.TH IP 4P "25 March 1982"
.UC 
.SH NAME
ip \- Internet Protocol
.SH SYNOPSIS
.B #include <sys/socket.h>
.br
.B #include <netinet/in.h>
.PP
.B s = socket(AF_INET, SOCK_RAW, 0);
.SH DESCRIPTION
IP is the transport layer protocol used
by the Internet protocol family.  It may be accessed
through a \*(lqraw socket\*(rq when developing new protocols, or
special purpose applications.  IP sockets are connectionless,
and are normally used with the
.I sendto 
and
.I recvfrom 
calls, though the
.IR connect (2)
call may also be used to fix the destination for future
packets (in which case the 
.IR read (2)
or
.IR recv (2)
and 
.IR write (2)
or
.IR send (2)
system calls may be used).
.PP
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.
.SH DIAGNOSTICS
A socket operation may fail with one of the following errors returned:
.TP 15
[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;
.TP 15
[ENOTCONN]
when trying to send a datagram, but
no destination address is specified, and the socket hasn't been
connected;
.TP 15
[ENOBUFS]
when the system runs out of memory for
an internal data structure;
.TP 15
[EADDRNOTAVAIL]
when an attempt is made to create a 
socket with a network address for which no network interface
exists.
.SH SEE ALSO
send(2), recv(2), intro(4N), inet(4F)
.SH BUGS
One should be able to send and receive ip options.
.PP
The protocol should be settable after socket creation.