OSF

NAME

ip − Internet Protocol

SYNOPSIS

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

s = socket(AF_INET, SOCK_RAW, proto);

DESCRIPTION

The Internet Protocol (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 the Transmission Control Protocol (TCP) and the User Datagram Package (UDP)).  It may also be accessed through a raw socket when developing new protocols, or special purpose applications. 

IP_OPTIONS is used to provide IP options to be transmitted in the IP header of each outgoing packet.  Options are set with the setsockopt() function and examined with the getsockopt() function.  The format of IP options to be sent is that specified by the IP 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() call may also be used to fix the destination for future packets, in which case the read() or recv() and write() or send() functions may be used. 

If proto is 0 (zero), the default protocol IPPROTO_RAW is used for outgoing packets, and only incoming packets destined for that protocol are received.  If proto is nonzero, 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 is set.  IP_HDRINCL specifies whether the IP header is provided by the sent packet.  Incoming packets are received with IP header and options intact. 

ERRORS

If a socket operation fails, errno may be set to one of the following values:

[EISCONN]The socket is already connected.  This error occurs when trying to establish connection on a socket or when trying to send a datagram with the destination address specified. 

[ENOTCONN]
The destination address of a datagram was not 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.

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. 

RELATED INFORMATION

Functions: getsockopt(2), send(2), recv(2)

Files: netintro(7), icmp(7), inet(7)