fix

added standard parameter format.

main.cpp

@@ -44,30 +44,57 @@ void outbound(int raw, int tun) {
     perror("outbound read");
 }
 
-int main(int argc, char *argv[]) {
-    ifreq ifr{};
-    ifr.ifr_flags = IFF_TUN | IFF_NO_PI;
+void show_usage() {
+    printf("Usage Help:\n\n");
+    printf("-i <IP>: IP to connect\n");
+    printf("-h: show this usage help");
+    return;
+}
 
-    auto raw = socket(AF_INET, SOCK_RAW, IPPROTO_IPIP);
-    if(raw < 0){
-        perror("socket init error");
+int main(int argc, char *argv[]) {
+    
+    if(argc <= 1){
+        printf("Wrong usage! Type -h to see usage help.");
+        return 0;
     }
-    auto tun = open("/dev/net/tun", O_RDWR);
-    if(tun < 0){
-        perror("tun init error");
+    if(argv[1] == "-h"){
+        show_usage();
+        return 0;
     }
+    if(argv[1] == "-i"){
+        ifreq ifr{};
+        ifr.ifr_flags = IFF_TUN | IFF_NO_PI;
+
+        auto raw = socket(AF_INET, SOCK_RAW, IPPROTO_IPIP);
+        if(raw < 0){
+            perror("socket init error");
+            return -1;
+        }
+        auto tun = open("/dev/net/tun", O_RDWR);
+        if(tun < 0){
+            perror("tun init error");
+            return -1;
+        }
     
-    if(ioctl(tun, TUNSETIFF, &ifr) < 0){
-        perror("ioctl error");
-    }
+        if(ioctl(tun, TUNSETIFF, &ifr) < 0){
+            perror("ioctl error");
+            return -1;
+        }
 
-    remote = inet_addr(argv[1]);
+        remote = inet_addr(argv[2]);
 
-    std::cout << raw << std::endl;
-    std::cout << tun << std::endl;
+        std::cout << raw << std::endl;
+        std::cout << tun << std::endl;
 
-    std::thread t1(inbound, raw, tun);
-    std::thread t2(outbound, raw, tun);
-    t1.join();
-    t2.join();
+        std::thread t1(inbound, raw, tun);
+        std::thread t2(outbound, raw, tun);
+        t1.join();
+        t2.join();
+        
+        return 0;
+    }
+    else {
+        printf("Wrong usage! Type -h to see usage help.");
+        return 0;
+    }
 }