test prep: pass reader/writer to handle_conn instead of conn

Because we don't want to keep the connection open while delaying for a
failed login, return the lock from handle_conn if the unlock should be
delayed. serve then closes the connection and sleeps before calling
Unlock().

goatherd.go

@@ -225,21 +225,12 @@ retry:
     }
 }
 
-func close(conn net.Conn, remote net.Addr) {
-    debugf("[%v] closing", remote)
-    conn.Close() // XXX: check err?
-}
-
-func handle_conn(db *sql.DB, conn net.Conn) {
-    remote := conn.RemoteAddr()
-    reader := bufio.NewReader(conn)
-    writer := bufio.NewWriter(conn)
-
+func handle_conn(db *sql.DB, remote string, reader *bufio.Reader,
+        writer *bufio.Writer) (delay *sync.Mutex) {
     debugf("[%v] reading name", remote)
     name, err := get_line(reader)
     if err != nil {
         log.Printf("[%v] %v", remote, err)
-        close(conn, remote)
         return
     }
     debugf("[%v] name: %v", remote, name)
@@ -248,7 +239,6 @@ func handle_conn(db *sql.DB, conn net.Conn) {
     offer, err := get_line(reader)
     if err != nil {
         log.Printf("[%v] %v", remote, err)
-        close(conn, remote)
         return
     }
 
@@ -256,7 +246,6 @@ func handle_conn(db *sql.DB, conn net.Conn) {
     result := "FAIL"
     match, err := check_offer(db, remote, name, offer)
     if err == sql.ErrNoRows {
-        close(conn, remote)
         return
     } else if err != nil {
         log.Panic(err)
@@ -271,43 +260,41 @@ func handle_conn(db *sql.DB, conn net.Conn) {
     // zeroed mutex if we used a concurrent map without a temporary variable
     // and further memory barriers)
     faildelay.RLock()
-    delay, exists := faildelay.userlocks[name]
+    userlock, exists := faildelay.userlocks[name]
     faildelay.RUnlock()
     if !exists {
         debugf("[%v] not yet in faildelay.userlocks", remote)
 
         faildelay.Lock()
-        delay, exists = faildelay.userlocks[name]
+        userlock, exists = faildelay.userlocks[name]
         if !exists {
-            delay = new(sync.Mutex)
-            faildelay.userlocks[name] = delay
+            userlock = new(sync.Mutex)
+            faildelay.userlocks[name] = userlock
         }
         faildelay.Unlock()
     }
 
-    delay.Lock()
+    userlock.Lock()
+    debugf("[%v] have lock", remote)
+    if !match {
+        // invalid offer, unlocked in serve after delaying further attempts
+        delay = userlock
+    } else {
+        defer userlock.Unlock()
+    }
 
     _, err = fmt.Fprintln(writer, result)
     if err != nil {
         log.Printf("[%v] %v", remote, err)
-        goto out
+        return
     }
     err = writer.Flush()
     if err != nil {
         log.Printf("[%v] %v", remote, err)
-        goto out
-    }
-
-out:
-    close(conn, remote)
-
-    if !match {
-        debugf("[%v] delaying for %v", remote, cfg.Faildelay.Duration)
-        time.Sleep(cfg.Faildelay.Duration)
+        return
     }
 
-    debugf("[%v] unlock", remote)
-    delay.Unlock()
+    return
 }
 
 
@@ -339,7 +326,22 @@ func serve(db *sql.DB) {
         log.Printf("new connection: %v\n", conn.RemoteAddr())
 
         // XXX: recover from database failure
-        go handle_conn(db, conn)
+        go func(conn net.Conn) {
+            remote := conn.RemoteAddr().String()
+            reader := bufio.NewReader(conn)
+            writer := bufio.NewWriter(conn)
+
+            delay := handle_conn(db, remote, reader, writer)
+            debugf("[%v] closing", remote)
+            conn.Close() // XXX: check err?
+
+            if delay != nil {
+                debugf("[%v] delaying for %v", remote, cfg.Faildelay.Duration)
+                time.Sleep(cfg.Faildelay.Duration)
+                debugf("[%v] unlock", remote)
+                delay.Unlock()
+            }
+        }(conn)
     }
 }