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Mitigate Direct Routing Instability from One-Byte Hop Hash Collisions #1776

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Mitigate Direct Routing Instability from One-Byte Hop Hash Collisions #1776

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74 changes: 62 additions & 12 deletions src/helpers/BaseChatMesh.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -39,7 +39,7 @@ mesh::Packet* BaseChatMesh::createSelfAdvert(const char* name, double lat, doubl
}

void BaseChatMesh::sendAckTo(const ContactInfo& dest, uint32_t ack_hash) {
if (dest.out_path_len < 0) {
if (!shouldUseDirectPath(dest)) {
mesh::Packet* ack = createAck(ack_hash);
if (ack) sendFloodScoped(dest, ack, TXT_ACK_DELAY);
} else {
Expand All @@ -55,6 +55,26 @@ void BaseChatMesh::sendAckTo(const ContactInfo& dest, uint32_t ack_hash) {
}
}

bool BaseChatMesh::isAmbiguousDirectPath(const ContactInfo& recipient) const {
if (recipient.out_path_len <= 0) return false;
for (int i = 0; i < recipient.out_path_len; i++) {
uint8_t hop = recipient.out_path[i];
bool seen_once = false;
for (int j = 0; j < num_contacts; j++) {
if (contacts[j].id.matches(recipient.id)) continue;
if (contacts[j].id.pub_key[0] == hop) {
if (seen_once) return true;
seen_once = true;
}
}
}
return false;
}

bool BaseChatMesh::shouldUseDirectPath(const ContactInfo& recipient) const {
return recipient.out_path_len >= 0 && !isAmbiguousDirectPath(recipient);
}

void BaseChatMesh::bootstrapRTCfromContacts() {
uint32_t latest = 0;
for (int i = 0; i < num_contacts; i++) {
Expand Down Expand Up @@ -263,17 +283,20 @@ void BaseChatMesh::onPeerDataRecv(mesh::Packet* packet, uint8_t type, int sender
} else {
mesh::Packet* reply = createDatagram(PAYLOAD_TYPE_RESPONSE, from.id, secret, temp_buf, reply_len);
if (reply) {
if (from.out_path_len >= 0) { // we have an out_path, so send DIRECT
if (shouldUseDirectPath(from)) { // we have an unambiguous out_path, so send DIRECT
sendDirect(reply, from.out_path, from.out_path_len, SERVER_RESPONSE_DELAY);
} else {
if (from.out_path_len >= 0) {
ambiguous_direct_avoids++;
}
sendFloodScoped(from, reply, SERVER_RESPONSE_DELAY);
}
}
}
}
} else if (type == PAYLOAD_TYPE_RESPONSE && len > 0) {
onContactResponse(from, data, len);
if (packet->isRouteFlood() && from.out_path_len >= 0) {
if (packet->isRouteFlood() && shouldUseDirectPath(from)) {
// we have direct path, but other node is still sending flood response, so maybe they didn't receive reciprocal path properly(?)
handleReturnPathRetry(from, packet->path, packet->path_len);
}
Expand Down Expand Up @@ -317,7 +340,7 @@ void BaseChatMesh::onAckRecv(mesh::Packet* packet, uint32_t ack_crc) {
txt_send_timeout = 0; // matched one we're waiting for, cancel timeout timer
packet->markDoNotRetransmit(); // ACK was for this node, so don't retransmit

if (packet->isRouteFlood() && from->out_path_len >= 0) {
if (packet->isRouteFlood() && shouldUseDirectPath(*from)) {
// we have direct path, but other node is still sending flood, so maybe they didn't receive reciprocal path properly(?)
handleReturnPathRetry(*from, packet->path, packet->path_len);
}
Expand All @@ -327,6 +350,12 @@ void BaseChatMesh::onAckRecv(mesh::Packet* packet, uint32_t ack_crc) {
void BaseChatMesh::handleReturnPathRetry(const ContactInfo& contact, const uint8_t* path, uint8_t path_len) {
// NOTE: simplest impl is just to re-send a reciprocal return path to sender (DIRECTLY)
// override this method in various firmwares, if there's a better strategy
if (!shouldUseDirectPath(contact)) {
if (contact.out_path_len >= 0) {
ambiguous_direct_avoids++;
}
return;
}
mesh::Packet* rpath = createPathReturn(contact.id, contact.getSharedSecret(self_id), path, path_len, 0, NULL, 0);
if (rpath) sendDirect(rpath, contact.out_path, contact.out_path_len, 3000); // 3 second delay
}
Expand Down Expand Up @@ -386,7 +415,10 @@ int BaseChatMesh::sendMessage(const ContactInfo& recipient, uint32_t timestamp,
uint32_t t = _radio->getEstAirtimeFor(pkt->getRawLength());

