chan_iax2: Block unnecessary control frames to/from the wire.

Establishing an IAX2 call between Asterisk v1.4 and v1.8 (or later)
results in an unexpected call disconnect.  The problem happens because
newer values in the enum ast_control_frame_type are not consistent between
the branch versions of Asterisk.

For example:
1) v1.4 calls v1.8 (or later) using IAX2

2) v1.8 answers and sends a connected line update control frame.  (on v1.8
AST_CONTROL_CONNECTED_LINE = 22)

3) v1.4 receives the control frame as an end-of-q (on v1.4
AST_CONTROL_END_OF_Q = 22)

4) v1.4 disconnects the call once the receive queue becomes empty.

Several things are done by this patch to fix the problem and attempt to
prevent it from happening again in the future:

* Added a warning at the definition of enum ast_control_frame_type about
how to add new control frame values.

* Made block sending and receiving control frames that have no reason to
go over the wire.

* Extended the connectedline iax.conf parameter to also include the
redirecting information updates.

* Updated the connectedline iax.conf parameter documentation to include a
notice that the parameter must be "no" when the peer is an Asterisk v1.4
instance.

(closes issue AST-1302)

Review: https://reviewboard.asterisk.org/r/3174/
........

Merged revisions 407678 from http://svn.asterisk.org/svn/asterisk/branches/1.8
........

Merged revisions 407727 from http://svn.asterisk.org/svn/asterisk/branches/11
........

Merged revisions 407729 from http://svn.asterisk.org/svn/asterisk/branches/12


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@407731 65c4cc65-6c06-0410-ace0-fbb531ad65f3

1 files changed, 146 insertions, 13 deletions

diff --git a/channels/chan_iax2.c b/channels/chan_iax2.c
index bb8c9eb5b..abeade87a 100644
--- a/channels/chan_iax2.c
+++ b/channels/chan_iax2.c
@@ -1332,6 +1332,103 @@ static void iax2_lock_owner(int callno)
 	}
 }
 
