SAToP: Add optional RTP header handling

1 files changed, 98 insertions, 28 deletions

diff --git a/epan/dissectors/packet-pw-satop.c b/epan/dissectors/packet-pw-satop.c
index 6cfe7f7768..1c81483713 100644
--- a/epan/dissectors/packet-pw-satop.c
+++ b/epan/dissectors/packet-pw-satop.c
@@ -14,7 +14,6 @@
  * 14.08.2009 added: support for IP/UDP demultiplexing
  * Not supported yet:
  * - Decoding of PW payload
- * - Optional RTP Headers (RFC3550)
  */
 
 #include "config.h"
@@ -24,6 +23,9 @@
 
 #include "packet-mpls.h"
 #include "packet-pw-common.h"
+#include "packet-rtp.h"
+
+#define SIZEOF_RTP 12
 
 void proto_register_pw_satop(void);
 void proto_reg_handoff_pw_satop(void);
@@ -53,9 +55,12 @@ static dissector_handle_t pw_padding_handle;
 static dissector_handle_t pw_satop_udp_handle;
 static dissector_handle_t pw_satop_mpls_handle;
 
+const char pwc_longname_pw_satop[] = "SAToP";
+static const char shortname[] = "SAToP";
 
-const char pwc_longname_pw_satop[] = "SAToP (no RTP support)";
-static const char shortname[] = "SAToP (no RTP)";
+/* Preferences */
+static gboolean pref_has_rtp_header       = FALSE;
+static gboolean pref_heuristic_rtp_header = TRUE;
 
 
 static
@@ -64,11 +69,16 @@ void dissect_pw_satop(tvbuff_t * tvb_original
 					,proto_tree * tree
 					,pwc_demux_type_t demux)
 {
-	const int encaps_size = 4; /*RTP header in encapsulation is not supported yet*/
+	int min_packet_size_this_dissector = PWC_SIZEOF_CW;
+	int encaps_size;
 	gint      packet_size;
+	gint      rtp_header_offset;
+	gint      cw_offset;
 	gint      payload_size;
 	gint      padding_size;
 	int properties;
+	guint16   sn;
+	gboolean  has_rtp_header;
 
 	enum {
 		PAY_NO_IDEA = 0
@@ -78,13 +88,27 @@ void dissect_pw_satop(tvbuff_t * tvb_original
 		,PAY_LIKE_OCTET_ALIGNED_T1
 	} payload_properties;
 
+	switch (demux)
+	{
+	case PWC_DEMUX_MPLS:
+		if (dissect_try_cw_first_nibble(tvb_original, pinfo, tree))
+		{
+			return;
+		}
+		break;
+	case PWC_DEMUX_UDP:
+		break;
+	default:
+		DISSECTOR_ASSERT_NOT_REACHED();
+		return;
+	}
+
 	packet_size = tvb_reported_length_remaining(tvb_original, 0);
-	/*
-	 * FIXME
-	 * "4" below should be replaced by something like "min_packet_size_this_dissector"
-	 * Also call to dissect_try_cw_first_nibble() should be moved before this block
-	 */
-	if (packet_size < 4) /* 4 is smallest size which may be sensible (for PWACH dissector) */
+	if (pref_has_rtp_header) {
+		min_packet_size_this_dissector += SIZEOF_RTP;
+	}
+
+	if (packet_size < min_packet_size_this_dissector)
 	{
 		proto_item  *item;
 		item = proto_tree_add_item(tree, proto, tvb_original, 0, -1, ENC_NA);
@@ -99,30 +123,59 @@ void dissect_pw_satop(tvbuff_t * tvb_original
 	switch (demux)
 	{
 	case PWC_DEMUX_MPLS:
-		if (dissect_try_cw_first_nibble(tvb_original, pinfo, tree))
-		{
-			return;
-		}
+		rtp_header_offset = PWC_SIZEOF_CW;
+		sn = tvb_get_guint16(tvb_original, 2, ENC_BIG_ENDIAN);
 		break;
 	case PWC_DEMUX_UDP:
+		rtp_header_offset = 0;
+		sn = tvb_get_guint16(tvb_original, SIZEOF_RTP + 2, ENC_BIG_ENDIAN);
 		break;
 	default:
 		DISSECTOR_ASSERT_NOT_REACHED();
 		return;
 	}
 
