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derp: rename some things in the server, add some docs

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pull/85/head
Brad Fitzpatrick 4 years ago
parent d298d5b1f8
commit 4b461c2e77
1 changed files with 68 additions and 53 deletions
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121
derp/derp_server.go
Unescape Escape View File

@ -25,6 +25,7 @@ import (
"tailscale.com/types/logger"
)
// Server is a DERP server.
type Server struct {
privateKey key.Private
publicKey key.Public
@ -32,26 +33,29 @@ type Server struct {
mu sync.Mutex
netConns map[net.Conn]chan struct{} // chan is closed when conn closes
clients map[key.Public]*client
clients map[key.Public]*sclient
}
// NewServer returns a new DERP server. It doesn't listen on its own.
// Connections are given to it via Server.Accept.
func NewServer(privateKey key.Private, logf logger.Logf) *Server {
s := &Server{
privateKey: privateKey,
publicKey: privateKey.Public(),
logf: logf,
clients: make(map[key.Public]*client),
clients: make(map[key.Public]*sclient),
netConns: make(map[net.Conn]chan struct{}),
}
return s
}
// Close closes the server and waits for the connections to disconnect.
func (s *Server) Close() error {
var closedChs []chan struct{}
s.mu.Lock()
for netConn, closed := range s.netConns {
netConn.Close()
for nc, closed := range s.netConns {
nc.Close()
closedChs = append(closedChs, closed)
}
s.mu.Unlock()
@ -63,34 +67,39 @@ func (s *Server) Close() error {
return nil
}
func (s *Server) Accept(netConn net.Conn, conn *bufio.ReadWriter) {
// Accept adds a new connection to the server.
// The provided bufio ReadWriter must be already connected to nc.
// Accept blocks until the Server is closed or the connection closes
// on its own.
func (s *Server) Accept(nc net.Conn, brw *bufio.ReadWriter) {
closed := make(chan struct{})
s.mu.Lock()
s.netConns[netConn] = closed
s.netConns[nc] = closed
s.mu.Unlock()
defer func() {
netConn.Close()
nc.Close()
close(closed)
s.mu.Lock()
delete(s.netConns, netConn)
delete(s.netConns, nc)
s.mu.Unlock()
}()
if err := s.accept(netConn, conn); err != nil {
s.logf("derp: %s: %v", netConn.RemoteAddr(), err)
if err := s.accept(nc, brw); err != nil {
s.logf("derp: %s: %v", nc.RemoteAddr(), err)
}
}
func (s *Server) accept(netConn net.Conn, conn *bufio.ReadWriter) error {
netConn.SetDeadline(time.Now().Add(10 * time.Second))
if err := s.sendServerKey(conn.Writer); err != nil {
func (s *Server) accept(nc net.Conn, brw *bufio.ReadWriter) error {
br, bw := brw.Reader, brw.Writer
nc.SetDeadline(time.Now().Add(10 * time.Second))
if err := s.sendServerKey(bw); err != nil {
return fmt.Errorf("send server key: %v", err)
}
netConn.SetDeadline(time.Now().Add(10 * time.Second))
clientKey, clientInfo, err := s.recvClientKey(conn)
nc.SetDeadline(time.Now().Add(10 * time.Second))
clientKey, clientInfo, err := s.recvClientKey(br)
if err != nil {
return fmt.Errorf("receive client key: %v", err)
}
@ -99,30 +108,31 @@ func (s *Server) accept(netConn net.Conn, conn *bufio.ReadWriter) error {
}
// At this point we trust the client so we don't time out.
netConn.SetDeadline(time.Time{})
nc.SetDeadline(time.Time{})
ctx, cancel := context.WithCancel(context.Background())
defer cancel()
c := &client{
key: clientKey,
netConn: netConn,
conn: conn,
c := &sclient{
key: clientKey,
nc: nc,
br: br,
bw: bw,
}
if clientInfo != nil {
c.info = *clientInfo
}
go func() {
if err := c.keepAlive(ctx); err != nil {
s.logf("derp: %s: client %x: keep alive failed: %v", netConn.RemoteAddr(), c.key, err)
s.logf("derp: %s: client %x: keep alive failed: %v", nc.RemoteAddr(), c.key, err)
}
}()
defer func() {
s.mu.Lock()
curClient := s.clients[c.key]
if curClient != nil && curClient.conn == conn {
s.logf("derp: %s: client %x: removing connection", netConn.RemoteAddr(), c.key)
if curClient != nil && curClient.nc == nc {
s.logf("derp: %s: client %x: removing connection", nc.RemoteAddr(), c.key)
delete(s.clients, c.key)
}
s.mu.Unlock()
@ -137,20 +147,20 @@ func (s *Server) accept(netConn net.Conn, conn *bufio.ReadWriter) error {
oldClient := s.clients[c.key]
s.clients[c.key] = c
s.mu.Unlock()
if err := s.sendServerInfo(conn, clientKey); err != nil {
if err := s.sendServerInfo(c.bw, clientKey); err != nil {
return fmt.Errorf("send server info: %v", err)
}
c.mu.Unlock()
if oldClient == nil {
s.logf("derp: %s: client %x: adding connection", netConn.RemoteAddr(), c.key)
s.logf("derp: %s: client %x: adding connection", nc.RemoteAddr(), c.key)
} else {
oldClient.netConn.Close()
s.logf("derp: %s: client %x: adding connection, replacing %s", netConn.RemoteAddr(), c.key, oldClient.netConn.RemoteAddr())
oldClient.nc.Close()
