Implemented basic DHCPv6 server handler (#157)

4 files changed, 217 insertions, 19 deletions

diff --git a/dhcpv6/client.go b/dhcpv6/client.go
index 10a20c9..24b6e0d 100644
--- a/dhcpv6/client.go
+++ b/dhcpv6/client.go
@@ -127,6 +127,13 @@ func (c *Client) sendReceive(ifname string, packet DHCPv6, expectedType MessageT
 		return nil, err
 	}
 	defer conn.Close()
+	// wait for the listener to be ready
+	for {
+		if conn.LocalAddr() != nil {
+			break
+		}
+		time.Sleep(10 * time.Millisecond)
+	}
 
 	// send the packet out
 	conn.SetWriteDeadline(time.Now().Add(c.WriteTimeout))
diff --git a/dhcpv6/client_test.go b/dhcpv6/client_test.go
new file mode 100644
index 0000000..d2efa1f
--- /dev/null
+++ b/dhcpv6/client_test.go
@@ -0,0 +1,14 @@
+package dhcpv6
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/require"
+)
+
+func TestNewClient(t *testing.T) {
+	c := NewClient()
+	require.NotNil(t, c)
+	require.Equal(t, DefaultReadTimeout, c.ReadTimeout)
+	require.Equal(t, DefaultWriteTimeout, c.WriteTimeout)
+}
diff --git a/dhcpv6/server.go b/dhcpv6/server.go
index e12136a..3fade87 100644
--- a/dhcpv6/server.go
+++ b/dhcpv6/server.go
@@ -4,43 +4,124 @@ import (
 	"fmt"
 	"log"
 	"net"
+	"sync"
+	"time"
 )
 
-type ResponseWriter interface {
-	LocalAddr() net.Addr
-	RemoteAddr() net.Addr
-	WriteMsg(DHCPv6) error
-	Write([]byte) (int, error)
-	Close() error
+/*
+  To use the DHCPv6 server code you have to call NewServer with two arguments:
+  - a handler function, that will be called every time a valid DHCPv6 packet is
+      received, and
+  - an address to listen on.
+
+  The handler is a function that takes as input a packet connection, that can be
+  used to reply to the client; a peer address, that identifies the client sending
+  the request, and the DHCPv6 packet itself. Just implement your custom logic in
+  the handler.
+
+  The address to listen on is used to know IP address, port and optionally the
+  scope to create and UDP6 socket to listen on for DHCPv6 traffic.
+
+  Example program:
+
+
+package main
+
+import (
+	"log"
+	"net"
+
+	"github.com/insomniacslk/dhcp/dhcpv6"
+)
+
+func handler(conn net.PacketConn, peer net.Addr, m dhcpv6.DHCPv6) {
+	// this function will just print the received DHCPv6 message, without replying
+	log.Print(m.Summary())
 }
 
-type Handler interface {
-	ServeDHCP(w ResponseWriter, m *DHCPv6)
+func main() {
+	laddr := net.UDPAddr{
+		IP:   net.ParseIP("::1"),
+		Port: 547,
+	}
+	server := dhcpv6.NewServer(laddr, handler)
+
+	defer server.Close()
+	if err := server.ActivateAndServe(); err != nil {
+		log.Panic(err)
+	}
 }
 
+*/
+
+// Handler is a type that defines the handler function to be called every time a
+// valid DHCPv6 message is received
+type Handler func(conn net.PacketConn, peer net.Addr, m DHCPv6)
+
+// Server represents a DHCPv6 server object
 type Server struct {
-	PacketConn net.PacketConn
+	conn       net.PacketConn
+	connMutex  sync.Mutex
+	shouldStop chan bool
 	Handler    Handler
+	localAddr  net.UDPAddr
+}
+
+// LocalAddr returns the local address of the listening socket, or nil if not
+// listening
+func (s *Server) LocalAddr() net.Addr {
+	s.connMutex.Lock()
+	defer s.connMutex.Unlock()
+	if s.conn == nil {
+		return nil
+	}
+	return s.conn.LocalAddr()
 }
 
