log to see what wrong with checksum computatio

ubuntu_intermediate/inter_op_ebpf.c

@@ -69,7 +69,7 @@ int inter_op_ebpf(struct xdp_md *ctx)
     int options_len = (ip->ihl * 4) - sizeof(struct iphdr);
     __u8 *options = (__u8 *)(ip + 1);
 
-    bpf_trace_printk("Packet received on interface %d and and ihl %d option length %d\n", ctx->ingress_ifindex, ip->ihl, options_len);
+//    bpf_trace_printk("Packet received on interface %d and and ihl %d option length %d\n", ctx->ingress_ifindex, ip->ihl, options_len);
 
     __u8 is_register = 1;
     __u8 is_exist_custom_option = 0;
@@ -175,9 +175,12 @@ int inter_op_ebpf(struct xdp_md *ctx)
             // bpf_trace_printk("Packet received on interface %d and option length %d\n", ctx->ingress_ifindex, options_len);
             // ip->check = iph_csum(ip, data_end);
         }
-    }
 
+        int old_check = ip->check;
         ip->check = iph_csum(ip, data_end);
-
+        if (old_check != ip->check){
+            bpf_trace_printk("Old checksum %d - New checksum %d\n", old_check, ip->check);
+        }
+    }
     return XDP_PASS;
 }