+	if ((pref_has_rtp_header) ||
+		((pref_heuristic_rtp_header) &&
+			/* Check for RTP version 2, the other fields must be zero */
+			(tvb_get_guint8(tvb_original, rtp_header_offset) == 0x80) &&
+			/* Check the marker is zero. Unfortnately PT is not always from the dynamic range */
+			((tvb_get_guint8(tvb_original, rtp_header_offset + 1) & 0x80) == 0) &&
+			/* The sequence numbers from cw and RTP header must match */
+			(tvb_get_ntohs(tvb_original, rtp_header_offset + 2) == sn)))
+	{
+		switch (demux)
+		{
+		case PWC_DEMUX_MPLS:
+			cw_offset = 0;
+			break;
+		case PWC_DEMUX_UDP:
+			cw_offset = SIZEOF_RTP;
+			break;
+		default:
+			DISSECTOR_ASSERT_NOT_REACHED();
+			return;
+		}
+		encaps_size = PWC_SIZEOF_CW + SIZEOF_RTP;
+		has_rtp_header = TRUE;
+	} else {
+		cw_offset = 0;
+		encaps_size = PWC_SIZEOF_CW;
+		has_rtp_header = FALSE;
+	}
+
 	/* check how "good" is this packet */
-	/* also decide payload length from packet size and CW */
+	/* also decide payload length from packet size, CW and optional RTP header */
 	properties = 0;
-	if (0 != (tvb_get_guint8(tvb_original, 0) & 0xf0 /*bits03*/))
+	if (0 != (tvb_get_guint8(tvb_original, cw_offset) & 0xf0 /*bits03*/))
 	{
 		properties |= PWC_CW_BAD_BITS03;
 	}
-	if (0 != (tvb_get_guint8(tvb_original, 0) & 0x03 /*rsv*/))
+	if (0 != (tvb_get_guint8(tvb_original, cw_offset) & 0x03 /*rsv*/))
 	{
 		properties |= PWC_CW_BAD_RSV;
 	}
-	if (0 != (tvb_get_guint8(tvb_original, 1) & 0xc0 /*frag*/))
+	if (0 != (tvb_get_guint8(tvb_original, cw_offset + 1) & 0xc0 /*frag*/))
 	{
 		properties |= PWC_CW_BAD_FRAG;
 	}
@@ -142,7 +195,7 @@ void dissect_pw_satop(tvbuff_t * tvb_original
 		int  cw_len;
 		gint payload_size_from_packet;
 
-		cw_len = tvb_get_guint8(tvb_original, 1) & 0x3f;
+		cw_len = tvb_get_guint8(tvb_original, cw_offset + 1) & 0x3f;
 		payload_size_from_packet = packet_size - encaps_size;
 		if (cw_len != 0)
 		{
@@ -186,7 +239,7 @@ void dissect_pw_satop(tvbuff_t * tvb_original
 		 * not blame packets with bad payload (including "bad" or "strange" SIZE of
 		 * payload) when L bit is set.
 		 */
-		if (0 == (tvb_get_guint8(tvb_original, 0) & 0x08 /*L bit*/))
+		if (0 == (tvb_get_guint8(tvb_original, cw_offset) & 0x08 /*L bit*/))
 		{
 			properties |= PWC_PAY_SIZE_BAD;
 		}
@@ -240,17 +293,22 @@ void dissect_pw_satop(tvbuff_t * tvb_original
 	{
 		proto_item* item;
 		item = proto_tree_add_item(tree, proto, tvb_original, 0, -1, ENC_NA);
-		pwc_item_append_cw(item,tvb_get_ntohl(tvb_original, 0),TRUE);
-		pwc_item_append_text_n_items(item,(int)payload_size,"octet");
+		pwc_item_append_cw(item, tvb_get_ntohl(tvb_original, cw_offset), TRUE);
+		pwc_item_append_text_n_items(item, (int)payload_size, "octet");
 		{
 			proto_tree* tree2;
 			tree2 = proto_item_add_subtree(item, ett_pw_satop);
+			if (has_rtp_header && demux == PWC_DEMUX_UDP)
+			{
+				dissect_rtp_shim_header(tvb_original, 0, pinfo, tree2, NULL);
+			}
+
 			{
 				tvbuff_t* tvb;
 				proto_item* item2;
-				tvb = tvb_new_subset_length(tvb_original, 0, PWC_SIZEOF_CW);
+				tvb = tvb_new_subset_length(tvb_original, cw_offset, PWC_SIZEOF_CW);
 				item2 = proto_tree_add_item(tree2, hf_cw, tvb, 0, -1, ENC_NA);
-				pwc_item_append_cw(item2, tvb_get_ntohl(tvb, 0),FALSE);
+				pwc_item_append_cw(item2, tvb_get_ntohl(tvb, 0), FALSE);
 				{
 					proto_tree* tree3;
 					tree3 = proto_item_add_subtree(item2, ett_pw_satop);
@@ -262,8 +320,8 @@ void dissect_pw_satop(tvbuff_t * tvb_original
 							expert_add_info(pinfo, item3, &ei_cw_bits03);
 						}
 
