icmp, ICMP - Internet Control Message Protocol
#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);
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(5) 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.
getprotobyname(3SOCKET), recv(3SOCKET), send(3SOCKET),
t_rcvudata(3NSL), t_sndudata(3NSL), privileges(5),
inet(7P), ip(7P), routing(7P)
Postel, Jon, Internet Control Message Protocol — DARPA
Internet Program Protocol Specification, RFC 792, Network
Information Center, SRI International, Menlo Park, Calif., September
1981.
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.
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.