IP6(4P) Protocols IP6(4P)

NAME

ip6 - Internet Protocol Version 6

SYNOPSIS

#include <sys/socket.h>
#include <netinet/in.h>
#include <netinet/ip6.h>


s = socket(AF_INET6, SOCK_RAW, proto);


t = t_open ("/dev/rawip6", O_RDWR);

DESCRIPTION

The IPv6 protocol is the next generation of the internetwork datagram
delivery protocol of the Internet protocol family. Programs may use
IPv6 through higher-level protocols such as the Transmission Control
Protocol (TCP) or the User Datagram Protocol (UDP), or may interface
directly to IPv6. See tcp(4P) and udp(4P). 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 and IPv6
extension headers defined in the IPv6 specification may be set in
outgoing datagrams.

APPLICATION PROGRAMMING INTERFACE

The STREAMS driver /dev/rawip6 is the TLI transport provider that
provides raw access to IPv6.


Raw IPv6 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 datagrams. In this case, the read(2) or
recv(3SOCKET) and write(2) or send(3SOCKET) calls may be used.
Ancillary data may also be sent or received over raw IPv6 sockets
using the sendmsg(3SOCKET) and recvmsg(3SOCKET) system calls.


Unlike raw IP, IPv6 applications do not include a complete IPv6
header when sending; there is no IPv6 analog to the IP IP_HDRINCL
socket option. IPv6 header values may be specified or received as
ancillary data to a sendmsg(3SOCKET) or recvmsg(3SOCKET) system call,
or may be specified as "sticky" options on a per-socket basis by
using the setsockopt(3SOCKET) system call. Such sticky options are
applied to all outbound packets unless overridden by ancillary data.
If any ancillary data is specified in a sendmsg(3SOCKET) call, all
sticky options not explicitly overridden revert to default values for
that datagram only; the sticky options persist as set for subsequent
datagrams.


Since sendmsg(3SOCKET) is not supported for SOCK_STREAM upper level
protocols such as TCP, ancillary data is unsupported for TCP. Sticky
options, however, are supported.


Since sendmsg(3SOCKET) is supported for SOCK_DGRAM upper level
protocols, both ancillary data and sticky options are supported for
UDP, ICMP6, and raw IPv6 sockets.


The socket options supported at the IPv6 level are:

IPV6_BOUND_IF
Limit reception and transmission of packets
to this interface. Takes an integer as an
argument; the integer is the selected
interface index.


IPV6_UNSPEC_SRC
Boolean. Allow/disallow sending with a zero
source address.


IPV6_UNICAST_HOPS
Default hop limit for unicast datagrams. This
option takes an integer as an argument. Its
value becomes the new default value for
ip6_hops that IPv6 will use on outgoing
unicast datagrams sent from that socket. The
initial default is 60.


IPV6_MINHOPCOUNT
Controls the minimum value of the IPv6 header's
hop limit field that is required in an IPv6
packet before accepting it. If the value is set
to 100, then only IPv6 packets with a TTL of
100 or higher are accepted. Packets with a TTL
less than the minimum are dropped. This option
takes an integer as an argument and must be in
the range of 0 to 255. A value of 0 indicates
that all packets should be accepted.


IPV6_CHECKSUM
Specify the integer offset in bytes into the
user data of the checksum location. Does not
apply to the ICMP6 protocol. Note: checksums
are required for all IPv6 datagrams; this is
different from IP, in which datagram
checksums were optional. IPv6 will compute
the ULP checksum if the value in the checksum
field is zero.


IPV6_SEC_OPT
Enable or obtain IPsec security settings for
this socket. For more details on the
protection services of IPsec, see ipsec(4P).


IPV6_DONTFRAG
Boolean. Control fragmentation.


IPV6_USE_MIN_MTU
Controls whether path MTU discovery is used.
If set to 1, path MTU discovery is never used
and IPv6 packets are sent with the IPv6
minimum MTU. If set to -1, path MTU discovery
is not used for multicast and multicast
packets are sent with the IPv6 minimum MTU.
If set to 0, path MTU is always performed.


IPV6_V6ONLY
Boolean. If set, only V6 packets can be sent
or received


IPV6_SRC_PREFERENCES
Enable or obtain Source Address Selection
rule settings for this socket. For more
details on the Source Address Selection
rules, see inet6(4P).


The following options are boolean switches controlling the reception
of ancillary data:

IPV6_RECVPKTINFO
Enable/disable receipt of the index of the
interface the packet arrived on, and of the
inbound packet's destination address.


IPV6_RECVHOPLIMIT
Enable/disable receipt of the inbound
packet's current hoplimit.


IPV6_RECVHOPOPTS
Enable/disable receipt of the inbound
packet's IPv6 hop-by-hop extension header.


IPV6_RECVDSTOPTS
Enable/disable receipt of the inbound
packet's IPv6 destination options extension
header.


IPV6_RECVRTHDR
Enable/disable receipt of the inbound
packet's IPv6 routing header.


