support craft packet from scratch

include/stellar/layer.h

@@ -79,12 +79,15 @@ int packet_get_layer_by_idx(const struct packet *pkt, int idx, struct layer *out
     for (int i = packet_get_layer_count(pkt) - 1; i >= 0 && packet_get_layer_by_idx(pkt, i, &layer) == 0; i--)
 
 #define PACKET_GETALL_LAYERS(pkt, layers)                                                 \
-    {                                                                                     \
-        int num = MIN(packet_get_layer_count(pkt), (sizeof(layers) / sizeof(layers[0]))); \
+    ({                                                                                    \
+        memset(layers, 0, sizeof(layers));                                                \
+        int size = sizeof(layers) / sizeof(layers[0]);                                    \
+        int count = packet_get_layer_count(pkt);                                          \
+        int num = count > size ? size : count;                                            \
         for (int i = 0; i < num && packet_get_layer_by_idx(pkt, i, &layers[i]) == 0; i++) \
             /* void */;                                                                   \
-        return num;                                                                       \
-    }
+        num;                                                                              \
+    })
 
 #ifdef __cplusplus
 }

include/stellar/packet.h

@@ -38,6 +38,7 @@ uint16_t packet_get_payload_len(const struct packet *pkt);
 
 struct packet *imitate_tcp_packet(const struct packet *origin_pkt, uint32_t tcp_seq, uint32_t tcp_ack, uint8_t tcp_flags, const char *tcp_payload, uint16_t tcp_payload_len);
 struct packet *imitate_udp_packet(const struct packet *origin_pkt, const char *udp_payload, uint16_t udp_payload_len);
+struct packet *craft_packet_from_scratch(const struct layer larers[], uint16_t layer_count, const char *payload, uint16_t payload_len);
 
 #ifdef __cplusplus
 }