From bd0e641633c0b2b2cd313323180e0b2ceba233ea Mon Sep 17 00:00:00 2001
From: David Rupprecht <david@srs.io>
Date: Fri, 10 Sep 2021 13:00:50 +0200
Subject: [PATCH] Added GTPU PDU Session header parsing

---
 lib/include/srsran/upper/gtpu.h |  3 +++
 lib/src/gtpu/gtpu.cc            | 31 ++++++++++++++++++++-----------
 2 files changed, 23 insertions(+), 11 deletions(-)

diff --git a/lib/include/srsran/upper/gtpu.h b/lib/include/srsran/upper/gtpu.h
index f78ac17b2..ba0943bdd 100644
--- a/lib/include/srsran/upper/gtpu.h
+++ b/lib/include/srsran/upper/gtpu.h
@@ -58,8 +58,11 @@ namespace srsran {
 #define GTPU_MSG_END_MARKER 254
 #define GTPU_MSG_DATA_PDU 255
 
+#define GTPU_EXT_NO_MORE_EXTENSION_HEADERS 0x00
 #define GTPU_EXT_HEADER_PDCP_PDU_NUMBER 0b11000000
+#define GTPU_EXT_HEADER_PDU_SESSION_CONTAINER 0x85
 
+#define GTPU_EXT_HEADER_PDU_SESSION_CONTAINER_LEN 4
 struct gtpu_header_t {
   uint8_t              flags             = 0;
   uint8_t              message_type      = 0;
diff --git a/lib/src/gtpu/gtpu.cc b/lib/src/gtpu/gtpu.cc
index aa616c411..9dda8ee93 100644
--- a/lib/src/gtpu/gtpu.cc
+++ b/lib/src/gtpu/gtpu.cc
@@ -112,17 +112,26 @@ bool gtpu_read_ext_header(srsran::byte_buffer_t* pdu,
     return true;
   }
 
-  if (header->next_ext_hdr_type == GTPU_EXT_HEADER_PDCP_PDU_NUMBER) {
-    pdu->msg += HEADER_PDCP_PDU_NUMBER_SIZE;
-    pdu->N_bytes -= HEADER_PDCP_PDU_NUMBER_SIZE;
-    header->ext_buffer.resize(HEADER_PDCP_PDU_NUMBER_SIZE);
-    for (size_t i = 0; i < HEADER_PDCP_PDU_NUMBER_SIZE; ++i) {
-      header->ext_buffer[i] = **ptr;
-      (*ptr)++;
-    }
-  } else {
-    logger.error("gtpu_read_header - Unhandled GTP-U Extension Header Type: 0x%x", header->next_ext_hdr_type);
-    return false;
+  // TODO: Iterate over next headers until no more extension headers
+  switch (header->next_ext_hdr_type) {
+    case GTPU_EXT_HEADER_PDCP_PDU_NUMBER:
+      pdu->msg += HEADER_PDCP_PDU_NUMBER_SIZE;
+      pdu->N_bytes -= HEADER_PDCP_PDU_NUMBER_SIZE;
+      header->ext_buffer.resize(HEADER_PDCP_PDU_NUMBER_SIZE);
+      for (size_t i = 0; i < HEADER_PDCP_PDU_NUMBER_SIZE; ++i) {
+        header->ext_buffer[i] = **ptr;
+        (*ptr)++;
+      }
+      break;
+    case GTPU_EXT_HEADER_PDU_SESSION_CONTAINER:
+      pdu->msg += GTPU_EXT_HEADER_PDU_SESSION_CONTAINER_LEN;
+      pdu->N_bytes -= GTPU_EXT_HEADER_PDU_SESSION_CONTAINER_LEN;
+      logger.warning("skip parsing of GTPU_EXT_HEADER_PDU_SESSION_CONTAINER");
+      // TODO: Save Header Extension
+      break;
+    default:
+      logger.error("gtpu_read_header - Unhandled GTP-U Extension Header Type: 0x%x", header->next_ext_hdr_type);
+      return false;
   }
   return true;
 }