diff --git a/include/CMakeLists.txt b/include/CMakeLists.txt
index e231241..2e5b316 100644
--- a/include/CMakeLists.txt
+++ b/include/CMakeLists.txt
@@ -1,5 +1,6 @@
 install(FILES stellar/utils.h DESTINATION include/stellar/ COMPONENT LIBRARIES)
 install(FILES stellar/layer.h DESTINATION include/stellar/ COMPONENT LIBRARIES)
+install(FILES stellar/tunnel.h DESTINATION include/stellar/ COMPONENT LIBRARIES)
 install(FILES stellar/packet.h DESTINATION include/stellar/ COMPONENT LIBRARIES)
 install(FILES stellar/session.h DESTINATION include/stellar/ COMPONENT LIBRARIES)
 install(FILES stellar/stellar.h DESTINATION include/stellar/ COMPONENT LIBRARIES)
diff --git a/include/stellar/layer.h b/include/stellar/layer.h
index fce1315..f77e021 100644
--- a/include/stellar/layer.h
+++ b/include/stellar/layer.h
@@ -81,15 +81,12 @@ int packet_get_layer(const struct packet *pkt, int idx, struct layer *out);
 #define PACKET_FOREACH_LAYER_REVERSE(pkt, layer) \
     for (int i = packet_get_layer_count(pkt) - 1; i >= 0 && packet_get_layer(pkt, i, &layer) == 0; i--)
 
-#define PACKET_GETALL_LAYERS(pkt, layers)                                          \
-    {                                                                              \
-        int size = sizeof(layers) / sizeof(layers[0]);                             \
-        int num = packet_get_layer_count(pkt);                                     \
-        if (num > size)                                                            \
-            num = size;                                                            \
-        for (int i = 0; i < num && packet_get_layer(pkt, i, &layers[i]) == 0; i++) \
-            /* void */;                                                            \
-        return num;                                                                \
+#define PACKET_GETALL_LAYERS(pkt, layers)                                                 \
+    {                                                                                     \
+        int num = MIN(packet_get_layer_count(pkt), (sizeof(layers) / sizeof(layers[0]))); \
+        for (int i = 0; i < num && packet_get_layer(pkt, i, &layers[i]) == 0; i++)        \
+            /* void */;                                                                   \
+        return num;                                                                       \
     }
 
 #ifdef __cplusplus
diff --git a/include/stellar/tunnel.h b/include/stellar/tunnel.h
new file mode 100644
index 0000000..b1ef626
--- /dev/null
+++ b/include/stellar/tunnel.h
@@ -0,0 +1,67 @@
+#ifndef _TUNNEL_H
+#define _TUNNEL_H
+
+#ifdef __cplusplus
+extern "C"
+{
+#endif
+
+#include <stdint.h>
+#include "layer.h"
+
+enum tunnel_type
+{
+    // none tunnel
+    TUNNEL_NONE = 0, // contain layers: IPv4 + TCP
+                     // contain layers: IPv4 + UDP
+                     // contain layers: IPv4
+                     // contain layers: IPv6 + TCP
+                     // contain layers: IPv6 + UDP
+                     // contain layers: IPv6
+
+    // GRE tunnel
+    TUNNEL_GRE, // contain layers: IPv4 + GRE
+                // contain layers: IPv6 + GRE
+
+    // GTP tunnel
+    TUNNEL_GTP, // contain layers: IPv4 + UDP + GTP
+                // contain layers: IPv6 + UDP + GTP
+
+    // IP tunnel
+    TUNNEL_IPV4, // contain layers: IPv4, (next inner layer must be IPv4 / IPv6)
+    TUNNEL_IPV6, // contain layers: IPv6, (next inner layer must be IPv4 / IPv6)
+};
+
+#define MAX_LAYERS_PER_TUNNEL 3
+struct tunnel
+{
+    enum tunnel_type type;
+
+    int used;
+    struct layer layers[MAX_LAYERS_PER_TUNNEL];
+};
+
+int packet_get_tunnel_count(const struct packet *pkt);
+// return  0: success 
+// return -1: failed
+int packet_get_tunnel(const struct packet *pkt, int idx, struct tunnel *out);
+
+#define PACKET_FOREACH_TUNNEL_INORDER(pkt, tunnel) \
+    for (int i = 0; i < packet_get_tunnel_count(pkt) && packet_get_tunnel(pkt, i, &tunnel) == 0; i++)
+
+#define PACKET_FOREACH_TUNNEL_REVERSE(pkt, tunnel) \
+    for (int i = packet_get_tunnel_count(pkt) - 1; i >= 0 && packet_get_tunnel(pkt, i, &tunnel) == 0; i--)
+
+#define PACKET_GETALL_TUNNELS(pkt, tunnels)                                                  \
+    {                                                                                        \
+        int num = MIN(packet_get_tunnel_count(pkt), (sizeof(tunnels) / sizeof(tunnels[0]))); \
+        for (int i = 0; i < num && packet_get_tunnel(pkt, i, &tunnels[i]) == 0; i++)         \
+            /* void */;                                                                      \
+        return num;                                                                          \
+    }
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif
diff --git a/src/packet/CMakeLists.txt b/src/packet/CMakeLists.txt
index c4195d5..c155847 100644
--- a/src/packet/CMakeLists.txt
+++ b/src/packet/CMakeLists.txt
@@ -1,4 +1,4 @@
-add_library(packet packet.cpp packet_utils.cpp packet_layer.cpp)
+add_library(packet packet.cpp packet_utils.cpp packet_layer.cpp packet_tunnel.cpp)
 target_include_directories(packet PUBLIC ${CMAKE_CURRENT_LIST_DIR})
 target_include_directories(packet PUBLIC ${CMAKE_SOURCE_DIR}/deps/uthash)
 target_include_directories(packet PUBLIC ${CMAKE_SOURCE_DIR}/include)
diff --git a/src/packet/packet_layer.cpp b/src/packet/packet_layer.cpp
index 1fe59ea..a9c37d4 100644
--- a/src/packet/packet_layer.cpp
+++ b/src/packet/packet_layer.cpp
@@ -1,23 +1,16 @@
 #include "packet_priv.h"
+#include "packet_utils.h"
 
