Handling A10 PCAP Files Using Automator in MacOS
I’m not a big user of Apple’s Automator tool, but sometimes it’s very useful. For example, A10 Networks load balancers make it pretty easy for administrators to capture packets without having to remember the syntax and appropriate command flags for a tcpdump command in the shell. Downloading the .pcap file is pretty easy too (especially using the web interface), but what gets downloaded is not just a single file; instead, it’s a gzip file containing a tar file which in turn contains (for the hardware I use) seventeen packet capture files. In this post I’ll explain what these files are, why it’s annoying, and how I work around this in MacOS.
Sixteen Candles
If you’re wondering how one packet capture turned into sixteen PCAP files, that’s perfectly reasonable and the answer is simple in its own way. The hardware I use has sixteen CPU cores, fifteen of which are used by default to process traffic, and inbound flows are spread across those cores. Thus when taking a packet capture, the system actually requests each core to dump the flows matching the filter specification. Each core effectively has awareness of both the client and server sides of any connection, so both Continue reading