ip(7P) ip(7P)
NAME
ip, IP - Internet Protocol
SYNOPSIS
#include <sys/socket.h>
#include <netinet/in.h>
s = socket(AF_INET, SOCK_RAW, proto);
t = t_open ("/dev/rawip", O_RDWR);
IP is the internetwork datagram delivery protocol that is central to the Internet protocol family. Programs may use IP through higher-level
protocols such as the Transmission Control Protocol (TCP) or the User Datagram Protocol (UDP), or may interface directly to IP. See tcp(7P)
and udp(7P). Direct access may be by means of the socket interface, using a "raw socket," or by means of the Transport Level Interface
(TLI). The protocol options defined in the IP specification may be set in outgoing datagrams.
Packets sent to or from this system may be subject to IPsec policy; see ipsec(7P) for more information.
APPLICATION PROGRAMMING INTERFACE
The STREAMS driver /dev/rawip is the TLI transport provider that provides raw access to IP.
Raw IP sockets are connectionless and are normally used with the sendto() and recvfrom() calls (see send(3SOCKET) and recv(3SOCKET)),
although the connect(3SOCKET) call may also be used to fix the destination for future datagram. In this case, the read(2) or recv(3SOCKET)
and write(2) or send(3SOCKET) calls may be used. If proto is IPPROTO_RAW or IPPROTO_IGMP, the application is expected to include a complete
IP header when sending. Otherwise, that protocol number will be set in outgoing datagrams and used to filter incoming datagrams and an IP
header will be generated and prepended to each outgoing datagram. In either case, received datagrams are returned with the IP header and
options intact.
If an application uses IP_HDRINCL and provides the IP header contents, the IP stack does not modify the following supplied fields under any
conditions: Type of Service, DF Flag, Protocol, and Destination Address. The IP Options and IHL fields are set by use of IP_OPTIONS, and
Total Length is updated to include any options. Version is set to the default. Identification is chosen by the normal IP ID selection
logic. The source address is updated if none was specified and the TTL is changed if the packet has a broadcast destination address. Since
an applicaton cannot send down fragments (as IP assigns the IP ID), Fragment Offset is always 0. The IP Checksum field is computed by IP.
None of the data beyond the IP header are changed, including the application-provided transport header.
The socket options supported at the IP level are:
IP_OPTIONS IP options for outgoing datagrams. This socket option may be used to set IP options to be included in each outgoing
datagram. IP options to be sent are set with setsockopt() (see getsockopt(3SOCKET)). The getsockopt(3SOCKET) call
returns the IP options set in the last setsockopt() call. IP options on received datagrams are visible to user pro-
grams only using raw IP sockets. The format of IP options given in setsockopt() matches those defined in the IP
specification with one exception: the list of addresses for the source routing 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 fam-
ily.
IP_SEC_OPT Enable or obtain IPsec security settings for this socket. For more details on the protection services of IPsec, see
ipsec(7P).
IP_ADD_MEMBERSHIP Join a multicast group.
IP_DROP_MEMBERSHIP Leave a multicast group.
These options take a struct ip_mreq as the parameter. The structure contains a multicast address which must be set to the CLASS-D IP multi-
cast address and an interface address. Normally the interface address is set to INADDR_ANY which causes the kernel to choose the interface
on which to join.
IP_BLOCK_SOURCE Block multicast packets whose source address matches the given source address. The specified group must be joined
previously using IP_ADD_MEMBERSHIP or MCAST_JOIN_GROUP.
IP_UNBLOCK_SOURCE Unblock (begin receiving) multicast packets which were previously blocked using IP_BLOCK_SOURCE.
IP_ADD_SOURCE_MEMBERSHIPBegin receiving packets for the given multicast group whose source address matches the specified address.
IP_DROP_SOURCE_MEMBERSHIStop receiving packets for the given multicast group whose source address matches the specified address.
These options take a struct ip_mreq_source as the parameter. The structure contains a multicast address (which must be set to the CLASS-D
IP multicast address), an interface address, and a source address.
MCAST_JOIN_GROUP Join a multicast group. Functionally equivalent to IP_ADD_MEMBERSHIP.
MCAST_BLOCK_SOURCE Block multicast packets whose source address matches the given source address. The specified group must be joined
previously using IP_ADD_MEMBERSHIP or MCAST_JOIN_GROUP.
