Packet mumcord p2p

Part of the Plugin data protocol. Flow: Flow-Direct-Connection.

Packet mumcord.p2p

Purpose. Introduces two Mumcord clients so they can open a direct, encrypted connection for large data (full images, screen share media). There is no STUN, TURN or relay server by design: candidates are the machine's IPv6 and LAN addresses and a router port mapping (PCP, NAT-PMP or UPnP). If no path works, features fall back to plugin data or are not available.

dataID	mumcord.p2p
Encoding	JSON object
Version sent / accepted	1 / 1 and higher (0 is dropped)
Sent to	one person who announced p2p, and only after the user allowed direct connections
Defined in	crates/p2p/src/signal.rs

Fields

Field	Type	Meaning
v	integer	Sent as 1.
t	string	offer, answer or decline.
s	string	Connection attempt id, exactly 16 lowercase hex digits. The answer repeats the offer's id.
c	array of strings	Address candidates ip:port (IPv6 in brackets), at most 8 (MAX_CANDIDATES). Port 0, unspecified, multicast, broadcast, IPv6 link-local and IPv4-mapped IPv6 addresses are rejected. Omitted when empty.
r	string	Only for decline: declined (user did not allow it) or unavailable (allowed, but could not be set up).

Examples

Addresses are documentation addresses, not real ones.

{"v":1,"t":"offer","s":"00ff00ff00ff00ff","c":["203.0.113.5:40000","[2001:db8::1]:40000"]}
{"v":1,"t":"answer","s":"00ff00ff00ff00ff","c":["198.51.100.7:41000"]}
{"v":1,"t":"decline","s":"00ff00ff00ff00ff","r":"declined"}

The connection

QUIC with mutual TLS and the ALPN mumcord-p2p/1. Each side presents its Mumble client certificate and accepts the other only if the certificate's hash equals the hash the Mumble server reports for that user (UserState.hash). There is one connection per pair of users on a server, shared by all features. The streams on it are in Flow-Direct-Connection.

Version and limits

• Signals are at most 1000 bytes (MAX_SIGNAL_BYTES).
• An offer waits 15 seconds for an answer; a wanted connection waits 60 seconds for the user's consent answer.

Privacy

The candidates are IP addresses of the user's machine, including LAN addresses. That is why nothing is sent without the user's consent. An offer that arrives before the user decided is declined. Receivers must never dial addresses they did not ask for.

Used in

Flow-Direct-Connection, and through it Flow-Full-Image and Flow-Screen-Share.