Allow non blocking UDP put_packet in C++.

- Add blocking mode option to PacketPeerUDP.
- put_packet returns ERR_UNAVAILABLE when operation would block.
- ENet module uses non-blocking UDP.

(cherry picked from commit 5f681d0b0f)

core/io/packet_peer_udp.cpp

@@ -32,6 +32,11 @@
 
 PacketPeerUDP *(*PacketPeerUDP::_create)() = NULL;
 
+void PacketPeerUDP::set_blocking_mode(bool p_enable) {
+
+	blocking = p_enable;
+}
+
 String PacketPeerUDP::_get_packet_ip() const {
 
 	return get_packet_address();
@@ -79,4 +84,6 @@ PacketPeerUDP *PacketPeerUDP::create() {
 }
 
 PacketPeerUDP::PacketPeerUDP() {
+
+	blocking = true;
 }

core/io/packet_peer_udp.h

@@ -37,6 +37,8 @@ class PacketPeerUDP : public PacketPeer {
 	OBJ_TYPE(PacketPeerUDP, PacketPeer);
 
 protected:
+	bool blocking;
+
 	static PacketPeerUDP *(*_create)();
 	static void _bind_methods();
 
@@ -45,6 +47,8 @@ protected:
 	Error _set_send_address(const String &p_address, int p_port);
 
 public:
+	void set_blocking_mode(bool p_enable);
+
 	virtual Error listen(int p_port, IP_Address p_bind_address = IP_Address("*"), int p_recv_buffer_size = 65536) = 0;
 	virtual void close() = 0;
 	virtual Error wait() = 0;

drivers/unix/packet_peer_udp_posix.cpp

@@ -108,10 +108,14 @@ Error PacketPeerUDPPosix::put_packet(const uint8_t *p_buffer, int p_buffer_size)
 	errno = 0;
 	int err;
 
+	_set_sock_blocking(blocking);
+
 	while ((err = sendto(sock, p_buffer, p_buffer_size, 0, (struct sockaddr *)&addr, addr_size)) != p_buffer_size) {
 
 		if (errno != EAGAIN) {
 			return FAILED;
+		} else if (!blocking) {
+			return ERR_UNAVAILABLE;
 		}
 	}
 
@@ -174,10 +178,12 @@ Error PacketPeerUDPPosix::_poll(bool p_wait) {
 		return FAILED;
 	}
 
+	_set_sock_blocking(p_wait);
+
 	struct sockaddr_storage from = { 0 };
 	socklen_t len = sizeof(struct sockaddr_storage);
 	int ret;
-	while ((ret = recvfrom(sockfd, recv_buffer, MIN((int)sizeof(recv_buffer), MAX(rb.space_left() - 24, 0)), p_wait ? 0 : MSG_DONTWAIT, (struct sockaddr *)&from, &len)) > 0) {
+	while ((ret = recvfrom(sockfd, recv_buffer, MIN((int)sizeof(recv_buffer), MAX(rb.space_left() - 24, 0)), 0, (struct sockaddr *)&from, &len)) > 0) {
 
 		uint32_t port = 0;
 
@@ -244,9 +250,35 @@ int PacketPeerUDPPosix::_get_socket() {
 
 	sockfd = _socket_create(sock_type, SOCK_DGRAM, IPPROTO_UDP);
 
+	if (sockfd != -1)
+		_set_sock_blocking(false);
+
 	return sockfd;
 }
 
+void PacketPeerUDPPosix::_set_sock_blocking(bool p_blocking) {
+
+	if (sock_blocking == p_blocking)
+		return;
+
+	sock_blocking = p_blocking;
+
+#ifndef NO_FCNTL
+	int opts = fcntl(sockfd, F_GETFL);
+	int ret = 0;
+	if (sock_blocking)
+		ret = fcntl(sockfd, F_SETFL, opts & ~O_NONBLOCK);
+	else
+		ret = fcntl(sockfd, F_SETFL, opts | O_NONBLOCK);
+	if (ret == -1)
+		perror("setting non-block mode");
+#else
+	int bval = sock_blocking ? 0 : 1;
+	if (ioctl(sockfd, FIONBIO, &bval) == -1)
+		perror("setting non-block mode");
+#endif
+}
+
 void PacketPeerUDPPosix::set_send_address(const IP_Address &p_address, int p_port) {
 
 	peer_addr = p_address;
@@ -265,6 +297,8 @@ void PacketPeerUDPPosix::make_default() {
 
