feat(net): Full TCP state machine, SYN-ACK packet handler, NetFilter integration, and dynamic netstat

include/net/tcp.h

@@ -3,6 +3,13 @@
 
 #include <net/net.h>
 
+#define TCP_FLAG_FIN 0x01
+#define TCP_FLAG_SYN 0x02
+#define TCP_FLAG_RST 0x04
+#define TCP_FLAG_PSH 0x08
+#define TCP_FLAG_ACK 0x10
+#define TCP_FLAG_URG 0x20
+
 #define TCP_STATE_CLOSED      0
 #define TCP_STATE_LISTEN      1
 #define TCP_STATE_SYN_SENT    2
@@ -27,7 +34,24 @@ typedef struct {
     uint16_t urgent_pointer;
 } __attribute__((packed)) tcp_header_t;
 
+typedef struct tcp_conn {
+    uint32_t local_ip;
+    uint32_t remote_ip;
+    uint16_t local_port;
+    uint16_t remote_port;
+    uint8_t  state;
+    uint32_t seq_num;
+    uint32_t ack_num;
+    bool     in_use;
+} tcp_conn_t;
+
 void tcp_init(void);
 void tcp_receive(const uint8_t* packet, uint16_t length, uint32_t src_ip);
+void tcp_send_packet(uint32_t dst_ip, uint16_t src_port, uint16_t dst_port,
+                     uint32_t seq, uint32_t ack, uint8_t flags,
+                     const void* payload, uint16_t payload_len);
+
+size_t tcp_get_connections_count(void);
+const tcp_conn_t* tcp_get_connection(size_t index);
 
 #endif // _NET_TCP_H