int rc;
if (recipient.out_path_len < 0) {
if (!shouldUseDirectPath(recipient)) {
if (recipient.out_path_len >= 0) {
ambiguous_direct_avoids++;
}
sendFloodScoped(recipient, pkt);
txt_send_timeout = futureMillis(est_timeout = calcFloodTimeoutMillisFor(t));
rc = MSG_SEND_SENT_FLOOD;
Expand All @@ -412,7 +444,10 @@ int BaseChatMesh::sendCommandData(const ContactInfo& recipient, uint32_t timest

uint32_t t = _radio->getEstAirtimeFor(pkt->getRawLength());
int rc;
if (recipient.out_path_len < 0) {
if (!shouldUseDirectPath(recipient)) {
if (recipient.out_path_len >= 0) {
ambiguous_direct_avoids++;
}
sendFloodScoped(recipient, pkt);
txt_send_timeout = futureMillis(est_timeout = calcFloodTimeoutMillisFor(t));
rc = MSG_SEND_SENT_FLOOD;
Expand Down Expand Up @@ -500,7 +535,10 @@ int BaseChatMesh::sendLogin(const ContactInfo& recipient, const char* password,
}
if (pkt) {
uint32_t t = _radio->getEstAirtimeFor(pkt->getRawLength());
if (recipient.out_path_len < 0) {
if (!shouldUseDirectPath(recipient)) {
if (recipient.out_path_len >= 0) {
ambiguous_direct_avoids++;
}
sendFloodScoped(recipient, pkt);
est_timeout = calcFloodTimeoutMillisFor(t);
return MSG_SEND_SENT_FLOOD;
Expand All @@ -525,7 +563,10 @@ int BaseChatMesh::sendAnonReq(const ContactInfo& recipient, const uint8_t* data,
}
if (pkt) {
uint32_t t = _radio->getEstAirtimeFor(pkt->getRawLength());
if (recipient.out_path_len < 0) {
if (!shouldUseDirectPath(recipient)) {
if (recipient.out_path_len >= 0) {
ambiguous_direct_avoids++;
}
sendFloodScoped(recipient, pkt);
est_timeout = calcFloodTimeoutMillisFor(t);
return MSG_SEND_SENT_FLOOD;
Expand All @@ -552,7 +593,10 @@ int BaseChatMesh::sendRequest(const ContactInfo& recipient, const uint8_t* req_
}
if (pkt) {
uint32_t t = _radio->getEstAirtimeFor(pkt->getRawLength());
if (recipient.out_path_len < 0) {
if (!shouldUseDirectPath(recipient)) {
if (recipient.out_path_len >= 0) {
ambiguous_direct_avoids++;
}
sendFloodScoped(recipient, pkt);
est_timeout = calcFloodTimeoutMillisFor(t);
return MSG_SEND_SENT_FLOOD;
Expand All @@ -579,7 +623,10 @@ int BaseChatMesh::sendRequest(const ContactInfo& recipient, uint8_t req_type, u
}
if (pkt) {
uint32_t t = _radio->getEstAirtimeFor(pkt->getRawLength());
if (recipient.out_path_len < 0) {
if (!shouldUseDirectPath(recipient)) {
if (recipient.out_path_len >= 0) {
ambiguous_direct_avoids++;
}
sendFloodScoped(recipient, pkt);
est_timeout = calcFloodTimeoutMillisFor(t);
return MSG_SEND_SENT_FLOOD;
Expand Down Expand Up @@ -683,8 +730,11 @@ void BaseChatMesh::checkConnections() {
MESH_DEBUG_PRINTLN("checkConnections(): Keep_alive contact not found!");
continue;
}
if (contact->out_path_len < 0) {
MESH_DEBUG_PRINTLN("checkConnections(): Keep_alive contact, no out_path!");
if (!shouldUseDirectPath(*contact)) {
MESH_DEBUG_PRINTLN("checkConnections(): Keep_alive contact, no direct path candidate");
if (contact->out_path_len >= 0) {
ambiguous_direct_avoids++;
}
continue;
}

Expand Down
4 changes: 4 additions & 0 deletions src/helpers/BaseChatMesh.h
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Original file line number Diff line number Diff line change
Expand Up @@ -70,8 +70,11 @@ class BaseChatMesh : public mesh::Mesh {
mesh::Packet* _pendingLoopback;
uint8_t temp_buf[MAX_TRANS_UNIT];
ConnectionInfo connections[MAX_CONNECTIONS];
uint32_t ambiguous_direct_avoids;

mesh::Packet* composeMsgPacket(const ContactInfo& recipient, uint32_t timestamp, uint8_t attempt, const char *text, uint32_t& expected_ack);
bool isAmbiguousDirectPath(const ContactInfo& recipient) const;
bool shouldUseDirectPath(const ContactInfo& recipient) const;
void sendAckTo(const ContactInfo& dest, uint32_t ack_hash);

protected:
Expand All @@ -85,6 +88,7 @@ class BaseChatMesh : public mesh::Mesh {
#endif
txt_send_timeout = 0;
_pendingLoopback = NULL;
ambiguous_direct_avoids = 0;
memset(connections, 0, sizeof(connections));
}

Expand Down