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package main
import (
"crypto/ed25519"
"encoding/binary"
"encoding/json"
"fmt"
"io"
"log"
"net"
"os"
"os/signal"
"strings"
"sync"
"sync/atomic"
"syscall"
"time"
"google.golang.org/protobuf/proto"
)
const (
MaxPacketSize = 65536
ServerVersion = "0.5.0"
MaxScarEntries = 1000
)
var (
agents = make(map[string]net.Conn) // "bot:weather" -> conn
connSrc = make(map[net.Conn]string) // conn -> "bot:weather" (reverse)
routeMu sync.RWMutex
// Server metrics
serverStart time.Time
totalPackets atomic.Int64
// Scar/barter tracking
scarCount = make(map[string]int64) // src -> count of scar-bearing packets
scarCountMu sync.Mutex
)
// registerConn registers a connection under the given agent identity.
// Last-write-wins: if the identity is already registered, the old connection is closed.
func registerConn(identity string, conn net.Conn) {
routeMu.Lock()
defer routeMu.Unlock()
if old, exists := agents[identity]; exists && old != conn {
log.Printf("Identity %q re-registered, closing old connection", identity)
// Clean up reverse map for old connection
delete(connSrc, old)
old.Close()
}
agents[identity] = conn
connSrc[conn] = identity
}
// unregisterConn removes a connection from the routing table.
func unregisterConn(conn net.Conn) {
routeMu.Lock()
defer routeMu.Unlock()
if identity, exists := connSrc[conn]; exists {
delete(agents, identity)
delete(connSrc, conn)
log.Printf("Unregistered %q", identity)
}
}
// readPacket reads a length-prefixed protobuf Packet from conn.
// Wire format: [4 bytes big-endian uint32 length][length bytes protobuf].
func readPacket(conn net.Conn) (*Packet, error) {
var lenBuf [4]byte
if _, err := io.ReadFull(conn, lenBuf[:]); err != nil {
return nil, err
}
msgLen := binary.BigEndian.Uint32(lenBuf[:])
if msgLen == 0 {
return nil, fmt.Errorf("zero-length packet")
}
if msgLen > MaxPacketSize {
return nil, fmt.Errorf("packet too large: %d > %d", msgLen, MaxPacketSize)
}
payload := make([]byte, msgLen)
if _, err := io.ReadFull(conn, payload); err != nil {
return nil, err
}
var p Packet
if err := proto.Unmarshal(payload, &p); err != nil {
return nil, fmt.Errorf("unmarshal: %w", err)
}
return &p, nil
}
// writePacket serializes a Packet with a 4-byte big-endian length prefix and writes it to conn.
func writePacket(conn net.Conn, p *Packet) error {
data, err := proto.Marshal(p)
if err != nil {
return fmt.Errorf("marshal: %w", err)
}
if len(data) > MaxPacketSize {
return fmt.Errorf("packet too large: %d > %d", len(data), MaxPacketSize)
}
var lenBuf [4]byte
binary.BigEndian.PutUint32(lenBuf[:], uint32(len(data)))
if _, err := conn.Write(lenBuf[:]); err != nil {
return err
}
if _, err := conn.Write(data); err != nil {
return err
}
return nil
}
func heartbeat() {
ticker := time.NewTicker(60 * time.Second)
defer ticker.Stop()
for range ticker.C {
hb := &Packet{
Typ: 2,
Src: "server",
}
routeMu.Lock()
for identity, conn := range agents {
if err := writePacket(conn, hb); err != nil {
log.Printf("Heartbeat fail %s: %v", identity, err)
delete(connSrc, conn)
delete(agents, identity)
conn.Close()
}
}
routeMu.Unlock()
}
}
// verifySig checks the ed25519 signature on a Packet.
// The signed payload is the Packet with sig and pk zeroed out, then serialized.
func verifySig(p *Packet) bool {
if len(p.Sig) == 0 || len(p.Pk) == 0 {
return false // unsigned packet
}
if len(p.Pk) != ed25519.PublicKeySize {
log.Printf("Malformed pk: expected %d bytes, got %d", ed25519.PublicKeySize, len(p.Pk))
return false
}
if len(p.Sig) != ed25519.SignatureSize {
log.Printf("Malformed sig: expected %d bytes, got %d", ed25519.SignatureSize, len(p.Sig))
return false
}
// Reconstruct the exact bytes that were signed:
// a copy of the packet with sig and pk cleared.
signCopy := &Packet{
Typ: p.Typ,
Id: p.Id,
Src: p.Src,
Dst: p.Dst,
Body: p.Body,
Fee: p.Fee,
Ttl: p.Ttl,
Scar: p.Scar,
// Sig and Pk intentionally omitted (zero value)
}
signBytes, err := proto.Marshal(signCopy)
if err != nil {
log.Printf("Marshal for verify failed: %v", err)
return false
}
return ed25519.Verify(p.Pk, signBytes, p.Sig)
}
// handleDiscover responds to discover:* queries with server metadata.
