trafgen: Add basic protocol generation logic

Add new trafgen_proto.c module with basic protocol header fields
generation logic. This will allow to support protocol specific keywords
in the trafgen configuration language.

Each protocol must implement struct proto_hdr and register it to the
global proto list.

Protocol headers consist of a set of fields, and each field must be
described via struct proto_field by specifying unique id, length and
offset (relative to the header start). Fields smaller than 8 bits can be
described via left shift & mask.

The following callbacks are invoked to perform special actions to build
the header during parsing:

    1) header_init - required fields must be added to the packet and
        initialized with default values.

    2) header_finish - it is invoked when header is specified, all user
        specified fields are set.

    3) packet_finish - callback is invoked from upper to lower header
	to calculate fields depending on upper layers such as total
	length or checksum.

The protocol generation API provides convenience protocol field
setters/getters to to be used in the parser while crafting the packet.

Signed-off-by: Vadim Kochan <vadim4j@gmail.com>
[tk: wordsmithing on commit message, minor variable type changes]
Signed-off-by: Tobias Klauser <tklauser@distanz.ch>

1 files changed, 97 insertions, 0 deletions

diff --git a/trafgen_proto.h b/trafgen_proto.h
new file mode 100644
index 0000000..8f1f201
--- /dev/null
+++ b/trafgen_proto.h
@@ -0,0 +1,97 @@
+#ifndef TRAFGEN_PROTO_I_H
+#define TRAFGEN_PROTO_I_H
+
+#include <stddef.h>
+#include <stdint.h>
+#include <stdbool.h>
+
+struct proto_ctx {
+	const char *dev;
+};
+
+enum proto_id {
+	PROTO_NONE,
+	PROTO_ETH,
+	PROTO_ARP,
+	PROTO_IP4,
+	PROTO_IP6,
+	PROTO_UDP,
+	PROTO_TCP,
+};
+
+enum proto_layer {
+	PROTO_L0, /* invalid layer */
+	PROTO_L2,
+	PROTO_L3,
+	PROTO_L4,
+};
+
+struct proto_field {
+	uint32_t id;
+	size_t len;
+	uint32_t shift;
+	uint32_t mask;
+	uint16_t offset;
+
+	bool is_set;
+	uint16_t pkt_offset;
+};
+
+struct proto_hdr {
+	enum proto_id id;
+	enum proto_layer layer;
+
+	struct proto_hdr *next;
+	struct proto_ctx *ctx;
+	uint16_t pkt_offset;
+	struct proto_field *fields;
+	size_t fields_count;
+
+	void (*header_init)(struct proto_hdr *hdr);
+	void (*header_finish)(struct proto_hdr *hdr);
+	void (*packet_finish)(struct proto_hdr *hdr);
+};
+
+extern void protos_init(const char *dev);
+extern void proto_header_register(struct proto_hdr *hdr);
+
+extern void proto_header_init(enum proto_id pid);
+extern void proto_header_finish(struct proto_hdr *hdr);
+extern void proto_packet_finish(void);
+extern void proto_lower_default_add(enum proto_id pid);
+
+extern struct proto_hdr *proto_current_header(void);
+extern struct proto_hdr *proto_lower_header(struct proto_hdr *hdr);
+extern uint8_t *proto_header_ptr(struct proto_hdr *hdr);
+
+extern void proto_header_fields_add(struct proto_hdr *hdr,
+				    struct proto_field *fields, size_t count);
+
+extern bool proto_field_is_set(struct proto_hdr *hdr, uint32_t fid);
+extern void proto_field_set_bytes(struct proto_hdr *hdr, uint32_t fid,
+				  uint8_t *bytes);
+extern void proto_field_set_u8(struct proto_hdr *hdr, uint32_t fid, uint8_t val);
+extern uint8_t proto_field_get_u8(struct proto_hdr *hdr, uint32_t fid);
+extern void proto_field_set_u16(struct proto_hdr *hdr, uint32_t fid, uint16_t val);
+extern uint16_t proto_field_get_u16(struct proto_hdr *hdr, uint32_t fid);
+extern void proto_field_set_u32(struct proto_hdr *hdr, uint32_t fid, uint32_t val);
+extern uint32_t proto_field_get_u32(struct proto_hdr *hdr, uint32_t fid);
+
+extern void proto_field_set_default_bytes(struct proto_hdr *hdr, uint32_t fid,
+					  uint8_t *bytes);
+extern void proto_field_set_default_u8(struct proto_hdr *hdr, uint32_t fid,
+				       uint8_t val);
+extern void proto_field_set_default_u16(struct proto_hdr *hdr, uint32_t fid,
+				        uint16_t val);
+extern void proto_field_set_default_u32(struct proto_hdr *hdr, uint32_t fid,
+				        uint32_t val);
+
+extern void proto_field_set_be16(struct proto_hdr *hdr, uint32_t fid, uint16_t val);
+extern void proto_field_set_be32(struct proto_hdr *hdr, uint32_t fid, uint32_t val);
+
+extern void proto_field_set_default_be16(struct proto_hdr *hdr, uint32_t fid,
+					 uint16_t val);
+extern void proto_field_set_default_be32(struct proto_hdr *hdr, uint32_t fid,
+					 uint32_t val);
+
+#endif /* TRAFGEN_PROTO_I_H */