DPI: remove zero data length check from dpi_ndpi_session_first_packet()

For TCP sessions, L4 payload data length of first packet
(SYN packet) is zero. So the first packet of TCP session
will not be sent to nDPI due to data_len != 0 checking in
dpi_ndpi_session_first_packet().

However, nDPI uses TCP SYN packets internally for connection
tracking and other purposes. For example, in nDPI library
function ndpi_detection_process_packet():
a) ndpi_connection_tracking() is called for connection
tracking and updating TCP flag states
b) app detection is given up for TCP sessions in some cases if
the first packet of session sent to nDPI is not a SYN packet

Hence, remove data_len != 0 check from the function
dpi_ndpi_session_first_packet() and send the first packet of
a session to nDPI irrespective of data length.

Co-authored-by: Subhajit Chatterjee <[email protected]>
Signed-off-by: Shubham Shrivastava <[email protected]>

src/npf/dpi/ndpi.c

@@ -289,7 +289,8 @@ dpi_ndpi_session_flow_destroy(struct dpi_engine_flow *dpi_flow)
 static int
 dpi_ndpi_session_first_packet(struct npf_session *se __unused,
 		struct npf_cache *npc __unused, struct rte_mbuf *mbuf,
-		int dir, uint32_t data_len, struct dpi_engine_flow **dpi_flow)
+		int dir, uint32_t data_len __unused,
+		struct dpi_engine_flow **dpi_flow)
 {
 	struct ndpi_flow *flow = zmalloc_aligned(sizeof(struct ndpi_flow));
 	if (!flow)
@@ -315,8 +316,7 @@ dpi_ndpi_session_first_packet(struct npf_session *se __unused,
 	if (!flow->dest_id)
 		goto dest_id_error;
 
-	if (data_len != 0 && !dpi_ndpi_process_pkt(
-				(struct dpi_engine_flow *)flow, mbuf, dir))
+	if (!dpi_ndpi_process_pkt((struct dpi_engine_flow *)flow, mbuf, dir))
 		return -EINVAL;
 
 	*dpi_flow = (struct dpi_engine_flow *)flow;