IPV6_RECVRTHDRDSTOPTS
Enable/disable receipt of the inbound
packet's intermediate-hops options extension
header. This option is obsolete.
IPV6_RECVDSTOPTS turns on receipt of both
destination option headers.


IPV6_RECVTCLASS
Enable/disable receipt of the traffic class
of the inbound packet.


IPV6_RECVPATHMTU
Enable/disable receipt of the path mtu of
the inbound packet.


The following options may be set as sticky options with
setsockopt(3SOCKET) or as ancillary data to a sendmsg(3SOCKET) system
call:

IPV6_PKTINFO
Set the source address and/or interface out
which the packet(s) will be sent. Takes a
struct in6_pktinfo as the parameter.


IPV6_HOPLIMIT
Set the initial hoplimit for outbound datagrams.
Takes an integer as the parameter. Note: This
option sets the hoplimit only for ancillary data
or sticky options and does not change the
default hoplimit for the socket; see
IPV6_UNICAST_HOPS and IPV6_MULTICAST_HOPS to
change the socket's default hoplimit.


IPV6_NEXTHOP
Specify the IPv6 address of the first hop, which
must be a neighbor of the sending host. Takes a
struct sockaddr_in6 as the parameter. When this
option specifies the same address as the
destination IPv6 address of the datagram, this
is equivalent to the existing SO_DONTROUTE
option.


IPV6_HOPOPTS
Specify one or more hop-by-hop options. Variable
length. Takes a complete IPv6 hop-by-hop options
extension header as the parameter.


IPV6_DSTOPTS
Specify one or more destination options.
Variable length. Takes a complete IPv6
destination options extension header as the
parameter.


IPV6_RTHDR
Specify the IPv6 routing header. Variable
length. Takes a complete IPv6 routing header as
the parameter. Currently, only type 0 routing
headers are supported.


IPV6_RTHDRDSTOPTS
Specify one or more destination options for all
intermediate hops. May be configured, but will
not be applied unless an IPv6 routing header is
also configured. Variable length. Takes a
complete IPv6 destination options extension
header as the parameter.


IPV6_PATHMTU
Get the path MTU associated with a connected
socket. Takes a ip6_mtuinfo as the parameter.


IPV6_TCLASS
Set the traffic class associated with outgoing
packets. The parameter is an integer. If the
parameter is less then -1 or greater then 256,
EINVAL is returned. If the parameter is equal to
-1, use the default. If the parameter is between
0 and 255 inclusive, use that value.


The following options affect the socket's multicast behavior:

IPV6_JOIN_GROUP
Join a multicast group. Takes a struct
ipv6_mreq as the parameter; the structure
contains a multicast address and an
interface index.


IPV6_LEAVE_GROUP
Leave a multicast group. Takes a struct
ipv6_mreq as the parameter; the structure
contains a multicast address and an
interface index.


MCAST_JOIN_GROUP
Functionally equivalent to
IPV6_JOIN_GROUP. Takes a struct group_req
as the parameter. The structure contains
a multicast address and an interface
index.


MCAST_BLOCK_SOURCE
Block multicast packets on a particular
multicast group whose source address
matches the given source address. The
specified group must be joined previously
using IPV6_JOIN_GROUP or
MCAST_JOIN_GROUP. Takes a struct
group_source_req as the parameter. The
structure contains an interface index, a
multicast address, and a source address.


MCAST_UNBLOCK_SOURCE
Unblock multicast packets which were
previously blocked using
MCAST_BLOCK_SOURCE. Takes a struct
group_source_req as the parameter. The
structure contains an interface index, a
multicast address, and a source address.


MCAST_LEAVE_GROUP
Functionally equivalent to
IPV6_LEAVE_GROUP. Takes a struct
group_req as the parameter. The structure
contains a multicast address and an
interface index.


MCAST_JOIN_SOURCE_GROUP
Begin receiving packets for the given
multicast group whose source address
matches the specified address. Takes a
struct group_source_req as the parameter.
The structure contains an interface
index, a multicast address, and a source
address.


MCAST_LEAVE_SOURCE_GROUP
Stop receiving packets for the given
multicast group whose source address
matches the specified address. Takes a
struct group_source_req as the parameter.
The structure contains an interface
index, a multicast address, and a source
address.


IPV6_MULTICAST_IF
The outgoing interface for multicast
packets. This option takes an integer as
an argument; the integer is the interface
index of the selected interface.


IPV6_MULTICAST_HOPS
Default hop limit for multicast
datagrams. This option takes an integer
as an argument. Its value becomes the new
default value for ip6_hops that IPv6 will
use on outgoing multicast datagrams sent
from that socket. The initial default is
1.


IPV6_MULTICAST_LOOP
Loopback for multicast datagrams.
Normally multicast datagrams are
delivered to members on the sending host.
Setting the unsigned character argument
to 0 will cause the opposite behavior.


The multicast socket options can be used with any datagram socket
type in the IPv6 family.


