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Early receives: allow nodes to process most incoming direct packets ASAP #2651

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Early receives: allow nodes to process most incoming direct packets ASAP #2651

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41 changes: 30 additions & 11 deletions src/Mesh.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -73,16 +73,6 @@ DispatcherAction Mesh::onRecvPacket(Packet* pkt) {
}

if (pkt->isRouteDirect() && pkt->getPathHashCount() > 0) {
// check for 'early received' ACK
if (pkt->getPayloadType() == PAYLOAD_TYPE_ACK) {
int i = 0;
uint32_t ack_crc;
memcpy(&ack_crc, &pkt->payload[i], 4); i += 4;
if (i <= pkt->payload_len) {
onAckRecv(pkt, ack_crc);
}
}

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@redxdev redxdev May 31, 2026

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Just noting that this is a slight behavior change, and opens up one weird edge case: if a packet has the local node as part of the path and as the destination (i.e. the full path is something like A,B,C with a destination of B) then the packet won't be received early as retransmit logic takes priority here. I could restructure the code to avoid this situation, but it's a bit nonsensical in the first place and I'm not sure it's worth fixing.

if (self_id.isHashMatch(pkt->path, pkt->getPathHashSize()) && allowPacketForward(pkt)) {
if (pkt->getPayloadType() == PAYLOAD_TYPE_MULTIPART) {
return forwardMultipartDirect(pkt);
Expand All @@ -101,7 +91,36 @@ DispatcherAction Mesh::onRecvPacket(Packet* pkt) {
return ACTION_RETRANSMIT_DELAYED(0, d); // Routed traffic is HIGHEST priority
}
}
return ACTION_RELEASE; // this node is NOT the next hop (OR this packet has already been forwarded), so discard.

// check if we're the destination or can otherwise receive this packet early - before the full path has been consumed
bool can_early_receive = false;
switch (pkt->getPayloadType()) {
case PAYLOAD_TYPE_ACK: {
int i = 0;
uint32_t ack_crc;
memcpy(&ack_crc, &pkt->payload[i], 4); i += 4;
if (i <= pkt->payload_len) {
can_early_receive = true;
}
break;
}

case PAYLOAD_TYPE_PATH:
case PAYLOAD_TYPE_REQ:
case PAYLOAD_TYPE_RESPONSE:
case PAYLOAD_TYPE_TXT_MSG:
case PAYLOAD_TYPE_ANON_REQ: {
// all of these payloads have the destination hash in the first byte
if (self_id.isHashMatch(pkt->payload, 1)) {
can_early_receive = true;
}
break;
}
}

if (!can_early_receive) {
return ACTION_RELEASE; // this node is NOT the next hop (OR this packet has already been forwarded), so discard.
}
}

if (pkt->isRouteFlood() && filterRecvFloodPacket(pkt)) return ACTION_RELEASE;
Expand Down