icmp -- Internet Control Message Protocol
socket(AF_INET, SOCK_RAW, proto);
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.
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
[EADDRNOTAVAIL] when an attempt is made to create a socket with a network
address for which no network interface exists.
recv(2), send(2), inet(4), intro(4), ip(4)
The icmp protocol appeared in 4.3BSD.
FreeBSD 5.2.1 March 21, 2003 FreeBSD 5.2.1 [ Back ]