At the socket level, the socket option SO_DONTROUTE may be applied.
This option forces datagrams being sent to bypass routing and
forwarding by forcing the IPv6 hoplimit field to 1, meaning that the
packet will not be forwarded by routers.


Raw IPv6 datagrams can also be sent and received using the TLI
connectionless primitives.


Datagrams flow through the IPv6 layer in two directions: from the
network up to user processes and from user processes down to the
network. Using this orientation, IPv6 is layered above the network
interface drivers and below the transport protocols such as UDP and
TCP. The Internet Control Message Protocol (ICMPv6) for the Internet
Protocol Version 6 (IPv6) is logically a part of IPv6. See icmp6(4P).


Unlike IP, IPv6 provides no checksum of the IPv6 header. Also unlike
IP, upper level protocol checksums are required. IPv6 will compute
the ULP/data portion checksum if the checksum field contains a zero
(see IPV6_CHECKSUM option above).


IPv6 extension headers in received datagrams are processed in the
IPv6 layer according to the protocol specification. Currently
recognized IPv6 extension headers include hop-by-hop options header,
destination options header, routing header (currently, only type 0
routing headers are supported), and fragment header.


By default, the IPv6 layer will not forward IPv6 packets that are not
addressed to it. This behavior can be overridden by using
routeadm(8) to enable the ipv6-forwarding option. IPv6 forwarding is
configured at boot time based on the setting of routeadm(8)'s
ipv6-forwarding option.


For backwards compatibility, IPv6 forwarding can be enabled or
disabled using ndd(8)'s ip_forwarding variable. It is set to 1 if
IPv6 forwarding is enabled, or 0 if it is disabled.


Additionally, finer-grained forwarding can be configured in IPv6.
Each interface can be configured to forward IPv6 packets by setting
the IFF_ROUTER interface flag. This flag can be set and cleared using
ifconfig(8)'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 ip6_forwarding variable sets all of the IPv6 interfaces'
IFF_ROUTER flags.


For backwards compatibility, each interface creates an
<ifname>ip6_forwarding /dev/ip6 variable that can be modified using
ndd(8). An interface's :ip6_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>:ip6_forwarding ndd variable is obsolete and may be
removed in a future release of Solaris. The ifconfig(8) router and
-router interfaces are preferred.


The IPv6 layer will send an ICMP6 message back to the source host in
many cases when it receives a datagram that can not be handled. A
"time exceeded" ICMP6 message will be sent if the ip6_hops field in
the IPv6 header drops to zero in the process of forwarding a
datagram. A "destination unreachable" message will be sent by a
router or by the originating host if a datagram can not be sent on
because there is no route to the final destination; it will be sent
by a router when it encounters a firewall prohibition; it will be
sent by a destination node when the transport protocol (that is, TCP)
has no listener. A "packet too big" message will be sent by a router
if the packet is larger than the MTU of the outgoing link (this is
used for Path MTU Discovery). A "parameter problem" message will be
sent if there is a problem with a field in the IPv6 header or any of
the IPv6 extension headers such that the packet cannot be fully
processed.


The IPv6 layer supports fragmentation and reassembly. Datagrams are
fragmented on output if the datagram is larger than the maximum
transmission 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 IPv6 back up to the user process.

SEE ALSO

svcs(1), read(2), write(2), bind(3SOCKET), connect(3SOCKET),
getsockopt(3SOCKET), recv(3SOCKET), recvmsg(3SOCKET), send(3SOCKET),
sendmsg(3SOCKET), setsockopt(3SOCKET), icmp6(4P), if_tcp(4P),
inet6(4P), ipsec(4P), routing(4P), tcp(4P), udp(4P),
defaultrouter(5), smf(7), ndd(8), routeadm(8), svcadm(8)


Deering, S. and Hinden, B. RFC 2460, Internet Protocol, Version 6
(IPv6) Specification. The Internet Society. December, 1998.


Stevens, W., and Thomas, M. RFC 2292, Advanced Sockets API for IPv6.
Network Working Group. February 1998.

DIAGNOSTICS

A socket operation may fail with one of the following errors
returned:

EPROTONOSUPPORT
Unsupported protocol (for example, IPPROTO_RAW.)


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 IPv6 option field improperly
formed; an option field was shorter than the
minimum value or longer than the option buffer
provided; the value in the option field was
invalid.


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 via
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.


ENOMEM
The system was unable to allocate memory for an
IPv6 socket option or other internal data
structures.


ENOPROTOOPT
An IP socket option was attempted on an IPv6
socket, or an IPv6 socket option was attempted on
an IP socket.


ENOPROTOOPT
Invalid socket type for the option.

NOTES

Applications using the sockets API must use the Advanced Sockets API
for IPv6 (RFC 2292) to see elements of the inbound packet's IPv6
header or extension headers.


The ip6 service is managed by the service management facility,
smf(7), under the service identifier:

svc:/network/initial:default


Administrative actions on this service, such as enabling, disabling,
or requesting restart, can be performed using svcadm(8). The
service's status can be queried using the svcs(1) command.

April 17, 2024 IP6(4P)