From b4a6149cee6d3d5b84f2bc396350a8fbb5f9be1c Mon Sep 17 00:00:00 2001
From: jdl <jdl@desktop>
Date: Sat, 14 Dec 2024 07:38:21 +0100
Subject: [PATCH] WIP

---
 peer/packets-helpers.go |  32 ++++++++++
 peer/packets.go         | 138 ++++++++++++++++++++++++++++++++++++++++
 2 files changed, 170 insertions(+)
 create mode 100644 peer/packets-helpers.go
 create mode 100644 peer/packets.go

diff --git a/peer/packets-helpers.go b/peer/packets-helpers.go
new file mode 100644
index 0000000..ad1eb65
--- /dev/null
+++ b/peer/packets-helpers.go
@@ -0,0 +1,32 @@
+package peer
+
+import (
+	"log"
+)
+
+func unmarshalPacket(nonce Nonce, data []byte) Packet {
+	var packet Packet
+
+	switch nonce.PacketType {
+	case PACKET_TYPE_PING:
+		packet = &Ping{}
+	case PACKET_TYPE_PONG:
+		packet = &Pong{}
+	case PACKET_TYPE_LIST_ADDR_REQ:
+		packet = &AddrListReq{}
+	case PACKET_TYPE_LIST_ADDR_RESP:
+		packet = &AddrListResp{}
+	default:
+		// TODO: Log.
+		return nil
+	}
+
+	if len(data) < packet.Size() {
+		log.Printf("Short packet[%d]: %d", nonce.PacketType, len(data))
+		return nil
+	}
+
+	packet.Parse(data[:packet.Size()])
+
+	return packet
+}
diff --git a/peer/packets.go b/peer/packets.go
new file mode 100644
index 0000000..1ccd64b
--- /dev/null
+++ b/peer/packets.go
@@ -0,0 +1,138 @@
+package peer
+
+import "unsafe"
+
+const (
+	PACKET_TYPE_DATA           = 0
+	PACKET_TYPE_PING           = 1
+	PACKET_TYPE_PONG           = 2
+	PACKET_TYPE_CONN_REQ       = 3
+	PACKET_TYPE_CONN_RESP      = 4
+	PACKET_TYPE_CONN_RESP_ACK  = 5
+	PACKET_TYPE_LIST_ADDR_REQ  = 6
+	PACKET_TYPE_LIST_ADDR_RESP = 7
+
+	CONN_REQ_SIZE      = 24
+	CONN_RESP_SIZE     = 8
+	CONN_RESP_ACK_SIZE = 8
+)
+
+type Packet interface {
+	Size() int
+	Parse(buf []byte)
+	Marshal(buf []byte) []byte
+}
+
+// ----------------------------------------------------------------------------
+
+type AddrListReq struct{} // Nothing.
+
+func (r *AddrListReq) Size() int { return 0 }
+
+func (r *AddrListReq) Parse(buf []byte) {}
+
+func (r *AddrListReq) Marshal(buf []byte) []byte { return buf[:0] }
+
+// ----------------------------------------------------------------------------
+
+type AddrListResp struct {
+	Addrs [][16]byte // All addresses are IPv6 or mapped IPv6.
+	Ports []uint16   // Ports.
+}
+
+func (r *AddrListResp) Size() int {
+	return 18 * MAX_IP
+}
+
+func (r *AddrListResp) Parse(buf []byte) {
+	r.Addrs = unsafe.Slice((*[16]byte)(unsafe.Pointer(&buf[0])), MAX_IP)
+	r.Ports = unsafe.Slice((*uint16)(unsafe.Pointer(&buf[16*MAX_IP])), MAX_IP)
+}
+
+func (r *AddrListResp) Marshal(buf []byte) []byte {
+	buf = buf[:18:MAX_IP]
+	addrs := unsafe.Slice((*[16]byte)(unsafe.Pointer(&buf[0])), MAX_IP)
+	copy(addrs, r.Addrs)
+	ports := unsafe.Slice((*uint16)(unsafe.Pointer(&buf[16*MAX_IP])), MAX_IP)
+	copy(ports, r.Ports)
+	return buf
+}
+
+// ----------------------------------------------------------------------------
+
+type ConnReq struct {
+	ReqID      uint64
+	SentAt     int64
+	Tiebreaker int64 // To determine which side is client or server.
+}
+
+func (r *ConnReq) Parse(buf []byte) {
+	r.ReqID = *(*uint64)(unsafe.Pointer(&buf[0]))
+	r.SentAt = *(*int64)(unsafe.Pointer(&buf[8]))
+	r.Tiebreaker = *(*int64)(unsafe.Pointer(&buf[16]))
+}
+
+func (r ConnReq) Marshal(buf []byte) []byte {
+	buf = buf[:24]
+	*(*uint64)(unsafe.Pointer(&buf[0])) = r.ReqID
+	*(*int64)(unsafe.Pointer(&buf[8])) = r.SentAt
+	*(*int64)(unsafe.Pointer(&buf[16])) = r.Tiebreaker
+	return buf
+}
+
+// ----------------------------------------------------------------------------
+
+type ConnResp struct {
+	ReqID uint64
+}
+
+func (r *ConnResp) Parse(buf []byte) {
+	r.ReqID = *(*uint64)(unsafe.Pointer(&buf[0]))
+}
+
+func (r ConnResp) Marshal(buf []byte) {
+	*(*uint64)(unsafe.Pointer(&buf[0])) = r.ReqID
+}
+
+// ----------------------------------------------------------------------------
+
+type ConnRespAck = ConnResp
+
+// ----------------------------------------------------------------------------
+
+type Ping struct {
+	SentAt int64 // unix milli
+}
+
+func (p *Ping) Size() int { return 8 }
+
+func (p *Ping) Parse(buf []byte) {
+	p.SentAt = *(*int64)(unsafe.Pointer(&buf[0]))
+}
+
+func (p *Ping) Marshal(buf []byte) []byte {
+	buf = buf[:8]
+	*(*int64)(unsafe.Pointer(&buf[0])) = p.SentAt
+	return buf
+}
+
+// ----------------------------------------------------------------------------
+
+type Pong struct {
+	SentAt  int64 // unix mili
+	RecvdAt int64 // unix mili
+}
+
+func (p *Pong) Size() int { return 16 }
+
+func (p *Pong) Parse(buf []byte) {
+	p.SentAt = *(*int64)(unsafe.Pointer(&buf[0]))
+	p.RecvdAt = *(*int64)(unsafe.Pointer(&buf[8]))
+}
+
+func (p *Pong) Marshal(buf []byte) []byte {
+	buf = buf[:16]
+	*(*int64)(unsafe.Pointer(&buf[0])) = p.SentAt
+	*(*int64)(unsafe.Pointer(&buf[8])) = p.RecvdAt
+	return buf
+}