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mIP - Minecraft Internet Protocol

About

This library is used by mTCP and other network protocols for packet routing.

Header structure

Low-level modem.send() call looks something like this:
modem.send(address, port, header: string, ...)
The 2 interesting things are:

  • header: structured string with mIP header (and maybe more headers)
  • ...: payload

Contents of data are not relevant to us now, we'll focus on header.

Everything field is aligned to bytes for simpler string operations (eg. string.byte(header:sub(offset, offset+size))). Every number with multiple bytes/bits is in little-endian (if I understand correctly).

Name Size Description
version 1 Protocol version, current is mIPv1 => 1
flowID 3 Unique ID, used to identify flows. See Packet flow
header 1 Type of next header. See Extension headers
hopLimit 1 -1 every hop, 0 => packet dies (unless on dst)
src 16 Source modem address
dst 16 Destination modem address

Total size: 1 + 3 + 1 + 1 + 16*2 + 2 (modem string overhead) = 60

Flags

  • END: This is the end of the flow. See Packet flow
  • DNF: Do Not Fragment, ignore flowID. See Packet flow
  • ``: ???

Quick FAQ

  • Q: Does mIP guarantee delivery?
    A: Nothing guarantees delivery, but try mTCP
  • Q:
    A:

Going deeper

Extension headers

Fragment

Name Size Description
packetID 3 Unique ID, used with flowID for caching and loop prevention
prevID 3 packetID of previous packet in flow. See Packet flow
flags 1 Bitmask, END, DNF, ???

Packet flow

Concept is somewhat similar to IPv6's Flow Label

A high-entropy identifier of a flow of packets between a source and destination. A flow is group of packets, e.g., a TCP session or a media stream (lol).

Packet flow is also responsible for package fragmentation. If flowID is 0 there is no flow. If flowPrev is 0 this is the beginning of a flow. End of the flow is indicated by the END flag.

The 3 bytes for packetID and flowID are generated like this:

local function genID()
  local x = math.random(1, 16777216) -- (2^8)^3
  return string.char(x%255, math.floor((x/255)%255), math.floor((x/65025)%255))
end

The lua random generator seed is distinct for every computer (as far as I know). Make an issue if you know a better method!

Protocols

Current list of protocols:

proto Name Description
0 Unknown Why though?
1 mICMP Forming OC Internet since 2020
2 mTCP
3 mUDP
4 mMCP WIP Wrap around vanilla OC messages
5 mVPN WIP? "Ha-ha, I'm someone else" (c) User
6 mLCB WIP To infinity and beyond!
7 mRWB WIP Connect multiple nets via internet
8-252 Unassigned New protocols coming soon! (no)
253-254 Testing Will be dropped by default
255 Reserved Will be dropped by default

Make an issue if you want your protocol here.

Path discovery

]]--

-- TODO: Read ICMPv6, NDP, ARP, IPv4, IPv6?, TCP, UDP

-- TODO: Make route discovery great again! Create mNDP?

-- TODO: Route Discovery packet or something? --[[

  • Cache local neighbours?
  • Send Route Discovery packet or something (A searches D)
  • Receive answer with route? A -> B -> C -> D
- dst A dst B dst C dst D
A - B* B B
B A* - C* C
C B B* - D*
D C C C* -
* Can be cached? They are neighbours, maybe instantly

No neighbours:

- dst A dst B dst C dst D
A - B B
B - C
C B -
D C C -

]]--

-- TODO: Return header hash/"hash"? To confirm identity

-- TODO: You are a client? Just broadcast ping and connect with nearest pong -- Server pongs every request from client? Must(?) if on move (tablet or etc.) -- And then communicate like there is no such thing as distance ;)

The Book

book = {
  ["34eb7b28-14d3-4767-b326-dd1609ba92e"] = {
    online = true,
    friends = {},
    cipher = {"AES"},
    sign = {"DSA"},
    public = "key data here"
  },
  ["12345678-1234-1234-1234-123456789ab"] = {
    online = true,
    friends = {}
  }
}

-- TODO: Call modem.send() last in tick, form send queue?

-- TODO: Make wrappers for protocols, like protoWrapper(data_and_things) -- Make a universal proto wrapper?