IP(4P)IP(4P)NAMEip - Internet Protocol
SYNOPSIS
#include <sys/socket.h>
#include <netinet/in.h>
s = socket(AF_INET, SOCK_RAW, proto);
DESCRIPTION
IP is the transport layer protocol used by the Internet protocol
family. Options may be set at the IP level when using higher-level
protocols that are based on IP (such as TCP and UDP). It may also be
accessed through a “raw socket” when developing new protocols, or
special purpose applications.
A single generic option is supported at the IP level, IP_OPTIONS, that
may be used to provide IP options to be transmitted in the IP header of
each outgoing packet. Options are set with setsockopt(2) and examined
with getsockopt(2). The format of IP options to be sent is that
specified by the IP protocol specification, with one exception: the
list of addresses for Source Route options must include the first-hop
gateway at the beginning of the list of gateways. The first-hop
gateway address will be extracted from the option list and the size
adjusted accordingly before use. IP options may be used with any
socket type in the Internet family.
Raw 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).
If proto is 0, the default protocol IPPROTO_RAW is used for outgoing
packets, and only incoming packets destined for that protocol are
received. If proto is non-zero, that protocol number will be used on
outgoing packets and to filter incoming packets.
Outgoing packets automatically have an IP header prepended to them
(based on the destination address and the protocol number the socket is
created with). Incoming packets are received with 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 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.
The following errors specific to IP may occur when setting or getting
IP options:
[EINVAL] An unknown socket option name was given.
[EINVAL] The IP option field was improperly formed; an option
field was shorter than the minimum value or longer than
the option buffer provided.
SEE ALSOgetsockopt(2), send(2), recv(2), intro(4N), icmp(4P), inet(4F)4.2 Berkeley Distribution May 16, 1986 IP(4P)
