Update README.md

README.md

@@ -16,9 +16,14 @@ Usage: goodbyedpi.exe [OPTION...]
  -p          block passive DPI
  -r          replace Host with hoSt
  -s          remove space between host header and its value
+ -m          mix Host header case (test.com -> tEsT.cOm)
  -f [value]  set HTTP fragmentation to value
  -e [value]  set HTTPS fragmentation to value
  -a          additional space between Method and Request-URI (enables -s, may break sites)
+ -w          try to find and parse HTTP traffic on all processed ports (not only on port 80)
+ --port      additional TCP port to perform fragmentation on (and HTTP tricks with -w)
+ --dns-addr  redirect UDP DNS requests to the supplied IP address (experimental)
+ --dns-port  redirect UDP DNS requests to the supplied port (53 by default)
 
  -1          -p -r -s -f 2 -e 2 (most compatible mode, default)
  -2          -p -r -s -f 2 -e 40 (better speed yet still compatible)
@@ -26,7 +31,7 @@ Usage: goodbyedpi.exe [OPTION...]
  -4          -p -r -s (best speed)
 ```
 
-Try to run `goodbyedpi.exe -1 -a` first. If you can open blocked websites it means your ISP has DPI which can be circumvented. This is the slowest and prone to break websites mode, but suitable for most DPI.
+Try to run `goodbyedpi.exe -1 -a -m --dns-addr 77.88.8.8 --dns-port 1253` first. This is the most hardcore mode which will show if this program is suitable for your ISP and DPI vendor. If you can open blocked websites with these options, it means your ISP has DPI which can be circumvented. This is the slowest and prone to break websites mode, but suitable for most DPI.
 
 Try `-1` to see if it works too.
 
@@ -48,6 +53,7 @@ Active DPI is more tricky to fool. Currently the software uses 4 methods to circ
 * Replacing `Host` header with `hoSt`
 * Removing space between header name and value in `Host` header
 * Adding additional space between HTTP Method (GET, POST etc) and URI
+* Mixing case of Host header value
 
 These methods should not break any website as they're fully compatible with TCP and HTTP standards, yet it's sufficient to prevent DPI data classification and to circumvent censorship. Additional space may break some websites, although it's acceptable by HTTP/1.1 specification (see 19.3 Tolerant Applications).
 

dnsredir.c

@@ -0,0 +1,178 @@
+/*
+ * DNS UDP Connection Tracker for GoodbyeDPI
+ *
+ * This is a simple connection tracker for DNS UDP data.
+ * It's not a proper one. The caveats as follows:
+ *    * Uses only source IP address and port as a hash key;
+ *    * One-shot only. Removes conntrack record as soon as gets the reply;
+ *    * Does not properly parse DNS request and response, only checks some bytes;
+ *
+ * But anyway, it works fine for DNS.
+ */
+
+#include <windows.h>
+#include <time.h>
+#include <stdio.h>
+#include "dnsredir.h"
+#include "uthash.h"
+
+// IPv6 incompatible!
+#define UDP_CONNRECORD_KEY_LEN 6
+
+#define DNS_CLEANUP_INTERVAL_SEC 30
+
+#ifndef debug
+#define debug(...) do {} while (0)
+#endif
+
+#ifndef debug
+#define debug(...) printf(...)
+#endif
+
+/* HACK!
+ * uthash uses strlen() for HASH_FIND_STR.
+ * We have null bytes in our key, so we can't use strlen()
+ * And since it's always UDP_CONNRECORD_KEY_LEN bytes long,
+ * we don't need to use any string function to determine length.
