TT#145450 cache last used PT to avoid repeated bsearch

Change-Id: I4d7d11f40a9c4225418b8f9835a8f2f5047dcdd2

kernel-module/xt_RTPENGINE.c

@@ -299,6 +299,7 @@ struct rtpengine_target {
 	atomic_t			refcnt;
 	uint32_t			table;
 	struct rtpengine_target_info	target;
+	unsigned int			last_pt; // index into payload_types[]
 
 	struct rtpengine_stats_a	stats;
 	struct rtpengine_rtp_stats_a	rtp_stats[RTPE_NUM_PAYLOAD_TYPES];
@@ -4184,11 +4185,18 @@ static int rtp_payload_match(const void *a, const void *b) {
 }
 #endif
 
-static inline int rtp_payload_type(const struct rtp_header *hdr, const struct rtpengine_target_info *tg) {
+static inline int rtp_payload_type(const struct rtp_header *hdr, const struct rtpengine_target_info *tg,
+		int *last_pt)
+{
 	struct rtpengine_payload_type pt;
 	const struct rtpengine_payload_type *match;
 
 	pt.pt_num = hdr->m_pt & 0x7f;
+	if (*last_pt < tg->num_payload_types) {
+		match = &tg->payload_types[*last_pt];
+		if (rtp_payload_match(match, &pt) == 0)
+			goto found;
+	}
 #if LINUX_VERSION_CODE >= KERNEL_VERSION(3,0,0)
 	match = bsearch(&pt, tg->payload_types, tg->num_payload_types, sizeof(pt), rtp_payload_match);
 #else
@@ -4197,11 +4205,12 @@ static inline int rtp_payload_type(const struct rtp_header *hdr, const struct rt
 			goto found;
 	}
 	match = NULL;
-found:
 #endif
 	if (!match)
 		return -1;
-	return match - tg->payload_types;
+found:
+	*last_pt = match - tg->payload_types;
+	return *last_pt;
 }
 
 static struct sk_buff *intercept_skb_copy(struct sk_buff *oskb, const struct re_address *src) {
@@ -4441,7 +4450,7 @@ src_check_ok:
 		goto not_rtp;
 	}
 
-	rtp_pt_idx = rtp_payload_type(rtp.header, &g->target);
+	rtp_pt_idx = rtp_payload_type(rtp.header, &g->target, &g->last_pt);
 
 	// Pass to userspace if SSRC has changed.
 	errstr = "SSRC mismatch";