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ip(4p)

ip(4P)                         Network Protocols                        ip(4P)



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);

DESCRIPTION
       IP  is  the  internetwork datagram delivery protocol that is central to
       the Internet protocol family. Programs can use IP through  higher-level
       protocols  such  as the Transmission Control Protocol (TCP) or the User
       Datagram Protocol (UDP), or can interface directly to IP.  See  tcp(4P)
       and  udp(4P).  Direct  access  can 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 can be set
       in outgoing datagrams.


       Packets sent to or from this system can be subject to IPsec policy. See
       ipsec(4P) for more information.

APPLICATION PROGRAMMING INTERFACE
       The  STREAMS  driver /dev/rawip is the TLI transport provider that pro‐
       vides raw access to IP.


       Raw IP sockets are  connectionless  and  are  normally  used  with  the
       sendto() and recvfrom() calls (see send(3C) and recv(3C)), although the
       connect(3C) call can also be used to fix  the  destination  for  future
       datagram.  In  this  case,  the  read(2)  or  recv(3C)  and write(2) or
       send(3C) calls can be used. If proto is  IPPROTO_RAW  or  IPPROTO_IGMP,
       the  application is expected to include a complete IP header when send‐
       ing. Otherwise, that protocol number is 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 data‐
       grams 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
       application cannot send down fragments (as IP assigns the IP ID), Frag‐
       ment Offset is always 0. The IP Checksum field is computed by IP.  None
       of  the  data  beyond the IP header are changed, including the applica‐
       tion-provided transport header.


       The socket options supported at the IP level are:

       IP_ADD_MEMBERSHIP     Join a multicast group.


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


       IP_DROP_MEMBERSHIP    Leave a multicast group.


       IP_OPTIONS            IP options for outgoing  datagrams.  This  socket
                             option  can  be  used  to  set  IP  options to be
                             included in each outgoing datagram. IP options to
                             be  sent  are set with setsockopt() (see getsock‐
                             opt(3C)). The getsockopt(3C) call returns the  IP
                             options  set  in  the  last setsockopt() call. IP
                             options on received datagrams are visible to user
                             programs only using raw IP sockets. The format of
                             IP options given in  setsockopt()  matches  those
                             defined  in  the IP specification with one excep‐
                             tion: the list of addresses for the source  rout‐
                             ing 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  can  be  used with any
                             socket type in the Internet family.


       IP_RECVTTL            Allow the user level  application,  mipagent,  to
                             read  the  IP  TTL (time to live) for an incoming
                             packet.


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



       The following options take in_pktinfo_t as the parameter:

       IP_PKTINFO

           Set the source address and/or transmit interface of the  packet(s).
           The  IP_BOUND_IF  socket option takes precedence over the interface
           index passed in IP_PKTINFO.




             struct in_pktinfo {
                unsigned int ipi_ifindex;/* send/recv interface index */
                struct in_addr ipi_spec_dst;/* matched source addr. */
                struct in_addr ipi_addr;/* src/dst addr. in IP hdr */
             } in_pktinfo_t;

           When passed in (on transmit) via ancillary  data  with  IP_PKTINFO,
           ipi_spec_dst  is used as the source address and ipi_ifindex is used
           as the interface index to send the packet out.


       IP_RECVPKTINFO

           Enable/disable receipt of the index of  the  interface  the  packet
           arrived  on,  the local address that was matched for reception, and
           the inbound packet's actual destination address. Takes  boolean  as
           the parameter. Returns struct in_pktinfo_t as ancillary data.



       The  following  options  take  a  struct  ip_mreq as the parameter. The
       structure contains a multicast address which must be set to the CLASS-D
       IP  multicast  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 previ‐
                                    ously    using    IP_ADD_MEMBERSHIP     or
                                    MCAST_JOIN_GROUP.


       IP_UNBLOCK_SOURCE            Unblock  (begin receiving) multicast pack‐
                                    ets which were  previously  blocked  using
                                    IP_BLOCK_SOURCE.


       IP_ADD_SOURCE_MEMBERSHIP     Begin receiving packets for the given mul‐
                                    ticast group whose source address  matches
                                    the specified address.


       IP_DROP_SOURCE_MEMBERSHIP    Stop  receiving packets for the given mul‐
                                    ticast group whose source address  matches
                                    the specified address.



       The  following  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 equiv‐
                                   alent to IP_ADD_MEMBERSHIP.