+ */
+#undef uthash_strlen
+#define uthash_strlen(s) UDP_CONNRECORD_KEY_LEN
+
+typedef struct udp_connrecord {
+    /* key (srcip[4] + srcport[2]) */
+    char key[UDP_CONNRECORD_KEY_LEN];
+    time_t time;         /* time when this record was added */
+    uint32_t dstip;
+    uint16_t dstport;
+    UT_hash_handle hh;   /* makes this structure hashable */
+} udp_connrecord_t;
+
+static time_t last_cleanup = 0;
+static udp_connrecord_t *conntrack = NULL;
+
+inline static void construct_key(const uint32_t srcip, const uint16_t srcport, char *key) {
+    debug("Construct key enter\n");
+    if (key) {
+        debug("Constructing key\n");
+
+        *(uint32_t*)(key) = srcip;
+        *(uint16_t*)(key + sizeof(srcip)) = srcport;
+    }
+    debug("Construct key end\n");
+}
+
+inline static void deconstruct_key(const char *key, udp_connrecord_t *connrecord,
+                                   conntrack_info_t *conn_info) {
+    debug("Deconstruct key enter\n");
+    if (key && conn_info) {
+        debug("Deconstructing key\n");
+
+        conn_info->srcip = *(uint32_t*)(key);
+        conn_info->srcport = *(uint16_t*)(key + sizeof(conn_info->srcip));
+        conn_info->dstip = connrecord->dstip;
+        conn_info->dstport = connrecord->dstport;
+    }
+    debug("Deconstruct key end\n");
+}
+
+static int check_get_udp_conntrack_key(const char *key, udp_connrecord_t **connrecord) {
+    udp_connrecord_t *tmp_connrecord = NULL;
+    if (!conntrack) return FALSE;
+
+    HASH_FIND_STR(conntrack, key, tmp_connrecord);
+    if (tmp_connrecord) {
+        if (connrecord)
+            *connrecord = tmp_connrecord;
+        debug("check_get_udp_conntrack_key found key\n");
+        return TRUE;
+    }
+    debug("check_get_udp_conntrack_key key not found\n");
+    return FALSE;
+}
+
+static int add_udp_conntrack(const uint32_t srcip, const uint16_t srcport,
+                             const uint32_t dstip, const uint16_t dstport) {
+    udp_connrecord_t *tmp_connrecord = malloc(sizeof(udp_connrecord_t));
+    if (!(srcip && srcport && dstip && dstport))
+        return FALSE;
+
+    construct_key(srcip, srcport, tmp_connrecord->key);
+
+    if (!check_get_udp_conntrack_key(tmp_connrecord->key, NULL)) {
+        tmp_connrecord->time = time(NULL);
+        tmp_connrecord->dstip = dstip;
+        tmp_connrecord->dstport = dstport;
+        HASH_ADD_STR(conntrack, key, tmp_connrecord);
+        debug("Added UDP conntrack\n");
+        return TRUE;
+    }
+    debug("Not added UDP conntrack\n");
+    return FALSE;
+}
+
+void dns_cleanup() {
+    udp_connrecord_t *tmp_connrecord, *tmp_connrecord2 = NULL;
+
+    if (last_cleanup == 0) {
+        last_cleanup = time(NULL);
+        return;
+    }
+
+    if (difftime(time(NULL), last_cleanup) >= DNS_CLEANUP_INTERVAL_SEC) {
+        last_cleanup = time(NULL);
+
+        HASH_ITER(hh, conntrack, tmp_connrecord, tmp_connrecord2) {
+            if (difftime(last_cleanup, tmp_connrecord->time) >= DNS_CLEANUP_INTERVAL_SEC) {
+                HASH_DEL(conntrack, tmp_connrecord);
+                free(tmp_connrecord);
+            }
+        }
+    }
+}
+
+int dns_handle_outgoing(const uint32_t srcip, const uint16_t srcport,
+                        const uint32_t dstip, const uint16_t dstport,
+                        const char *packet_data, const UINT packet_dataLen) {
+
+    if (packet_dataLen < 16)
+        return FALSE;
+
+    dns_cleanup();
+
+    if ((ntohs(*(const uint16_t*)(packet_data + 2)) & 0xFA00) == 0 &&
+        (ntohs(*(const uint32_t*)(packet_data + 6))) == 0) {
+        /* Looks like DNS request */
+        debug("trying to add srcport = %hu, dstport = %hu\n", ntohs(srcport), ntohs(dstport));
+        return add_udp_conntrack(srcip, srcport, dstip, dstport);
+    }
+    debug("____dns_handle_outgoing FALSE: srcport = %hu, dstport = %hu\n", ntohs(srcport), ntohs(dstport));
+    return FALSE;
+}
+
+int dns_handle_incoming(const uint32_t srcip, const uint16_t srcport,
+                        const uint32_t dstip, const uint16_t dstport,
+                        const char *packet_data, const UINT packet_dataLen,
+                        conntrack_info_t *conn_info) {
+
+    char key[UDP_CONNRECORD_KEY_LEN];
+    udp_connrecord_t *tmp_connrecord = NULL;
+
+    if (packet_dataLen < 16 || !conn_info)
