Add KCP protocol dissector. (#2257)

Signed-off-by: Toni Uhlig <matzeton@googlemail.com>

2 files changed, 114 insertions, 0 deletions

diff --git a/src/lib/ndpi_main.c b/src/lib/ndpi_main.c
index 2e088306d..d9ba5b952 100644
--- a/src/lib/ndpi_main.c
+++ b/src/lib/ndpi_main.c
@@ -2239,6 +2239,10 @@ static void ndpi_init_protocol_defaults(struct ndpi_detection_module_struct *ndp
 			  "Roughtime", NDPI_PROTOCOL_CATEGORY_SYSTEM_OS,
 			  ndpi_build_default_ports(ports_a, 2002, 0, 0, 0, 0) /* TCP */,
 			  ndpi_build_default_ports(ports_b, 2002, 0, 0, 0, 0) /* UDP */);
+  ndpi_set_proto_defaults(ndpi_str, 1 /* cleartext */, 0 /* nw proto */, NDPI_PROTOCOL_ACCEPTABLE, NDPI_PROTOCOL_KCP,
+			  "KCP", NDPI_PROTOCOL_CATEGORY_NETWORK,
+			  ndpi_build_default_ports(ports_a, 0, 0, 0, 0, 0) /* TCP */,
+			  ndpi_build_default_ports(ports_b, 0, 0, 0, 0, 0) /* UDP */);
 
 #ifdef CUSTOM_NDPI_PROTOCOLS
 #include "../../../nDPI-custom/custom_ndpi_main.c"
@@ -5760,6 +5764,9 @@ static int ndpi_callback_init(struct ndpi_detection_module_struct *ndpi_str) {
   /* Roughtime */
   init_roughtime_dissector(ndpi_str, &a);
 
+  /* KCP */
+  init_kcp_dissector(ndpi_str, &a);
+
 #ifdef CUSTOM_NDPI_PROTOCOLS
 #include "../../../nDPI-custom/custom_ndpi_main_init.c"
 #endif
diff --git a/src/lib/protocols/kcp.c b/src/lib/protocols/kcp.c
new file mode 100644
index 000000000..906737179
--- /dev/null
+++ b/src/lib/protocols/kcp.c
@@ -0,0 +1,107 @@
+/*
+ * kcp.c
+ *
+ * Copyright (C) 2024 - ntop.org
+ *
+ * nDPI is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Lesser General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * nDPI is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public License
+ * along with nDPI.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ */
+
+
+#include "ndpi_protocol_ids.h"
+
+#define NDPI_CURRENT_PROTO NDPI_PROTOCOL_KCP
+
+#include "ndpi_api.h"
+#include "ndpi_private.h"
+
+PACK_ON
+struct kcp_header {
+  uint32_t conversation_id;
+  uint8_t command;
+  uint8_t fragment_count;
+  uint16_t window_size;
+  uint32_t timestamp;
+  uint32_t serial_number;
+  uint32_t unacknowledged_serial_number;
+  uint32_t length;
+  uint8_t data[0];
+} PACK_OFF;
+
+enum kcp_commands {
+  IKCP_CMD_PUSH = 81,
+  IKCP_CMD_ACK  = 82,
+  IKCP_CMD_WASK = 83,
+  IKCP_CMD_WINS = 84
+};
+
+static void ndpi_int_kcp_add_connection(struct ndpi_detection_module_struct * const ndpi_struct,
+                                        struct ndpi_flow_struct * const flow)
+{
+  NDPI_LOG_INFO(ndpi_struct, "found kcp\n");
+  ndpi_set_detected_protocol(ndpi_struct, flow,
+                             NDPI_PROTOCOL_KCP,
+                             NDPI_PROTOCOL_UNKNOWN,
+                             NDPI_CONFIDENCE_DPI);
+}
+
+static void ndpi_search_kcp(struct ndpi_detection_module_struct *ndpi_struct,
+                            struct ndpi_flow_struct *flow)
+{
+  struct ndpi_packet_struct const * const packet = &ndpi_struct->packet;
+  struct kcp_header const * const kcp_header = (struct kcp_header *)packet->payload;
+
+  NDPI_LOG_INFO(ndpi_struct, "search kcp\n");
+
+  if (packet->payload_packet_len < sizeof(*kcp_header))
+  {
+    NDPI_EXCLUDE_PROTO(ndpi_struct, flow);
+    return;
+  }
+
+  switch (kcp_header->command)
+  {
+    case IKCP_CMD_PUSH:
+    case IKCP_CMD_ACK:
+    case IKCP_CMD_WASK:
+    case IKCP_CMD_WINS:
+      break;
+    default:
+      NDPI_EXCLUDE_PROTO(ndpi_struct, flow);
+      return;
+  }
+
+  uint32_t const kcp_pdu_length = le32toh(kcp_header->length);
+  if (kcp_pdu_length + sizeof(*kcp_header) != packet->payload_packet_len)
+  {
+    NDPI_EXCLUDE_PROTO(ndpi_struct, flow);
+    return;
+  }
+
+  ndpi_int_kcp_add_connection(ndpi_struct, flow);
+}
+
+void init_kcp_dissector(struct ndpi_detection_module_struct *ndpi_struct,
+                        u_int32_t *id)
+{
+  ndpi_set_bitmask_protocol_detection("KCP", ndpi_struct, *id,
+    NDPI_PROTOCOL_KCP,
+    ndpi_search_kcp,
+    NDPI_SELECTION_BITMASK_PROTOCOL_V4_V6_TCP_OR_UDP_WITH_PAYLOAD_WITHOUT_RETRANSMISSION,
+    SAVE_DETECTION_BITMASK_AS_UNKNOWN,
+    ADD_TO_DETECTION_BITMASK
+  );
+
+  *id += 1;
+}