 int packet_get_layer(const struct packet *pkt, int idx, struct layer *out)
 {
-    if (pkt == NULL || out == NULL)
+    const struct raw_layer *raw = packet_get_raw_layer(pkt, idx);
+    if (raw == NULL)
     {
         return -1;
     }
-
-    if (idx < 0 || idx >= pkt->layers_used)
+    else
     {
-        return -1;
+        layer_convert(raw, out);
+        return 0;
     }
-
-    const struct raw_layer *raw = &pkt->layers[idx];
-    out->proto = raw->proto;
-    out->header_len = raw->hdr_len;
-    out->payload_len = raw->pld_len;
-    out->header.raw = raw->hdr_ptr;
-    out->payload = raw->pld_ptr;
-
-    return 0;
 }
diff --git a/src/packet/packet_tunnel.cpp b/src/packet/packet_tunnel.cpp
new file mode 100644
index 0000000..e05bd15
--- /dev/null
+++ b/src/packet/packet_tunnel.cpp
@@ -0,0 +1,99 @@
+#include <assert.h>
+
+#include "stellar/tunnel.h"
+#include "packet_priv.h"
+#include "packet_utils.h"
+
+static void layers_to_tunnel(const struct raw_layer *curr, const struct raw_layer *next1, const struct raw_layer *next2, struct tunnel *out)
+{
+    assert(curr);
+
+    // GRE tunnel
+    if (next1 && next1->proto == LAYER_PROTO_GRE)
+    {
+        out->type = TUNNEL_GRE;
+        out->used = 2;
+        layer_convert(curr, &out->layers[0]);
+        layer_convert(next1, &out->layers[1]);
+        return;
+    }
+
+    // GTP tunnel
+    if (next1 && next1->proto == LAYER_PROTO_UDP && next2 && next2->proto == LAYER_PROTO_GTPV1_U)
+    {
+        out->type = TUNNEL_GTP;
+        out->used = 3;
+        layer_convert(curr, &out->layers[0]);
+        layer_convert(next1, &out->layers[1]);
+        layer_convert(next2, &out->layers[2]);
+        return;
+    }
+
+    // IP tunnel
+    if (next1 && (next1->proto == LAYER_PROTO_IPV4 || next1->proto == LAYER_PROTO_IPV6))
+    {
+        out->type = curr->proto == LAYER_PROTO_IPV4 ? TUNNEL_IPV4 : TUNNEL_IPV6;
+        out->used = 1;
+        layer_convert(curr, &out->layers[0]);
+        return;
+    }
+
+    // none tunnel
+    out->type = TUNNEL_NONE;
+    layer_convert(curr, &out->layers[out->used++]);
+    if (next1 && (next1->proto == LAYER_PROTO_TCP || next1->proto == LAYER_PROTO_UDP))
+    {
+        layer_convert(next1, &out->layers[out->used++]);
+    }
+    return;
+}
+
+int packet_get_tunnel_count(const struct packet *pkt)
+{
+    int count = 0;
+    int used = packet_get_layer_count(pkt);
+    const struct raw_layer *curr = NULL;
+
+    for (int i = 0; i < used; i++)
+    {
+        curr = packet_get_raw_layer(pkt, i);
+        if (curr->proto == LAYER_PROTO_IPV4 || curr->proto == LAYER_PROTO_IPV6)
+        {