+        return FALSE;
+
+    dns_cleanup();
+
+    if ((ntohs(*(const uint16_t*)(packet_data + 2)) & 0xF800) == 0x8000) {
+        /* Looks like DNS response */
+        construct_key(srcip, srcport, key);
+        if (check_get_udp_conntrack_key(key, &tmp_connrecord) && tmp_connrecord) {
+            /* Connection exists in conntrack, moving on */
+            deconstruct_key(key, tmp_connrecord, conn_info);
+            HASH_DEL(conntrack, tmp_connrecord);
+            free(tmp_connrecord);
+            return TRUE;
+        }
+    }
+    debug("____dns_handle_incoming FALSE: srcport = %hu, dstport = %hu\n", ntohs(srcport), ntohs(dstport));
+    return FALSE;
+}

dnsredir.h

@@ -0,0 +1,17 @@
+#include <stdint.h>
+
+typedef struct conntrack_info {
+    uint32_t srcip;
+    uint16_t srcport;
+    uint32_t dstip;
+    uint16_t dstport;
+} conntrack_info_t;
+
+int dns_handle_incoming(const uint32_t srcip, const uint16_t srcport,
+                        const uint32_t dstip, const uint16_t dstport,
+                        const char *packet_data, const UINT packet_dataLen,
+                        conntrack_info_t *conn_info);
+
+int dns_handle_outgoing(const uint32_t srcip, const uint16_t srcport,
+                        const uint32_t dstip, const uint16_t dstport,
+                        const char *packet_data, const UINT packet_dataLen);

goodbyedpi.c

@@ -4,18 +4,20 @@
 
 #include <stdio.h>
 #include <stdlib.h>
+#include <ctype.h>
 #include <signal.h>
 #include <unistd.h>
 #include <string.h>
-#include <winsock2.h>
+#include <getopt.h>
 #include "windivert.h"
+#include "dnsredir.h"
 
 #define die() do { printf("Something went wrong!\n" \
     "Make sure you're running this program with administrator privileges\n"); \
     sleep(10); exit(EXIT_FAILURE); } while (0)
 
 #define MAX_FILTERS 4
-#define MAX_PACKET_SIZE 1516
+#define MAX_PACKET_SIZE 9016
 #define IPV4_HDR_LEN 20
 #define TCP_HDR_LEN 20
 #define IPV4_TOTALLEN_OFFSET 2
@@ -55,9 +57,45 @@ static const char *http_methods[] = {
     "OPTIONS ",
 };
 
+static struct option long_options[] = {
+    {"port",      required_argument, 0,  'z' },
+    {"dns-addr",  required_argument, 0,  'd' },
+    {"dns-port",  required_argument, 0,  'g' },
+    {0,           0,                 0,   0  }
+};
+
+static char *filter_string = "(ip and tcp and "
+        "(inbound and (("
+         "((ip.Id == 0x0001 or ip.Id == 0x0000) and tcp.SrcPort == 80 and tcp.Ack) or "
+         "((tcp.SrcPort == 80 or tcp.SrcPort == 443) and tcp.Ack and tcp.Syn)"
+         ") and " DIVERT_NO_LOCALNETS_SRC ") or "
+        "(outbound and "
+         "(tcp.DstPort == 80 or tcp.DstPort == 443) and tcp.Ack and "
+         DIVERT_NO_LOCALNETS_DST ")"
+        "))";
+
+static void add_filter_str(int proto, int port) {
+    const char *udp = " or (ip and udp and (udp.SrcPort == %d or udp.DstPort == %d))";
+    const char *tcp = " or (ip and tcp and (tcp.SrcPort == %d or tcp.DstPort == %d))";
+
+    char *current_filter = filter_string;
+    int new_filter_size = strlen(current_filter) +
+            (proto == IPPROTO_UDP ? strlen(udp) : strlen(tcp)) + 16;
+    char *new_filter = malloc(new_filter_size);
+
+    strcpy(new_filter, current_filter);
+    if (proto == IPPROTO_UDP)
+        sprintf(&(new_filter[strlen(new_filter)]), udp, port, port);
+    else
+        sprintf(&(new_filter[strlen(new_filter)]), tcp, port, port);
+
+    filter_string = new_filter;
+    free(current_filter);
+}
+
 static char* dumb_memmem(const char* haystack, int hlen, const char* needle, int nlen) {
     // naive implementation
-    if (nlen > hlen) return 0;
+    if (nlen > hlen) return NULL;
     int i;
     for (i=0; i<hlen-nlen+1; i++) {
         if (memcmp(haystack+i,needle,nlen)==0) {
@@ -83,9 +121,9 @@ static HANDLE init(char *filter, UINT64 flags) {
 static int deinit(HANDLE handle) {
     if (handle) {
         WinDivertClose(handle);
-        return 1;
+        return TRUE;
     }
-    return 0;
+    return FALSE;
 }
 
 static void deinit_all() {
@@ -99,6 +137,17 @@ static void sigint_handler(int sig) {
     exit(EXIT_SUCCESS);
 }
 
+static void mix_case(char *pktdata, int pktlen) {
+    int i;
+
+    if (pktlen <= 0) return;
+    for (i = 0; i < pktlen; i++) {
+        if (i % 2) {
+            pktdata[i] = toupper(pktdata[i]);