MCAST_UNBLOCK_SOURCE Unblock (begin receiving) multicast packets which were previously blocked using MCAST_BLOCK_SOURCE.
MCAST_LEAVE_GROUP Leave a multicast group. Functionally equivalent to IP_DROP_MEMBERSHIP.
MCAST_JOIN_SOURCE_GROUP Begin receiving packets for the given multicast group whose source address matches the specified address.
MCAST_LEAVE_SOURCE_GROUPStop receiving packets for the given multicast group whose source address matches the specified address.
These options take a struct group_req or struct group_source_req as the parameter. The `group_req structure contains an interface index and
a multicast address which must be set to the CLASS-D multicast address. The group_source_req structure is used for those options which
include a source address. It contains an interface index, multicast address, and source address.
IP_MULTICAST_IF The outgoing interface for multicast packets. This option takes a struct in_addr as an argument, and it selects
that interface for outgoing IP multicast packets. If the address specified is INADDR_ANY, it uses the unicast rout-
ing table to select the outgoing interface (which is the default behavior).
IP_MULTICAST_TTL Time to live for multicast datagrams. This option takes an unsigned character as an argument. Its value is the TTL
that IP uses on outgoing multicast datagrams. The default is 1.
IP_MULTICAST_LOOP Loopback for multicast datagrams. Normally multicast datagrams are delivered to
members on the sending host (or sending zone). Setting the unsigned character argument to 0 causes the opposite
behavior, meaning that when multiple zones are present, the datagrams are delivered to all zones except the sending
zone.
IP_RECVIF Receive the inbound interface index.
IP_TOS This option takes an integer argument as its input value. The least significant 8 bits of the value are used to set
the Type Of Service field in the IP header of the outgoing packets.
The multicast socket options can be used with any datagram socket type in the Internet family.
At the socket level, the socket option SO_DONTROUTE may be applied. This option forces datagrams being sent to bypass routing and forward-
ing by forcing the IP Time To Live field to 1, meaning that the packet will not be forwarded by routers.
Raw IP datagrams can also be sent and received using the TLI connectionless primitives.
Datagrams flow through the IP layer in two directions: from the network up to user processes and from user processes down to the network.
Using this orientation, IP is layered above the network interface drivers and below the transport protocols such as UDP and TCP. The Inter-
net Control Message Protocol (ICMP) is logically a part of IP. See icmp(7P).
IP provides for a checksum of the header part, but not the data part, of the datagram. The checksum value is computed and set in the
process of sending datagrams and checked when receiving datagrams.
IP options in received datagrams are processed in the IP layer according to the protocol specification. Currently recognized IP options
include: security, loose source and record route (LSRR), strict source and record route (SSRR), record route, and internet timestamp.
By default, the IP layer will not forward IPv4 packets that are not addressed to it. This behavior can be overridden by using routeadm(1M)
to enable the ipv4-forwarding option. IPv4 forwarding is configured at boot time based on the setting of routeadm(1M)'s ipv4-forwarding
option.
For backwards compatibility, IPv4 forwarding can be enabled or disabled using ndd(1M)'s ip_forwarding variable. It is set to 1 if IPv4
forwarding is enabled, or 0 if it is disabled.
Additionally, finer-grained forwarding can be configured in IP. Each interface can be configured to forward IP packets by setting the
IFF_ROUTER interface flag. This flag can be set and cleared using ifconfig(1M)'s router and router options. If an interface's IFF_ROUTER
flag is set, packets can be forwarded to or from the interface. If it is clear, packets will neither be forwarded from this interface to
others, nor forwarded to this interface. Setting the ip_forwarding variable sets all of the IPv4 interfaces' IFF_ROUTER flags.
For backwards compatibility, each interface creates an <ifname>:ip_forwarding /dev/ip variable that can be modified using ndd(1M). An
interface's :ip_forwarding ndd variable is a boolean variable that mirrors the status of its IFF_ROUTER interface flag. It is set to 1 if
the flag is set, or 0 if it is clear. This interface specific <ifname> :ip_forwarding ndd variable is obsolete and may be removed in a
future release of Solaris. The ifconfig(1M) router and -router interfaces are preferred.