       MCAST_BLOCK_SOURCE          Block   multicast   packets   whose  source
                                   address matches the given  source  address.
                                   The  specified  group must be joined previ‐
                                   ously    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  mul‐
                                   ticast  group  whose source address matches
                                   the specified address.


       MCAST_LEAVE_SOURCE_GROUP    Stop receiving packets for the given multi‐
                                   cast group whose source address matches the
                                   specified address.



       The   following   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 multi‐
                            cast  packets.  If  the   address   specified   is
                            INADDR_ANY,  it  uses the unicast routing 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 multi‐
                            cast datagrams. The default is 1.


       IP_MULTICAST_LOOP    Loopback for multicast datagrams. Normally  multi‐
                            cast  datagrams  are  delivered  to members on the
                            sending  host  (or  sending  zone).  Setting   the
                            unsigned  character argument to 0 causes the oppo‐
                            site 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.

                            Note  that  this  value will be overwritten if the
                            administrator configures flow DSCP  marking  using
                            flowadm(8) or ipqos(4IPP), and the packet is clas‐
                            sified to the configured flow.


       IP_DONTFRAG          This option controls whether IP allows  fragmenta‐
                            tion  both locally (fragmenting the packets before
                            sending them out on the wire), and in the  network
                            (whether  or not the Don't Fragment flag is set in
                            the IPv4 header). Setting the option to  any  non-
                            zero  value  disables  fragmentation.  Setting the
                            option to zero enables fragmentation.  When  frag‐
                            mentation  is disabled then IP does not create any
                            Path MTU state on behalf of this socket.


       IP_NEXTHOP           This option specifies the address  of  the  onlink
                            nexthop  for traffic originating from that socket.
                            It causes the routing table  to  be  bypassed  and
                            outgoing traffic is sent directly to the specified
                            nexthop. This option takes  an  ipaddr_t  argument
                            representing  the  IPv4  address of the nexthop as
                            the  input  value.  The  IP_NEXTHOP  option  takes
                            precedence   over   IPOPT_LSRR.   IP_BOUND_IF  and
                            SO_DONTROUTE take precedence over IP_NEXTHOP. This
                            option  has no meaning for broadcast and multicast
                            packets. The  application  must  ensure  that  the
                            specified  nexthop  is  alive.  An application can
                            want to specify the IP_NEXTHOP  option  on  a  TCP
                            listener  socket  only  for incoming requests to a
                            particular IP address. In this case, it must avoid
                            binding  the socket to INADDR_ANY and instead must
                            bind  the  listener  socket  to  the  specific  IP
                            address.  In  addition,  typically the application
                            can want the incoming and outgoing interface to be
                            the  same.  In  this  case,  the  application must
                            select a  suitable  nexthop  that  is  onlink  and
                            reachable  via the desired interface and do a set‐
                            sockopt (IP_NEXTHOP) on it. Then it must  bind  to
                            the  IP  address of the desired interface. Setting
                            the     IP_NEXTHOP     option     requires     the
                            PRIV_SYS_NET_CONFIG privilege.



       The   multicast   socket  options  (IP_MULTICAST_IF,  IP_MULTICAST_TTL,
       IP_MULTICAST_LOOP and IP_RECVIF) can be used with any  datagram  socket
       type in the Internet family.


       At  the  socket  level,  the socket option SO_DONTROUTE can 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
       is not be forwarded by routers.


       Raw IP datagrams can also be sent and received using  the  TLI  connec‐
       tionless 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 Internet Control
       Message Protocol (ICMP) is logically a part of IP. See icmp(4P).


       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 accord‐
       ing 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 does not forward IPv4  packets  that  are  not
       addressed  to  it. This behavior can be overridden by using routeadm(8)
       to enable the ipv4-forwarding option. IPv4 forwarding is configured  at
       boot time based on the setting of routeadm(8)'s ipv4-forwarding option.
       IPv4 forwarding is configured at boot time  based  on  the  setting  of
       routeadm's  ipv4-forwarding option. ipadm(8) can also be used to enable
       ipv4 forwarding on a global basis. The ipadm  set-prop subcommand along
       with  forwarding  property  is used to enable system-wide forwarding of
       packets. The protocol for which forwarding needs to be enabled is spec‐
       ified using the -m option. See ipadm(8).