+        }
+    }
+}
+
 static int is_passivedpi_redirect(const char *pktdata, int pktlen) {
     /* First check if this is HTTP 302 redirect */
     if (memcmp(pktdata, http11_redirect_302, strlen(http11_redirect_302)) == 0 ||
@@ -107,26 +156,49 @@ static int is_passivedpi_redirect(const char *pktdata, int pktlen) {
         /* Then check if this is a redirect to new http site with Connection: close */
         if (dumb_memmem(pktdata, pktlen, location_http, strlen(location_http)) &&
             dumb_memmem(pktdata, pktlen, connection_close, strlen(connection_close))) {
-            return 1;
+            return TRUE;
         }
     }
-    return 0;
+    return FALSE;
 }
 
-/* Finds Host header with \r\n before it */
-static PVOID find_host_header(const char *pktdata, int pktlen) {
-    return dumb_memmem(pktdata, pktlen,
-                http_host_find, strlen(http_host_find));
-}
+static int find_header_and_get_info(const char *pktdata, int pktlen,
+                const char *hdrname,
+                char **hdrnameaddr,
+                char **hdrvalueaddr, int *hdrvaluelen) {
+    char *data_addr_rn;
+    char *hdr_begin;
 
-/* Finds User-Agent header with \r\n before it */
-static PVOID find_useragent_header(const char *pktdata, int pktlen) {
-    return dumb_memmem(pktdata, pktlen,
-                http_useragent_find, strlen(http_useragent_find));
+    *hdrvaluelen = 0;
+    *hdrnameaddr = NULL;
+    *hdrvalueaddr = NULL;
+
+    /* Search for the header */
+    hdr_begin = dumb_memmem(pktdata, pktlen,
+                hdrname, strlen(hdrname));
+    if (!hdr_begin) return FALSE;
+    if ((PVOID)pktdata > (PVOID)hdr_begin) return FALSE;
+
+    /* Set header address */
+    *hdrnameaddr = hdr_begin;
+    *hdrvalueaddr = (PVOID)hdr_begin + strlen(hdrname);
+
+    /* Search for header end (\r\n) */
+    data_addr_rn = dumb_memmem(*hdrvalueaddr,
+                        pktlen - ((PVOID)*hdrvalueaddr - (PVOID)pktdata),
+                        "\r\n", 2);
+    if (data_addr_rn) {
+        *hdrvaluelen = (PVOID)data_addr_rn - (PVOID)*hdrvalueaddr;
+        if (*hdrvaluelen > 0 && *hdrvaluelen <= 512)
+            return TRUE;
+    }
+    return FALSE;
 }
 
 static void change_window_size(const char *pkt, int size) {
-    *(uint16_t*)(pkt + IPV4_HDR_LEN + TCP_WINDOWSIZE_OFFSET) = htons(size);
+    if (size >= 1 && size <= 65535) {
+        *(uint16_t*)(pkt + IPV4_HDR_LEN + TCP_WINDOWSIZE_OFFSET) = htons(size);
+    }
 }
 
 /* HTTP method end without trailing space */
@@ -161,14 +233,23 @@ int main(int argc, char *argv[]) {
     UINT packet_dataLen;
     PWINDIVERT_IPHDR ppIpHdr;
     PWINDIVERT_TCPHDR ppTcpHdr;
+    PWINDIVERT_UDPHDR ppUdpHdr;
+    conntrack_info_t dns_conn_info;
 
     int do_passivedpi = 0, do_fragment_http = 0,
         do_fragment_https = 0, do_host = 0,
-        do_host_removespace = 0, do_additional_space = 0;
+        do_host_removespace = 0, do_additional_space = 0,
+        do_http_allports = 0,
+        do_host_mixedcase = 0, do_dns_redirect = 0;
     int http_fragment_size = 2;
     int https_fragment_size = 2;
-    char *data_addr, *data_addr_rn, *host_addr, *useragent_addr, *method_addr;
-    int data_len, host_len;
+    uint32_t dns_addr = 0;
+    uint16_t dns_port = htons(53);
+    char *host_addr, *useragent_addr, *method_addr;
+    int host_len, useragent_len;
+
+    char *hdr_name_addr = NULL, *hdr_value_addr = NULL;
+    int hdr_value_len;
 
     printf("GoodbyeDPI: Passive DPI blocker and Active DPI circumvention utility\n");
 
@@ -178,7 +259,7 @@ int main(int argc, char *argv[]) {
             = do_fragment_http = do_fragment_https = 1;
     }
 
-    while ((opt = getopt(argc, argv, "1234prsaf:e:")) != -1) {
+    while ((opt = getopt_long(argc, argv, "1234prsaf:e:mw", long_options, NULL)) != -1) {
         switch (opt) {
             case '1':
                 do_passivedpi = do_host = do_host_removespace \
@@ -209,6 +290,9 @@ int main(int argc, char *argv[]) {
                 do_additional_space = 1;
                 do_host_removespace = 1;
                 break;
+            case 'm':
+                do_host_mixedcase = 1;
+                break;
             case 'f':
                 do_fragment_http = 1;
                 http_fragment_size = atoi(optarg);
