Add utility functions for TCP sockets

src/common.c

@@ -397,6 +397,74 @@ check_topdomain(char *str, char **errormsg)
 	return 0;
 }
 
+int
+socket_set_blocking(int fd, int blocking)
+{
+	/* Set non-blocking socket mode */
+#ifdef WINDOWS32
+	if (ioctlsocket(fd, FIONBIO, &blocking) != 0) {
+		return WSAGetLastError();
+	}
+#else
+	int flags;
+	if ((flags = fcntl(fd, F_GETFL, 0)) < 0) {
+	    return flags;
+	}
+
+	if (fcntl(fd, F_SETFL, blocking ? (flags | O_NONBLOCK) : (flags & (~O_NONBLOCK))) == -1)
+		return errno;
+
+#endif
+	return 0;
+}
+
+int
+open_tcp_nonblocking(struct sockaddr_storage *addr, char **errormsg)
+/* Open TCP connection to given address without blocking */
+{
+	int fd, ret;
+	if ((fd = socket(addr->ss_family, SOCK_STREAM, IPPROTO_TCP)) == -1) {
+		if (errormsg)
+			*errormsg = strerror(errno);
+		return -1;
+	}
+
+	if ((ret = socket_set_blocking(fd, 0)) != 0) {
+		if (errormsg)
+			*errormsg = strerror(ret);
+		return -1;
+	}
+
+	if ((ret = connect(fd, (struct sockaddr *)addr, sizeof(struct sockaddr_storage)))
+		== -1 && errno != EINPROGRESS) {
+		if (errormsg)
+			*errormsg = strerror(errno);
+		return -1;
+	}
+
+	return fd;
+}
+
+int
+check_tcp_status(int fd, char **error)
+/* checks connected status of given socket.
+ * returns error code. 0 if connected or EINPROGRESS if connecting */
+{
+	int errornum = 0;
+	socklen_t len = sizeof(int);
+
+	if (getsockopt(fd, SOL_SOCKET, SO_ERROR, &errornum, &len) != 0) {
+		if (error)
+			*error = "getsockopt failed.";
+		return -1;
+	}
+
+	if (error)
+		*error = strerror(errornum);
+
+	return errornum;
+}
+
 #if defined(WINDOWS32) || defined(ANDROID)
 #ifndef ANDROID
 int

src/common.h

@@ -161,6 +161,9 @@ int open_dns_opt(struct sockaddr_storage *sockaddr, size_t sockaddr_len, int v6o
 int open_dns_from_host(char *host, int port, int addr_family, int flags);
 void close_dns(int);
 
+int open_tcp_nonblocking(struct sockaddr_storage *addr, char **error);
+int check_tcp_status(int fd, char **error);
+
 void do_chroot(char *);
 void do_setcon(char *);
 void do_detach();