MT#55283 fix padding/SRTP order

The packet must be decrypted first before RTP padding can be considered,
as the padding count is part of the encrypted payload as well.

Change-Id: I6aecff636efd420401856bb8110b3d784f989179
(cherry picked from commit 9e09cf3c40)

daemon/media_socket.c

@@ -1866,8 +1866,6 @@ static void media_packet_rtp_in(struct packet_handler_ctx *phc)
 	bool unkern = false;
 
 	if (G_LIKELY(!phc->rtcp && !rtp_payload(&phc->mp.rtp, &phc->mp.payload, &phc->s))) {
-		rtp_padding(phc->mp.rtp, &phc->mp.payload);
-
 		unkern = __stream_ssrc_in(phc->in_srtp, phc->mp.rtp->ssrc, &phc->mp.ssrc_in,
 				phc->mp.media->monologue->ssrc_hash);
 
@@ -2406,6 +2404,8 @@ static int stream_packet(struct packet_handler_ctx *phc) {
 	if (handler_ret < 0)
 		goto out; // receive error
 
+	rtp_padding(phc->mp.rtp, &phc->mp.payload);
+
 	// If recording pcap dumper is set, then we record the call.
 	if (phc->mp.call->recording)
 		dump_packet(&phc->mp, &phc->s);

lib/rtplib.c

@@ -107,6 +107,8 @@ error:
 
 
 int rtp_padding(struct rtp_header *header, str *payload) {
+	if (!header || payload->s)
+		return 0;
 	if (!(header->v_p_x_cc & 0x20))
 		return 0; // no padding
 	if (payload->len == 0)