From 48eb7da9d2e95b4f73983b4cc7e932227f7eaa70 Mon Sep 17 00:00:00 2001
From: Martin Lang <Martin.Lang@rwth-aachen.de>
Date: Tue, 8 Dec 2020 22:43:28 +0100
Subject: [PATCH] Callfork: Inconsistent group progression

Callforks support three types of call legs:
- regular
- auxiliar
- persistent

These different types change the behavior of how groups progress.
If no regular calls are left in a group, the fork progresses
immediately to the next group, drops all auxiliar children and keeps
the persistent ones. However, there is inconsistent behavior depending
on whether the creation of a call leg is successful or not.

Currently, the check if there are regular calls left in the current
group is only implemented in lostSlave(). So, if you have a group
with one persistent member (ringback) and one regular member, you can
observe different behavior in the case that routing for the member fails
and in the situation that the call is started but then rejected on a remote
end.

If the regular member is remote, forkSlave() will succeed and initiate a sip
call. The callContinue() function will return. Then, the sip call might fail
because the remote member is offline. Now lostSlave() is called, the module
detects that this was the last regular member and immediately progresses
to the next group.

If the regular member, however, is local, the routing knows that the member
is offline and fails. In this case forkSlave() will fail. Nonetheless, forks = 1
because creation of the persistent slave (ringback) was succesful. Consequently,
the call continues but it is ringing nowhere. In case that the next group is timed,
the caller will just hear the ringback for a while. If the next group isn't timed
but expected to progress if all calls in the current group have failed, the call
is actually stuck and the caller will hear the ringback indefinately while it is
nowhere ringing.

This patch fixes this behavior by checking if regular call legs are active before
returning from callContinue(). If this isn't the case, it will trigger progression
to the next group immediately.
---
 modules/callfork.cpp | 27 +++++++++++++++++++++++++--
 1 file changed, 25 insertions(+), 2 deletions(-)

diff --git a/modules/callfork.cpp b/modules/callfork.cpp
index 8df84fef..eb414bff 100644
--- a/modules/callfork.cpp
+++ b/modules/callfork.cpp
@@ -366,6 +366,7 @@ bool ForkMaster::startCalling(Message& msg)
     m_rtpForward = msg.getBoolValue("rtp_forward");
     m_rtpStrict = msg.getBoolValue("rtpstrict");
     if (!callContinue()) {
+	Debug(&__plugin,DebugNote,"Fork '%s' startCalling() failed. No successful peers", id().c_str());
 	const char* err = m_exec->getValue("reason");
 	if (err)
 	    msg.setParam("reason",err);
@@ -430,8 +431,30 @@ bool ForkMaster::callContinue()
 			getPeerId().c_str(),dest->c_str(),this);
 	    }
 	    dest->destruct();
-	    if (forks)
-		break;
+	    if (forks) {
+		unsigned int regulars = 0;
+		unsigned int auxiliars = 0;
+		unsigned int persistents = 0;
+		for (ObjList* l = m_slaves.skipNull(); l; l = l->skipNext()) {
+		    switch (static_cast<const ForkSlave*>(l->get())->type()) {
+			case ForkSlave::Auxiliar:
+			    auxiliars++;
+			    break;
+			case ForkSlave::Persistent:
+			    persistents++;
+			    break;
+			default:
+			    regulars++;
+			    break;
+		    }
+		}
+		if (regulars > 0) {
+		    break;
+		} else {
+		    clear(true);
+		    forks = persistents;
+		}
+	    }
 	    m_timer = 0;
 	    m_timerDrop = false;
 	    continue;