wifinina: fix concurrency issues with multiple sockets

wifinina driver was not handling concurrent socket connections
correctly.  When trying to make multiple socket connections, the sockfd
returned by the first Socket() call would be the same sockfd returned by
subsequent Socket() calls.  The problem is the sockfd returned by
Socket() isn't used until Connect() (or Appect()).  This would result in
Connect() trying to use the same sockfd for multiple connections,
causing wifinina fw to lock up.

The solution in this PR is to create a new sockfd space managed by the
driver that gives the app a unique, safe sockfd for each connection.
The real underlying sock fd returned by fw is set on Connect() (or
Accept()), and mapped back to the apps sockfd using a map:

    sockets map[int]*Socket // keyed by sockfd

Where Socket has a reference to the fw sock:

    type Socket struct {
            protocol        int
            clientConnected bool
            laddr           netip.AddrPort // Set in Bind()
            raddr           netip.AddrPort // Set in Connect()
            sock                           // Device socket, as returned from w.getSocket()
    }

wifinina/wifinina.go

@@ -163,11 +163,12 @@ type encryptionType uint8
 type sock uint8
 type hwerr uint8
 
-type socket struct {
-	protocol int
-	laddr    netip.AddrPort // Set in Bind()
-	raddr    netip.AddrPort // Set in Connect()
-	inuse    bool
+type Socket struct {
+	protocol        int
+	clientConnected bool
+	laddr           netip.AddrPort // Set in Bind()
+	raddr           netip.AddrPort // Set in Connect()
+	sock                           // Device socket, as returned from w.getSocket()
 }
 
 type Config struct {
@@ -214,17 +215,13 @@ type wifinina struct {
 	killWatchdog chan bool
 	fault        error
 
-	sockets map[sock]*socket // keyed by sock as returned by getSocket()
-}
-
-func newSocket(protocol int) *socket {
-	return &socket{protocol: protocol, inuse: true}
+	sockets map[int]*Socket // keyed by sockfd
 }
 
 func New(cfg *Config) *wifinina {
 	w := wifinina{
 		cfg:          cfg,
-		sockets:      make(map[sock]*socket),
+		sockets:      make(map[int]*Socket),
 		killWatchdog: make(chan bool),
 		cs:           cfg.Cs,
 		ack:          cfg.Ack,
@@ -505,6 +502,12 @@ func (w *wifinina) GetHostByName(name string) (netip.Addr, error) {
 		fmt.Printf("[GetHostByName] name: %s\r\n", name)
 	}
 
+	// If it's already in dotted-decimal notation, return a copy
+	// per gethostbyname(3).
+	if ip, err := netip.ParseAddr(name); err == nil {
+		return ip, nil
+	}
+
 	w.mu.Lock()
 	defer w.mu.Unlock()
 
@@ -547,6 +550,20 @@ func (w *wifinina) Addr() (netip.Addr, error) {
 	return ip, nil
 }
 
+// newSockfd returns the next available sockfd, or -1 if none available
+func (w *wifinina) newSockfd() int {
+	if len(w.sockets) >= maxNetworks {
+		return -1
+	}
+	// Search for the next available sockfd starting at 0
+	for sockfd := 0; ; sockfd++ {
+		if _, ok := w.sockets[sockfd]; !ok {
+			return sockfd
+		}
+	}
+	return -1
+}
+
 // See man socket(2) for standard Berkely sockets for Socket, Bind, etc.
 // The driver strives to meet the function and semantics of socket(2).
 
