fix config

src/config.h

@@ -0,0 +1,5 @@
+#pragma once
+#include <linux/bpf.h>
+#define LOW_PORT 1
+const __u16 open_ports[] = {22};
+#define HIGH_PORT 65535

src/main.c

@@ -1,5 +1,6 @@
 #include <linux/bpf.h>
 #define fuck_formater
+#include "config.h"
 #include <bpf/bpf_endian.h>
 #include <bpf/bpf_helpers.h>
 
@@ -47,9 +48,7 @@
 #define SYN_MASK 0b00000010
 #define ACK_MASK 0b00010000
 
-#define LOW_PORT 4000
+
-const __u16 open_ports[] = {4444};
-#define HIGH_PORT 5000
 
 #define MAX_ITERATIONS 1024
 
@@ -221,6 +220,9 @@ int xdp_drop_prog(struct xdp_md *ctx) {
 
   // check SYN
   if (tcp_flags & SYN_MASK) {
+    if (tcp_flags & ACK_MASK) {
+      return XDP_PASS; // pass if syn-ack;
+    }
     if (mulberry32_at((__u32)time_seed, dst_port) % 3 == 0) {
       __u16 *src_port_ptr = (__u16 *)(tcp_packet_data + TCP_SRC_PORT_OFFSET);
       const __u16 src_port = bpf_ntohs(*src_port_ptr);
@@ -336,10 +338,10 @@ int xdp_drop_prog(struct xdp_md *ctx) {
         __builtin_memcpy((__u8 *)data, src_mac, MAC_SIZE);
       }
       return XDP_TX;
-    }
     } else {
       return XDP_DROP;
     }
+  }
 
   return XDP_PASS;
 }