document the support for running a server on TCP/TLS and

opening an SSL socket.

We are almost ready to make this code available to other modules.



git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@48073 65c4cc65-6c06-0410-ace0-fbb531ad65f3

main/http.c

@@ -58,13 +58,28 @@ ASTERISK_FILE_VERSION(__FILE__, "$Revision$")
 #define DEFAULT_PREFIX "/asterisk"
 
 /*!
- * In order to have SSL support, we need the openssl libraries.
+ * In order to have TLS/SSL support, we need the openssl libraries.
  * Still we can decide whether or not to use them by commenting
  * in or out the DO_SSL macro.
+ * TLS/SSL support is basically implemented by reading from a config file
+ * (currently http.conf) the names of the certificate and cipher to use,
+ * and then run ssl_setup() to create an appropriate SSL_CTX (ssl_ctx)
+ * If we support multiple domains, presumably we need to read multiple
+ * certificates.
+ * When we are requested to open a TLS socket, we run make_file_from_fd()
+ * on the socket, to do the necessary setup. At the moment the context's name
+ * is hardwired in the function, but we can certainly make it into an extra
+ * parameter to the function.
+ *
  * We declare most of ssl support variables unconditionally,
  * because their number is small and this simplifies the code.
- * XXX this eventually goes into a generic header file.
+ *
+ * NOTE: the ssl-support variables (ssl_ctx, do_ssl, certfile, cipher)
+ * and their setup should be moved to a more central place, e.g. asterisk.conf
+ * and the source files that processes it. Similarly, ssl_setup() should
+ * be run earlier in the startup process so modules have it available.
  */
+
 #if defined(HAVE_OPENSSL) && (defined(HAVE_FUNOPEN) || defined(HAVE_FOPENCOOKIE))
 #define	DO_SSL	/* comment in/out if you want to support ssl */
 #endif
@@ -73,6 +88,8 @@ ASTERISK_FILE_VERSION(__FILE__, "$Revision$")
 #include <openssl/ssl.h>
 #include <openssl/err.h>
 static SSL_CTX* ssl_ctx;
+#else
+typedef struct {} SSL;	/* so we can define a pointer to it */
 #endif /* DO_SSL */
 
 /* SSL support */
@@ -81,16 +98,44 @@ static int do_ssl;
 static char *certfile;
 static char *cipher;
 
+/*!
+ * The following code implements a generic mechanism for starting
+ * services on a TCP or TLS socket.
+ * The service is configured in the struct server_args, and
+ * then started by calling server_start(desc) on the descriptor.
+ * server_start() first verifies if an instance of the service is active,
+ * and in case shuts it down. Then, if the service must be started, creates
+ * a socket and a thread in charge of doing the accept().
+ *
+ * The body of the thread is desc->accept_fn(desc), which the user can define
+ * freely. We supply a sample implementation, server_root(), structured as an
+ * infinite loop. At the beginning of each iteration it runs periodic_fn()
+ * if defined (e.g. to perform some cleanup etc.) then issues a poll()
+ * or equivalent with a timeout of 'poll_timeout' milliseconds, and if the
+ * following accept() is successful it creates a thread in charge of
+ * running the session, whose body is desc->worker_fn(). The argument of
+ * worker_fn() is a struct server_instance, which contains the address
+ * of the other party, a pointer to desc, the file descriptors (fd) on which
+ * we can do a select/poll (but NOT IO/, and a FILE * on which we can do I/O.
+ * We have both because we want to support plain and SSL sockets, and
+ * going through a FILE * lets us provide the encryption/decryption
+ * on the stream without using an auxiliary thread.
+ *
+ * NOTE: in order to let other parts of asterisk use these services,
+ * we need to do the following:
+ *    + move struct server_instance and struct server_args to
+ *	a common header file, together with prototypes for
+ *	server_start() and server_root().
+ *    +
+ */
+ 
 /*!
  * describes a server instance
  */
 struct server_instance {
 	FILE *f;	/* fopen/funopen result */
 	int fd;		/* the socket returned by accept() */
-	int is_ssl;	/* is this an ssl session ? */
-#ifdef DO_SSL
 	SSL *ssl;	/* ssl state */
-#endif
 	struct sockaddr_in requestor;
 	struct server_args *parent;
 };
@@ -103,13 +148,15 @@ struct server_args {
 	struct sockaddr_in oldsin;
 	int is_ssl;		/* is this an SSL accept ? */
 	int accept_fd;
+	int poll_timeout;
 	pthread_t master;
 	void *(*accept_fn)(void *);	/* the function in charge of doing the accept */
+	void (*periodic_fn)(void *);	/* something we may want to run before after select on the accept socket */
 	void *(*worker_fn)(void *);	/* the function in charge of doing the actual work */
 	const char *name;
 };
 
-static void *http_root(void *arg);
+static void *server_root(void *arg);
 static void *httpd_helper_thread(void *arg);
 
 /*!
@@ -120,7 +167,7 @@ static struct server_args http_desc = {
 	.master = AST_PTHREADT_NULL,
 	.is_ssl = 0,
 	.name = "http server",
-	.accept_fn = http_root,
+	.accept_fn = server_root,
 	.worker_fn = httpd_helper_thread,
 };
 
@@ -129,7 +176,7 @@ static struct server_args https_desc = {
 	.master = AST_PTHREADT_NULL,
 	.is_ssl = 1,
 	.name = "https server",
-	.accept_fn = http_root,
+	.accept_fn = server_root,
 	.worker_fn = httpd_helper_thread,
 };
 
@@ -496,7 +543,7 @@ static void *make_file_from_fd(void *data)
 	/*
 	 * open a FILE * as appropriate.
 	 */
-	if (!ser->is_ssl)
+	if (!ser->parent->is_ssl)
 		ser->f = fdopen(ser->fd, "w+");
 #ifdef DO_SSL
 	else if ( (ser->ssl = SSL_new(ssl_ctx)) ) {
@@ -656,7 +703,7 @@ done:
 	return NULL;
 }
 
-static void *http_root(void *data)
+static void *server_root(void *data)
 {
 	struct server_args *desc = data;
 	int fd;
@@ -667,9 +714,13 @@ static void *http_root(void *data)
 	pthread_attr_t attr;
 	
 	for (;;) {
-		int flags;
+		int i, flags;
 
-		ast_wait_for_input(desc->accept_fd, -1);
+		if (desc->periodic_fn)
+			desc->periodic_fn(desc);
+		i = ast_wait_for_input(desc->accept_fd, desc->poll_timeout);
+		if (i <= 0)
+			continue;
 		sinlen = sizeof(sin);
 		fd = accept(desc->accept_fd, (struct sockaddr *)&sin, &sinlen);
 		if (fd < 0) {
@@ -686,7 +737,6 @@ static void *http_root(void *data)
 		flags = fcntl(fd, F_GETFL);
 		fcntl(fd, F_SETFL, flags & ~O_NONBLOCK);
 		ser->fd = fd;
-		ser->is_ssl = desc->is_ssl;
 		ser->parent = desc;
 		memcpy(&ser->requestor, &sin, sizeof(ser->requestor));