mirror of
https://github.com/permissionlesstech/bitchat-android.git
synced 2026-07-25 07:25:20 +00:00
Gossip mesh topology + source-based routing (#445)
* wip mesh graph * gossip fix * gossip works * source-based routing wip * log * update spec to be explicit about intermediate hops only * drop duplicate hops * add to spec * test * forgot comma * source routing v2 * add compression bomb protection * v2 source routing * fragmented packets inherit route * update spec * Gossip routing tmp with connection limit fixed (#569) * fix: r8 exception for LocationManager (#566) * fragmented packets inherit route * update spec * fix connection limits * fix: deserialization issue with routed packets * log * dynamic fragment size * fragment size * add tests * feat(gossip): implement two-way handshake for source routing edges - Update MeshGraphService to track directed announcements - Require bidirectional announcements for a 'confirmed' edge - Update RoutePlanner to strictly use confirmed edges - Update Mesh Topology debug view to show confirmed vs unconfirmed edges (solid vs dotted) * docs: update SOURCE_ROUTING.md with two-way handshake requirement * evict stale peers from mesh graph service * better logging * fix announce spe * fix: empty route * fix spec * fix: compile error in DebugSettingsSheet and potential NPE in RoutePlanner * revert * try again
This commit is contained in:
callebtc
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package com.bitchat.android.services.meshgraph
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import android.util.Log
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/**
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* Gossip TLV helpers for embedding direct neighbor peer IDs in ANNOUNCE payloads.
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* Uses compact TLV: [type=0x04][len=1 byte][value=N*8 bytes of peerIDs]
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*/
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object GossipTLV {
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// TLV type for a compact list of direct neighbor peerIDs (each 8 bytes)
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const val DIRECT_NEIGHBORS_TYPE: UByte = 0x04u
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/**
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* Encode up to 10 unique peerIDs (hex string up to 16 chars) as TLV value.
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*/
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fun encodeNeighbors(peerIDs: List<String>): ByteArray {
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val unique = peerIDs.distinct().take(10)
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val valueBytes = unique.flatMap { id -> hexStringPeerIdTo8Bytes(id).toList() }.toByteArray()
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if (valueBytes.size > 255) {
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// Safety check, though 10*8 = 80 bytes, so well under 255
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Log.w("GossipTLV", "Neighbors value exceeds 255, truncating")
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}
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return byteArrayOf(DIRECT_NEIGHBORS_TYPE.toByte(), valueBytes.size.toByte()) + valueBytes
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}
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/**
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* Scan a TLV-encoded announce payload and extract neighbor peerIDs.
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* Returns null if the TLV is not present at all; returns an empty list if present with length 0.
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*/
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fun decodeNeighborsFromAnnouncementPayload(payload: ByteArray): List<String>? {
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val result = mutableListOf<String>()
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var offset = 0
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while (offset + 2 <= payload.size) {
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val type = payload[offset].toUByte()
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val len = payload[offset + 1].toUByte().toInt()
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offset += 2
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if (offset + len > payload.size) break
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val value = payload.sliceArray(offset until offset + len)
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offset += len
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if (type == DIRECT_NEIGHBORS_TYPE) {
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// Value is N*8 bytes of peer IDs
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var pos = 0
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while (pos + 8 <= value.size) {
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val idBytes = value.sliceArray(pos until pos + 8)
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result.add(bytesToPeerIdHex(idBytes))
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pos += 8
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}
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return result // present (possibly empty)
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}
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}
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// Not present
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return null
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}
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private fun hexStringPeerIdTo8Bytes(hexString: String): ByteArray {
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val clean = hexString.lowercase().take(16)
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val result = ByteArray(8) { 0 }
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var idx = 0
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var out = 0
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while (idx + 1 < clean.length && out < 8) {
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val byteStr = clean.substring(idx, idx + 2)
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val b = byteStr.toIntOrNull(16)?.toByte() ?: 0
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result[out++] = b
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idx += 2
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}
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return result
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}
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private fun bytesToPeerIdHex(bytes: ByteArray): String {
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val sb = StringBuilder()
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for (b in bytes.take(8)) {
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sb.append(String.format("%02x", b))
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}
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return sb.toString()
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}
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}
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package com.bitchat.android.services.meshgraph
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import kotlinx.coroutines.flow.MutableStateFlow
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import kotlinx.coroutines.flow.StateFlow
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import kotlinx.coroutines.flow.asStateFlow
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import java.util.concurrent.ConcurrentHashMap
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/**
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* Maintains an internal graph of the mesh based on gossip.
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* Nodes are peers (peerID), edges are direct connections.
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*/
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class MeshGraphService private constructor() {
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data class GraphNode(val peerID: String, val nickname: String?)
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data class GraphEdge(val a: String, val b: String, val isConfirmed: Boolean, val confirmedBy: String? = null)
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data class GraphSnapshot(val nodes: List<GraphNode>, val edges: List<GraphEdge>)
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// Map peerID -> nickname (may be null if unknown)
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private val nicknames = ConcurrentHashMap<String, String?>()
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// Announcements: peerID -> set of neighbor peerIDs that *this* peer claims to see
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private val announcements = ConcurrentHashMap<String, Set<String>>()
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// Latest announcement timestamp per peer (ULong from packet)
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private val lastUpdate = ConcurrentHashMap<String, ULong>()
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private val _graphState = MutableStateFlow(GraphSnapshot(emptyList(), emptyList()))
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val graphState: StateFlow<GraphSnapshot> = _graphState.asStateFlow()
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/**
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* Update graph from a verified announcement.
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* Replaces previous neighbors for origin if this is newer (by timestamp).
