[tor-bugs] #21493 [Core Tor/Tor]: When reachable addresses change, mark connections using those addresses

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#21493: When reachable addresses change, mark connections using those addresses
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 Reporter:  teor          |          Owner:
     Type:  defect        |         Status:  new
 Priority:  Medium        |      Milestone:  Tor: unspecified
Component:  Core Tor/Tor  |        Version:
 Severity:  Normal        |     Resolution:
 Keywords:  ipv6          |  Actual Points:
Parent ID:                |         Points:  1
 Reviewer:                |        Sponsor:
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Comment (by teor):

 Replying to [comment:3 cypherpunks]:
 > Replying to [comment:2 teor]:
 > > Replying to [comment:1 cypherpunks]:
 > > > Replying to [ticket:21493 teor]:
 > > > Are you sure about both? Personally,
 > > > > When a client's reachable addresses change, we should:
 > > > > * mark connections that are on non-preferred connections as "not
 for new streams".
 > > > this seems fine to me
 > > > > * close connections that are on newly unreachable addresses
 > > > not so sure about this.
 > > >
 > > > There are situations when it's preferable to leave existing streams
 be, but fewer (I can't think of any) when it would be bothersome to leave
 them alone.
 > >
 > > I can think of several, in approximate order of prevalence:
 > > * the client wants their unreachable connections to fail and be
 reestablished, rather than waiting for them to time out,
 > > * the client has moved to a network where data to some IP addresses is
 restricted or costly, and they want to avoid those addresses,
 > > * the client has moved to a network where connecting to certain IP
 addresses is bad for their anonymity.
 > Good points. Additionally, keeping in mind things like long-running non-
 resumable transfers, IRC, and similar applications where a broken
 connection is a nuisance, and times when the client wants to keep a change
 in their reachable addresses (that could be due to changing location)
 private, it seems best for this behavior to be configurable.

 The behaviour is configurable in this design: if you don't want tor to
 terminate your connections, don't tell it that those addresses are
 unreachable. Anything else changes the semantics of reachable addresses.

 If you want to be able to prefer smaller sets of addresses than the whole
 of IPv4 or IPv6, that's another feature ticket - please feel free to open
 it.

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Ticket URL: <https://trac.torproject.org/projects/tor/ticket/21493#comment:4>
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