1icmp(7P)                           Protocols                          icmp(7P)
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NAME

6       icmp, ICMP - Internet Control Message Protocol
7

SYNOPSIS

9       #include <sys/socket.h>
10       #include <netinet/in.h>
11       #include <netinet/ip_icmp.h>
12       s = socket(AF_INET, SOCK_RAW, proto);
13       t = t_open("/dev/icmp", O_RDWR);
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15

DESCRIPTION

17       ICMP  is  the  error  and control message protocol used by the Internet
18       protocol family. It is used by the kernel to handle and  report  errors
19       in  protocol  processing. It may also be accessed by programs using the
20       socket interface or the Transport Level  Interface  (TLI)  for  network
21       monitoring  and  diagnostic functions. When used with the socket inter‐
22       face, a "raw socket" type is used. The protocol number for  ICMP,  used
23       in the proto parameter to the socket call, can be obtained from getpro‐
24       tobyname(3SOCKET). ICMP file descriptors and  sockets  are  connection‐
25       less,  and  are  normally used with the t_sndudata / t_rcvudata and the
26       sendto() / recvfrom() calls.
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29       Outgoing packets automatically have an Internet  Protocol  (IP)  header
30       prepended  to  them. Incoming packets are provided to the user with the
31       IP header and options intact.
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34       ICMP is an datagram protocol layered above IP. It is used internally by
35       the  protcol  code for various purposes including routing, fault isola‐
36       tion, and congestion control. Receipt of  an  ICMP  "redirect"  message
37       will  add  a new entry in the routing table, or modify an existing one.
38       ICMP messages are routinely sent by the protocol  code.  Received  ICMP
39       messages  may be reflected back to users of higher-level protocols such
40       as TCP or UDP as error returns from system calls. A copy  of  all  ICMP
41       message  received  by the system is provided to every holder of an open
42       ICMP socket or TLI descriptor.
43

SEE ALSO

45       getprotobyname(3SOCKET),    recv(3SOCKET),    send(3SOCKET),    t_rcvu‐
46       data(3NSL), t_sndudata(3NSL), inet(7P), ip(7P), routing(7P)
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48
49       Postel, Jon, Internet Control Message Protocol — DARPA Internet Program
50       Protocol Specification, RFC 792, Network Information Center, SRI Inter‐
51       national, Menlo Park, Calif., September 1981.
52

DIAGNOSTICS

54       A socket operation may fail with one of the following errors returned:
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56       EISCONN          An  attempt  was  made  to establish a connection on a
57                        socket which already has one, or when trying to send a
58                        datagram  with  the  destination address specified and
59                        the socket is already connected.
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62       ENOTCONN         An attempt was made to send a datagram, but no  desti‐
63                        nation  address  is  specified, and the socket has not
64                        been connected.
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67       ENOBUFS          The system ran out of  memory  for  an  internal  data
68                        structure.
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71       EADDRNOTAVAIL    An  attempt was made to create a socket with a network
72                        address for which no network interface exists.
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NOTES

76       Replies to ICMP "echo" messages which are source routed  are  not  sent
77       back  using inverted source routes, but rather go back through the nor‐
78       mal routing mechanisms.
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82SunOS 5.11                        3 Jul 1990                          icmp(7P)
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