NAME    [Toc]    [Back]

     icmp - Internet Control Message Protocol

SYNOPSIS    [Toc]    [Back]

     #include <sys/socket.h>
     #include <netinet/in.h>

     int
     socket(AF_INET, SOCK_RAW, proto);

DESCRIPTION    [Toc]    [Back]

     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    [Toc]    [Back]

     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    [Toc]    [Back]

     recv(2), send(2), inet(4), ip(4), netintro(4)

HISTORY    [Toc]    [Back]

     The icmp protocol appeared in 4.3BSD.

OpenBSD      3.6                           June      5,      1993