spec_port_forwarding_v0.1.md

Port forwarding in tox

(maybe more generic?)

This specification describes how 2 or more tox clients can setup and run tcp/udp traffic forwarding. A common usecase for this is securely exposing local webserver to a friend or forwarding game traffic without setting up a vpn or punching holes into a firewall.

Setup flow

If a successful setup is performed,

• peer A sends an Offer to B,
• B sends an Accept back
• and A Acknowlages with an Ack-Acc. After that Data packets can flow in both directions, until either side sends a Deny/Kill packet. There might be an unspecified delay between Offer and Accept, since the user needs to manually accept, or might just ignore it all together. Instead of Accept, a Deny/Kill might also be sent instead to tell the Offer is no longer valid (from the offerer) or is not wanted right now (offer receiver).

Packets

Offer Port Mapping

• random msg_id (namespace is shared between sender and receiver, but not anyone else)
• type (tcp/udp)
• direction (eg is it a server offer or a connection offer)
• suggested port (usually the port the offerer used, 0 for random)
• name (human readable, might be an application name or other to identify the purpose)

Accept Port Mapping

• the msg_id of the offer

Ack-Acc

• the msg_id of the accept/offer

Deny/Kill Port Mapping

• the msg_id of the accept/offer/running mapping

Data (udp/lossy)

• the msg_id of the running mapping Usually sent via lossy packets. Since its for udp, too large packets can be dropped. (no reassembly support for now)

Data (tcp/lossless)

• the msg_id of the running mapping Usually sent via "lossless" packets. Might need reassambly

Contact Specifics

ToxFriend

ToxGroup (NGC)

ToxConference (ToxFriend specialcase)

Changelog

• 08.05.2024 Green-Sky: wrote down inital spec (v0.1)