Initialize file descriptors for dummy channels to -1.

Dummy channels usually aren't read from, but functions like SHELL and CURL
use autoservice on the channel.

(closes issue ASTERISK-20283)
Reported by: Gareth Palmer
Patches:
      svn-371580.patch (license #5169) patch uploaded by Gareth Palmer (modified)
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Merged revisions 371888 from http://svn.asterisk.org/svn/asterisk/branches/1.8
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Merged revisions 371890 from http://svn.asterisk.org/svn/asterisk/branches/10
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Merged revisions 371891 from http://svn.asterisk.org/svn/asterisk/branches/11


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@371892 65c4cc65-6c06-0410-ace0-fbb531ad65f3

main/channel.c

@@ -1208,6 +1208,18 @@ struct ast_channel *ast_dummy_channel_alloc(void)
 	ast_pbx_hangup_handler_init(tmp);
 	AST_LIST_HEAD_INIT_NOLOCK(ast_channel_datastores(tmp));
 
+	/*
+	 * Init file descriptors to unopened state just in case
+	 * autoservice is called on the channel or something tries to
+	 * read a frame from it.
+	 */
+	ast_channel_timingfd_set(tmp, -1);
+	ast_channel_internal_alertpipe_clear(tmp);
+	ast_channel_internal_fd_clear_all(tmp);
+#ifdef HAVE_EPOLL
+	ast_channel_epfd(tmp) = -1;
+#endif
+
 	headp = ast_channel_varshead(tmp);
 	AST_LIST_HEAD_INIT_NOLOCK(headp);