coap: Distinguish observe option for request and response

The observe option has different values for request and response. For
request it identifies register or deregister, and for response it is a
sequence number for reordering detection. RFC 7641 chapter 2.

Change-Id: I09515864997a32f7259e344532ea770b74030b04
Reviewed-on: https://code.wireshark.org/review/34368
Petri-Dish: Stig Bjørlykke <stig@bjorlykke.org>
Tested-by: Petri Dish Buildbot
Reviewed-by: Michael Mann <mmann78@netscape.net>

3 files changed, 24 insertions, 11 deletions

diff --git a/epan/dissectors/packet-coap.c b/epan/dissectors/packet-coap.c
index 3acff1a913..3622be3094 100644
--- a/epan/dissectors/packet-coap.c
+++ b/epan/dissectors/packet-coap.c
@@ -662,7 +662,7 @@ dissect_coap_opt_uri_port(tvbuff_t *tvb, proto_item *head_item, proto_tree *subt
  * return the total length of the option including the header (e.g. delta and length).
  */
 static int
-dissect_coap_options_main(tvbuff_t *tvb, packet_info *pinfo, proto_tree *coap_tree, gint offset, guint8 opt_count, guint *opt_num, gint offset_end, coap_info *coinfo, coap_common_dissect_t *dissect_hf)
+dissect_coap_options_main(tvbuff_t *tvb, packet_info *pinfo, proto_tree *coap_tree, gint offset, guint8 opt_count, guint *opt_num, gint offset_end, guint8 code_class, coap_info *coinfo, coap_common_dissect_t *dissect_hf)
 {
 	guint8      opt_jump;
 	gint        opt_length, opt_length_ext, opt_delta, opt_delta_ext;
@@ -850,8 +850,15 @@ dissect_coap_options_main(tvbuff_t *tvb, packet_info *pinfo, proto_tree *coap_tr
 		    opt_length, coinfo, dissect_hf->hf.opt_uri_path);
 		break;
 	case COAP_OPT_OBSERVE:
-		dissect_coap_opt_uint(tvb, item, subtree, offset,
-		    opt_length, dissect_hf->hf.opt_observe);
+		if (code_class == 0) {
+			/* Request */
+			dissect_coap_opt_uint(tvb, item, subtree, offset,
+			    opt_length, dissect_hf->hf.opt_observe_req);
+		} else {
+			/* Response */
+			dissect_coap_opt_uint(tvb, item, subtree, offset,
+			    opt_length, dissect_hf->hf.opt_observe_rsp);
+		}
 		break;
 	case COAP_OPT_ACCEPT:
 		dissect_coap_opt_ctype(tvb, item, subtree, offset,
@@ -894,7 +901,7 @@ dissect_coap_options_main(tvbuff_t *tvb, packet_info *pinfo, proto_tree *coap_tr
  * or the end of the data.
  */
 int
-dissect_coap_options(tvbuff_t *tvb, packet_info *pinfo, proto_tree *coap_tree, gint offset, gint offset_end, coap_info *coinfo, coap_common_dissect_t *dissect_hf)
+dissect_coap_options(tvbuff_t *tvb, packet_info *pinfo, proto_tree *coap_tree, gint offset, gint offset_end, guint8 code_class, coap_info *coinfo, coap_common_dissect_t *dissect_hf)
 {
 	guint  opt_num = 0;
 	int    i;
@@ -903,7 +910,7 @@ dissect_coap_options(tvbuff_t *tvb, packet_info *pinfo, proto_tree *coap_tree, g
 	/* loop for dissecting options */
 	for (i = 1; offset < offset_end; i++) {
 		offset = dissect_coap_options_main(tvb, pinfo, coap_tree,
-		    offset, i, &opt_num, offset_end, coinfo, dissect_hf);
+		    offset, i, &opt_num, offset_end, code_class, coinfo, dissect_hf);
 		if (offset == -1)
 			return -1;
 		if (offset >= offset_end)
@@ -1147,7 +1154,7 @@ dissect_coap_message(tvbuff_t *tvb, packet_info *pinfo, proto_tree *parent_tree,
 	}
 