@@ -574,34 +591,46 @@ func (w *wifinina) Socket(domain int, stype int, protocol int) (int, error) {
 	w.mu.Lock()
 	defer w.mu.Unlock()
 
-	sock := w.getSocket()
-	if sock == noSocketAvail {
+	sockfd := w.newSockfd()
+	if sockfd == -1 {
 		return -1, netdev.ErrNoMoreSockets
 	}
 
-	socket := newSocket(protocol)
-	w.sockets[sock] = socket
+	w.sockets[sockfd] = &Socket{
+		protocol: protocol,
+		sock:     noSocketAvail,
+	}
 
-	return int(sock), nil
+	if debugging(debugNetdev) {
+		fmt.Printf("[Socket] <-- sockfd %d\r\n", sockfd)
+	}
+
+	return sockfd, nil
 }
 
 func (w *wifinina) Bind(sockfd int, ip netip.AddrPort) error {
 
 	if debugging(debugNetdev) {
-		fmt.Printf("[Bind] sockfd: %d, addr: %s\r\n", sockfd, ip)
+		fmt.Printf("[Bind] sockfd: %d, addr: %s:%d\r\n", sockfd, ip.Addr(), ip.Port())
 	}
 
 	w.mu.Lock()
 	defer w.mu.Unlock()
 
-	var sock = sock(sockfd)
-	var socket = w.sockets[sock]
+	socket, ok := w.sockets[sockfd]
+	if !ok {
+		return netdev.ErrInvalidSocketFd
+	}
 
 	switch socket.protocol {
 	case netdev.IPPROTO_TCP:
 	case netdev.IPPROTO_TLS:
 	case netdev.IPPROTO_UDP:
-		w.startServer(sock, ip.Port(), protoModeUDP)
+		socket.sock = w.getSocket()
+		if socket.sock == noSocketAvail {
+			return netdev.ErrNoMoreSockets
+		}
+		w.startServer(socket.sock, ip.Port(), protoModeUDP)
 	}
 
 	socket.laddr = ip
@@ -629,22 +658,40 @@ func (w *wifinina) Connect(sockfd int, host string, ip netip.AddrPort) error {
 	w.mu.Lock()
 	defer w.mu.Unlock()
 
-	var sock = sock(sockfd)
-	var socket = w.sockets[sock]
+	socket, ok := w.sockets[sockfd]
+	if !ok {
+		return netdev.ErrInvalidSocketFd
+	}
 
 	// Start the connection
 	switch socket.protocol {
+
 	case netdev.IPPROTO_TCP:
-		w.startClient(sock, "", toUint32(ip.Addr().As4()), ip.Port(), protoModeTCP)
+		socket.sock = w.getSocket()
+		if socket.sock == noSocketAvail {
+			return netdev.ErrNoMoreSockets
+		}
+		w.startClient(socket.sock, "", toUint32(ip.Addr().As4()), ip.Port(), protoModeTCP)
+
 	case netdev.IPPROTO_TLS:
-		w.startClient(sock, host, 0, ip.Port(), protoModeTLS)
+		socket.sock = w.getSocket()
+		if socket.sock == noSocketAvail {
+			return netdev.ErrNoMoreSockets
+		}
+		w.startClient(socket.sock, host, 0, ip.Port(), protoModeTLS)
+
 	case netdev.IPPROTO_UDP:
+		if socket.sock == noSocketAvail {
+			return fmt.Errorf("Must Bind before Connecting")
+		}
 		// See start in sendUDP()
 		socket.raddr = ip
+		socket.clientConnected = true
 		return nil
 	}
 
-	if w.getClientState(sock) == tcpStateEstablished {
+	if w.getClientState(socket.sock) == tcpStateEstablished {
+		socket.clientConnected = true
 		return nil
 	}
 
@@ -664,12 +711,18 @@ func (w *wifinina) Listen(sockfd int, backlog int) error {
 	w.mu.Lock()
 	defer w.mu.Unlock()
 
-	var sock = sock(sockfd)
-	var socket = w.sockets[sock]
+	socket, ok := w.sockets[sockfd]
+	if !ok {
+		return netdev.ErrInvalidSocketFd
+	}
 
 	switch socket.protocol {
 	case netdev.IPPROTO_TCP:
-		w.startServer(sock, socket.laddr.Port(), protoModeTCP)
+		socket.sock = w.getSocket()
+		if socket.sock == noSocketAvail {
+			return netdev.ErrNoMoreSockets
+		}
+		w.startServer(socket.sock, socket.laddr.Port(), protoModeTCP)
 	case netdev.IPPROTO_UDP:
 	default:
 		return netdev.ErrProtocolNotSupported
@@ -687,9 +740,10 @@ func (w *wifinina) Accept(sockfd int) (int, netip.AddrPort, error) {
 	w.mu.Lock()
 	defer w.mu.Unlock()
 
