1 2 The following instructions apply if you have a Linux or FreeBSD platform and 3 want libpcap to support the DAG range of passive network monitoring cards from 4 Endace (http://www.endace.com, see below for further contact details). 5 6 1) Install and build the DAG software distribution by following the 7 instructions supplied with that package. Current Endace customers can download 8 the DAG software distibution from https://www.endace.com 9 10 2) Configure libcap. To allow the 'configure' script to locate the DAG 11 software distribution use the '--with-dag' option: 12 13 ./configure --with-dag=DIR 14 15 Where DIR is the root of the DAG software distribution, for example 16 /var/src/dag. If the DAG software is correctly detected 'configure' will 17 report: 18 19 checking whether we have DAG API... yes 20 21 If 'configure' reports that there is no DAG API, the directory may have been 22 incorrectly specified or the DAG software was not built before configuring 23 libpcap. 24 25 See also the libpcap INSTALL.txt file for further libpcap configuration 26 options. 27 28 Building libpcap at this stage will include support for both the native packet 29 capture stream (linux or bpf) and for capturing from DAG cards. To build 30 libpcap with only DAG support specify the capture type as 'dag' when 31 configuring libpcap: 32 33 ./configure --with-dag=DIR --with-pcap=dag 34 35 Applications built with libpcap configured in this way will only detect DAG 36 cards and will not capture from the native OS packet stream. 37 38 ---------------------------------------------------------------------- 39 40 Libpcap when built for DAG cards against dag-2.5.1 or later releases: 41 42 Timeouts are supported. pcap_dispatch() will return after to_ms milliseconds 43 regardless of how many packets are received. If to_ms is zero pcap_dispatch() 44 will block waiting for data indefinitely. 45 46 pcap_dispatch() will block on and process a minimum of 64kB of data (before 47 filtering) for efficiency. This can introduce high latencies on quiet 48 interfaces unless a timeout value is set. The timeout expiring will override 49 the 64kB minimum causing pcap_dispatch() to process any available data and 50 return. 51 52 pcap_setnonblock is supported. When nonblock is set, pcap_dispatch() will 53 check once for available data, process any data available up to count, then 54 return immediately. 55 56 pcap_findalldevs() is supported, e.g. dag0, dag1... 57 58 Some DAG cards can provide more than one 'stream' of received data. 59 This can be data from different physical ports, or separated by filtering 60 or load balancing mechanisms. Receive streams have even numbers, e.g. 61 dag0:0, dag0:2 etc. Specifying transmit streams for capture is not supported. 62 63 pcap_setfilter() is supported, BPF programs run in userspace. 64 65 pcap_setdirection() is not supported. Only received traffic is captured. 66 DAG cards normally do not have IP or link layer addresses assigned as 67 they are used to passively monitor links. 68 69 pcap_breakloop() is supported. 70 71 pcap_datalink() and pcap_list_datalinks() are supported. The DAG card does 72 not attempt to set the correct datalink type automatically where more than 73 one type is possible. 74 75 pcap_stats() is supported. ps_drop is the number of packets dropped due to 76 RX stream buffer overflow, this count is before filters are applied (it will 77 include packets that would have been dropped by the filter). The RX stream 78 buffer size is user configurable outside libpcap, typically 16-512MB. 79 80 pcap_get_selectable_fd() is not supported, as DAG cards do not support 81 poll/select methods. 82 83 pcap_inject() and pcap_sendpacket() are not supported. 84 85 Some DAG cards now support capturing to multiple virtual interfaces, called 86 streams. Capture streams have even numbers. These are available via libpcap 87 as separate interfaces, e.g. dag0:0, dag0:2, dag0:4 etc. dag0:0 is the same 88 as dag0. These are visible via pcap_findalldevs(). 89 90 libpcap now does NOT set the card's hardware snaplen (slen). This must now be 91 set using the appropriate DAG coniguration program, e.g. dagthree, dagfour, 92 dagsix, dagconfig. This is because the snaplen is currently shared between 93 all of the streams. In future this may change if per-stream slen is 94 implemented. 95 96 DAG cards by default capture entire packets including the L2 97 CRC/FCS. If the card is not configured to discard the CRC/FCS, this 98 can confuse applications that use libpcap if they're not prepared for 99 packets to have an FCS. 100 101 Libpcap now reads the environment variable ERF_FCS_BITS to determine 102 how many bits of CRC/FCS to strip from the end of the captured 103 frame. This defaults to 32 for use with Ethernet. If the card is 104 configured to strip the CRC/FCS, then set ERF_FCS_BITS=0. If used with 105 a HDLC/PoS/PPP/Frame Relay link with 16 bit CRC/FCS, then set 106 ERF_FCS_BITS=16. 107 108 If you wish to create a pcap file that DOES contain the Ethernet FCS, 109 specify the environment variable ERF_DONT_STRIP_FCS. This will cause 110 the existing FCS to be captured into the pcap file. Note some 111 applications may incorrectly report capture errors or oversize packets 112 when reading these files. 113 114 ---------------------------------------------------------------------- 115 116 Please submit bug reports via <support (a] endace.com>. 117 118 Please also visit our Web site at: 119 120 http://www.endace.com/ 121 122 For more information about Endace DAG cards contact <sales (a] endace.com>. 123
