float ip

main.cpp

@@ -10,18 +10,49 @@
 #include <unistd.h>
 #include <arpa/inet.h>
 #include <boost/program_options.hpp>
+#include <netdb.h>
+//#include <net/checksum.h>
+
+struct Meta {
+    unsigned char src_id;
+    unsigned char dst_id;
+    unsigned short reversed;
+};
 
 #define decrypt_package encrypt_package
 
-namespace po = boost::program_options;
+unsigned char local_id;
+unsigned char remote_id;
+sockaddr_in remote_addr{.sin_family = AF_INET};
+
+/* Checksum a block of data */
+uint16_t csum(uint16_t *packet, int packlen) {
+
+    unsigned long sum = 0;
+
+    while (packlen > 1) {
+
+        sum += *(packet++);
+        packlen -= 2;
+    }
+
+    if (packlen > 0)
+        sum += *(unsigned char *) packet;
+
+    /* TODO: this depends on byte order */
+
+    while (sum >> 16)
+        sum = (sum & 0xffff) + (sum >> 16);
 
-in_addr_t remote;
-auto cipher = (unsigned char *) "Mathematics is the art of giving the same name to different things.";
-auto cipher_length = strlen((char *) cipher);
+    return (uint16_t) ~sum;
+}
+
+char *secret;
+size_t secret_length = strlen(secret);
 
 void encrypt_package(unsigned char *buffer, size_t length) {
     for (auto i = 0; i < length; i++) {
-        buffer[i] ^= cipher[i % cipher_length];
+        buffer[i] ^= secret[i % secret_length];
     }
 }
 
@@ -35,14 +66,20 @@ void inbound(int raw, int tun) {
         auto *packet = (iphdr *) buffer;
         auto overhead = packet->ihl * 4;
         auto payload = buffer + overhead;
-//        auto inner = (iphdr *) payload;
+        auto meta = (Meta *) payload;
+        if (!(meta->src_id == remote_id && meta->dst_id == local_id && meta->reversed == 0)) continue;
+        auto inner = (iphdr *) (payload + sizeof(Meta));
+        auto payload_length = packet_length - overhead - sizeof(Meta);
+        decrypt_package((unsigned char *) inner, payload_length);
+//        if (ip_fast_csum(inner, inner->ihl)) continue;
+        if (csum((uint16_t *) inner, inner->ihl * 4)) continue;
 //        std::cout << "packet_length " << packet_length
 //                  << " tot_len " << ntohs(packet->tot_len)
 //                  << " inner->tot_len " << ntohs(inner->tot_len)
 //                  << " from " << inet_ntoa(address.sin_addr) << std::endl;
-        auto payload_length = packet_length - overhead;
-        decrypt_package(payload, payload_length);
-        if (write(tun, payload, payload_length) < 0) {
+        remote_addr = address;
+
+        if (write(tun, inner, payload_length) < 0) {
             perror("inbound write");
         }
     }
@@ -52,12 +89,15 @@ void inbound(int raw, int tun) {
 // tun -> internet
 void outbound(int raw, int tun) {
     unsigned char buffer[ETH_DATA_LEN];
-    sockaddr_in address{.sin_family = AF_INET};
-    address.sin_addr.s_addr = remote;
+    auto meta = (Meta *) buffer;
+    meta->src_id = local_id;
+    meta->dst_id = remote_id;
+    meta->reversed = 0;
+    auto inner = buffer + sizeof(Meta);
     size_t packet_length;
-    while ((packet_length = read(tun, buffer, sizeof(buffer))) >= 0) {
-        encrypt_package(buffer, packet_length);
-        if (sendto(raw, buffer, packet_length, 0, (sockaddr *) &address, sizeof(address)) < 0) {
+    while ((packet_length = read(tun, inner, sizeof(buffer) - sizeof(Meta))) >= 0) {
+        encrypt_package(inner, packet_length);
+        if (sendto(raw, buffer, packet_length + sizeof(Meta), 0, (sockaddr *) &remote_addr, sizeof(remote_addr)) < 0) {
             perror("outbound write");
         }
     }
@@ -66,28 +106,21 @@ void outbound(int raw, int tun) {
 
 int main(int argc, char *argv[]) {
 
-    po::options_description desc("Allowed options");
-    desc.add_options()
-            ("help,h", "see how to use me elegantly")
-            ("IP,i", po::value<std::string>(), "IP to connect")
-            ("dev,d", po::value<std::string>(), "tunnel device's name")
-            ("postup,p", po::value<std::string>(), "post up script");
+    local_id = atoi(getenv("local_id"));
+    remote_id = atoi(getenv("remote_id"));
+    auto endpoint = gethostbyname(getenv("endpoint"));
+    unsigned char proto = atoi(getenv("proto"));
+    secret = getenv("secret");
+    auto dev = getenv("dev");
+    auto up = getenv("up");
 
-    po::variables_map args;
-    po::store(po::parse_command_line(argc, argv, desc), args);
-    po::notify(args);
-
-    if (args.count("help") || !args.count("IP") || !args.count("dev")) {
-        std::cout << desc << std::endl;
-        return -1;
-    }
+    remote_addr.sin_addr.s_addr = ((in_addr *) endpoint->h_name)->s_addr;
 
     ifreq ifr{};
     ifr.ifr_flags = IFF_TUN | IFF_NO_PI;
-    strncpy(ifr.ifr_name, args["dev"].as<std::string>().c_str(), IFNAMSIZ);
-    remote = inet_addr(args["IP"].as<std::string>().c_str());
+    strncpy(ifr.ifr_name, dev, IFNAMSIZ);
 
-    auto raw = socket(AF_INET, SOCK_RAW, 144);
+    auto raw = socket(AF_INET, SOCK_RAW, proto);
     if (raw < 0) {
         perror("socket init error");
         return -1;
@@ -103,9 +136,7 @@ int main(int argc, char *argv[]) {
         return -1;
     }
 
-    if (args.count("postup")) {
-        system(args["postup"].as<std::string>().c_str());
-    }
+    system(up);
 
     std::thread t1(inbound, raw, tun);
     std::thread t2(outbound, raw, tun);
@@ -114,3 +145,4 @@ int main(int argc, char *argv[]) {
 
     return 0;
 }
+