MT#55283 trigger rekernel for SSRC-less streams

If a stream has been pushed to the kernel from anything other than RTP,
even though RTP is expected, we get a forwarding entries without any
SSRCs. This is valid, but once actual RTP is received, it needs to be
passed on to user space, so that SSRC contexts can be set up.

Possible fix for #1855

Change-Id: I51b82d3cf79cf66780fdde154bebe56e0f43174b

kernel-module/xt_RTPENGINE.c

@@ -6374,7 +6374,7 @@ static unsigned int rtpengine46(struct sk_buff *skb, struct sk_buff *oskb,
 		// Look for matching SSRC index if any SSRC were given
 		ssrc_idx = target_find_ssrc(g, rtp.rtp_header->ssrc);
 		errstr = "SSRC mismatch";
-		if (ssrc_idx == -2)
+		if (ssrc_idx == -2 || (ssrc_idx == -1 && g->target.rtp))
 			goto out_error;
 
 		pkt_idx = rtp_packet_index(&g->decrypt_rtp, &g->target.decrypt, rtp.rtp_header, ssrc_idx,