dial_service.h File Reference

Dialing a specific endpoint over a specific wire — the capability a NAT-traversal module needs and the ordinary connect() cannot express. More...

#include "librats/core/address.h"
#include "librats/core/types.h"

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Classes
class	librats::DialService

Namespaces
namespace	librats

Detailed Description

Dialing a specific endpoint over a specific wire — the capability a NAT-traversal module needs and the ordinary connect() cannot express.

PeerNetwork::connect(Address) is deliberately opinionated: it hands the target to the Dialer, which picks a transport, races the other one in after the fallback delay, and remembers what it learned for next time (see node/dialer.h). That is exactly right for "connect me to this peer" and exactly wrong for a hole punch, which needs three things the race cannot give:

• the datagram wire and nothing else. A punch is only possible on the shared UDP socket; racing TCP alongside it spends a connect attempt on a path that a NAT will refuse by construction.
• a dial that starts NOW, at a moment agreed with the peer. A punch works because two Syns cross mid-path; a fallback delay measured from our own clock has nothing to do with that instant.
• a different retry shape (see DialProfile) — dense probes rather than a long patient tail, because the early Syns are expected to die on the peer's NAT.

So this is the narrow escape hatch, published by the Node in its ServiceRegistry and resolved by whoever needs it:

if (auto* dial = ctx.services.get<DialService>())
    dial->dial_direct(addr, TransportKind::Udp, DialProfile::punch());

It is deliberately not on PeerNetwork: every subsystem sees that interface, and "dial exactly this, exactly this way" is a capability one module needs rather than a contract all of them should have. Everything else about the resulting connection is ordinary — the same handshake, the same identify, the same duplicate resolution in PeerTable if the peer dialed us back at the same moment.

Definition in file dial_service.h.