IP(7P)                                                     IP(7P)



     NAME
          ip - Internet Protocol - TCP

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

          s = socket(AFINET, SOCKRAW, proto);

     DESCRIPTION
          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
          TCP and UDP).  It may also be accessed through a "raw
          socket" when developing new protocols, or special purpose
          applications.

          A single generic option is supported at the IP level,
          IP_OPTIONS, that may be used to provide IP options to be
          transmitted in the IP header of each outgoing packet.
          Options are examined with getsockopt(2).  The format of IP
          options to be sent is that specified by the IP protocol
          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(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).

          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).  Incoming packets are
          received with IP header and options intact.

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

          [EISCONN]      when trying to establish a connection on a
                         socket which already has one, or when trying



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     IP(7P)                                                     IP(7P)



                         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 ALSO
          getsockopt(2), send(2), recv(2), icmp(7P), inet(7P)

     ORIGIN
          4.3 BSD
























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