README.dag - platform/external/libpcap - Git at Google


 The following instructions apply if you have a Linux or FreeBSD platform and
 want libpcap to support the DAG range of passive network monitoring cards from
 Endace (http://www.endace.com, see below for further contact details).

 1) Install and build the DAG software distribution by following the
 instructions supplied with that package. Current Endace customers can download
 the DAG software distibution from https://www.endace.com

 2) Configure libcap. To allow the 'configure' script to locate the DAG
 software distribution use the '--with-dag' option:

         ./configure --with-dag=DIR

 Where DIR is the root of the DAG software distribution, for example
 /var/src/dag. If the DAG software is correctly detected 'configure' will
 report:

         checking whether we have DAG API... yes

 If 'configure' reports that there is no DAG API, the directory may have been
 incorrectly specified or the DAG software was not built before configuring
 libpcap.

 See also the libpcap INSTALL.txt file for further libpcap configuration
 options.

 Building libpcap at this stage will include support for both the native packet
 capture stream (linux or bpf) and for capturing from DAG cards. To build
 libpcap with only DAG support specify the capture type as 'dag' when
 configuring libpcap:

         ./configure --with-dag=DIR --with-pcap=dag

 Applications built with libpcap configured in this way will only detect DAG
 cards and will not capture from the native OS packet stream.

 ----------------------------------------------------------------------

 Libpcap when built for DAG cards against dag-2.5.1 or later releases:

 Timeouts are supported. pcap_dispatch() will return after to_ms milliseconds
 regardless of how many packets are received. If to_ms is zero pcap_dispatch()
 will block waiting for data indefinitely.

 pcap_dispatch() will block on and process a minimum of 64kB of data (before
 filtering) for efficiency. This can introduce high latencies on quiet
 interfaces unless a timeout value is set. The timeout expiring will override
 the 64kB minimum causing pcap_dispatch() to process any available data and
 return.

 pcap_setnonblock is supported. When nonblock is set, pcap_dispatch() will
 check once for available data, process any data available up to count, then
 return immediately.

 pcap_findalldevs() is supported, e.g. dag0, dag1...

 Some DAG cards can provide more than one 'stream' of received data.
 This can be data from different physical ports, or separated by filtering
 or load balancing mechanisms. Receive streams have even numbers, e.g.
 dag0:0, dag0:2 etc. Specifying transmit streams for capture is not supported.

 pcap_setfilter() is supported, BPF programs run in userspace.

 pcap_setdirection() is not supported. Only received traffic is captured.
 DAG cards normally do not have IP or link layer addresses assigned as
 they are used to passively monitor links.

 pcap_breakloop() is supported.

 pcap_datalink() and pcap_list_datalinks() are supported. The DAG card does
 not attempt to set the correct datalink type automatically where more than
 one type is possible.

 pcap_stats() is supported. ps_drop is the number of packets dropped due to
 RX stream buffer overflow, this count is before filters are applied (it will
 include packets that would have been dropped by the filter). The RX stream
 buffer size is user configurable outside libpcap, typically 16-512MB.

 pcap_get_selectable_fd() is not supported, as DAG cards do not support
 poll/select methods.

 pcap_inject() and pcap_sendpacket() are not supported.

 Some DAG cards now support capturing to multiple virtual interfaces, called
 streams. Capture streams have even numbers. These are available via libpcap
 as separate interfaces, e.g. dag0:0, dag0:2, dag0:4 etc. dag0:0 is the same
 as dag0. These are visible via pcap_findalldevs().

 libpcap now does NOT set the card's hardware snaplen (slen). This must now be
 set using the appropriate DAG coniguration program, e.g. dagthree, dagfour,
 dagsix, dagconfig. This is because the snaplen is currently shared between
 all of the streams. In future this may change if per-stream slen is
 implemented.

 DAG cards by default capture entire packets including the L2
 CRC/FCS. If the card is not configured to discard the CRC/FCS, this
 can confuse applications that use libpcap if they're not prepared for
 packets to have an FCS. Libpcap now reads the environment variable
 ERF_FCS_BITS to determine how many bits of CRC/FCS to strip from the
 end of the captured frame. This defaults to 32 for use with
 Ethernet. If the card is configured to strip the CRC/FCS, then set
 ERF_FCS_BITS=0. If used with a HDLC/PoS/PPP/Frame Relay link with 16
 bit CRC/FCS, then set ERF_FCS_BITS=16.

 ----------------------------------------------------------------------

 Please submit bug reports via <support@endace.com>.

 Please also visit our Web site at:

         http://www.endace.com/

 For more information about Endace DAG cards contact <sales@endace.com>.

