noxnet: Add proxy for capturing the network data, decode some messages.

cmd/opennox-packet-decode/main.go

@@ -0,0 +1,153 @@
+package main
+
+import (
+	"encoding/hex"
+	"encoding/json"
+	"flag"
+	"fmt"
+	"io"
+	"os"
+
+	"github.com/noxworld-dev/opennox-lib/noxnet"
+)
+
+var (
+	fIn  = flag.String("i", "network.jsonl", "input file with packet capture")
+	fOut = flag.String("o", "network-dec.jsonl", "output file for decoded packets")
+)
+
+func main() {
+	flag.Parse()
+	if err := run(); err != nil {
+		fmt.Fprintln(os.Stderr, err)
+		os.Exit(1)
+	}
+}
+
+func run() error {
+	f, err := os.Open(*fIn)
+	if err != nil {
+		return err
+	}
+	defer f.Close()
+	dec := json.NewDecoder(f)
+
+	w, err := os.Create(*fOut)
+	if err != nil {
+		return err
+	}
+	defer w.Close()
+	enc := json.NewEncoder(w)
+
+	for {
+		var r RecordIn
+		err := dec.Decode(&r)
+		if err == io.EOF {
+			break
+		} else if err != nil {
+			return err
+		}
+		r2 := r.Decode()
+		if err = enc.Encode(r2); err != nil {
+			return err
+		}
+	}
+	return w.Close()
+}
+
+type RecordIn struct {
+	SrcID uint32 `json:"src_id"`
+	DstID uint32 `json:"dst_id"`
+	Src   string `json:"src"`
+	Dst   string `json:"dst"`
+	Data  string `json:"data"`
+}
+
+func (r RecordIn) Decode() RecordOut {
+	o := RecordOut{
+		SrcID: r.SrcID,
+		DstID: r.DstID,
+		Src:   r.Src,
+		Dst:   r.Dst,
+		Data:  r.Data,
+	}
+	raw, err := hex.DecodeString(r.Data)
+	if err != nil {
+		return o
+	}
+	o.Len = len(raw)
+	if len(raw) < 2 {
+		return o
+	}
+	hdr, data := raw[:2], raw[2:]
+	o.Hdr = hex.EncodeToString(hdr)
+	if hdr[0] == 0xff {
+		o.SID = 0xff
+	} else {
+		o.Reliable = hdr[0]&0x80 != 0
+		o.SID = hdr[0] &^ 0x80
+		o.Seq = hdr[1]
+	}
+	if len(data) == 1 {
+		op := noxnet.Op(data[0])
+		if _, _, err := noxnet.DecodeAnyPacket(o.SrcID == 0, data); err != nil {
+			s := op.String()
+			o.Op = &s
+			return o
+		}
+	}
+	allSplit := true
+	for len(data) != 0 {
+		op := noxnet.Op(data[0])
+		sz := len(data)
+		var v any
+		lenOK := false
+		if n := op.Len(); n >= 0 && n <= len(data) {
+			sz = n + 1
+			lenOK = true
+		}
+		if m, n, err := noxnet.DecodeAnyPacket(o.SrcID == 0, data); err == nil && n > 0 {
+			sz = n
+			v = m
+			lenOK = true
+		}
+		if !lenOK {
+			allSplit = false
+		}
+		msg := data[:sz]
+		data = data[sz:]
+		m := Msg{
+			Op:     op.String(),
+			Len:    len(msg),
+			Data:   hex.EncodeToString(msg),
+			Fields: v,
+		}
+		o.Msgs = append(o.Msgs, m)
+	}
+	if allSplit {
+		o.Data = ""
+	}
+	return o
+}
+
+type RecordOut struct {
+	SrcID    uint32  `json:"src_id"`
+	DstID    uint32  `json:"dst_id"`
+	Src      string  `json:"src"`
+	Dst      string  `json:"dst"`
+	Hdr      string  `json:"hdr"`
+	Reliable bool    `json:"reliable"`
+	SID      byte    `json:"sid"`
+	Seq      byte    `json:"seq"`
+	Len      int     `json:"len"`
+	Op       *string `json:"op,omitempty"`
+	Msgs     []Msg   `json:"msgs,omitempty"`
+	Data     string  `json:"data,omitempty"`
+}
+
+type Msg struct {
+	Op     string `json:"op,omitempty"`
+	Fields any    `json:"fields,omitempty"`
+	Len    int    `json:"len"`
+	Data   string `json:"data"`
+}

cmd/opennox-proxy/README.md

@@ -0,0 +1,40 @@
+# OpenNox net proxy
+
+This tool helps debug networking problems by sitting between Nox/OpenNox clients and the server.
+
+```
+/        \<--|        |<--|               |<--|          |
+|Client 1|   |        |   | C1 proxy port |   |          |
+\        /-->| Proxy  |-->|               |-->| Real Nox |
+             | server |                       | server   |
+/        \-->| port   |-->|               |-->|          |
+|Client 2|   |        |   | C2 proxy port |   |          |
+\        /<--|        |<--|               |<--|          |
+```
+
+## Flow from client
+1. Packets from clients are accepted on the server proxy port.
+2. Proxy then allocates a unique proxy port for each client (since Nox uses ip+port for client id).
+3. Client packets are then sent from client proxy port to the real server.
+
+## Flow from server
+1. Packets are received on unique client proxy port.
+2. They are then sent from server proxy port to the client.
+
+## How to run
+
+```shell
+go run ./cmd/opennox-proxy --server=<server-ip>:18590 --host=0.0.0.0:18600 --file=network.jsonl
+```
+
+This will run a proxy on port `18600`, which is not standard for Nox, thus server discovery will not find it.
+
+You must add the proxy address to `game_ip.txt` file in Nox directory (as `127.0.0.1:18600`).
+
+After this, you should see a new server in the server list, you will recognize it by "Proxy:" prefix.
+
+While you are connected to this server, all network messages are logged to `network.jsonl`.
+Once you're done with testing, disconnect from the proxy, and close it.
+
+Now you can run `go run ./cmd/opennox-packet-decode` that will decode known network messages
+in `network.jsonl` and will write them to `network-dec.jsonl`, which can then be inspected.