Re: [tcpdump-workers] tcpdump and BPF filters

2011-07-11 Thread Geoffrey Sisson
Guy Harris wrote: > > On Jul 10, 2011, at 6:57 PM, Geoffrey Sisson wrote: > > > The catch is that domain names comprise a variable number of > > variable-length fields. > > ...and include pointers back to other labels, for compression. It's unlikely this would be used for much besides filtering

Re: [tcpdump-workers] timestamp in Packet Data

2011-07-11 Thread Mcmillan, Scott A
There are many factors that make the timestamps an approximation. In addition to the ones already mentioned, the timestamps is typically taken several kernel layers higher than the driver. You can avoid these approximations on Linux by using tcpdump -j / -J with a NIC that is capable of hard

Re: [tcpdump-workers] tcpdump and BPF filters

2011-07-11 Thread Guy Harris
On Jul 10, 2011, at 6:57 PM, Geoffrey Sisson wrote: > The catch is that domain names comprise a variable number of > variable-length fields. ...and include pointers back to other labels, for compression. If the queries you're can be expressed in a syntax that could be added to the libpcap filt