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)
