Protocols                                                icmp(7P)



NAME
     icmp, ICMP - Internet Control Message Protocol

SYNOPSIS
     #include 
     #include 
     #include 
     s = socket(AFINET, SOCKRAW, proto);
     t = topen("/dev/icmp", ORDWR);


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 Tran-
     sport Level Interface (TLI) for network monitoring and diag-
     nostic  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 tsndudata / trcvudata and the  sendto()  /  recvfrom()
     calls.


     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 protcol code for various purposes includ-
     ing  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  mes-
     sages are routinely sent by the protocol code. Received ICMP
     messages may be reflected back to users of higher-level pro-
     tocols  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
     getprotobyname(3SOCKET),    recv(3SOCKET),    send(3SOCKET),
     trcvudata(3NSL),    tsndudata(3NSL),   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.,



SunOS 5.11           Last change: 3 Jul 1990                    1






Protocols                                                icmp(7P)



     September 1981.

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

     EISCON          An attempt was made to establish a  connec-
                      tion  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.


     ENOTCON         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  inter-
                      nal data structure.


     EADRNOTAVAIL    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.
























SunOS 5.11           Last change: 3 Jul 1990                    2