[tor-bugs] #4696 [Tor Client]: add OutboundBindInterface option to torrc

Tor Bug Tracker & Wiki torproject-admin at torproject.org
Sun Dec 11 15:55:32 UTC 2011

#4696: add OutboundBindInterface option to torrc
 Reporter:  mr-4         |          Owner:               
     Type:  enhancement  |         Status:  new          
 Priority:  normal       |      Milestone:               
Component:  Tor Client   |        Version:  Tor:
 Keywords:               |         Parent:               
   Points:               |   Actualpoints:               
 First, I am well-aware that there is OutboundBindAddress option in tor.

 I am also aware that tor "automatically" chooses an IP address/interface
 to bind to (if OutboundBindAddress is not specified) based on the current
 routing table.

 There are quite a few instances where OutboundBindAddress option is not
 suitable, particularly where the IP address changes frequently (vpn as
 well as most dhcp-dependant interfaces).

 Whether I use OutboundBindAddress or just leave tor to make a decision
 which address to bind to is not suitable (at least) in the following two

 1. When I temporarily loose my IP address which tor has used up until now
 due to dhcp client renewing its lease (and receive a new IP address) and
 that doesn't happen - for whatever reason - instantly.

 This results in one of two possible - wrong - outcomes: a) in case of
 absence of OutboundBindAddress option, Tor decides that my IP address "has
 changed" and tries to bind to the default interface, which may not be the
 one I have used previously; or b) when OutboundBindAddress is specified,
 tor just sits there trying to use the "old" address specified, resulting
 in a stall.

 2. When I temporarily loose my current IP address due to vpn connection
 becoming (temporarily) unstable and it takes a bit of time for my machine
 to renew its IP address (this may take from a minute to up to 20+ minutes
 depending on the status of the vpn server at the other end) the outcome is
 exactly the same as I listed above - tor either tries to use the default
 interface (wrong!) or tries to bind to the IP address I specified with
 OutboundBindAddress (wrong again).

 With the introduction of this new (OutboundBindInterface) option, tor can
 follow the IP address on the specified *interface* (regardless of what
 that might be) and the above - erroneous - outcome could be avoided.

Ticket URL: <https://trac.torproject.org/projects/tor/ticket/4696>
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