@@ -225,14 +309,50 @@ int main(int argc, char *argv[]) {
                     exit(EXIT_FAILURE);
                 }
                 break;
+            case 'w':
+                do_http_allports = 1;
+                break;
+            case 'z':
+                /* i is used as a temporary variable here */
+                i = atoi(optarg);
+                if (i <= 0 || i > 65535) {
+                    printf("Port parameter error!\n");
+                    exit(EXIT_FAILURE);
+                }
+                add_filter_str(IPPROTO_TCP, i);
+                i = 0;
+                break;
+            case 'd':
+                do_dns_redirect = 1;
+                dns_addr = inet_addr(optarg);
+                if (!dns_addr) {
+                    printf("DNS address parameter error!\n");
+                    exit(EXIT_FAILURE);
+                }
+                add_filter_str(IPPROTO_UDP, 53);
+                break;
+            case 'g':
+                dns_port = atoi(optarg);
+                if (dns_port <= 0 || dns_port > 65535) {
+                    printf("DNS port parameter error!\n");
+                    exit(EXIT_FAILURE);
+                }
+                add_filter_str(IPPROTO_UDP, dns_port);
+                dns_port = ntohs(dns_port);
+                break;
             default:
                 printf("Usage: goodbyedpi.exe [OPTION...]\n"
                 " -p          block passive DPI\n"
                 " -r          replace Host with hoSt\n"
                 " -s          remove space between host header and its value\n"
                 " -a          additional space between Method and Request-URI (enables -s, may break sites)\n"
+                " -m          mix Host header case (test.com -> tEsT.cOm)\n"
                 " -f [value]  set HTTP fragmentation to value\n"
                 " -e [value]  set HTTPS fragmentation to value\n"
+                " -w          try to find and parse HTTP traffic on all processed ports (not only on port 80)\n"
+                " --port      additional TCP port to perform fragmentation on (and HTTP tricks with -w)\n"
+                " --dns-addr  redirect UDP DNS requests to the supplied IP address (experimental)\n"
+                " --dns-port  redirect UDP DNS requests to the supplied port (53 by default)\n"
                 "\n"
                 " -1          -p -r -s -f 2 -e 2 (most compatible mode, default)\n"
                 " -2          -p -r -s -f 2 -e 40 (better speed yet still compatible)\n"
@@ -243,10 +363,13 @@ int main(int argc, char *argv[]) {
     }
 
     printf("Block passive: %d, Fragment HTTP: %d, Fragment HTTPS: %d, "
-           "hoSt: %d, Host no space: %d, Additional space: %d\n",
+           "hoSt: %d, Host no space: %d, Additional space: %d, Mix Host: %d, "
+           "HTTP AllPorts: %d, DNS redirect: %d\n",
            do_passivedpi, (do_fragment_http ? http_fragment_size : 0),
            (do_fragment_https ? https_fragment_size : 0),
-           do_host, do_host_removespace, do_additional_space);
+           do_host, do_host_removespace, do_additional_space, do_host_mixedcase,
+           do_http_allports, do_dns_redirect
+          );
 
     if (do_fragment_http && http_fragment_size > 2) {
         printf("WARNING: HTTP fragmentation values > 2 are not fully compatible "
@@ -272,16 +395,7 @@ int main(int argc, char *argv[]) {
      * IPv4 filter for inbound HTTP redirection packets and
      * active DPI circumvention
      */
-    filters[filter_num] = init("ip and tcp and "
-        "(inbound and (("
-         "((ip.Id == 0x0001 or ip.Id == 0x0000) and tcp.SrcPort == 80 and tcp.Ack) or "
-         "((tcp.SrcPort == 80 or tcp.SrcPort == 443) and tcp.Ack and tcp.Syn)"
-         ") and " DIVERT_NO_LOCALNETS_SRC ") or "
-        "(outbound and "
-         "(tcp.DstPort == 80 or tcp.DstPort == 443) and tcp.Ack and "
-         DIVERT_NO_LOCALNETS_DST ")"
-        ")",
-        0);
+    filters[filter_num] = init(filter_string, 0);
 
     w_filter = filters[filter_num];
     filter_num++;
@@ -304,7 +418,7 @@ int main(int argc, char *argv[]) {
             if (WinDivertHelperParsePacket(packet, packetLen, &ppIpHdr,
                 NULL, NULL, NULL, &ppTcpHdr, NULL, &packet_data, &packet_dataLen)) {
