
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.

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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, DAG cards do not support
poll/select methods.

pcap_inject() and pcap_sendpacket() are not supported.

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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>.
