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fix(dcutr): always check for relayed connection first #3982

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merged 11 commits into from
May 31, 2023
Merged

fix(dcutr): always check for relayed connection first #3982

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4ed1427
Fix DCUtR NetworkBehavior's established connection handler
arpankapoor May 24, 2023
bf1dfce
Use early return
arpankapoor May 25, 2023
770e9d0
Assert that outgoing_direct_connection_attempts entry was removed
arpankapoor May 25, 2023
527371e
Fix failing test
arpankapoor May 25, 2023
3b444eb
Add back removal of outgoing_direct_connection_attempts entry
arpankapoor May 25, 2023
5e9e0a3
Add assert on Listener for outgoing_direct_connection_attempts entry …
arpankapoor May 26, 2023
d1aba5f
Return dummy handler directly in inbound handler
arpankapoor May 29, 2023
b3c0996
Fix clippy warning
arpankapoor May 29, 2023
5948aee
Add comment
arpankapoor May 30, 2023
981735b
Merge branch 'master' into dcutr-fix
thomaseizinger May 30, 2023
bf8d1b6
Merge branch 'master' into dcutr-fix
mergify[bot] May 31, 2023
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90 changes: 43 additions & 47 deletions protocols/dcutr/src/behaviour_impl.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -246,33 +246,30 @@ impl NetworkBehaviour for Behaviour {
local_addr: &Multiaddr,
remote_addr: &Multiaddr,
) -> Result<THandler<Self>, ConnectionDenied> {
match self
.outgoing_direct_connection_attempts
.remove(&(connection_id, peer))
{
None => {
let handler = if is_relayed(local_addr) {
Either::Left(handler::relayed::Handler::new(ConnectedPoint::Listener {
local_addr: local_addr.clone(),
send_back_addr: remote_addr.clone(),
})) // TODO: We could make two `handler::relayed::Handler` here, one inbound one outbound.
} else {
Either::Right(Either::Right(dummy::ConnectionHandler))
};

Ok(handler)
}
Some(_) => {
assert!(
!is_relayed(local_addr),
"`Prototype::DirectConnection` is never created for relayed connection."
);
if is_relayed(local_addr) {
return Ok(Either::Left(handler::relayed::Handler::new(
ConnectedPoint::Listener {
local_addr: local_addr.clone(),
send_back_addr: remote_addr.clone(),
},
))); // TODO: We could make two `handler::relayed::Handler` here, one inbound one outbound.
}

Ok(Either::Right(Either::Left(
handler::direct::Handler::default(),
)))
}
if let Some(&relayed_connection_id) = self.direct_to_relayed_connections.get(&connection_id)
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I don't think this can ever be hit actually. In hole-punching, we cannot for sure tell which inbound connection was the one that the remote achieved through hole punching.

Plus, all this state tracking here uses ConnectionIds that are created as part of dialing, i.e. outbound connections.

So unless I am missing something, this function can be reduced to always return a dummy::ConnectionHandler for non-relayed connections.

@mxinden Thoughts?

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I think I agree with your assessment. I'll make this change after @mxinden's comments.

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You are right @thomaseizinger.

For what it is worth, likely my train of thought that ended up with the code above:

In NetworkBehaviour::on_connection_handler_event on OutboundConnectNegotiated we trigger a Dial with role_override() (i.e. as_listener) and then insert the maybe_direct_connection_id from the DialOpts into self.direct_to_relayed_connections.

rust-libp2p/protocols/dcutr/src/behaviour_impl.rs

Lines 379 to 395 in d4c4078

Either::Left(handler::relayed::Event::OutboundConnectNegotiated { remote_addrs }) => {
let opts = DialOpts::peer_id(event_source)
.condition(dial_opts::PeerCondition::Always)
.addresses(remote_addrs)
.override_role()
.build();
let maybe_direct_connection_id = opts.connection_id();
self.direct_to_relayed_connections
.insert(maybe_direct_connection_id, relayed_connection_id);
*self
.outgoing_direct_connection_attempts
.entry((relayed_connection_id, event_source))
.or_default() += 1;
self.queued_events.push_back(ToSwarm::Dial { opts });
}

On success this would be reported to the Behaviour via NetworkBehaviour::handle_established_outbound_connection and not as assumed here in NetworkBehaviour::handle_established_inbound_connection.

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How about adding an assert here, that connection_id is not in self.direct_to_relayed_connections?

{
assert!(
self.outgoing_direct_connection_attempts
.remove(&(relayed_connection_id, peer))
.is_some(),
"DCUtR state tracking is buggy!"
);

return Ok(Either::Right(Either::Left(
handler::direct::Handler::default(),
)));
}

Ok(Either::Right(Either::Right(dummy::ConnectionHandler)))
}

fn handle_established_outbound_connection(
Expand All @@ -282,33 +279,32 @@ impl NetworkBehaviour for Behaviour {
addr: &Multiaddr,
role_override: Endpoint,
) -> Result<THandler<Self>, ConnectionDenied> {
match self
.outgoing_direct_connection_attempts
.remove(&(connection_id, peer))
if is_relayed(addr) {
return Ok(Either::Left(handler::relayed::Handler::new(
ConnectedPoint::Dialer {
address: addr.clone(),
role_override,
},
))); // TODO: We could make two `handler::relayed::Handler` here, one inbound one outbound.
}

if let Some(&relayed_connection_id) = self.direct_to_relayed_connections.get(&connection_id)
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{
None => {
let handler = if is_relayed(addr) {
Either::Left(handler::relayed::Handler::new(ConnectedPoint::Dialer {
address: addr.clone(),
role_override,
})) // TODO: We could make two `handler::relayed::Handler` here, one inbound one outbound.
} else {
Either::Right(Either::Right(dummy::ConnectionHandler))
};

Ok(handler)
}
Some(_) => {
if role_override == Endpoint::Listener {
assert!(
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!is_relayed(addr),
"`Prototype::DirectConnection` is never created for relayed connection."
self.outgoing_direct_connection_attempts
.remove(&(relayed_connection_id, peer))
.is_some(),
"DCUtR state tracking is buggy!"
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);

Ok(Either::Right(Either::Left(
handler::direct::Handler::default(),
)))
}

return Ok(Either::Right(Either::Left(
handler::direct::Handler::default(),
)));
Comment on lines +296 to +298
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With recent refactorings in libp2p-swarm, there is actually no more need for handler::direct::Handler at all. The only thing that it does is report an event to the behaviour that is then bubbled to the user. The behaviour could as well just bubble the event to the user here already and return just a dummy handler.

The above improvement is only slightly related to this pull request. In case you want to tackle it @arpankapoor in this pull request, that would be much appreciated. Though I am happy to merge as is and tackle it some other time.

Idea raised by @thomaseizinger in a synchronous discussion just now.

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I am in favor of that refactoring but no need to include in this PR.

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Yeah, it could be tackled in another PR perhaps.

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Thanks! I'll merge this as is then :)

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Tracked here #4013. Also unresolving here for easier discovery in the future.

}

Ok(Either::Right(Either::Right(dummy::ConnectionHandler)))
}

fn on_connection_handler_event(
Expand Down