The IP layer sends an ICMP message back to the source host in many cases when it receives a datagram that can not be handled. A "time
exceeded" ICMP message is sent if the "time to live" field in the IP header drops to zero in the process of forwarding a datagram. A "des-
tination unreachable" message is sent if a datagram can not be forwarded because there is no route to the final destination, or if it can
not be fragmented. If the datagram is addressed to the local host but is destined for a protocol that is not supported or a port that is
not in use, a destination unreachable message is also sent. The IP layer may send an ICMP "source quench" message if it is receiving data-
grams too quickly. ICMP messages are only sent for the first fragment of a fragmented datagram and are never returned in response to errors
in other ICMP messages.
The IP layer supports fragmentation and reassembly. Datagrams are fragmented on output if the datagram is larger than the maximum transmis-
sion unit (MTU) of the network interface. Fragments of received datagrams are dropped from the reassembly queues if the complete datagram
is not reconstructed within a short time period.
Errors in sending discovered at the network interface driver layer are passed by IP back up to the user process.
Multi-Data Transmit allows more than one packet to be sent from the IP module to another in a given call, thereby reducing the per-packet
processing costs. The behavior of Multi-Data Transmit can be overrideen by using ndd(1M) to set the /dev/ip variable, ip_multidata_outbound
to 0. Note, the IP module will only initiate Multi-Data Transmit if the network interface driver supports it.
ifconfig(1M), routeadm(1M), ndd(1M), read(2), write(2), bind(3SOCKET), connect(3SOCKET), getsockopt(3SOCKET), recv(3SOCKET), send(3SOCKET),
defaultrouter(4), icmp(7P), if_tcp(7P), inet(7P), ip6(7P), ipsec(7P),routing(7P), tcp(7P), udp(7P)
Braden, R., RFC 1122, Requirements for Internet Hosts - Communication Layers, Information Sciences Institute, University of Southern Cali-
fornia, October 1989.
Postel, J., RFC 791, Internet Protocol - DARPA Internet Program Protocol Specification, Information Sciences Institute, University of
Southern California, September 1981.
A socket operation may fail with one of the following errors returned:
EACCES A bind() operation was attempted with a "reserved" port number and the effective user ID of the process was not the
privileged user.
EADDRINUSE A bind() operation was attempted on a socket with a network address/port pair that has already been bound to
another socket.
EADDRNOTAVAIL A bind() operation was attempted for an address that is not configured on this machine.
EINVAL A sendmsg() operation with a non-NULL msg_accrights was attempted.
EINVAL A getsockopt() or setsockopt() operation with an unknown socket option name was given.
EINVAL A getsockopt() or setsockopt() operation was attempted with the IP option field improperly formed; an option field
was shorter than the minimum value or longer than the option buffer provided.
EISCONN A connect() operation was attempted on a socket on which a connect() operation had already been performed, and the
socket could not be successfully disconnected before making the new connection.
EISCONN A sendto() or sendmsg() operation specifying an address to which the message should be sent was attempted on a
socket on which a connect() operation had already been performed.
EMSGSIZE A send(), sendto(), or sendmsg() operation was attempted to send a datagram that was too large for an interface,
but was not allowed to be fragmented (such as broadcasts).
ENETUNREACH An attempt was made to establish a connection by means of connect(), or to send a datagram by means of sendto() or
sendmsg(), where there was no matching entry in the routing table; or if an ICMP "destination unreachable" message
was received.
ENOTCONN A send() or write() operation, or a sendto() or sendmsg() operation not specifying an address to which the message
should be sent, was attempted on a socket on which a connect() operation had not already been performed.
ENOBUFS The system ran out of memory for fragmentation buffers or other internal data structures.
ENOBUFS SO_SNDBUF or SO_RCVBUF exceeds a system limit.
EINVAL Invalid length for IP_OPTIONS.
EHOSTUNREACH Invalid address for IP_MULTICAST_IF.
EINVAL Not a multicast address for IP_ADD_MEMBERSHIP and IP_DROP_MEMBERSHIP.
EADDRNOTAVAIL Bad interface address for IP_ADD_MEMBERSHIP and IP_DROP_MEMBERSHIP.
EADDRINUSE Address already joined for IP_ADD_MEMBERSHIP.
ENOENT Address not joined for IP_DROP_MEMBERSHIP.
ENOPROTOOPT Invalid socket type.
EPERM No permissions.
Raw sockets should receive ICMP error packets relating to the protocol; currently such packets are simply discarded.
Users of higher-level protocols such as TCP and UDP should be able to see received IP options.
10 Mar 2005 ip(7P)