Manual Pages for UNIX Operating System command usage for man packet

Protocols                                              packet(7P)



NAME
     packet, PF_PACKET - packet interface on device level

SYNOPSIS
     #include 


     #include 


     #include 


     packet_socket = socket(2,7,n)(PF_PACKET, int socket_type, int protocol);


DESCRIPTION
     Packet sockets are used to receive or send  packets  at  the
     device  driver  (OSI  Layer  2)  level. These allow users to
     implement protocol modules in (1,8) user space on top of the
     physical layer.


     The socket_type is either SOCK_RAW for raw packets including
     the link (1,2) level header or SOCK_DGRAM for cooked packets
     with the link (1,2) level header  removed.  The  link  (1,2)
     level header information is available in (1,8) a common for-
     mat in (1,8) a sockaddr_ll. protocol is the IEEE 802.3  pro-
     tocol    number    in   (1,8)   network   order.   See   the
      include file (1,n) for a  list  of  allowed
     protocols.  When  protocol  is set (7,n,1 builtins) to htons
     (ETH_P_ALL) then all protocols are  received.  All  incoming
     packets of that protocol type is passed to the packet socket
     (2,7,n) before they are passed to the protocols  implemented
     in (1,8) the kernel.


     Only process with the net_rawaccesss  privilege  may  create
     PF_PACKET  sockets. Processes in the global zone may bind to
     any network interface that is displayed using  the  command:
     dladm show-link.


     SOCK_RAW packets are passed to and from  the  device  driver
     without any changes in (1,8) the packet data. When receiving
     a packet, the address is still parsed and passed in (1,8)  a
     standard  sockaddr_ll address structure. When transmitting a
     packet, the user supplied buffer should contain the physical
     layer  header.  That packet is then queued unmodified to the
     network driver of the interface defined by  the  destination
     address.




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Protocols                                              packet(7P)



     SOCK_DGRAM operates on a slightly higher level. The physical
     header  is  removed before the packet is passed to the user.
     Packets sent through a SOCK_DGRAM packet socket (2,7,n)  get
     a suitable physical layer header based on the information in
     (1,8) the sockaddr_ll destination address  before  they  are
     queued.


     By default, all packets of the specified protocol  type  are
     passed  to  a  packet  socket.  To  only  get packets from a
     specific interface use bind (2,n,1  builtins)(2)  specifying
     an  address  in  (1,8)  a  struct sockaddr_ll to bind (2,n,1
     builtins) the packet socket (2,7,n)  to an  interface.  Only
     the sll_protocol and the sll_ifindex address fields are used
     for purposes of binding.


     The connect(3SOCKET) operation is not  supported  on  packet
     sockets.

  Address Types
     The sockaddr_ll  is  a  device  independent  physical  layer
     address.

       struct sockaddr_ll {
          unsigned short sll_family; /* Always AF_PACKET */
          unsigned short  sll_protocol;  /* Physical layer protocol */
          int             sll_ifindex;   /* Interface number */
          unsigned short  sll_hatype;    /* Header type */
          unsigned char   sll_pkttype;   /* Packet type */
          unsigned char   sll_halen;     /* Length of address */
          unsigned char   sll_addr[8];   /* Physical layer address */
       };



     sll_protocol is the standard ethernet protocol type in (1,8)
     network order as defined in (1,8) the sys/ethernet.h include
     file.  It  defaults  to  the  socket   (2,7,n)'s   protocol.
     sll_ifindex   is  the  interface  index  of  the  interface.
     sll_hatype  is  a  ARP  type  as  defined   in   (1,8)   the
     sys/ethernet.h include file. sll_pkttype contains the packet
     type. Valid types are PACKET_HOST for a packet addressed  to
     the  local  host(1,5), PACKET_BROADCAST for a physical layer
     broadcast packet, PACKET_MULTICAST for a packet  sent  to  a
     physical  layer  multicast  address,  PACKET_OTHERHOST for a
     packet to some other host (1,5) that has been  caught  by  a
     device driver in (1,8) promiscuous mode, and PACKET_OUTGOING
     for a packet originated from the local host  (1,5)  that  is
     looped  back to a packet socket. These types make only sense
     for receiving. sll_addr and sll_halen contain  the  physical
     layer,  for example, IEEE 802.3, address and its length. The



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Protocols                                              packet(7P)



     exact interpretation depends on the device.


     When  you  send  (2,n)  packets  it  is  enough  to  specify
     sll_family,  sll_addr,  sll_halen,  sll_ifindex.  The  other
     fields should be  0.  sll_hatype  and  sll_pkttype  are  set
     (7,n,1  builtins)  on received packets for your information.
     For bind (2,n,1 builtins) only sll_protocol and  sll_ifindex
     are used.

  Socket Options
     Packet sockets can be used to configure physical layer  mul-
     ticasting   and   promiscuous  mode.  It  works  by  calling
     setsockopt(3SOCKET)  on  a   packet   socket   (2,7,n)   for
     SOL_PACKET  and  one of the options PACKET_ADD_MEMBERSHIP to
     add a binding or PACKET_DROP_MEMBERSHIP to  drop   it.  They
     both expect a packet_mreq structure as argument:

       struct packet_mreq
       {
          int             mr_ifindex;    /* interface index */
          unsigned short  mr_type;       /* action */
          unsigned short  mr_alen;       /* address length */
          unsigned char   mr_address[8]; /* physical layer address */
       };



     mr_ifindex contains the interface index  for  the  interface
     whose status should be changed. The mr_type parameter speci-
     fies which  action  to  perform.  PACKET_MR_PROMISC  enables
     receiving  all  packets  on  a  shared medium often known as
     promiscuous  mode,  PACKET_MR_MULTICAST  binds  the   socket
     (2,7,n)  to  the physical layer multicast group specified in
     (1,8) mr_address and mr_alen.  PACKET_MR_ALLMULTI  sets  the
     socket  (2,7,n) up to receive all multicast packets arriving
     at the interface.


     In   addition   the   traditional   ioctls,    SIOCSIFFLAGS,
     SIOCADDMULTI, and SIOCDELMULTI can be used for the same pur-
     pose.

SEE ALSO
     connect(3SOCKET), setsockopt(3SOCKET)

NOTES
     For portable programs it is suggested to usepcap(3C) instead
     of  PF_PACKET;  although  this  only  covers a subset of the
     PF_PACKET features.





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Protocols                                              packet(7P)



     The SOCK_DGRAM packet sockets make no attempt to  create  or
     parse the IEEE 802.2 LLC header for a IEEE 802.3 frame. When
     ETH_P_802_3 is specified as protocol for sending the  kernel
     creates  the 802.3 frame and fills out the length field; the
     user has to supply the LLC header to get a fully  conforming
     packet.  Incoming  802.3  packets are not multiplexed on the
     DSAP/SSAP protocol fields; instead they are supplied to  the
     user  as protocol ETH_P_802_2 with the LLC header prepended.
     It is therefore not possible to  bind  (2,n,1  builtins)  to
     ETH_P_802_3;  bind  (2,n,1  builtins) to ETH_P_802_2 instead
     and do the protocol  multiplex  yourself.  The  default  for
     sending  is the standard Ethernet DIX encapsulation with the
     protocol filled in.


     Packet sockets are  not  subject  to  the  input  or  output
     firewall chains.






































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