+// ActivateAndServe starts the DHCPv6 server
 func (s *Server) ActivateAndServe() error {
-	if s.PacketConn == nil {
-		return fmt.Errorf("Error: no packet connection specified")
+	s.connMutex.Lock()
+	if s.conn == nil {
+		conn, err := net.ListenUDP("udp6", &s.localAddr)
+		if err != nil {
+			return err
+		}
+		s.conn = conn
 	}
-	var pc *net.UDPConn
-	var ok bool
-	if pc, ok = s.PacketConn.(*net.UDPConn); !ok {
+	defer func() {
+		s.conn.Close()
+		s.conn = nil
+	}()
+	s.connMutex.Unlock()
+	var (
+		pc *net.UDPConn
+		ok bool
+	)
+	if pc, ok = s.conn.(*net.UDPConn); !ok {
 		return fmt.Errorf("Error: not an UDPConn")
 	}
 	if pc == nil {
 		return fmt.Errorf("ActivateAndServe: Invalid nil PacketConn")
 	}
-	log.Print("Handling requests")
+	log.Printf("Server listening on %s", pc.LocalAddr())
+	log.Print("Ready to handle requests")
 	for {
-		rbuf := make([]byte, 1024) // FIXME this is bad
+		select {
+		case <-s.shouldStop:
+			break
+		case <-time.After(time.Millisecond):
+		}
+		pc.SetReadDeadline(time.Now().Add(time.Second))
+		rbuf := make([]byte, 4096) // FIXME this is bad
 		n, peer, err := pc.ReadFrom(rbuf)
 		if err != nil {
-			log.Printf("Error reading from packet conn: %v", err)
+			switch err.(type) {
+			case net.Error:
+				// silently skip and continue
+			default:
+				//complain and continue
+				log.Printf("Error reading from packet conn: %v", err)
+			}
 			continue
 		}
 		log.Printf("Handling request from %v", peer)
@@ -49,8 +130,27 @@ func (s *Server) ActivateAndServe() error {
 			log.Printf("Error parsing DHCPv6 request: %v", err)
 			continue
 		}
-		log.Print(m.Summary())
-		// FIXME use s.Handler
+		s.Handler(pc, peer, m)
 	}
 	return nil
 }
+
+// Close sends a termination request to the server, and closes the UDP listener
+func (s *Server) Close() error {
+	s.shouldStop <- true
+	s.connMutex.Lock()
+	defer s.connMutex.Unlock()
+	if s.conn != nil {
+		return s.conn.Close()
+	}
+	return nil
+}
+
+// NewServer initializes and returns a new Server object
+func NewServer(addr net.UDPAddr, handler Handler) *Server {
+	return &Server{
+		localAddr:  addr,
+		Handler:    handler,
+		shouldStop: make(chan bool, 1),
+	}
+}
diff --git a/dhcpv6/server_test.go b/dhcpv6/server_test.go
new file mode 100644
index 0000000..066fe3a
--- /dev/null
+++ b/dhcpv6/server_test.go
@@ -0,0 +1,77 @@
+package dhcpv6
+
+import (
+	"log"
+	"net"
+	"testing"
+	"time"
+
+	"github.com/stretchr/testify/require"
+)
+
+// utility function to set up a client and a server instance and run it in
+// background. The caller needs to call Server.Close() once finished.
+func setUpClientAndServer(handler Handler) (*Client, *Server) {
+	laddr := net.UDPAddr{
+		IP:   net.ParseIP("::1"),
+		Port: 0,
+		Zone: "lo",
+	}
+	s := NewServer(laddr, handler)
+	go s.ActivateAndServe()
+
+	c := NewClient()
+	c.LocalAddr = &net.UDPAddr{
+		IP:   net.ParseIP("::1"),
+		Zone: "lo",
+	}
+	for {
+		if s.LocalAddr() != nil {
+			break
+		}
+		time.Sleep(10 * time.Millisecond)
+		log.Printf("Waiting for server to run...")
+	}
+	c.RemoteAddr = &net.UDPAddr{
+		IP:   net.ParseIP("::1"),
+		Port: s.LocalAddr().(*net.UDPAddr).Port,
+		Zone: "lo",
+	}
+
+	return c, s
+}
+
+func TestNewServer(t *testing.T) {
+	laddr := net.UDPAddr{
+		IP:   net.ParseIP("::1"),
+		Port: 0,
+		Zone: "lo",
+	}
+	handler := func(conn net.PacketConn, peer net.Addr, m DHCPv6) {}
+	s := NewServer(laddr, handler)
+	defer s.Close()
+
+	require.NotNil(t, s)
+	require.Nil(t, s.conn)
+	require.Equal(t, laddr, s.localAddr)
+	require.NotNil(t, s.Handler)
+}
+
+func TestServerActivateAndServe(t *testing.T) {
+	handler := func(conn net.PacketConn, peer net.Addr, m DHCPv6) {
+		adv, err := NewAdvertiseFromSolicit(m)
+		if err != nil {
+			log.Printf("NewAdvertiseFromSolicit failed: %v", err)
+			return
+		}
+		if _, err := conn.WriteTo(adv.ToBytes(), peer); err != nil {
+			log.Printf("Cannot reply to client: %v", err)
+		}
+	}
+	c, s := setUpClientAndServer(handler)
+	defer s.Close()
+
+	_, _, err := c.Solicit("lo", nil)
+
+	require.NoError(t, err)
+}