       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(8)'s router and router options. Also, the ipadm(8)  set-ifprop
       subcommand can be used to enable/disable per-interface ipv4 forwarding.
       The ipadm  set-ifprop  interfaces  are  preferred.  If  an  interface's
       IFF_ROUTER  flag is set, packets can be forwarded to or from the inter‐
       face. If it is clear, packets are not forwarded from this interface  to
       others,  nor forwarded to this interface. Setting the global forwarding
       variable for ipv4, sets all of the IPv4 interfaces IFF_ROUTER flags.


       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 "desti‐
       nation 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  des‐
       tined  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  can
       send  an  ICMP "source quench" message if it is receiving datagrams too
       quickly. ICMP messages are only sent for the first fragment of a  frag‐
       mented  datagram  and are never returned in response to errors in other
       ICMP messages.


       The IP layer supports fragmentation and reassembly. Datagrams are frag‐
       mented  on  output if the datagram is larger than the maximum transmis‐
       sion unit (MTU) of the network interface. Fragments of  received  data‐
       grams  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.

PACKET EVENTS
       Through  the  netinfo  framework,  this  driver  provides the following
       packet events:

       Physical in     Packets received on a network interface from an  exter‐
                       nal source.


       Physical out    Packets to be sent out a network interface.


       Forwarding      Packets  being  forwarded  through this host to another
                       network.


       loopback in     Packets that have been sent by a local  application  to
                       another.


       loopback out    Packets  about  to  be  received by a local application
                       from another.



       Currently, only a single function can be registered for each event.  As
       a result, if the slot for an event is already occupied by someone else,
       a second attempt to register a callback fails.


       To receive packet events in a kernel module, it is first  necessary  to
       obtain  a  handle  for either IPv4 or IPv6 traffic. This is achieved by
       passing NHF_INET or NHF_INET6 through to a net_protocol_lookup()  call.
       The  value  returned  from this call must then be passed into a call to
       net_register_hook(), along with a description of the hook to add. For a
       description  of  the  structure  passed  through  to  the callback, see
       hook_pkt_event(9S). For IP packets, this structure  is  filled  out  as
       follows:

       hpe_ifp    Identifier  indicating  the  inbound  interface  for packets
                  received with the physical in event.


       hpe_ofp    Identifier indicating the  outbound  interface  for  packets
                  received with the physical out event.


       hpe_hdr    Pointer  to  the  start  of  the IP header (not the ethernet
                  header).


       hpe_mp     Pointer to the start of the mblk_t chain containing  the  IP
                  packet.


       hpe_mb     Pointer to the mblk_t with the IP header in it.


NETWORK INTERFACE EVENTS
       In  addition to events describing packets as they move through the sys‐
       tem, it is also possible to receive notification of events relating  to
       network interfaces. These events are all reported back through the same
       callback. The list of events is as follows:

       plumb             A new network interface has been instantiated.


       unplumb           A network interface is no longer associated with this
                         protocol.


       up                At  least  one  logical  interface  is  now  ready to
                         receive packets.


       down              There are no logical interfaces expecting to  receive
                         packets.


       address change    An address has changed on a logical interface.


SEE ALSO
       read(2),  write(2),  connect(3C),  bind(3C),  getsockopt(3C), recv(3C),
       send(3C), icmp(4P), if_tcp(4P),  inet(4P),  ip6(4P),  ipsec(4P),  rout‐
       ing(4P),  tcp(4P), udp(4P), ifconfig(8), ipadm(8), ndd(8), routeadm(8),
       net_hook_register(9F), hook_pkt_event(9S)


       Braden, R., RFC 1122, Requirements for Internet Hosts  −  Communication
       Layers, Information Sciences Institute, University of Southern Califor‐
       nia, October 1989.


       Postel, J., RFC 791, Internet Protocol − DARPA Internet Program  Proto‐
       col Specification, Information Sciences Institute, University of South‐
       ern California, September 1981.

DIAGNOSTICS
       A socket operation can 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.

                        Setting the IP_NEXTHOP  was  attempted  by  a  process
                        lacking the PRIV_SYS_NET_CONFIG privilege.


       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  per‐
                        formed,  and the socket could not be successfully dis‐
                        connected 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.

                        Invalid (offlink) nexthop address for IP_NEXTHOP.


       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.


NOTES
       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.



Oracle Solaris 11.4               1 Sep 2014                            ip(4P)
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