hs-v3: Don't warn so loudly when tor is unable to decode a descriptor
With legacy/trac#20700 (moved), we introduce client authorization making tor client without it trying to access a .onion with it to be unable to decode the descriptor. This leads to big warnings:
Sep 07 13:55:44.156 [info] handle_response_fetch_hsdesc_v3(): Received v3 hsdesc (body size 14111, status 200 ("OK"))
Sep 07 13:55:44.157 [warn] Encrypted service descriptor MAC check failed
Sep 07 13:55:44.157 [warn] Decrypting encrypted desc failed.
Sep 07 13:55:44.157 [warn] Service descriptor decryption failed.
Sep 07 13:55:44.157 [warn] Could not parse received descriptor as client.
...We should definitely not print warning if decoding fails but maybe a "unable to use descriptor" instead and the rest at info level.
Second, there is the retry behavior. Two cases:
- Tor is configured with client authorization for A.onion:
If we get the descriptor and unable to decode A.onion while we know we have a client authorization configured, I think we should make Tor stop and just tell the user that it didn't worked.
- Tor doesn't have client authorization for A.onion
In that case, if the decoding fails, we should probably make Tor stop trying on all HSDir and instead go at notice level saying "Unable to access A.onion. Maybe you need authorization?" kind of message.
Failing to decode a descriptor now is imo highly unlikely so we could assume that in this case, chances are that you'll get a better descriptor at the next HSDir are thin!