Start refactoring out a client and library

client/lib/snowflake.go

@@ -0,0 +1,69 @@
+package lib
+
+import (
+	"errors"
+	"io"
+	"log"
+	"net"
+	"sync"
+)
+
+const (
+	ReconnectTimeout = 10
+	SnowflakeTimeout = 30
+)
+
+// When a connection handler starts, +1 is written to this channel; when it
+// ends, -1 is written.
+var HandlerChan = make(chan int)
+
+// Given an accepted SOCKS connection, establish a WebRTC connection to the
+// remote peer and exchange traffic.
+func Handler(socks SocksConnector, snowflakes SnowflakeCollector) error {
+	HandlerChan <- 1
+	defer func() {
+		HandlerChan <- -1
+	}()
+	// Obtain an available WebRTC remote. May block.
+	snowflake := snowflakes.Pop()
+	if nil == snowflake {
+		socks.Reject()
+		return errors.New("handler: Received invalid Snowflake")
+	}
+	defer socks.Close()
+	defer snowflake.Close()
+	log.Println("---- Handler: snowflake assigned ----")
+	err := socks.Grant(&net.TCPAddr{IP: net.IPv4zero, Port: 0})
+	if err != nil {
+		return err
+	}
+
+	go func() {
+		// When WebRTC resets, close the SOCKS connection too.
+		snowflake.WaitForReset()
+		socks.Close()
+	}()
+
+	// Begin exchanging data. Either WebRTC or localhost SOCKS will close first.
+	// In eithercase, this closes the handler and induces a new handler.
+	copyLoop(socks, snowflake)
+	log.Println("---- Handler: closed ---")
+	return nil
+}
+
+// Exchanges bytes between two ReadWriters.
+// (In this case, between a SOCKS and WebRTC connection.)
+func copyLoop(a, b io.ReadWriter) {
+	var wg sync.WaitGroup
+	wg.Add(2)
+	go func() {
+		io.Copy(b, a)
+		wg.Done()
+	}()
+	go func() {
+		io.Copy(a, b)
+		wg.Done()
+	}()
+	wg.Wait()
+	log.Println("copy loop ended")
+}