Use select call for socket waiting (Fixes guanzhi#1788)

It eliminates the (perhaps non-blocking version of) speedup loop by using a
generic `select` call which should be available both to POSIX and Winsock2.

include/gmssl/socket.h

@@ -36,7 +36,6 @@ typedef int tls_socklen_t;
 #define tls_socket_send(sock,buf,len,flags)	send(sock,buf,(int)(len),flags)
 #define tls_socket_recv(sock,buf,len,flags)	recv(sock,buf,(int)(len),flags)
 #define tls_socket_close(sock)			closesocket(sock)
-#define tls_socket_wait()			Sleep(1)
 
 #else
 
@@ -45,6 +44,7 @@ typedef int tls_socklen_t;
 #include <arpa/inet.h>
 #include <sys/types.h>
 #include <sys/socket.h>
+#include <sys/select.h>
 #include <netinet/in.h>
 #include <unistd.h>
 
@@ -56,7 +56,6 @@ typedef socklen_t tls_socklen_t;
 #define tls_socket_send(sock,buf,len,flags)	send(sock,buf,len,flags)
 #define tls_socket_recv(sock,buf,len,flags)	recv(sock,buf,len,flags)
 #define tls_socket_close(sock)			close(sock)
-#define tls_socket_wait()			usleep(1000)
 
 #endif
 
@@ -67,7 +66,8 @@ int tls_socket_connect(tls_socket_t sock, const struct sockaddr_in *addr);
 int tls_socket_bind(tls_socket_t sock, const struct sockaddr_in *addr);
 int tls_socket_listen(tls_socket_t sock, int backlog);
 int tls_socket_accept(tls_socket_t sock, struct sockaddr_in *addr, tls_socket_t *conn_sock);
-
+int tls_socket_wait_recv(tls_socket_t sock);
+int tls_socket_wait_send(tls_socket_t sock);
 
 #ifdef __cplusplus
 }

src/socket.c

@@ -168,3 +168,21 @@ int tls_socket_accept(tls_socket_t sock, struct sockaddr_in *addr, tls_socket_t
 	return 1;
 }
 #endif
+
+int tls_socket_wait_recv(tls_socket_t sock)
+{
+	fd_set readfds;
+	FD_ZERO(&readfds);
+	FD_SET(sock, &readfds);
+
+	return select(sock+1, &readfds, NULL, NULL, NULL);
+}
+
+int tls_socket_wait_send(tls_socket_t sock)
+{
+	fd_set writefds;
+	FD_ZERO(&writefds);
+	FD_SET(sock, &writefds);
+
+	return select(sock+1, NULL, &writefds, NULL, NULL);
+}

src/tls.c

@@ -1476,16 +1476,14 @@ int tls_record_send(const uint8_t *record, size_t recordlen, tls_socket_t sock)
 			recordlen -= n;
 
 		} else if (n == 0) {
-			if (errno == EAGAIN || errno == EWOULDBLOCK) {
-				tls_socket_wait();
-			} else {
+			if ((errno != EAGAIN && errno != EWOULDBLOCK)
+			    || tls_socket_wait_send(sock)) {
 				error_puts("TCP connection closed");
 				return 0;
 			}
 		} else {
-			if (errno == EAGAIN || errno == EWOULDBLOCK) {
-				tls_socket_wait();
-			} else {
+			if ((errno != EAGAIN && errno != EWOULDBLOCK)
+			    || tls_socket_wait_send(sock)) {
 				error_print();
 				return -1;
 			}
@@ -1514,12 +1512,17 @@ int tls_record_recv(uint8_t *record, size_t *recordlen, tls_socket_t sock)
 				if (len == 5) {
 					return -EAGAIN;
 				}
-				tls_socket_wait();
 			} else {
 				perror("recv");
 				error_print();
 				return -1;
 			}
+
+			if (tls_socket_wait_recv(sock)) {
+				perror("recv");
+				error_print();
+				return -1;
+			}
 		}
 	}
 	if (!tls_record_type_name(tls_record_type(record))) {
@@ -1548,9 +1551,8 @@ int tls_record_recv(uint8_t *record, size_t *recordlen, tls_socket_t sock)
 			*recordlen = 0;
 			return 0;
 		} else {
-			if (errno == EAGAIN || errno == EWOULDBLOCK) {
-				tls_socket_wait();
-			} else {
+			if ((errno != EAGAIN && errno != EWOULDBLOCK)
+			    || tls_socket_wait_recv(sock)) {
 				perror("recv");
 				error_print();
 				return -1;