packet(7P) Protocols packet(7P)NAME
packet, PF_PACKET - packet interface on device level
SYNOPSIS
#include <sys/socket.h>
#include <netpacket/packet.h>
#include <sys/ethernet.h>
packet_socket = socket(2,7,n)(PF_PACKET, int socket_type, int protocol);
DESCRIPTION
Packet sockets are used to receive or send (2,n) raw ( 3x,7, 8,3x
cbreak) 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 (3x,7,8,3x cbreak) 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 format in (1,8) a sock‐
addr_ll. protocol is the IEEE 802.3 protocol number in (1,8) network
order. See the <sys/ethernet.h> 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 unmodi‐
fied to the network driver of the interface defined by the destination
address.
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. See netdevice(7). 0 matches any interface (only legal
for binding). sll_hatype is a ARP type as defined in (1,8) the sys/eth‐
ernet.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_MULTI‐
CAST 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 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 multicasting 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_MEMBER‐
SHIP 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 specifies which action to per‐
form. 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 purpose.
SEE ALSOconnect(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 fea‐
tures.
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 spec‐
ified 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 multi‐
plexed 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 encapsu‐
lation with the protocol filled in.
Packet sockets are not subject to the input or output firewall chains.
SunOS 5.11 28 Oct 2009 packet(7P)
