new minor packetdrill feature: print the name and contents of TCP options, not numerical kind

[Neal Cardwell]

I just uploaded this small quality-of-life improvement:

https://github.com/google/packetdrill/commit/1866fd111a6197f83f7fcdbb58dbe63936e2dad2

net-test: packetdrill: print the name and contents of TCP options, not numerical kind

Currently, when packetdrill notices that an outbound TCP option does not have the expected value, the error message is confusing. For example, for the following line in a packetdrill script: +.000 > S. 0:0(0) ack 1 <mss 1000,nop,nop,sackOK,nop,wscale 8> ... the error message might be: error handling packet: bad value outbound TCP option 2 This is unclear. It's unclear whether "2" here means option #2 in the list of options (here a "nop"), or the option with the "kind" of "2" (here "mss"). It turns out packetdrill meant option "kind" of "2". But most people do not have option kind code points memorized, so this is unclear. This commit changes packetdrill to print the name and contents of TCP options, not numerical kind. So the error message in the case above now looks like: error handling packet: bad value in outbound TCP option (kind=2): expected: mss 1000 actual: mss 1460 Signed-off-by: Neal Cardwell <ncar...@google.com> Change-Id: I0375ba54ab3d0696df3682950f84084a309676ad