rpc: disable mDNS when force_relay or force_p2p is set#183
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force_relay/force_p2p force a connection through a specific WebRTC transport, but the dialer attempts mDNS local discovery first and will connect via plain gRPC over LAN/loopback when the target is locally reachable, bypassing WebRTC/ICE and silently ignoring the flag. Disable mDNS in both builders so the FFI (and all consumers) get correct behavior.
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Problem
force_relay/force_p2pexist to force a connection through a specific WebRTC transport (relay-only TURN, or host/srflx-only). But the dialer attempts mDNS local discovery first, and when the target machine is reachable on the LAN/loopback it connects via plain gRPC over mDNS — bypassing WebRTC/ICE entirely and silently ignoringforce_relay/force_p2p.Observed in the SDK dial-options integration tests against the Python SDK (which dials via these FFI bindings): a
force_relayconnection that should route through TURN instead connected locally over mDNS (no relaycandidate_pairever appears), and aforce_relayconnection with a deliberately-invalid TURN URI (which must fail) succeeded over mDNS.RUST_LOG=debugshowedStarting mDNS query→Found address via mDNS→mDNS create_channel: loopback 127.0.0.1with no TURN allocation.Fix
Disable mDNS in the
force_relay()andforce_p2p()builders. Since the FFI (viam_dial_opts_set_force_relay/viam_dial_opts_set_force_p2p) routes through these builders, Python/C consumers pick this up automatically (aviam-python-sdkbundled-rust-utils bump is the follow-up to ship it). Mirrors the Go dialer behavior.Draft for review/discussion.