$Id: README,v 1.14 1999/03/28 18:32:01 gram Exp $ Wiretap is a library that is being developed as a future replacement for libpcap, the current standard Unix library for packet capturing. Libpcap is great in that it is very platform independent and has a wonderful BPF optimizing engine. But it has some shortcomings as well. These shortcomings came to a head during the development of Ethereal (http://ethereal.zing.org), a packet analyzer. As such, I began developing wiretap so that: 1. The library can easily be amended with new packet filtering objects. Libpcap is very TCP/IP-oriented. I want to filter on IPX objects, SNA objects, etc. I also want any decent programmer to be able to add new filters to the library. 2. The library can read file formats from many packet-capturing utilities. Libpcap only reads Libpcap files. 3. The library can capture on more than one network interface at a time, and save this trace in one file. 4. Network names can be resolved immediately after a trace and saved in the trace file. That way, I can ship a trace of my firewall-protected network to a colleague, and he'll see the proper hostnames for the IP addresses in the packet capture, even though he doesn't have access to the DNS server behind my LAN's firewall. 5. I want to look into the possibility of compressing packet data when saved to a file, like Sniffer. 6. The packet-filter can be optimized for the host OS. Not all OSes have BPF; SunOS has NIT and Solaris has DLPI, which both use the CMU/Stanford packet-filter psuedomachine. RMON has another type of packet-filter syntax which we could support. Wiretap is very good at reading many file formats, as per #2 above. Display filters are now appearing in wiretap, but they are still basic. Development is continuing on the BPF compiler, so display filters will continue to be enhanced. Please read the README.filters file for information regarding the syntax of wiretap filters. File Formats ============ Libpcap ------- The "libpcap" file format was determined by reading the "libpcap" code; wiretap reads the "libpcap" file format with its own code, rather than using the "libpcap" library's code to read it. Sniffer (uncompressed) ------- The Sniffer format is documented in the Sniffer manual. Unfortunately, Sniffer manuals tend to document only the format for the Sniffer model they document. Token-Ring and ethernet seems to work well, though. If you have an ATM Sniffer file, both Guy and Gilbert would be *very* interested in receiving a sample. (see 'AUTHORS' file for our e-mail addresses). ATM sniffers are claimed by the manual to record a mixture of cells and frames; there's currently no "raw ATM" encapsulation in wiretap to allow us to return that directly, so we assume that the traffic of interest is all LANE or all RFC 1483 traffic, search in the file for the first AAL5 frame that's either LANE or RFC 1483, set the encapsulation based on which of those we saw, and discard all non-AAL5 cells as well as AAL5 frames not of the specified type. We also discard the 2-byte LANE header at the front of the frame, leaving only the emulated Ethernet or Token Ring frame. Given that wiretap now returns packet encapsulation types on a per-packet basis, we could, instead, discard all non-AAL5 cells and AAL5 frames that are neither LANE nor RFC 1483, and return the appropriate encapsulation for the packet as we read it. LANalyzer --------- The LANalyzer format is available from http://www.novell.com. Search their knowledge base for "Trace File Format". Network Monitor --------------- Microsoft's Network Monitor file format is supported, at least under Ethernet and token-ring. If you have capture files of other datalink types, please send them to Guy. "snoop" ------- The Solaris 2.x "snoop" program's format is documented in RFC 1761. "iptrace" --------- This is the capture program that comes with AIX 3.x and 4.x. Right now wiretap only supports iptrace 2.0 (AIX4) because I don't have access to an AIX3 machine. iptrace has an undocumented, yet very simple, file format. The interesting thing about iptrace is that it will record packets coming in from all network interfaces; a single iptrace file can contain multiple datalink types. I have tested iptrace on ethernet and token-ring; if you can provide an iptrace file with any other datalink type, I would appreciate a copy. (with the output from 'ipreport' too, if possible). Sniffer Basic (NetXRay)/Windows Sniffer Pro ------------------------------------------- Network Associates' Sniffer Basic (formerly NetXRay from Cinco Networks) file format is now supported, at least for Ethernet and token-ring. Network Associates' Windows Sniffer Pro appears to use a variant of that format; it's supported to the same extent. Gilbert Ramirez Guy Harris