-	var client sock
-	var sock = sock(sockfd)
-	var socket = w.sockets[sock]
+	socket, ok := w.sockets[sockfd]
+	if !ok {
+		return -1, netip.AddrPort{}, netdev.ErrInvalidSocketFd
+	}
 
 	switch socket.protocol {
 	case netdev.IPPROTO_TCP:
@@ -697,8 +751,9 @@ func (w *wifinina) Accept(sockfd int) (int, netip.AddrPort, error) {
 		return -1, netip.AddrPort{}, netdev.ErrProtocolNotSupported
 	}
 
+skip:
 	for {
-		// Accept() will be sleeping most of the time, checking for a
+		// Accept() will be sleeping most of the time, checking for
 		// new clients every 1/10 sec.
 		w.mu.Unlock()
 		time.Sleep(100 * time.Millisecond)
@@ -709,48 +764,43 @@ func (w *wifinina) Accept(sockfd int) (int, netip.AddrPort, error) {
 			return -1, netip.AddrPort{}, w.fault
 		}
 
-		// TODO: BUG: Currently, a sock that is 100% busy will always be
-		// TODO: returned by w.accept(sock), starving other socks
-		// TODO: from begin serviced.  Need to figure out how to
-		// TODO: service socks fairly (round-robin?) so no one sock
-		// TODO: can dominate.
-
 		// Check if a client has data
-		client = w.accept(sock)
+		var client sock = w.accept(socket.sock)
 		if client == noSocketAvail {
 			// None ready
 			continue
 		}
 
-		raddr := w.getRemoteData(client)
-
-		// If we've already seen this socket, we can reuse
-		// the socket and return it.  But, only if the socket
-		// is closed.  If it's not closed, we'll just come back
-		// later to reuse it.
-
-		clientSocket, ok := w.sockets[client]
-		if ok {
-			// Wait for client to Close
-			if clientSocket.inuse {
-				continue
+		// If we already have a socket for the client, skip
+		for _, s := range w.sockets {
+			if s.sock == client {
+				continue skip
 			}
-			// Reuse client socket
-			return int(client), raddr, nil
 		}
 
-		// Create new socket for client and return fd
-		w.sockets[client] = newSocket(socket.protocol)
-		return int(client), raddr, nil
+		// Otherwise, create a new socket
+		clientfd := w.newSockfd()
+		if clientfd == -1 {
+			return -1, netip.AddrPort{}, netdev.ErrNoMoreSockets
+		}
+
+		w.sockets[clientfd] = &Socket{
+			protocol:        netdev.IPPROTO_TCP,
+			sock:            client,
+			clientConnected: true,
+		}
+
+		raddr := w.getRemoteData(client)
+
+		return clientfd, raddr, nil
 	}
 }
 
-func (w *wifinina) sockDown(sock sock) bool {
-	var socket = w.sockets[sock]
+func (w *wifinina) sockDown(socket *Socket) bool {
 	if socket.protocol == netdev.IPPROTO_UDP {
 		return false
 	}
-	return w.getClientState(sock) != tcpStateEstablished
+	return w.getClientState(socket.sock) != tcpStateEstablished
 }
 
 func (w *wifinina) sendTCP(sock sock, buf []byte, deadline time.Time) (int, error) {
@@ -778,7 +828,7 @@ func (w *wifinina) sendTCP(sock sock, buf []byte, deadline time.Time) (int, erro
 		}
 
 		// Check if socket went down
-		if w.sockDown(sock) {
+		if w.getClientState(sock) != tcpStateEstablished {
 			return -1, io.EOF
 		}
 