+/*!
+ * \internal
+ * \brief Check if a control subtype is allowed on the wire.
+ *
+ * \param subtype Control frame subtype to check if allowed to/from the wire.
+ *
+ * \retval non-zero if allowed.
+ */
+static int iax2_is_control_frame_allowed(int subtype)
+{
+	enum ast_control_frame_type control = subtype;
+	int is_allowed;
+
+	/*
+	 * Note: If we compare the enumeration type, which does not have any
+	 * negative constants, the compiler may optimize this code away.
+	 * Therefore, we must perform an integer comparison here.
+	 */
+	if (subtype == -1) {
+		return -1;
+	}
+
+	/* Default to not allowing control frames to pass. */
+	is_allowed = 0;
+
+	/*
+	 * The switch default is not present in order to take advantage
+	 * of the compiler complaining of a missing enum case.
+	 */
+	switch (control) {
+	/*
+	 * These control frames make sense to send/receive across the link.
+	 */
+	case AST_CONTROL_HANGUP:
+	case AST_CONTROL_RING:
+	case AST_CONTROL_RINGING:
+	case AST_CONTROL_ANSWER:
+	case AST_CONTROL_BUSY:
+	case AST_CONTROL_TAKEOFFHOOK:
+	case AST_CONTROL_OFFHOOK:
+	case AST_CONTROL_CONGESTION:
+	case AST_CONTROL_FLASH:
+	case AST_CONTROL_WINK:
+	case AST_CONTROL_OPTION:
+	case AST_CONTROL_RADIO_KEY:
+	case AST_CONTROL_RADIO_UNKEY:
+	case AST_CONTROL_PROGRESS:
+	case AST_CONTROL_PROCEEDING:
+	case AST_CONTROL_HOLD:
+	case AST_CONTROL_UNHOLD:
+	case AST_CONTROL_VIDUPDATE:
+	case AST_CONTROL_CONNECTED_LINE:
+	case AST_CONTROL_REDIRECTING:
+	case AST_CONTROL_T38_PARAMETERS:
+	case AST_CONTROL_AOC:
+	case AST_CONTROL_INCOMPLETE:
+	case AST_CONTROL_MCID:
+		is_allowed = -1;
+		break;
+
+	/*
+	 * These control frames do not make sense to send/receive across the link.
+	 */
+	case _XXX_AST_CONTROL_T38:
+		/* The control value is deprecated in favor of AST_CONTROL_T38_PARAMETERS. */
+	case AST_CONTROL_SRCUPDATE:
+		/* Across an IAX link the source is still the same. */
+	case AST_CONTROL_TRANSFER:
+		/* A success/fail status report from calling ast_transfer() on this machine. */
+	case AST_CONTROL_CC:
+		/* The payload contains pointers that are valid for the sending machine only. */
+	case AST_CONTROL_SRCCHANGE:
+		/* Across an IAX link the source is still the same. */
+	case AST_CONTROL_READ_ACTION:
+		/* The action can only be done by the sending machine. */
+	case AST_CONTROL_END_OF_Q:
+		/* This frame would cause the call to unexpectedly hangup. */
+	case AST_CONTROL_UPDATE_RTP_PEER:
+		/* Only meaningful across a bridge on this machine for direct-media exchange. */
+	case AST_CONTROL_PVT_CAUSE_CODE:
+		/* Intended only for the sending machine's local channel structure. */
+	case AST_CONTROL_STREAM_STOP:
+	case AST_CONTROL_STREAM_SUSPEND:
+	case AST_CONTROL_STREAM_RESTART:
+	case AST_CONTROL_STREAM_REVERSE:
+	case AST_CONTROL_STREAM_FORWARD:
+		/* None of these playback stream control frames should go across the link. */
+	case AST_CONTROL_RECORD_CANCEL:
+	case AST_CONTROL_RECORD_STOP:
+	case AST_CONTROL_RECORD_SUSPEND:
+	case AST_CONTROL_RECORD_MUTE:
+		/* None of these media recording control frames should go across the link. */
+		break;
+	}
+	return is_allowed;
+}
+
 static void mwi_event_cb(void *userdata, struct stasis_subscription *sub, struct stasis_message *msg)
 {
 	/* The MWI subscriptions exist just so the core knows we care about those
@@ -5615,8 +5712,13 @@ static int iax2_indicate(struct ast_channel *c, int condition, const void *data,
 		}
 		break;
 	case AST_CONTROL_CONNECTED_LINE:
-		if (!ast_test_flag64(pvt, IAX_SENDCONNECTEDLINE))
+	case AST_CONTROL_REDIRECTING:
+		if (!ast_test_flag64(pvt, IAX_SENDCONNECTEDLINE)) {
+			/* We are not configured to allow sending these updates. */
+			ast_debug(2, "Callno %u: Config blocked sending control frame %d.\n",
+				callno, condition);
 			goto done;
+		}
 		break;
 	case AST_CONTROL_PVT_CAUSE_CODE:
 		res = -1;
@@ -7557,6 +7659,12 @@ static int __send_command(struct chan_iax2_pvt *i, char type, int command, unsig
 
 static int send_command(struct chan_iax2_pvt *i, char type, int command, unsigned int ts, const unsigned char *data, int datalen, int seqno)
 {
+	if (type == AST_FRAME_CONTROL && !iax2_is_control_frame_allowed(command)) {
+		/* Control frame should not go out on the wire. */
+		ast_debug(2, "Callno %u: Blocked sending control frame %d.\n",
+			i->callno, command);
+		return 0;
+	}
 	return __send_command(i, type, command, ts, data, datalen, seqno, 0, 0, 0);
 }
 