	The following instructions apply if you have a Linux or FreeBSD platform and
	want libpcap to support the DAG range of passive network monitoring cards from
	Endace (http://www.endace.com, see below for further contact details).

	1) Install and build the DAG software distribution by following the
	instructions supplied with that package. Current Endace customers can download
	the DAG software distibution from https://www.endace.com

	2) Configure libcap. To allow the 'configure' script to locate the DAG
	software distribution use the '--with-dag' option:

	./configure --with-dag=DIR

	Where DIR is the root of the DAG software distribution, for example
	/var/src/dag. If the DAG software is correctly detected 'configure' will
	report:

	checking whether we have DAG API... yes

	If 'configure' reports that there is no DAG API, the directory may have been
	incorrectly specified or the DAG software was not built before configuring
	libpcap.

	See also the libpcap INSTALL.txt file for further libpcap configuration
	options.

	Building libpcap at this stage will include support for both the native packet
	capture stream (linux or bpf) and for capturing from DAG cards. To build
	libpcap with only DAG support specify the capture type as 'dag' when
	configuring libpcap:

	./configure --with-dag=DIR --with-pcap=dag

	Applications built with libpcap configured in this way will only detect DAG
	cards and will not capture from the native OS packet stream.

	----------------------------------------------------------------------

	Libpcap when built for DAG cards against dag-2.5.1 or later releases:

	Timeouts are supported. pcap_dispatch() will return after to_ms milliseconds
	regardless of how many packets are received. If to_ms is zero pcap_dispatch()
	will block waiting for data indefinitely.

	pcap_dispatch() will block on and process a minimum of 64kB of data (before
	filtering) for efficiency. This can introduce high latencies on quiet
	interfaces unless a timeout value is set. The timeout expiring will override
	the 64kB minimum causing pcap_dispatch() to process any available data and
	return.

	pcap_setnonblock is supported. When nonblock is set, pcap_dispatch() will
	check once for available data, process any data available up to count, then
	return immediately.

	pcap_findalldevs() is supported, e.g. dag0, dag1...

	Some DAG cards can provide more than one 'stream' of received data.
	This can be data from different physical ports, or separated by filtering
	or load balancing mechanisms. Receive streams have even numbers, e.g.
	dag0:0, dag0:2 etc. Specifying transmit streams for capture is not supported.

	pcap_setfilter() is supported, BPF programs run in userspace.

	pcap_setdirection() is not supported. Only received traffic is captured.
	DAG cards normally do not have IP or link layer addresses assigned as
	they are used to passively monitor links.

	pcap_breakloop() is supported.

	pcap_datalink() and pcap_list_datalinks() are supported. The DAG card does
	not attempt to set the correct datalink type automatically where more than
	one type is possible.

	pcap_stats() is supported. ps_drop is the number of packets dropped due to
	RX stream buffer overflow, this count is before filters are applied (it will
	include packets that would have been dropped by the filter). The RX stream
	buffer size is user configurable outside libpcap, typically 16-512MB.

	pcap_get_selectable_fd() is not supported, as DAG cards do not support
	poll/select methods.

	pcap_inject() and pcap_sendpacket() are not supported.

	Some DAG cards now support capturing to multiple virtual interfaces, called
	streams. Capture streams have even numbers. These are available via libpcap
	as separate interfaces, e.g. dag0:0, dag0:2, dag0:4 etc. dag0:0 is the same
	as dag0. These are visible via pcap_findalldevs().

	libpcap now does NOT set the card's hardware snaplen (slen). This must now be
	set using the appropriate DAG coniguration program, e.g. dagthree, dagfour,
	dagsix, dagconfig. This is because the snaplen is currently shared between
	all of the streams. In future this may change if per-stream slen is
	implemented.

	DAG cards by default capture entire packets including the L2
	CRC/FCS. If the card is not configured to discard the CRC/FCS, this
	can confuse applications that use libpcap if they're not prepared for
	packets to have an FCS. Libpcap now reads the environment variable
	ERF_FCS_BITS to determine how many bits of CRC/FCS to strip from the
	end of the captured frame. This defaults to 32 for use with
	Ethernet. If the card is configured to strip the CRC/FCS, then set
	ERF_FCS_BITS=0. If used with a HDLC/PoS/PPP/Frame Relay link with 16
	bit CRC/FCS, then set ERF_FCS_BITS=16.

	----------------------------------------------------------------------

	Please submit bug reports via <support@endace.com>.

	Please also visit our Web site at:

	http://www.endace.com/

	For more information about Endace DAG cards contact <sales@endace.com>.