[tor-bugs] #8215 [Tor]: Simple Relay: random unknown UDP port in listen mode

[Tor Bug Tracker & Wiki]

#8215: Simple Relay: random unknown UDP port in listen mode
----------------------------+-----------------------------------------------
    Reporter:  elgo         |       Owner:                  
        Type:  enhancement  |      Status:  reopened        
    Priority:  normal       |   Milestone:  Tor: unspecified
   Component:  Tor          |     Version:                  
  Resolution:               |    Keywords:  tor-relay       
      Parent:               |      Points:                  
Actualpoints:               |  
----------------------------+-----------------------------------------------

Comment(by elgo):

 Waaaw, that is quite an awesome answer :) Really many thanks for taking
 time to explain this to me. That is crystal clear now on the "how".
 Now, I have some questions about "why", but new ones ;)

 So, in the "multiple_requests" scenario of Tor, you designed your DNS
 client like a sort of "deamon" and then never close this client DNS
 socket? Is it really worthy rather than opening 1:1 UDP socket to DNS
 servers? I mean, 1:1 UDP socket have the advantage of not accepting data
 from any source (which could not be a previously requested DNS server),
 compared to a "listening" UDP socket (I'm not considering the case of
 having a stateful FW in protecting Tor running box, I'm considering
 security matter of Tor itself).
 This random "listening UDP DNS client socket" has the disadvantage of
 being persistent through the whole "life" of Tor process, and is a new
 potential entry point to Tor (beyond ORPort and DirPort for a simple
 relay).

-- 
Ticket URL: <https://trac.torproject.org/projects/tor/ticket/8215#comment:9>
Tor Bug Tracker & Wiki <https://trac.torproject.org/>
The Tor Project: anonymity online