 	/* process options */
-	offset = dissect_coap_options(tvb, pinfo, coap_tree, offset, coap_length, coinfo, &dissect_coap_hf);
+	offset = dissect_coap_options(tvb, pinfo, coap_tree, offset, coap_length, code_class, coinfo, &dissect_coap_hf);
 	if (offset == -1)
 		return tvb_captured_length(tvb);
 
diff --git a/epan/dissectors/packet-coap.h b/epan/dissectors/packet-coap.h
index b8783c7ce2..f641921cdc 100644
--- a/epan/dissectors/packet-coap.h
+++ b/epan/dissectors/packet-coap.h
@@ -85,7 +85,8 @@ typedef struct coap_common_dissect {
 		int opt_location_query;
 		int opt_uri_path;
 		int opt_uri_path_recon;
-		int opt_observe;
+		int opt_observe_req;
+		int opt_observe_rsp;
 		int opt_accept;
 		int opt_if_match;
 		int opt_block_number;
@@ -126,7 +127,7 @@ typedef struct coap_common_dissect {
 } coap_common_dissect_t;
 
 guint8 dissect_coap_code(tvbuff_t *tvb, proto_tree *coap_tree, gint *offset, coap_common_dissect_t *dissect_hf, guint8 *code_class);
-int dissect_coap_options(tvbuff_t *tvb, packet_info *pinfo, proto_tree *coap_tree, gint offset, gint offset_end, coap_info *coinfo, coap_common_dissect_t *dissect_hf);
+int dissect_coap_options(tvbuff_t *tvb, packet_info *pinfo, proto_tree *coap_tree, gint offset, gint offset_end, guint8 code_class, coap_info *coinfo, coap_common_dissect_t *dissect_hf);
 void dissect_coap_payload(tvbuff_t *tvb, packet_info *pinfo, proto_tree *coap_tree, proto_tree *parent_tree, gint offset, gint offset_end, guint8 code_class, coap_info *coinfo, coap_common_dissect_t *dissect_hf, gboolean oscore);
 
 extern const value_string coap_vals_observe_options[];
@@ -140,7 +141,7 @@ coap_common_dissect_t name = {							\
 		-1, -1, -1, -1, -1, -1, -1, -1, -1, -1,				\
 		-1, -1, -1, -1, -1, -1, -1, -1, -1, -1,				\
 		-1, -1, -1, -1, -1, -1, -1, -1, -1, -1,				\
-		-1,								\
+		-1, -1,								\
 		},								\
 	/* ett */ {								\
 		-1, -1,								\
@@ -318,11 +319,16 @@ coap_common_dissect_t name = {							\
 	    FT_STRING, BASE_NONE, NULL, 0x0,					\
 	    NULL, HFILL }							\
 	},									\
-	{ & name .hf.opt_observe,						\
+	{ & name .hf.opt_observe_req,						\
 	  { "Observe",  prefix ".opt.observe",					\
 	    FT_UINT32, BASE_DEC, VALS(coap_vals_observe_options), 0x0,		\
 	    NULL, HFILL }							\
 	},									\
+	{ & name .hf.opt_observe_rsp,						\
+	  { "Observe sequence number",  prefix ".opt.observe",			\
+	    FT_UINT32, BASE_DEC, NULL, 0x0,					\
+	    NULL, HFILL }							\
+	},									\
 	{ & name .hf.opt_accept,						\
 	  { "Accept",  prefix ".opt.accept",					\
 	    FT_STRING, BASE_NONE, NULL, 0x0,					\
diff --git a/epan/dissectors/packet-oscore.c b/epan/dissectors/packet-oscore.c
index 1bdb776b07..2cc4bdde81 100644
--- a/epan/dissectors/packet-oscore.c
+++ b/epan/dissectors/packet-oscore.c
@@ -733,7 +733,7 @@ oscore_dissect(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree,
 
     if (coinfo) {
         dissect_coap_code(tvb_decrypted, oscore_tree, &offset, &dissect_oscore_hf, &code_class);
-        offset = dissect_coap_options(tvb_decrypted, pinfo, oscore_tree, offset, oscore_length, coinfo, &dissect_oscore_hf);
+        offset = dissect_coap_options(tvb_decrypted, pinfo, oscore_tree, offset, oscore_length, code_class, coinfo, &dissect_oscore_hf);
         if (oscore_length > offset) {
             dissect_coap_payload(tvb_decrypted, pinfo, oscore_tree, tree, offset, oscore_length, code_class, coinfo, &dissect_oscore_hf, TRUE);
         }