NAME

ip − Internet Protocol

SYNOPSIS

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

s = socket(AF_INET, SOCK_RAW, 0);

DESCRIPTION

IP is the transport layer protocol used by the Internet protocol family.  It may be accessed through a “raw socket” when developing new protocols, or special purpose applications.  IP 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 and the protocol number the socket is created with).  Likewise, incoming packets have their IP header stripped before being sent to the user. 

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 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

send(2), recv(2), intro(4N), inet(4F)

BUGS

One should be able to send and receive ip options. 

The protocol should be settable after socket creation. 

4BSD