                 //printf("Got parsed packet, len=%d!\n", packet_dataLen);
-                /* Got a packet WITH DATA */
+                /* Got a TCP packet WITH DATA */
 
                 /* Handle INBOUND packet with data and find HTTP REDIRECT in there */
                 if (addr.Direction == WINDIVERT_DIRECTION_INBOUND && packet_dataLen > 16) {
@@ -316,42 +430,55 @@ int main(int argc, char *argv[]) {
                         should_reinject = 0;
                     }
                 }
-                /* Handle OUTBOUND packet, search for Host header */
+                /* Handle OUTBOUND packet on port 80, search for Host header */
                 else if (addr.Direction == WINDIVERT_DIRECTION_OUTBOUND && 
-                        packet_dataLen > 16 && ppTcpHdr->DstPort == htons(80) &&
+                        packet_dataLen > 16 &&
+                        (do_http_allports ? 1 : (ppTcpHdr->DstPort == htons(80))) &&
                         find_http_method_end(packet_data,
                                              (do_fragment_http ? http_fragment_size : 0)) &&
-                        (do_host || do_host_removespace))
+                        (do_host || do_host_removespace || do_host_mixedcase))
                 {
 
-                    data_addr = find_host_header(packet_data, packet_dataLen);
-                    if (data_addr) {
+                    /* Find Host header */
+                    if (find_header_and_get_info(packet_data, packet_dataLen,
+                        http_host_find, &hdr_name_addr, &hdr_value_addr, &hdr_value_len)) {
+                        host_addr = hdr_value_addr;
+                        host_len = hdr_value_len;
+
+                        if (do_host_mixedcase && host_len > 0 && host_len <= 253) {
+                            mix_case(host_addr, host_len);
+                            should_recalc_checksum = 1;
+                        }
 
                         if (do_host) {
                             /* Replace "Host: " with "hoSt: " */
-                            memcpy(data_addr, http_host_replace, strlen(http_host_replace));
+                            memcpy(hdr_name_addr, http_host_replace, strlen(http_host_replace));
                             should_recalc_checksum = 1;
                             //printf("Replaced Host header!\n");
                         }
 
+                        /* If removing space between host header and its value
+                         * and adding additional space between Method and Request-URI */
                         if (do_additional_space && do_host_removespace) {
                             /* End of "Host:" without trailing space */
-                            host_addr = data_addr + strlen(http_host_find) - 1;
                             method_addr = find_http_method_end(packet_data,
                                                             (do_fragment_http ? http_fragment_size : 0));
 
                             if (method_addr) {
-                                memmove(method_addr + 1, method_addr, (PVOID)host_addr - (PVOID)method_addr);
+                                memmove(method_addr + 1, method_addr,
+                                        (PVOID)host_addr - (PVOID)method_addr - 1);
                                 should_recalc_checksum = 1;
                             }
                         }
+                        /* If just removing space between host header and its value */
                         else if (do_host_removespace) {
-                            host_addr = data_addr + strlen(http_host_find);
+                            if (find_header_and_get_info(packet_data, packet_dataLen,
+                                                        http_useragent_find, &hdr_name_addr,
+                                                         &hdr_value_addr, &hdr_value_len))
+                            {
+                                useragent_addr = hdr_value_addr;
+                                useragent_len = hdr_value_len;
 
-                            data_addr_rn = dumb_memmem(host_addr,
-                                                       packet_dataLen - ((PVOID)host_addr - packet_data),
-                                                       "\r\n", 2);
-                            if (data_addr_rn) {
