ast_write() ignores ast_audiohook_write() results

In ast_write(), if a channel has a list of audiohooks, those
lists are written to and the resulting frame is what ast_write()
should continue with.  The problem was the returned audiohook frame
was not being handled at all, and the original frame passed
into it did not contain the mixed audio, so essentially audio
was being lost.  One result of this was chan_spy's whisper
mode no longer worked.  To complicate the issue, frames
passed into ast_write may either be a single frame, or a list
of frames.  So, as the list of frames is processed in the
audiohook_write, the returned frames had to be added to a new
list.

(closes issue #15660)
Reported by: corruptor
Tested by: dvossel



git-svn-id: https://origsvn.digium.com/svn/asterisk/branches/1.4@214194 65c4cc65-6c06-0410-ace0-fbb531ad65f3

main/channel.c

@@ -2933,13 +2933,36 @@ int ast_write(struct ast_channel *chan, struct ast_frame *fr)
 		}
 
 		if (chan->audiohooks) {
-			struct ast_frame *new_frame, *cur;
+			struct ast_frame *prev = NULL, *new_frame, *cur, *dup;
 
+			/* Since ast_audiohook_write may return a new frame, and the cur frame is
+			 * an item in a list of frames, create a new list adding each cur frame back to it
+			 * regardless if the cur frame changes or not. */
 			for (cur = f; cur; cur = AST_LIST_NEXT(cur, frame_list)) {
 				new_frame = ast_audiohook_write_list(chan, chan->audiohooks, AST_AUDIOHOOK_DIRECTION_WRITE, cur);
+
+				/* if this frame is different than cur, preserve the end of the list,
+				 * free the old frames, and set cur to be the new frame */
 				if (new_frame != cur) {
-					ast_frfree(new_frame);
+					/* doing an ast_frisolate here seems silly, but we are not guaranteed the new_frame
+					 * isn't part of local storage, meaning if ast_audiohook_write is called multiple
+					 * times it may override the previous frame we got from it unless we dup it */
+					if ((dup = ast_frisolate(new_frame))) {
+						AST_LIST_NEXT(dup, frame_list) = AST_LIST_NEXT(cur, frame_list);
+						ast_frfree(new_frame);
+						ast_frfree(cur);
+						cur = dup;
+					}
+				}
+
+				/* now, regardless if cur is new or not, add it to the new list,
+				 * if the new list has not started, cur will become the first item. */
+				if (prev) {
+					AST_LIST_NEXT(prev, frame_list) = cur;
+				} else {
+					f = cur; /* set f to be the beginning of our new list */
 				}
+				prev = cur;
 			}
 		}