utils: Wrap socket() and pipe() to reduce syscalls

Some platforms provide an implementation of socket() and pipe2() that allow the
caller to specify that the resulting file descriptors should be non-blocking.

Using these allows us to potentially elide 3 calls into 1 by avoiding extraneous
calls to fcntl() to set the O_NONBLOCK flag afterwards.

In passing, change ast_alertpipe_init() to use pipe2() directly instead of the
wrapper if it is available.

Change-Id: I3ebe654fb549587537161506c6c950f4ab298bb0

include/asterisk/autoconfig.h.in

@@ -609,6 +609,9 @@
 /* Define to indicate presence of the pg_encoding_to_char API. */
 #undef HAVE_PGSQL_pg_encoding_to_char
 
+/* Define to 1 if you have the `pipe2' function. */
+#undef HAVE_PIPE2
+
 /* Define if your system has the PJPROJECT libraries. */
 #undef HAVE_PJPROJECT
 
@@ -877,6 +880,9 @@
 /* Define to 1 if you have the `socket' function. */
 #undef HAVE_SOCKET
 
+/* Define to 1 if your socket() implementation can accept SOCK_NONBLOCK. */
+#undef HAVE_SOCK_NONBLOCK
+
 /* Define to 1 if your system has soxmix application. */
 #undef HAVE_SOXMIX
 

include/asterisk/utils.h

@@ -913,6 +913,40 @@ enum ast_fd_flag_operation {
 int __ast_fd_set_flags(int fd, int flags, enum ast_fd_flag_operation op,
 	const char *file, int lineno, const char *function);
 
+/*!
+ * \brief Create a non-blocking socket
+ * \since 13.25
+ *
+ * Wrapper around socket(2) that sets the O_NONBLOCK flag on the resulting
+ * socket.
+ *
+ * \details
+ * For parameter and return information, see the man page for
+ * socket(2).
+ */
+#ifdef HAVE_SOCK_NONBLOCK
+# define ast_socket_nonblock(domain, type, protocol) socket((domain), (type) | SOCK_NONBLOCK, (protocol))
+#else
+int ast_socket_nonblock(int domain, int type, int protocol);
+#endif
+
+/*!
+ * \brief Create a non-blocking pipe
+ * \since 13.25
+ *
+ * Wrapper around pipe(2) that sets the O_NONBLOCK flag on the resulting
+ * file descriptors.
+ *
+ * \details
+ * For parameter and return information, see the man page for
+ * pipe(2).
+ */
+#ifdef HAVE_PIPE2
+# define ast_pipe_nonblock(filedes) pipe2((filedes), O_NONBLOCK)
+#else
+int ast_pipe_nonblock(int filedes[2]);
+#endif
+
 /*!
  * \brief Set the current thread's user interface status.
  *