Adds pjmedia probation concepts to res_rtp_asterisk's learning mode.

In order to better handle RTP sources with strictrtp enabled (which is now default in 10)
using the learning mode to figure out new sources when they change is handled by checking
for a number of consecutive (by sequence number) packets received to an rtp struct
based on a new configurable value called 'probation'. Also, during learning mode instead
of liberally accepting all packets received, we now reject packets until a clear source
has been determined.

Review: https://reviewboard.asterisk.org/r/1663/
........

Merged revisions 351287 from http://svn.asterisk.org/svn/asterisk/branches/1.8
........

Merged revisions 351289 from http://svn.asterisk.org/svn/asterisk/branches/10


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@351290 65c4cc65-6c06-0410-ace0-fbb531ad65f3

1 files changed, 78 insertions, 1 deletions

diff --git a/res/res_rtp_asterisk.c b/res/res_rtp_asterisk.c
index 62d314446..1cd68736e 100644
--- a/res/res_rtp_asterisk.c
+++ b/res/res_rtp_asterisk.c
@@ -80,6 +80,8 @@ ASTERISK_FILE_VERSION(__FILE__, "$Revision$")
 
 #define ZFONE_PROFILE_ID 0x505a
 
+#define DEFAULT_LEARNING_MIN_SEQUENTIAL 4
+
 extern struct ast_srtp_res *res_srtp;
 static int dtmftimeout = DEFAULT_DTMF_TIMEOUT;
 
@@ -96,7 +98,8 @@ static int rtcpdebugport;		/*< Debug only RTCP packets from IP or IP+Port if por
 #ifdef SO_NO_CHECK
 static int nochecksums;
 #endif
-static int strictrtp;
+static int strictrtp;			/*< Only accept RTP frames from a defined source. If we receive an indication of a changing source, enter learning mode. */
+static int learning_min_sequential;	/*< Number of sequential RTP frames needed from a single source during learning mode to accept new source. */
 
 enum strict_rtp_state {
 	STRICT_RTP_OPEN = 0, /*! No RTP packets should be dropped, all sources accepted */
@@ -176,6 +179,13 @@ struct ast_rtp {
 	struct ast_sockaddr strict_rtp_address;  /*!< Remote address information for strict RTP purposes */
 	struct ast_sockaddr alt_rtp_address; /*!<Alternate remote address information */
 
+	/*
+	 * Learning mode values based on pjmedia's probation mode.  Many of these values are redundant to the above,
+	 * but these are in place to keep learning mode sequence values sealed from their normal counterparts.
+	 */
+	uint16_t learning_max_seq;		/*!< Highest sequence number heard */
+	int learning_probation;		/*!< Sequential packets untill source is valid */
+
 	struct rtp_red *red;
 };
 
@@ -460,6 +470,52 @@ static int create_new_socket(const char *type, int af)
 	return sock;
 }
 
+/*!
+ * \internal
+ * \brief Initializes sequence values and probation for learning mode.
+ * \note This is an adaptation of pjmedia's pjmedia_rtp_seq_init function.
+ *
+ * \param rtp pointer to rtp struct used with the received rtp packet.
+ * \param seq sequence number read from the rtp header
+ */
+static void rtp_learning_seq_init(struct ast_rtp *rtp, uint16_t seq)
+{
+	rtp->learning_max_seq = seq - 1;
+	rtp->learning_probation = learning_min_sequential;
+}
+
+/*!
+ * \internal
+ * \brief Updates sequence information for learning mode and determines if probation/learning mode should remain in effect.
+ * \note This function was adapted from pjmedia's pjmedia_rtp_seq_update function.
+ *
+ * \param rtp pointer to rtp struct used with the received rtp packet.
+ * \param seq sequence number read from the rtp header
+ * \return boolean value indicating if probation mode is active at the end of the function
+ */
+static int rtp_learning_rtp_seq_update(struct ast_rtp *rtp, uint16_t seq)
+{
+	int probation = 0;
+
+	ast_debug(1, "%p -- probation = %d, seq = %d\n", rtp, rtp->learning_probation, seq);
+
+	probation = 1;
+
+	if (seq == rtp->learning_max_seq + 1) {
+		/* packet is in sequence */
+		rtp->learning_probation--;
+		rtp->learning_max_seq = seq;
+		if (rtp->learning_probation == 0) {
+			probation = 0;
+		}
+	} else {
+		rtp->learning_probation = learning_min_sequential - 1;
+		rtp->learning_max_seq = seq;
+	}
+
+	return probation;
+}
+
 static int ast_rtp_new(struct ast_rtp_instance *instance,
 		       struct ast_sched_context *sched, struct ast_sockaddr *addr,
 		       void *data)
@@ -476,6 +532,9 @@ static int ast_rtp_new(struct ast_rtp_instance *instance,
 	rtp->ssrc = ast_random();
 	rtp->seqno = ast_random() & 0xffff;
 	rtp->strict_rtp_state = (strictrtp ? STRICT_RTP_LEARN : STRICT_RTP_OPEN);
+	if (strictrtp) {
+		rtp_learning_seq_init(rtp, (uint16_t)rtp->seqno);
+	}
 
