[tor-dev] How to introduce new RELAY_COMMAND_* types and newcell fields?

[tordev123 at Safe-mail.net]

>> 3. Additional RELAY_COMMAND_* types for clients to request out-of-band
>> HMAC request cells for Proposal 253.

Do you need to request that data? How about always sending it from middle nodes? (Less leakage about the client.)

>> 4. Additional RELAY_COMMAND_* opcodes for clients to request padding
>> from relays (for an upcoming padding negotiation proposal).
>>
>> However, for items #3 and #4, if I introduce a new RELAY_COMMAND type
>> and send it to a relay that doesn't support it, then that relay will
>> emit a warning log message from connection_edge_process_relay_cell() in
>> relay.c. How should I detect support? Based on advertised relay version
>> in the consensus? What about non-standard relay implementations that
>> don't use Tor's versioning?
>
> I don't think you can use the consensus for this: for HS connections you
> wont have any relay info.

Wouldn't matter for 4, right?

> How about introducing very basic version info into 
> created2/extended/rendezvous cells? You'd have to be really careful to 
> not leak too much version info, of course.

It seems much better to avoid that, if there is a workaround.