Opened 5 years ago

Closed 4 years ago

#13593 closed defect (duplicate)

Is "Link 1 2" in the descriptors obsolete?

Reported by: arma Owned by:
Priority: Very Low Milestone: Tor: 0.2.7.x-final
Component: Core Tor/Tor Version:
Severity: Keywords:
Cc: Actual Points:
Parent ID: #14165 Points:
Reviewer: Sponsor:

Description (last modified by arma)

It looks like we're up to link protocol 4 in practice, but the descriptors still write this static string:

                    "protocols Link 1 2 Circuit 1\n"

dir-spec.txt tells us

       Both lists are space-separated sequences of numbers, to indicate which
       protocols the server supports.  As of 30 Mar 2008, specified
       protocols are "Link 1 2 Circuit 1".  See section 4.1 of tor-spec.txt
       for more information about link protocol versions.

but Section 4.1 of tor-spec.txt indeed admits to link protocols 3 and 4.

It looks like nothing in routerparse.c or anywhere else looks at the 'protocols' line of the descriptor. Heck, normal clients don't even get the descriptor anymore.

I assume the last Tor version to not understand link protocol 2 is way obsolete (Tor 0.2.0.x era I think).

And if clients never see the descriptors, it's hard to imagine how we'll be able to tell them a different Circuit protocol either.

Should we dump this line? Have we accidentally lost anything here?

Child Tickets

Change History (8)

comment:1 Changed 5 years ago by arma

Description: modified (diff)

comment:2 Changed 5 years ago by Sebastian

In the case of microdescriptors, we could conceivably set a flag based on the original descriptor, so maybe dropping the line is a bad choice?

comment:3 Changed 5 years ago by nickm

We could indeed remove this without ill effect. Current Tors don't parse it AFAICT.

IIRC the intended purpose was to enable a client to notice that relay A and relay B have no link protocols in common. But current clients can't use it to do that, and currently we require all relays on the network to share at least one link protocol.

comment:4 Changed 5 years ago by arma

Milestone: Tor: unspecifiedTor: 0.2.6.x-final

comment:5 Changed 5 years ago by nickm

Milestone: Tor: 0.2.6.x-finalTor: 0.2.7.x-final
Priority: normaltrivial

I've noted in dir-spec that we will be removing this, but I'm leaving it in for now in case some other implementation erroneously thinks it's mandatory (even though we said "at most once" in dir-spec). Let's excise it it in 0.2.7.

comment:6 Changed 4 years ago by nickm

Parent ID: #14165

comment:7 Changed 4 years ago by nickm

Status: newassigned

comment:8 Changed 4 years ago by nickm

Resolution: duplicate
Status: assignedclosed

Resolving in favor of #14165

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