 	/* Create a new socket for us to listen on and use */
 	if ((rtp->s =
@@ -2082,7 +2141,17 @@ static struct ast_frame *ast_rtp_read(struct ast_rtp_instance *instance, int rtc
 
 	/* If strict RTP protection is enabled see if we need to learn the remote address or if we need to drop the packet */
 	if (rtp->strict_rtp_state == STRICT_RTP_LEARN) {
+		ast_debug(1, "%p -- start learning mode pass with addr = %s\n", rtp, ast_sockaddr_stringify(&addr));
+		/* For now, we always copy the address. */
 		ast_sockaddr_copy(&rtp->strict_rtp_address, &addr);
+
+		/* Send the rtp and the seqno from header to rtp_learning_rtp_seq_update to see whether we can exit or not*/
+		if (rtp_learning_rtp_seq_update(rtp, ntohl(rtpheader[0]))) {
+			ast_debug(1, "%p -- Condition for learning hasn't exited, so reject the frame.\n", rtp);
+			return &ast_null_frame;
+		}
+
+		ast_debug(1, "%p -- Probation Ended. Set strict_rtp_state to STRICT_RTP_CLOSED with address %s\n", rtp, ast_sockaddr_stringify(&addr));
 		rtp->strict_rtp_state = STRICT_RTP_CLOSED;
 	} else if (rtp->strict_rtp_state == STRICT_RTP_CLOSED) {
 		if (ast_sockaddr_cmp(&rtp->strict_rtp_address, &addr)) {
@@ -2497,6 +2566,7 @@ static void ast_rtp_remote_address_set(struct ast_rtp_instance *instance, struct
 
 	if (strictrtp) {
 		rtp->strict_rtp_state = STRICT_RTP_LEARN;
+		rtp_learning_seq_init(rtp, rtp->seqno);
 	}
 
 	return;
@@ -2884,6 +2954,7 @@ static int rtp_reload(int reload)
 	rtpend = DEFAULT_RTP_END;
 	dtmftimeout = DEFAULT_DTMF_TIMEOUT;
 	strictrtp = STRICT_RTP_CLOSED;
+	learning_min_sequential = DEFAULT_LEARNING_MIN_SEQUENTIAL;
 	if (cfg) {
 		if ((s = ast_variable_retrieve(cfg, "general", "rtpstart"))) {
 			rtpstart = atoi(s);
@@ -2927,6 +2998,12 @@ static int rtp_reload(int reload)
 		if ((s = ast_variable_retrieve(cfg, "general", "strictrtp"))) {
 			strictrtp = ast_true(s);
 		}
+		if ((s = ast_variable_retrieve(cfg, "general", "probation"))) {
+			if ((sscanf(s, "%d", &learning_min_sequential) <= 0) || learning_min_sequential <= 0) {
+				ast_log(LOG_WARNING, "Value for 'probation' could not be read, using default of '%d' instead\n",
+					DEFAULT_LEARNING_MIN_SEQUENTIAL);
+			}
+		}
 		ast_config_destroy(cfg);
 	}
 	if (rtpstart >= rtpend) {