packetdrill updates for remote mode testing and a --debug command line argument

[Neal Cardwell]

Hi all,

I've pushed some updates to https://github.com/google/packetdrill (the commits ending at c2b94c5eba9b) with the following improvements:

(1) The wire_server may now be specified with a new --wire_server_at=<name_or_ip> command line argument that accepts DNS names or IPv6 addresses, so that you can conduct remote mode testing on an IPv6 network, or specify the wire server using a DNS name.

(2) By default, remote mode tests now use the "primary" IP address of the client and server machines for the test traffic (where the "primary" address is the IP address to which the hostname resolves). With this configuration, the client and server can be anywhere in the same layer-3 routable domain (though it is highly recommended to only use packetrill in an internal RFC 1918 IP address space, for "lab" testing, rather than in the public Internet).

(3) There is now a --debug command line argument so you can see many internal details of what packetdrill is doing, to facilitate debugging and provide more information in bug reports. (Thanks to Luigi Rizzo for making this a command line argument.)

(4) The README.md has been updated with more information about local mode tests, remote mode tests, and IP addresses used for testing.

Best regards,

neal