
isolation, and congestion control. Receipt of an ICMP "redirect" message
will add a new entry in the routing table, or modify an existing one.
ICMP messages are routinely sent by the protocol code. Received ICMP
messages may be reflected back to users of higher-level protocols such as
TCP or UDP as error returns from system calls. A copy of all ICMP message
received by the system is provided to every holder of an open ICMP socket
or TLI descriptor.

SEE ALSO

t_rcvudata(3NSL), t_sndudata(3NSL), getprotobyname(3SOCKET),
recv(3SOCKET), send(3SOCKET), inet(4P), ip(4P), routing(4P),
privileges(7)


Postel, Jon, Internet Control Message Protocol -- DARPA Internet Program
Protocol Specification, RFC 792, Network Information Center, SRI
International, Menlo Park, Calif., September 1981.

DIAGNOSTICS

A socket operation may fail with one of the following errors returned:

EISCONN
An attempt was made 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
An attempt was made to send a datagram, but no
destination address is specified, and the socket has not
been connected.


ENOBUFS
The system ran out of memory for an internal data
structure.


EADDRNOTAVAIL
An attempt was made to create a socket with a network
address for which no network interface exists.

NOTES

Replies to ICMP "echo" messages which are source routed are not sent back
using inverted source routes, but rather go back through the normal
routing mechanisms.

December 3, 2015 ICMP(4P)