IP(7P)IP(7P)NAMEip - Internet Protocol
SYNOPSIS
#include <sys/socket.h>
#include <netinet/in.h>
s = socket(AF_INET, SOCK_RAW, proto);
DESCRIPTION
IP is the network 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.
There are several IP-level setsockopt(2)/getsockopt(2) options.
IP_OPTIONS may be used to provide IP header options to be transmitted in
each outgoing packet or to examine the header options on incoming
packets. IP_OPTIONS may be used with any socket type in the Internet
family. The format of IP options to be sent is that specified by the IP
protocol specification (RFC-791), 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. To disable previously specified options, use a zero-length
buffer:
setsockopt(s, IPPROTO_IP, IP_OPTIONS, NULL, 0);
IP_TOS and IP_TTL may be used to set the type-of-service and time-to-live
fields in the IP header for SOCK_STREAM and SOCK_DGRAM sockets. For
example,
int tos = IPTOS_LOWDELAY; /* see <netinet/ip.h> */
int ttl = 60; /* max = 255 */
setsockopt(s, IPPROTO_IP, IP_TOS, &tos, sizeof(tos));
setsockopt(s, IPPROTO_IP, IP_TTL, &ttl, sizeof(ttl));
IP_HDRINCL indicates the complete IP header is included with the data and
may be used only with the SOCK_RAW type.
int hincl = 1; /* 1 = on, 0 = off */
setsockopt(s, IPPROTO_IP, IP_HDRINCL, &hincl, sizeof(hincl));
Raw IP Sockets
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). Only the super-user
can create raw IP sockets.
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IP(7P)IP(7P)
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), unless the IP_HDRINCL option has been set. Incoming packets are
received with IP header and options intact.
DIAGNOSTICS
A socket operation may fail with one of the following errors returned:
[EACESS] Permission to create a raw IP socket is denied.
[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(3), icmp(7P), inet(7F), route(7F),
IRIX Network Programming Guide
RFC-791
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