-						proto_tree_add_item(tree3, hf_cw_l  , tvb, 0, 1, ENC_BIG_ENDIAN);
-						proto_tree_add_item(tree3, hf_cw_r  , tvb, 0, 1, ENC_BIG_ENDIAN);
+						proto_tree_add_item(tree3, hf_cw_l, tvb, 0, 1, ENC_BIG_ENDIAN);
+						proto_tree_add_item(tree3, hf_cw_r, tvb, 0, 1, ENC_BIG_ENDIAN);
 
 						item3 = proto_tree_add_item(tree3, hf_cw_rsv, tvb, 0, 1, ENC_BIG_ENDIAN);
 						if (properties & PWC_CW_BAD_RSV)
@@ -301,6 +359,11 @@ void dissect_pw_satop(tvbuff_t * tvb_original
 					}
 				}
 			}
+
+			if (has_rtp_header && demux != PWC_DEMUX_UDP)
+			{
+				dissect_rtp_shim_header(tvb_original, PWC_SIZEOF_CW, pinfo, tree2, NULL);
+			}
 		}
 
 		/* payload */
@@ -321,9 +384,9 @@ void dissect_pw_satop(tvbuff_t * tvb_original
 			{
 				proto_item* item2;
 				tvbuff_t* tvb;
-				tvb = tvb_new_subset_length(tvb_original, PWC_SIZEOF_CW, payload_size);
+				tvb = tvb_new_subset_length(tvb_original, encaps_size, payload_size);
 				item2 = proto_tree_add_item(tree2, hf_payload, tvb, 0, -1, ENC_NA);
-				pwc_item_append_text_n_items(item2,(int)payload_size,"octet");
+				pwc_item_append_text_n_items(item2, (int)payload_size, "octet");
 				{
 					proto_tree* tree3;
 					const char* s;
@@ -443,6 +506,8 @@ void proto_register_pw_satop(void)
 		{ &ei_payload_size_invalid, { "pwsatop.payload.size_invalid", PI_MALFORMED, PI_ERROR, "Bad Length: too small", EXPFILL }},
 		{ &ei_payload_size_invalid_undecoded, { "pwsatop.payload.undecoded", PI_UNDECODED, PI_NOTE, "SAToP payload: omitted to conserve bandwidth", EXPFILL }},
 	};
+
+	module_t *pwsatop_module;
 	expert_module_t* expert_pwsatop;
 
 	proto = proto_register_protocol(pwc_longname_pw_satop, shortname, "pwsatopcw");
@@ -450,6 +515,11 @@ void proto_register_pw_satop(void)
 	proto_register_subtree_array(ett_array, array_length(ett_array));
 	expert_pwsatop = expert_register_protocol(proto);
 	expert_register_field_array(expert_pwsatop, ei, array_length(ei));
+	pwsatop_module = prefs_register_protocol(proto, NULL);
+	prefs_register_bool_preference(pwsatop_module, "rtp_header", "RTP header in SAToP header",
+					"Whether or not the RTP header is present in the SAToP header.", &pref_has_rtp_header);
+	prefs_register_bool_preference(pwsatop_module, "rtp_header_heuristic", "Try to find RTP header in SAToP header",
+					"Heuristically determine if an RTP header is present in the SAToP header.", &pref_heuristic_rtp_header);
 	pw_satop_mpls_handle = register_dissector("pw_satop_mpls", dissect_pw_satop_mpls, proto);
 	pw_satop_udp_handle = register_dissector("pw_satop_udp", dissect_pw_satop_udp, proto);
 }