                                 /* We move Host header value by one byte to the left and then
                                  * "insert" stolen space to the end of User-Agent value because
                                  * some web servers are not tolerant to additional space in the
@@ -359,58 +486,48 @@ int main(int argc, char *argv[]) {
                                  *
                                  * Nothing is done if User-Agent header is missing.
                                  */
-                                host_len = data_addr_rn - host_addr;
-                                useragent_addr = find_useragent_header(packet_data, packet_dataLen);
-                                if (host_len <= 253 && useragent_addr) {
-                                    useragent_addr += strlen(http_useragent_find);
+                                if (host_len > 0 && host_len <= 253 &&
+                                    useragent_addr && useragent_len > 0) {
                                     /* useragent_addr is in the beginning of User-Agent value */
 
-                                    data_len = packet_dataLen - ((PVOID)useragent_addr - packet_data);
-                                    data_addr_rn = dumb_memmem(useragent_addr,
-                                                            data_len, "\r\n", 2);
-                                    /* data_addr_rn is in the end of User-Agent value */
+                                    if (useragent_addr > host_addr) {
+                                        /* Move one byte to the LEFT from "Host:"
+                                        * to the end of User-Agent
+                                        */
+                                        memmove(host_addr - 1, host_addr, useragent_len);
+                                        host_addr -= 1;
+                                        /* Put space in the end of User-Agent header */
+                                        *(char*)((PVOID)useragent_addr + useragent_len - 1) = ' ';
+                                        should_recalc_checksum = 1;
+                                        //printf("Replaced Host header!\n");
+                                    }
+                                    else {
+                                        /* User-Agent goes BEFORE Host header */
 
-                                    if (data_addr_rn) {
-                                        if (useragent_addr > host_addr) {
-                                            /* User-Agent goes AFTER Host header */
-                                            data_len = (PVOID)data_addr_rn - (PVOID)host_addr;
-
-                                            /* Move one byte to the LEFT from "Host:"
-                                            * to the end of User-Agent
-                                            */
-                                            memmove(host_addr - 1, host_addr, data_len);
-                                            /* Put space in the end of User-Agent header */
-                                            *(char*)(data_addr_rn - 1) = ' ';
-                                            should_recalc_checksum = 1;
-                                            //printf("Replaced Host header!\n");
-                                        }
-                                        else {
-                                            /* User-Agent goes BEFORE Host header */
-                                            data_len = (PVOID)host_addr - (PVOID)data_addr_rn - 1;
-
-                                            /* Move one byte to the RIGHT from the end of User-Agent
-                                            * to the "Host:"
-                                            */
-                                            memmove(data_addr_rn + 1, data_addr_rn, data_len);
-                                            /* Put space in the end of User-Agent header */
-                                            *(char*)(data_addr_rn) = ' ';
-                                            should_recalc_checksum = 1;
-                                            //printf("Replaced Host header!\n");
-                                        }
-                                    } /* if (dara_addr_rn) */
