[tor-dev] Question about HS code

[Michael Rogers]

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Hi,

I've been trying to get to grips with the hidden service code, and I
have a question that I was hoping someone on the list could answer.

The constant REND_HID_SERV_DIR_REQUERY_PERIOD is defined as 15 * 60
(15 minutes) in rendclient.c, with the comment "The period for which a
hidden service directory cannot be queried for the same descriptor ID
again." As far as I can tell, the purpose of this constant is to
prevent a client from repeatedly asking an HS directory for a
descriptor that the directory doesn't have.

However, when a descriptor fetch fails and there's no reusable cached
descriptor, rend_client_desc_trynow(query) calls
rend_client_note_connection_attempt_ended(onion_address), which calls
purge_hid_serv_from_last_hid_serv_requests(onion_address), which (as
far as I can tell) forgets which HS directories have been tried for
the descriptor, allowing the same directories to be tried again before
REND_HID_SERV_DIR_REQUERY_PERIOD elapses.

So what's the effect of REND_HID_SERV_DIR_REQUERY_PERIOD?

Thanks for any guidance,
Michael
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