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*/
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fun updateFromAnnouncement(originPeerID: String, originNickname: String?, neighborsOrNull: List<String>?, timestamp: ULong) {
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synchronized(this) {
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// Always update nickname if provided
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if (originNickname != null) nicknames[originPeerID] = originNickname
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// If no neighbors TLV present, do not modify edges or timestamps
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if (neighborsOrNull == null) {
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publishSnapshot()
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return
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}
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// Newer-only replacement per origin (based on TLV-bearing announcements only)
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val prevTs = lastUpdate[originPeerID]
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if (prevTs != null && prevTs >= timestamp) {
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// Older or equal TLV-bearing update: ignore
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return
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}
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lastUpdate[originPeerID] = timestamp
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// Update what originPeerID announces
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// Filter out self-loops just in case
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val newSet = neighborsOrNull.distinct().take(10).filter { it != originPeerID }.toSet()
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announcements[originPeerID] = newSet
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publishSnapshot()
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}
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}
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fun updateNickname(peerID: String, nickname: String?) {
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if (nickname == null) return
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nicknames[peerID] = nickname
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publishSnapshot()
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}
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/**
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* Remove a peer from the graph completely (e.g. when stale/offline).
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*/
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fun removePeer(peerID: String) {
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synchronized(this) {
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nicknames.remove(peerID)
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announcements.remove(peerID)
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lastUpdate.remove(peerID)
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publishSnapshot()
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}
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}
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private fun publishSnapshot() {
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// Collect all known nodes from nicknames and announcements
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val allNodes = mutableSetOf<String>()
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allNodes.addAll(nicknames.keys)
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announcements.forEach { (origin, neighbors) ->
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allNodes.add(origin)
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allNodes.addAll(neighbors)
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}
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val nodeList = allNodes.map { GraphNode(it, nicknames[it]) }.sortedBy { it.peerID }
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val edges = mutableListOf<GraphEdge>()
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val processedPairs = mutableSetOf<Pair<String, String>>()
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// We only care about connections that exist in at least one direction.
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// So iterating through all entries in `announcements` covers every declared edge.
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announcements.forEach { (source, targets) ->
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targets.forEach { target ->
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val pair = if (source <= target) source to target else target to source
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if (processedPairs.add(pair)) {
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// This is a new pair we haven't evaluated yet
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val (a, b) = pair
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val aAnnouncesB = announcements[a]?.contains(b) == true
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val bAnnouncesA = announcements[b]?.contains(a) == true
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if (aAnnouncesB && bAnnouncesA) {
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edges.add(GraphEdge(a, b, isConfirmed = true))
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} else if (aAnnouncesB) {
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edges.add(GraphEdge(a, b, isConfirmed = false, confirmedBy = a))
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} else if (bAnnouncesA) {
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edges.add(GraphEdge(a, b, isConfirmed = false, confirmedBy = b))
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}
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}
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}
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}
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val sortedEdges = edges.sortedWith(compareBy({ it.a }, { it.b }))
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_graphState.value = GraphSnapshot(nodeList, sortedEdges)
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}
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companion object {
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@Volatile private var INSTANCE: MeshGraphService? = null
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fun getInstance(): MeshGraphService = INSTANCE ?: synchronized(this) {
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INSTANCE ?: MeshGraphService().also { INSTANCE = it }
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}
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}
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}
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@@ -0,0 +1,68 @@
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package com.bitchat.android.services.meshgraph
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import android.util.Log
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import java.util.PriorityQueue
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/**
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* Computes shortest paths on the current mesh graph snapshot using Dijkstra.
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* Assumes unit edge weights.
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*/
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object RoutePlanner {
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private const val TAG = "RoutePlanner"
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/**
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* Return full path [src, ..., dst] if reachable, else null.
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*/
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fun shortestPath(src: String, dst: String): List<String>? {
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if (src == dst) return listOf(src)
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val snapshot = MeshGraphService.getInstance().graphState.value
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val neighbors = mutableMapOf<String, MutableSet<String>>()
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// Only consider confirmed edges for routing
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snapshot.edges.filter { it.isConfirmed }.forEach { e ->
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neighbors.getOrPut(e.a) { mutableSetOf() }.add(e.b)
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neighbors.getOrPut(e.b) { mutableSetOf() }.add(e.a)
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}
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// Ensure nodes known even if isolated
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snapshot.nodes.forEach { n -> neighbors.putIfAbsent(n.peerID, mutableSetOf()) }
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if (!neighbors.containsKey(src) || !neighbors.containsKey(dst)) return null
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val dist = mutableMapOf<String, Int>()
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val prev = mutableMapOf<String, String?>()
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val pq = PriorityQueue<Pair<String, Int>>(compareBy { it.second })
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neighbors.keys.forEach { v ->
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dist[v] = if (v == src) 0 else Int.MAX_VALUE
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prev[v] = null
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}
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pq.add(src to 0)
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while (pq.isNotEmpty()) {
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val top = pq.poll() ?: break
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val (u, d) = top
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if (d > (dist[u] ?: Int.MAX_VALUE)) continue
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if (u == dst) break
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neighbors[u]?.forEach { v ->
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val alt = d + 1
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if (alt < (dist[v] ?: Int.MAX_VALUE)) {
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dist[v] = alt
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prev[v] = u
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pq.add(v to alt)
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}
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}
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}
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if ((dist[dst] ?: Int.MAX_VALUE) == Int.MAX_VALUE) return null
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val path = mutableListOf<String>()
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var cur: String? = dst
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while (cur != null) {
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path.add(cur)
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cur = prev[cur]
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}
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path.reverse()
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Log.d(TAG, "Computed path $path")
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return path
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}
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}
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