s.logf("derp: %s: client %x: adding connection, replacing %s", nc.RemoteAddr(), c.key, oldClient.nc.RemoteAddr())
}
for {
dstKey, contents, err := s.recvPacket(c.conn.Reader)
dstKey, contents, err := s.recvPacket(c.br)
if err != nil {
return fmt.Errorf("client %x: recv: %v", c.key, err)
}
@ -160,29 +170,29 @@ func (s *Server) accept(netConn net.Conn, conn *bufio.ReadWriter) error {
s.mu.Unlock()
if dst == nil {
s.logf("derp: %s: client %x: dropping packet for unknown %x", netConn.RemoteAddr(), c.key, dstKey)
s.logf("derp: %s: client %x: dropping packet for unknown %x", nc.RemoteAddr(), c.key, dstKey)
continue
}
dst.mu.Lock()
err = s.sendPacket(dst.conn.Writer, c.key, contents)
err = s.sendPacket(dst.bw, c.key, contents)
dst.mu.Unlock()
if err != nil {
s.logf("derp: %s: client %x: dropping packet for %x: %v", netConn.RemoteAddr(), c.key, dstKey, err)
s.logf("derp: %s: client %x: dropping packet for %x: %v", nc.RemoteAddr(), c.key, dstKey, err)
// If we cannot send to a destination, shut it down.
// Let its receive loop do the cleanup.
s.mu.Lock()
if s.clients[dstKey].conn == dst.conn {
s.clients[dstKey].netConn.Close()
if s.clients[dstKey] == dst {
s.clients[dstKey].nc.Close()
}
s.mu.Unlock()
}
}
}
func (s *Server) verifyClient(clientKey key.Public, info *clientInfo) error {
func (s *Server) verifyClient(clientKey key.Public, info *sclientInfo) error {
// TODO(crawshaw): implement policy constraints on who can use the DERP server
return nil
}
@ -200,7 +210,7 @@ func (s *Server) sendServerKey(bw *bufio.Writer) error {
return bw.Flush()
}
func (s *Server) sendServerInfo(conn *bufio.ReadWriter, clientKey key.Public) error {
func (s *Server) sendServerInfo(bw *bufio.Writer, clientKey key.Public) error {
var nonce [24]byte
if _, err := crand.Read(nonce[:]); err != nil {
return err
@ -208,24 +218,24 @@ func (s *Server) sendServerInfo(conn *bufio.ReadWriter, clientKey key.Public) er
msg := []byte("{}") // no serverInfo for now
msgbox := box.Seal(nil, msg, &nonce, clientKey.B32(), s.privateKey.B32())
if err := typeServerInfo.Write(conn); err != nil {
if err := typeServerInfo.Write(bw); err != nil {
return err
}
if _, err := conn.Write(nonce[:]); err != nil {
if _, err := bw.Write(nonce[:]); err != nil {
return err
}
if err := putUint32(conn, uint32(len(msgbox))); err != nil {
if err := putUint32(bw, uint32(len(msgbox))); err != nil {
return err
}
if _, err := conn.Write(msgbox); err != nil {
if _, err := bw.Write(msgbox); err != nil {
return err
}
return conn.Flush()
return bw.Flush()
}
// recvClientKey reads the client's hello (its proof of identity) upon its initial connection.
// It should be considered especially untrusted at this point.
func (s *Server) recvClientKey(br *bufio.ReadWriter) (clientKey key.Public, info *clientInfo, err error) {
func (s *Server) recvClientKey(br *bufio.Reader) (clientKey key.Public, info *sclientInfo, err error) {
if _, err := io.ReadFull(br, clientKey[:]); err != nil {
return key.Public{}, nil, err
}
@ -247,7 +257,7 @@ func (s *Server) recvClientKey(br *bufio.ReadWriter) (clientKey key.Public, info
if !ok {
return key.Public{}, nil, fmt.Errorf("msgbox: cannot open len=%d with client key %x", msgLen, clientKey[:])
}
info = new(clientInfo)
info = new(sclientInfo)
if err := json.Unmarshal(msg, info); err != nil {
return key.Public{}, nil, fmt.Errorf("msg: %v", err)
}
@ -285,19 +295,23 @@ func (s *Server) recvPacket(br *bufio.Reader) (dstKey key.Public, contents []byt
return dstKey, contents, nil
}
type client struct {
netConn net.Conn
key key.Public
info clientInfo
// sclient is a client connection to the server.
//
// (The "s" prefix is to more explicitly distinguish it from Client in derp_client.go)
type sclient struct {
nc net.Conn
key key.Public
info sclientInfo
keepAliveTimer *time.Timer
keepAliveReset chan struct{}
mu sync.Mutex
conn *bufio.ReadWriter
mu sync.Mutex // mu guards writing to bw
br *bufio.Reader
bw *bufio.Writer
}
func (c *client) keepAlive(ctx context.Context) error {
func (c *sclient) keepAlive(ctx context.Context) error {
jitterMs, err := crand.Int(crand.Reader, big.NewInt(5000))
if err != nil {
panic(err)
@ -316,22 +330,23 @@ func (c *client) keepAlive(ctx context.Context) error {
c.keepAliveTimer.Reset(keepAlive + jitter)
case <-c.keepAliveTimer.C:
c.mu.Lock()
err := typeKeepAlive.Write(c.conn)
err := typeKeepAlive.Write(c.bw)
if err == nil {
err = c.conn.Flush()
err = c.bw.Flush()
}
c.mu.Unlock()
if err != nil {
// TODO log
c.netConn.Close()
c.nc.Close()
return err
}
}
}
}
type clientInfo struct {
// sclientInfo is the client info sent by the client to the server.
type sclientInfo struct {
}
type serverInfo struct {

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