Refactored packet API to support struct layer (using union to contain different types of encapsulation headers)

src/packet/packet_layer.cpp

@@ -0,0 +1,23 @@
+#include "packet_priv.h"
+
+int packet_get_layer(const struct packet *pkt, int idx, struct layer *out)
+{
+    if (pkt == NULL || out == NULL)
+    {
+        return -1;
+    }
+
+    if (idx < 0 || idx >= pkt->layers_used)
+    {
+        return -1;
+    }
+
+    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;
+}