 PacketPeerUDPPosix::PacketPeerUDPPosix() {
 
+	blocking = true;
+	sock_blocking = true;
 	sockfd = -1;
 	packet_port = 0;
 	queue_count = 0;

drivers/unix/packet_peer_udp_posix.h

@@ -48,6 +48,7 @@ class PacketPeerUDPPosix : public PacketPeerUDP {
 	mutable int packet_port;
 	mutable int queue_count;
 	int sockfd;
+	bool sock_blocking;
 	IP::Type sock_type;
 
 	IP_Address peer_addr;
@@ -56,6 +57,7 @@ class PacketPeerUDPPosix : public PacketPeerUDP {
 	_FORCE_INLINE_ int _get_socket();
 
 	static PacketPeerUDP *_create();
+	void _set_sock_blocking(bool p_blocking);
 	virtual Error _poll(bool p_block);
 
 public:

platform/windows/packet_peer_udp_winsock.cpp

@@ -83,7 +83,7 @@ Error PacketPeerUDPWinsock::put_packet(const uint8_t *p_buffer, int p_buffer_siz
 	struct sockaddr_storage addr;
 	size_t addr_size = _set_sockaddr(&addr, peer_addr, peer_port, sock_type);
 
-	_set_blocking(true);
+	_set_sock_blocking(blocking);
 
 	errno = 0;
 	int err;
@@ -91,7 +91,9 @@ Error PacketPeerUDPWinsock::put_packet(const uint8_t *p_buffer, int p_buffer_siz
 
 		if (WSAGetLastError() != WSAEWOULDBLOCK) {
 			return FAILED;
-		};
+		} else if (!blocking) {
+			return ERR_UNAVAILABLE;
+		}
 	}
 
 	return OK;
@@ -102,15 +104,13 @@ int PacketPeerUDPWinsock::get_max_packet_size() const {
 	return 512; // uhm maybe not
 }
 
-void PacketPeerUDPWinsock::_set_blocking(bool p_blocking) {
-	//am no windows expert
-	//hope this is the right thing
+void PacketPeerUDPWinsock::_set_sock_blocking(bool p_blocking) {
 
-	if (blocking == p_blocking)
+	if (sock_blocking == p_blocking)
 		return;
 
-	blocking = p_blocking;
-	unsigned long par = blocking ? 0 : 1;
+	sock_blocking = p_blocking;
+	unsigned long par = sock_blocking ? 0 : 1;
 	if (ioctlsocket(sockfd, FIONBIO, &par)) {
 		perror("setting non-block mode");
 		//close();
@@ -140,8 +140,6 @@ Error PacketPeerUDPWinsock::listen(int p_port, IP_Address p_bind_address, int p_
 		return ERR_UNAVAILABLE;
 	}
 
-	blocking = true;
-
 	printf("UDP Connection listening on port %i\n", p_port);
 	rb.resize(nearest_shift(p_recv_buffer_size));
 	return OK;
@@ -167,7 +165,7 @@ Error PacketPeerUDPWinsock::_poll(bool p_wait) {
 		return FAILED;
 	}
 
-	_set_blocking(p_wait);
+	_set_sock_blocking(p_wait);
 
 	struct sockaddr_storage from = { 0 };
 	int len = sizeof(struct sockaddr_storage);
@@ -253,6 +251,9 @@ int PacketPeerUDPWinsock::_get_socket() {
 
 	sockfd = _socket_create(sock_type, SOCK_DGRAM, IPPROTO_UDP);
 
+	if (sockfd != -1)
+		_set_sock_blocking(false);
+
 	return sockfd;
 }
 
@@ -274,6 +275,8 @@ PacketPeerUDP *PacketPeerUDPWinsock::_create() {
 
 PacketPeerUDPWinsock::PacketPeerUDPWinsock() {
 
+	blocking = true;
+	sock_blocking = true;
 	sockfd = -1;
 	packet_port = 0;
 	queue_count = 0;

platform/windows/packet_peer_udp_winsock.h

@@ -46,6 +46,7 @@ class PacketPeerUDPWinsock : public PacketPeerUDP {
 	mutable int packet_port;
 	mutable int queue_count;
 	int sockfd;
+	bool sock_blocking;
 	IP::Type sock_type;
 
 	IP_Address peer_addr;
@@ -55,8 +56,7 @@ class PacketPeerUDPWinsock : public PacketPeerUDP {
 
 	static PacketPeerUDP *_create();
 
-	bool blocking;
-	void _set_blocking(bool p_blocking);
+	void _set_sock_blocking(bool p_blocking);
 
 	Error _poll(bool p_wait);