func handleDiscover(c net.Conn, p *Packet) {
suffix := strings.TrimPrefix(p.Dst, "discover:")
var body string
switch suffix {
case "info":
routeMu.RLock()
online := len(agents)
routeMu.RUnlock()
data, _ := json.Marshal(map[string]any{
"version": ServerVersion,
"agents_online": online,
"uptime_sec": int(time.Since(serverStart).Seconds()),
})
body = string(data)
case "agents":
routeMu.RLock()
list := make([]string, 0, len(agents))
for identity := range agents {
list = append(list, identity)
}
routeMu.RUnlock()
data, _ := json.Marshal(map[string]any{
"agents": list,
})
body = string(data)
case "stats":
scarCountMu.Lock()
counts := make(map[string]int64, len(scarCount))
for k, v := range scarCount {
counts[k] = v
}
scarCountMu.Unlock()
data, _ := json.Marshal(map[string]any{
"scar_exchanges": counts,
"total_packets": totalPackets.Load(),
})
body = string(data)
default:
body = "error:unknown_discovery"
}
resp := &Packet{
Id: p.Id,
Typ: 1,
Src: "server",
Body: body,
}
if err := writePacket(c, resp); err != nil {
log.Printf("Write error (discover): %v", err)
}
log.Printf("Discover %s -> %s: %s", p.Src, suffix, body)
}
func handleConnection(c net.Conn) {
defer c.Close()
addr := c.RemoteAddr().String()
defer unregisterConn(c)
for {
p, err := readPacket(c)
if err != nil {
if err != io.EOF {
log.Printf("Read error from %s: %v", addr, err)
}
return
}
// Signature is REQUIRED — unsigned packets are logged and dropped
if len(p.Sig) == 0 && len(p.Pk) == 0 {
log.Printf("DROPPED unsigned packet from %s (src=%s body=%q)", addr, p.Src, p.Body)
continue
}
if !verifySig(p) {
log.Printf("DROPPED invalid sig from %s (src=%s)", addr, p.Src)
continue
}
// Register agent identity from first valid packet's src field
if p.Src != "" {
registerConn(p.Src, c)
}
totalPackets.Add(1)
// Log scar/barter exchanges
if len(p.Scar) > 0 {
log.Printf("SCAR %s -> %s (%d bytes)", p.Src, p.Dst, len(p.Scar))
scarCountMu.Lock()
if len(scarCount) < MaxScarEntries {
scarCount[p.Src]++
} else if _, exists := scarCount[p.Src]; exists {
scarCount[p.Src]++
}
scarCountMu.Unlock()
}
log.Printf("From %s (typ %d): %s -> %s", p.Src, p.Typ, p.Body, p.Dst)
// Route based on dst field
switch {
case strings.HasPrefix(p.Dst, "discover:"):
handleDiscover(c, p)
case p.Dst == "server" || p.Dst == "":
// Backward compatible: reply "done"
resp := &Packet{
Id: p.Id,
Typ: 1,
Src: "server",
Body: "done",
}
if err := writePacket(c, resp); err != nil {
log.Printf("Write error to %s: %v", addr, err)
return
}
default:
// Forward to registered agent
routeMu.RLock()
target, exists := agents[p.Dst]
routeMu.RUnlock()
if !exists {
resp := &Packet{
Id: p.Id,
Typ: 1,
Src: "server",
Body: "error:offline",
}
if err := writePacket(c, resp); err != nil {
log.Printf("Write error to %s: %v", addr, err)
return
}
log.Printf("Route %s -> %s: offline", p.Src, p.Dst)
continue
}
// Forward original signed packet (preserving signature)
if err := writePacket(target, p); err != nil {
resp := &Packet{
Id: p.Id,
Typ: 1,
Src: "server",
Body: "error:delivery_failed",
}
if writeErr := writePacket(c, resp); writeErr != nil {
log.Printf("Write error to %s: %v", addr, writeErr)
return
}
log.Printf("Route %s -> %s: delivery failed: %v", p.Src, p.Dst, err)
continue
}
log.Printf("Routed %s -> %s", p.Src, p.Dst)
}
}
}
func main() {
serverStart = time.Now()
l, err := net.Listen("tcp", ":9009")
if err != nil {
log.Fatal(err)
}
log.Printf("keep %s listening on :9009", ServerVersion)
go heartbeat()
sig := make(chan os.Signal, 1)
signal.Notify(sig, syscall.SIGINT, syscall.SIGTERM)
go func() {
<-sig
log.Println("Shutdown")
os.Exit(0)
}()
for {
conn, err := l.Accept()
if err != nil {
continue
}
go handleConnection(conn)
}
}