+            count++;
+        }
+    }
+
+    return count;
+}
+
+// return  0: success 
+// return -1: failed
+int packet_get_tunnel(const struct packet *pkt, int idx, struct tunnel *out)
+{
+    int count = 0;
+    int used = packet_get_layer_count(pkt);
+    const struct raw_layer *curr = NULL;
+    const struct raw_layer *next1 = NULL;
+    const struct raw_layer *next2 = NULL;
+    memset(out, 0, sizeof(struct tunnel));
+
+    for (int i = 0; i < used; i++)
+    {
+        curr = packet_get_raw_layer(pkt, i);
+        next1 = packet_get_raw_layer(pkt, i + 1);
+        next2 = packet_get_raw_layer(pkt, i + 2);
+
+        if (curr->proto == LAYER_PROTO_IPV4 || curr->proto == LAYER_PROTO_IPV6)
+        {
+            if (count == idx)
+            {
+                layers_to_tunnel(curr, next1, next2, out);
+                return 0;
+            }
+
+            count++;
+        }
+    }
+
+    return -1;
+}
diff --git a/src/packet/packet_utils.cpp b/src/packet/packet_utils.cpp
index 6fb52fa..ac413dc 100644
--- a/src/packet/packet_utils.cpp
+++ b/src/packet/packet_utils.cpp
@@ -186,4 +186,18 @@ void packet_free(struct packet *pkt)
     {
         free((void *)pkt);
     }
+}
+
+void layer_convert(const struct raw_layer *in, struct layer *out)
+{
+    if (in == NULL || out == NULL)
+    {
+        return;
+    }
+
+    out->proto = in->proto;
+    out->header_len = in->hdr_len;
+    out->payload_len = in->pld_len;
+    out->header.raw = in->hdr_ptr;
+    out->payload = in->pld_ptr;
 }
\ No newline at end of file
diff --git a/src/packet/packet_utils.h b/src/packet/packet_utils.h
index 55bf1e6..f609556 100644
--- a/src/packet/packet_utils.h
+++ b/src/packet/packet_utils.h
@@ -50,6 +50,8 @@ struct packet *packet_new(uint16_t pkt_len);
 struct packet *packet_dup(const struct packet *pkt);
 void packet_free(struct packet *pkt);
 
+void layer_convert(const struct raw_layer *in, struct layer *out);
+
 #ifdef __cplusplus
 }
 #endif
diff --git a/src/stellar/version.map b/src/stellar/version.map
index f3d0576..d6b92df 100644
--- a/src/stellar/version.map
+++ b/src/stellar/version.map
@@ -1,16 +1,20 @@
 LIBSTELLAR_DEVEL {
 global:
-	packet_get_direction;
-	packet_get_session_id;
-	packet_prepend_sids;
 	packet_get_layer_count;
 	packet_get_layer;
+
+	packet_get_tunnel_count;
+	packet_get_tunnel;
+
+	packet_prepend_sids;
+	packet_get_direction;
+	packet_get_session_id;
+	packet_set_action;
+	packet_get_action;
 	packet_get_raw_data;
 	packet_get_raw_len;
 	packet_get_payload;
 	packet_get_payload_len;
-	packet_set_action;
-	packet_get_action;
 
 	session_exdata_free;
 	stellar_session_exdata_new_index;