Visit Our UNIX and Linux User Community

Linux and UNIX Man Pages

Test Your Knowledge in Computers #884
Difficulty: Easy
A backdoor in a computer system, a cryptosystem or an algorithm, is any secret method of bypassing normal authentication or security controls.
True or False?
Linux & Unix Commands - Search Man Pages

icmp(4p) [bsd man page]

ICMP(4P)																  ICMP(4P)

NAME
icmp - Internet Control Message Protocol SYNOPSIS
#include <sys/socket.h> #include <netinet/in.h> s = socket(AF_INET, SOCK_RAW, proto); DESCRIPTION
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 getprotoby- name(3N). ICMP sockets are connectionless, and are normally used with the sendto and recvfrom 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
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 destina- tion 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
send(2), recv(2), intro(4N), inet(4F), ip(4P) 4.3 Berkeley Distribution May 16, 1986 ICMP(4P)

Check Out this Related Man Page

icmp(7P)							     Protocols								  icmp(7P)

NAME
icmp, ICMP - Internet Control Message Protocol SYNOPSIS
#include <sys/socket.h> #include <netinet/in.h> #include <netinet/ip_icmp.h> s = socket(AF_INET, SOCK_RAW, proto); t = t_open("/dev/icmp", O_RDWR); 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 Transport Level Interface (TLI) for network monitoring and diagnostic 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 connection- less, and are normally used with the t_sndudata / t_rcvudata 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 including routing, fault iso- lation, and congestion control. Receipt of an ICMP "redirect" message will add a new entry in the routing table, or modify an existing one. ICMP messages are routinely sent by the protocol code. Received ICMP messages may be reflected back to users of higher-level protocols 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), t_rcvudata(3NSL), t_sndudata(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., September 1981. DIAGNOSTICS
A socket operation may fail with one of the following errors returned: EISCONN An attempt was made 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 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 internal data structure. EADDRNOTAVAIL 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 nor- mal routing mechanisms. SunOS 5.11 3 Jul 1990 icmp(7P)

Featured Tech Videos