reactor
/
ptth
1
0
Fork 0
Code Issues Pull Requests Projects Releases Wiki Activity
ptth/docs/explanation/ptth_direc.md

2.4 KiB
Raw Blame History

PTTH_DIREC - Direct P2P connections

It could work, even!

To keep each ridiculous new feature simple, we'll rely on bootstrapping:

  1. PTTH is just HTTPS connections
  2. PTTH_QUIC uses a PTTH relay to download the QUIC cert and bootstrap
  3. PTTH_DIREC will use a PTTH_QUIC relay to bootstrap

Overview

Given that:

  • P2 is connected to P3
  • P4 is connected to P3

Steps:

  • S1. P2 starts a bi stream to P3
  • S2.0. P2 says, "I want to initiate a PTTH_DIREC connection..."
  • "... And I'll send you cookie X to do hole-punching..."
  • "... And I want to connect to end server Y..."
  • S3.0. P3 creates an ID for this connection
  • S3.1. P3 replies "go ahead" to P2
  • S4. P3 starts a bi stream to P4 (end server Y)
  • S5. P3 says, "I want you to accept a PTTH_DIREC connection..."
  • "... And you should send me cookie Z to do hole-punching..."
  • "... And the client will be client W..."
  • S6. P3 waits for P4 to accept the offer
  • S7. P3 waits for both cookies to arrive
  • S8. When the cookies arrive, P3 learns the WAN addresses of P2 and P4
  • S9. P3 sends the WAN addresses of P2 and P4 to each other (on the existing bi streams)
  • S10. P4 tries to connect directly to P2
  • S11. P2 does the same to P4
  • S12. When P4 sees round-tripped data, it attempts to upgrade to QUIC
  • S13. When P2 sees round-tripped data, it attempts to upgrade to QUIC
  • Cool stuff happens over QUIC
  • ReactorScram implements the rest of the protocol

P2's PoV:

  • S1. Start a bi stream to P3
  • S2.0. Send cookie and server ID
  • S2.1. Wait for go-ahead signal (this may contain the hole-punch address and a new cookie for P4)
  • S2.2. Send cookie to hole-punch address repeatedly
  • S2.3. While you're sending the cookie, wait to hear P4's WAN address
  • S9. Learn P4's WAN address
  • S10. Send the new cookie to P4's address
  • S12. When you see round-tripped data, upgrade to QUIC

P4's PoV:

  • S4. Accept a bi stream from P3
  • S5. Receive cookie and client ID
  • S6. Reply "OK"
  • S7.0. Send cookie to hole-punch address repeatedly
  • S7.1. While sending the cookie, wait to hear P2's WAN address
  • S9. Learn P2's WAN address
  • S10. Try to connect directly to P2
  • S12. When you see round-tripped data, upgrade to QUIC

Commands needed:

  • ???

Decisions

I'll add a delay between giving P2's address to P4, and giving P4's address to P2. This miiiight change things slightly if P4's firewall is suspicious of packets coming in too early, but I doubt it.

The delay is easy to remove relay-side if it doesn't help.