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NAME    [Toc]    [Back]

     icmp -- Internet Control Message Protocol

SYNOPSIS    [Toc]    [Back]

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

     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.

   MIB Variables    [Toc]    [Back]
     The ICMP protocol implements a number of variables in the net.inet.icmp
     branch of the sysctl(3) MIB.

     maskrepl	     (boolean) Enable/disable replies to ICMP Address Mask
		     Request packets.  Defaults to false.

     maskfake	     (unsigned integer) When maskrepl is set and this value is
		     non-zero, it will be used instead of the real address
		     mask when the system replies to an ICMP Address Mask
		     Request packet.  Defaults to 0.

     icmplim	     (integer) Bandwidth limit for ICMP replies in packets/second.
  Used when icmplim_output is non-zero.
		     Defaults to 200.

     icmplim_output  (boolean) Enable/disable bandwidth limiting of ICMP
		     replies.  Defaults to true.

     drop_redirect   (boolean) Enable/disable dropping of ICMP Redirect packets.
  Defaults to false.

     log_redirect    (boolean) Enable/disable logging of ICMP Redirect packets.
  Defaults to false.

     bmcastecho      (boolean) Enable/disable ICMP replies received via broadcast
 or multicast.  Defaults to false.

ERRORS    [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), intro(4), ip(4)

HISTORY    [Toc]    [Back]

     The icmp protocol appeared in 4.3BSD.

FreeBSD 5.2.1			March 21, 2003			 FreeBSD 5.2.1
[ Back ]
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