More protocols

protocol/aprs/aprsis/proxy.go

@@ -0,0 +1,188 @@
+package aprsis
+
+import (
+	"bufio"
+	"bytes"
+	"fmt"
+	"net"
+	"strings"
+	"sync"
+
+	"git.maze.io/go/ham/protocol"
+	"github.com/sirupsen/logrus"
+)
+
+const (
+	DefaultListenAddr = ":14580"
+	DefaultServerAddr = "rotate.aprs2.net:14580"
+)
+
+type Proxy struct {
+	Logger  *logrus.Logger
+	Filter  string
+	server  string
+	listen  net.Listener
+	packets chan *protocol.Packet
+}
+
+func NewProxy(listen, server string) (*Proxy, error) {
+	if _, err := net.ResolveTCPAddr("tcp", server); err != nil {
+		return nil, fmt.Errorf("aprsis: error resolving %q: %v", server, err)
+	}
+
+	listenAddr, err := net.ResolveTCPAddr("tcp", listen)
+	if err != nil {
+		return nil, fmt.Errorf("aprsis: error listening on %s: %v", listen, err)
+	}
+
+	listener, err := net.ListenTCP("tcp", listenAddr)
+	if err != nil {
+		return nil, fmt.Errorf("aprsis: error listening on %s: %v", listen, err)
+	}
+
+	proxy := &Proxy{
+		Logger: logrus.New(),
+		server: server,
+		listen: listener,
+	}
+	go proxy.accept()
+
+	return proxy, nil
+}
+
+func (proxy *Proxy) Close() error {
+	if proxy.packets != nil {
+		close(proxy.packets)
+		proxy.packets = nil
+	}
+	return proxy.listen.Close()
+}
+
+func (proxy *Proxy) RawPackets() <-chan *protocol.Packet {
+	if proxy.packets == nil {
+		proxy.packets = make(chan *protocol.Packet, 16)
+	}
+	return proxy.packets
+}
+
+func (proxy *Proxy) accept() {
+	for {
+		client, err := proxy.listen.Accept()
+		if err != nil {
+			proxy.Logger.Errorf("aprs-is proxy: error accepting client: %v", err)
+			continue
+		}
+
+		go proxy.handle(client)
+	}
+}
+
+func (proxy *Proxy) handle(client net.Conn) {
+	defer func() { _ = client.Close() }()
+
+	host, _, _ := net.SplitHostPort(client.RemoteAddr().String())
+	proxy.Logger.Infof("aprs-is proxy[%s]: new connection", host)
+
+	server, err := net.Dial("tcp", proxy.server)
+	if err != nil {
+		proxy.Logger.Warnf("aprs-is proxy[%s]: can't connecto to APRS-IS server %s: %v", host, proxy.server, err)
+		return
+	}
+	defer func() { _ = server.Close() }()
+
+	var (
+		wait sync.WaitGroup
+		call string
+	)
+	wait.Go(func() { proxy.proxy(client, server, host, "->", &call) })
+	wait.Go(func() { proxy.proxy(server, client, host, "<-", nil) })
+	wait.Wait()
+}
+
+func (proxy *Proxy) proxy(dst, src net.Conn, host, dir string, call *string) {
+	defer func() {
+		if tcp, ok := dst.(*net.TCPConn); ok {
+			_ = tcp.CloseWrite()
+		} else {
+			_ = dst.Close()
+		}
+	}()
+
+	reader := bufio.NewReader(src)
+	for {
+		line, err := reader.ReadBytes('\n')
+		if err != nil {
+			proxy.Logger.Warnf("aprs-is proxy[%s]: %s read error: %v", host, src.RemoteAddr(), err)
+			return
+		}
+
+		// proxy to remote unaltered
+		if len(line) > 0 {
+			if _, err = dst.Write(line); err != nil {
+				proxy.Logger.Warnf("aprs-is proxy[%s]: %s write error: %v", host, dst.RemoteAddr(), err)
+				return
+			}
+		}
+
+		// parse line
+		line = bytes.TrimRight(line, "\r\n")
+		if len(line) > 0 {
+			proxy.Logger.Tracef("aprs-is proxy[%s]: %s %s", host, dir, string(line))
+
+			if call != nil && strings.HasPrefix(string(line), "# logresp ") {
+				// server responds to client login
+				part := strings.SplitN(string(line), " ", 5)
+				if len(part) > 4 && part[3] == "verified," {
+					*call = part[2]
+					proxy.Logger.Infof("aprs-is proxy[%s]: logged in as %s", host, *call)
+
+					if proxy.Filter != "" {
+						proxy.Logger.Tracef("aprs-is proxy[%s]: %s filter %s", host, dir, proxy.Filter)
+						if _, err = fmt.Fprintf(src, "filter %s\r\n", proxy.Filter); err != nil {
+							proxy.Logger.Warnf("aprs-is proxy[%s]: %s write error: %v", host, src.RemoteAddr(), err)
+							return
+						}
+					}
+				}
+			}
+
+			if !isCommand(line) {
+				proxy.handleRawPacket(line)
+			}
+		}
+	}
+}
+
+func (proxy *Proxy) handleRawPacket(data []byte) {
+	if proxy.packets == nil {
+		return
+	}
+
+	select {
+	case proxy.packets <- &protocol.Packet{
+		Protocol: "aprs",
+		Raw:      data,
+	}:
+	default:
+		proxy.Logger.Warn("aprs-is proxy: raw packet channel full, dropping packet")
+	}
+}
+
+func isCommand(line []byte) bool {
+	if len(line) == 0 {
+		return true
+	}
+
+	if line[0] == '#' {
+		return true
+	}
+
+	if i := bytes.IndexByte(line, ' '); i > -1 {
+		switch strings.ToLower(string(line[:i])) {
+		case "user", "filter":
+			return true
+		}
+	}
+
+	return false
+}