@@ -817,8 +867,10 @@ func (w *wifinina) sendUDP(sock sock, raddr netip.AddrPort, buf []byte, deadline
 }
 
 func (w *wifinina) sendChunk(sockfd int, buf []byte, deadline time.Time) (int, error) {
-	var sock = sock(sockfd)
-	var socket = w.sockets[sock]
+	socket, ok := w.sockets[sockfd]
+	if !ok {
+		return -1, netdev.ErrInvalidSocketFd
+	}
 
 	// Check if we've timed out
 	if !deadline.IsZero() {
@@ -829,9 +881,9 @@ func (w *wifinina) sendChunk(sockfd int, buf []byte, deadline time.Time) (int, e
 
 	switch socket.protocol {
 	case netdev.IPPROTO_TCP, netdev.IPPROTO_TLS:
-		return w.sendTCP(sock, buf, deadline)
+		return w.sendTCP(socket.sock, buf, deadline)
 	case netdev.IPPROTO_UDP:
-		return w.sendUDP(sock, socket.raddr, buf, deadline)
+		return w.sendUDP(socket.sock, socket.raddr, buf, deadline)
 	}
 
 	return -1, netdev.ErrProtocolNotSupported
@@ -876,7 +928,10 @@ func (w *wifinina) Recv(sockfd int, buf []byte, flags int,
 	w.mu.Lock()
 	defer w.mu.Unlock()
 
-	var sock = sock(sockfd)
+	socket, ok := w.sockets[sockfd]
+	if !ok {
+		return -1, netdev.ErrInvalidSocketFd
+	}
 
 	// Limit max read size to chunk large read requests
 	var max = len(buf)
@@ -897,22 +952,22 @@ func (w *wifinina) Recv(sockfd int, buf []byte, flags int,
 		// doesn't return unless there is data, even a single byte, or
 		// on error such as timeout or EOF.
 
-		n := int(w.getDataBuf(sock, buf[:max]))
+		n := int(w.getDataBuf(socket.sock, buf[:max]))
 		if n > 0 {
 			if debugging(debugNetdev) {
 				fmt.Printf("[<--Recv] sockfd: %d, n: %d\r\n",
-					sock, n)
+					sockfd, n)
 			}
 			return n, nil
 		}
 
 		// Check if socket went down
-		if w.sockDown(sock) {
+		if w.sockDown(socket) {
 			// Get any last bytes
-			n = int(w.getDataBuf(sock, buf[:max]))
+			n = int(w.getDataBuf(socket.sock, buf[:max]))
 			if debugging(debugNetdev) {
 				fmt.Printf("[<--Recv] sockfd: %d, n: %d, EOF\r\n",
-					sock, n)
+					sockfd, n)
 			}
 			if n > 0 {
 				return n, io.EOF
@@ -941,34 +996,18 @@ func (w *wifinina) Close(sockfd int) error {
 	w.mu.Lock()
 	defer w.mu.Unlock()
 
-	var sock = sock(sockfd)
-	var socket = w.sockets[sock]
-
-	if !socket.inuse {
-		return nil
+	socket, ok := w.sockets[sockfd]
+	if !ok {
+		return netdev.ErrInvalidSocketFd
 	}
 
-	w.stopClient(sock)
-
-	if socket.protocol == netdev.IPPROTO_UDP {
-		socket.inuse = false
-		return nil
+	if socket.clientConnected {
+		w.stopClient(socket.sock)
 	}
 
-	start := time.Now()
-	for time.Since(start) < 5*time.Second {
+	delete(w.sockets, sockfd)
 
-		if w.getClientState(sock) == tcpStateClosed {
-			socket.inuse = false
-			return nil
-		}
-
-		w.mu.Unlock()
-		time.Sleep(100 * time.Millisecond)
-		w.mu.Lock()
-	}
-
-	return netdev.ErrClosingSocket
+	return nil
 }
 
 func (w *wifinina) SetSockOpt(sockfd int, level int, opt int, value interface{}) error {