@@ -10417,13 +10525,6 @@ static int socket_process_helper(struct iax2_thread *thread)
 				iaxs[fr->callno]->videoformat = ast_format_to_old_bitfield(&f.subclass.format);
 			}
 		}
-		if (f.frametype == AST_FRAME_CONTROL && iaxs[fr->callno]->owner) {
-			if (f.subclass.integer == AST_CONTROL_BUSY) {
-				ast_channel_hangupcause_set(iaxs[fr->callno]->owner, AST_CAUSE_BUSY);
-			} else if (f.subclass.integer == AST_CONTROL_CONGESTION) {
-				ast_channel_hangupcause_set(iaxs[fr->callno]->owner, AST_CAUSE_CONGESTION);
-			}
-		}
 		if (f.frametype == AST_FRAME_IAX) {
 			AST_SCHED_DEL(sched, iaxs[fr->callno]->initid);
 			/* Handle the IAX pseudo frame itself */
@@ -11607,17 +11708,48 @@ immediatedial:
 		ast_mutex_unlock(&iaxsl[fr->callno]);
 		return 1;
 	}
-	/* Don't allow connected line updates unless we are configured to */
-	if (f.frametype == AST_FRAME_CONTROL && f.subclass.integer == AST_CONTROL_CONNECTED_LINE) {
-		struct ast_party_connected_line connected;
 
-		if (!ast_test_flag64(iaxs[fr->callno], IAX_RECVCONNECTEDLINE)) {
+	if (f.frametype == AST_FRAME_CONTROL) {
+		if (!iax2_is_control_frame_allowed(f.subclass.integer)) {
+			/* Control frame not allowed to come from the wire. */
+			ast_debug(2, "Callno %u: Blocked receiving control frame %d.\n",
+				fr->callno, f.subclass.integer);
 			ast_variables_destroy(ies.vars);
 			ast_mutex_unlock(&iaxsl[fr->callno]);
 			return 1;
 		}
+		if (f.subclass.integer == AST_CONTROL_CONNECTED_LINE
+			|| f.subclass.integer == AST_CONTROL_REDIRECTING) {
+			if (!ast_test_flag64(iaxs[fr->callno], IAX_RECVCONNECTEDLINE)) {
+				/* We are not configured to allow receiving these updates. */
+				ast_debug(2, "Callno %u: Config blocked receiving control frame %d.\n",
+					fr->callno, f.subclass.integer);
+				ast_variables_destroy(ies.vars);
+				ast_mutex_unlock(&iaxsl[fr->callno]);
+				return 1;
+			}
+		}
+
+		iax2_lock_owner(fr->callno);
+		if (iaxs[fr->callno] && iaxs[fr->callno]->owner) {
+			if (f.subclass.integer == AST_CONTROL_BUSY) {
+				ast_channel_hangupcause_set(iaxs[fr->callno]->owner, AST_CAUSE_BUSY);
+			} else if (f.subclass.integer == AST_CONTROL_CONGESTION) {
+				ast_channel_hangupcause_set(iaxs[fr->callno]->owner, AST_CAUSE_CONGESTION);
+			}
+			ast_channel_unlock(iaxs[fr->callno]->owner);
+		}
+	}
+
+	if (f.frametype == AST_FRAME_CONTROL
+		&& f.subclass.integer == AST_CONTROL_CONNECTED_LINE) {
+		struct ast_party_connected_line connected;
 
-		/* Initialize defaults */
+		/*
+		 * Process a received connected line update.
+		 *
+		 * Initialize defaults.
+		 */
 		ast_party_connected_line_init(&connected);
 		connected.id.number.presentation = iaxs[fr->callno]->calling_pres;
 		connected.id.name.presentation = iaxs[fr->callno]->calling_pres;
@@ -11640,6 +11772,7 @@ immediatedial:
 		}
 		ast_party_connected_line_free(&connected);
 	}
+
 	/* Common things */
 	f.src = "IAX2";
 	f.mallocd = 0;