trafgen: proto: Split static protocol definition out of struct proto_hdr

Currently struct proto_hdr is used twofold:

  1) Statically define protocol behavior, i.e. all the *_hdr definitions in
     trafgen_l{2,3,4}.c which map a protocol id/layer to a set of callback
     functions.

  2) For each packet created at parse time the struct is memcpy()'ed
     (including all the static information from 1) and then used to store
     dynamic information at parse/run time.

Thus, struct proto_hdr members such as the proto id, layer and the
pointers callback functions get copied for each created packet (in
addition to the other fields which get changed during parsing). Also,
static/dynamic information get mixed and we e.g. can't make the protocol
definitions const to ensure they'll not get changed by mistake.

Rather than copying the struct proto_hdr for every packet, clearly
separate the two purposes defined above by splitting struct proto_hdr
into two structs:

  1) struct proto_ops for the static (const) protocol behavior definition

  2) struct proto_hdr (reduced) for dynamic information

struct proto_hdr keeps a pointer to the corresponding proto_ops instance
and uses it to execute the corresponding callbacks.

Reference: https://groups.google.com/forum/#!msg/netsniff-ng/20RvwJdh50Y/eMkbmKSaBgAJ
Acked-by: Vadim Kochan <vadim4j@gmail.com>
Signed-off-by: Tobias Klauser <tklauser@distanz.ch>

1 files changed, 34 insertions, 31 deletions

diff --git a/trafgen_proto.c b/trafgen_proto.c
index 4219794..d976c14 100644
--- a/trafgen_proto.c
+++ b/trafgen_proto.c
@@ -27,7 +27,7 @@ struct ctx {
 };
 static struct ctx ctx;
 
-static const struct proto_hdr *registered[__PROTO_MAX];
+static const struct proto_ops *registered_ops[__PROTO_MAX];
 
 struct proto_hdr *proto_lower_header(struct proto_hdr *hdr)
 {
@@ -52,19 +52,18 @@ uint8_t *proto_header_ptr(struct proto_hdr *hdr)
 	return &packet_get(hdr->pkt_id)->payload[hdr->pkt_offset];
 }
 
-static const struct proto_hdr *proto_header_by_id(enum proto_id id)
+static const struct proto_ops *proto_ops_by_id(enum proto_id id)
 {
-	bug_on(id >= __PROTO_MAX);
-	return registered[id];
+	const struct proto_ops *ops = registered_ops[id];
+
+	bug_on(ops->id != id);
+	return ops;
 }
 
-void proto_header_register(struct proto_hdr *hdr)
+void proto_ops_register(const struct proto_ops *ops)
 {
-	bug_on(hdr->id >= __PROTO_MAX);
-	registered[hdr->id] = hdr;
-
-	hdr->fields = NULL;
-	hdr->fields_count = 0;
+	bug_on(ops->id >= __PROTO_MAX);
+	registered_ops[ops->id] = ops;
 }
 
 static void proto_fields_realloc(struct proto_hdr *hdr, size_t count)
@@ -120,52 +119,55 @@ bool proto_field_is_set(struct proto_hdr *hdr, uint32_t fid)
 	return field ? field->is_set : false;
 }
 
-struct proto_hdr *proto_header_init(enum proto_id pid)
+struct proto_hdr *proto_header_push(enum proto_id pid)
 {
 	struct proto_hdr **headers = current_packet()->headers;
-	const struct proto_hdr *hdr = proto_header_by_id(pid);
-	struct proto_hdr *new_hdr;
+	const struct proto_ops *ops = proto_ops_by_id(pid);
+	struct proto_hdr *hdr;
 
 	bug_on(current_packet()->headers_count >= PROTO_MAX_LAYERS);
 
-	new_hdr = xmalloc(sizeof(*new_hdr));
-	memcpy(new_hdr, hdr, sizeof(*new_hdr));
+	hdr = xzmalloc(sizeof(*hdr));
+	hdr->ops = ops;
+	hdr->pkt_id = current_packet_id();
 
-	new_hdr->pkt_id = current_packet_id();
+	if (ops && ops->header_init)
+		ops->header_init(hdr);
 
-	if (new_hdr->header_init)
-		new_hdr->header_init(new_hdr);
+	headers[current_packet()->headers_count++] = hdr;
 
-	headers[current_packet()->headers_count++] = new_hdr;
-	return new_hdr;
+	return hdr;
 }
 
 void proto_header_finish(struct proto_hdr *hdr)
 {
-	if (hdr && hdr->header_finish)
-		hdr->header_finish(hdr);
+	if (hdr && hdr->ops && hdr->ops->header_finish)
+		hdr->ops->header_finish(hdr);
 }
 
-struct proto_hdr *proto_lower_default_add(struct proto_hdr *hdr,
+struct proto_hdr *proto_lower_default_add(struct proto_hdr *upper,
 					  enum proto_id pid)
 {
 	struct proto_hdr *current;
 	size_t headers_count = current_packet()->headers_count;
+	const struct proto_ops *ops;
 
 	if (headers_count > 0) {
 		current = current_packet()->headers[headers_count - 1];
+		ops = current->ops;
 
-		if (current->layer >= proto_header_by_id(pid)->layer)
+		if (ops->layer >= proto_ops_by_id(pid)->layer)
 			goto set_proto;
-		if (current->id == pid)
+		if (ops->id == pid)
 			goto set_proto;
 	}
 
-	current = proto_header_init(pid);
+	current = proto_header_push(pid);
+	ops = current->ops;
 
 set_proto:
-	if (current->set_next_proto)
-		current->set_next_proto(current, hdr->id);
+	if (ops && ops->set_next_proto)
+		ops->set_next_proto(current, upper->ops->id);
 
 	return current;
 }
@@ -415,9 +417,10 @@ void proto_packet_finish(void)
 
 	/* Go down from upper layers to do last calculations (checksum) */
 	for (i = headers_count - 1; i >= 0; i--) {
-		struct proto_hdr *p = headers[i];
+		struct proto_hdr *hdr = headers[i];
+		const struct proto_ops *ops = hdr->ops;
 
-		if (p->packet_finish)
-			p->packet_finish(p);
+		if (ops && ops->packet_finish)
+			ops->packet_finish(hdr);
 	}
 }