+                                        /* Move one byte to the RIGHT from the end of User-Agent
+                                        * to the "Host:"
+                                        */
+                                        memmove((PVOID)useragent_addr + useragent_len + 1,
+                                                (PVOID)useragent_addr + useragent_len,
+                                                useragent_len - 1);
+                                        /* Put space in the end of User-Agent header */
+                                        *(char*)((PVOID)useragent_addr + useragent_len) = ' ';
+                                        should_recalc_checksum = 1;
+                                        //printf("Replaced Host header!\n");
+                                    }
                                 } /* if (host_len <= 253 && useragent_addr) */
-                            } /* if (data_addr_rn) */
+                            } /* if (find_header_and_get_info http_useragent) */
                         } /* else if (do_host_removespace) */
-                    } /* if (data_addr) */
+                    } /* if (find_header_and_get_info http_host) */
                 } /* Handle OUTBOUND packet with data */
-            } /* Handle packet with data */
+            } /* Handle TCP packet with data */
 
             /* Else if we got TCP packet without data */
             else if (WinDivertHelperParsePacket(packet, packetLen, &ppIpHdr,
                 NULL, NULL, NULL, &ppTcpHdr, NULL, NULL, NULL)) {
-                /* If we got SYN+ACK packet */
-                if (addr.Direction == WINDIVERT_DIRECTION_INBOUND && 
-                    ppTcpHdr->Syn == 1) {
+                /* If we got INBOUND SYN+ACK packet */
+                if (addr.Direction == WINDIVERT_DIRECTION_INBOUND &&
+                    ppTcpHdr->Syn == 1 && ppTcpHdr->Ack == 1) {
                     //printf("Changing Window Size!\n");
                     if (do_fragment_http && ppTcpHdr->SrcPort == htons(80)) {
                         change_window_size(packet, http_fragment_size);
@@ -423,6 +540,45 @@ int main(int argc, char *argv[]) {
                 }
             }
 
+            /* Else if we got UDP packet with data */
+            else if (WinDivertHelperParsePacket(packet, packetLen, &ppIpHdr,
+                NULL, NULL, NULL, NULL, &ppUdpHdr, &packet_data, &packet_dataLen)) {
+
+                if (addr.Direction == WINDIVERT_DIRECTION_INBOUND) {
+                    if (dns_handle_incoming(ppIpHdr->DstAddr, ppUdpHdr->DstPort,
+                                        ppIpHdr->SrcAddr, ppUdpHdr->SrcPort,
+                                        packet_data, packet_dataLen,
+                                        &dns_conn_info))
+                    {
+                        /* Changing source IP and port to the values
+                         * from DNS conntrack */
+                        ppIpHdr->SrcAddr = dns_conn_info.dstip;
+                        ppUdpHdr->DstPort = dns_conn_info.srcport;
+                        ppUdpHdr->SrcPort = dns_conn_info.dstport;
+                        should_recalc_checksum = 1;
+                    }
+                    else {
+                        printf("[DNS] Error handling incoming packet!\n");
+                    }
+                }
+
+                else if (addr.Direction == WINDIVERT_DIRECTION_OUTBOUND) {
+                    if (dns_handle_outgoing(ppIpHdr->SrcAddr, ppUdpHdr->SrcPort,
+                                        ppIpHdr->DstAddr, ppUdpHdr->DstPort,
+                                        packet_data, packet_dataLen))
+                    {
+                        /* Changing destination IP and port to the values
+                         * from configuration */
+                        ppIpHdr->DstAddr = dns_addr;
+                        ppUdpHdr->DstPort = dns_port;
+                        should_recalc_checksum = 1;
+                    }
+                    else {
+                        printf("[DNS] Error handling outgoing packet!\n");
+                    }
+                }
+            }
+
             if (should_reinject) {
                 //printf("Re-injecting!\n");
                 if (should_recalc_checksum) {