Merge branch 'ipv6' into masterv6

Some DPI send several TCP RST or HTTP redirection packets with
increasing IP ID number. Handle them all.

README.md

@@ -24,6 +24,8 @@ Usage: goodbyedpi.exe [OPTION...]
  -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      [value]    additional TCP port to perform fragmentation on (and HTTP tricks with -w)
+ --ip-id     [value]    handle additional IP ID (decimal, drop redirects and TCP RSTs with this ID).
+                        This option can be supplied multiple times.
  --dns-addr  [value]    redirect UDP DNS requests to the supplied IP address (experimental)
  --dns-port  [value]    redirect UDP DNS requests to the supplied port (53 by default)
  --dns-verb             print verbose DNS redirection messages
@@ -48,11 +50,11 @@ Use `goodbyedpi.exe -4` if it works for your ISP's DPI. This is the fastest mode
 
 ### Passive DPI
 
-Most Passive DPI send HTTP 302 Redirect if you try to access blocked website over HTTP and TCP Reset in case of HTTPS, faster than destination website. Packets sent by DPI always have IP Identification field equal to `0x0000` or `0x0001`, as seen with Russian providers. These packets, if they redirect you to another website (censorship page), are blocked by GoodbyeDPI.
+Most Passive DPI send HTTP 302 Redirect if you try to access blocked website over HTTP and TCP Reset in case of HTTPS, faster than destination website. Packets sent by DPI usually have IP Identification field equal to `0x0000` or `0x0001`, as seen with Russian providers. These packets, if they redirect you to another website (censorship page), are blocked by GoodbyeDPI.
 
 ### Active DPI
 
-Active DPI is more tricky to fool. Currently the software uses 4 methods to circumvent Active DPI:
+Active DPI is more tricky to fool. Currently the software uses 6 methods to circumvent Active DPI:
 
 * TCP-level fragmentation for first data packet
 * TCP-level fragmentation for persistent (keep-alive) HTTP sessions
@@ -79,26 +81,8 @@ And for x86_64:
 
 # How to install as Windows Service
 
-One way is using an [srvstart](http://www.rozanski.org.uk/software) program.  
-Unpack it to `goodbyedpi` directory and create 3 files:
-
-*goodbyedpi.ini*
-```INI
-[GoodByeDPI]
-startup=goodbyedpi.exe
-shutdown_method=winmessage
-auto_restart=n
-```
-*srvinstall.bat*
-```Batchfile
-srvstart install GoodByeDPI -c %CD%\goodbyedpi.ini
-```
-*srvremove.bat*
-```Batchfile
-srvstart remove GoodByeDPI
-```
-Run these batch files as Administrator to install/remove service.  
-Open Windows Services panel to run service or make it start automaticaly.
+Use `service_install_russia_blacklist.cmd`, `service_install_russia_blacklist_dnsredir.cmd` and `service_remove.cmd` scripts.  
+Modify them according to your own needs.
 
 # Similar projects
 

dnsredir.c

@@ -17,8 +17,8 @@
 #include "dnsredir.h"
 #include "uthash.h"
 
-// IPv6 incompatible!
-#define UDP_CONNRECORD_KEY_LEN 6
+/* key ('4' for IPv4 or '6' for IPv6 + srcip[16] + srcport[2]) */
+#define UDP_CONNRECORD_KEY_LEN 19
 
 #define DNS_CLEANUP_INTERVAL_SEC 30
 
@@ -32,10 +32,10 @@
 #define uthash_strlen(s) UDP_CONNRECORD_KEY_LEN
 
 typedef struct udp_connrecord {
-    /* key (srcip[4] + srcport[2]) */
+    /* key ('4' for IPv4 or '6' for IPv6 + srcip[16] + srcport[2]) */
     char key[UDP_CONNRECORD_KEY_LEN];
     time_t time;         /* time when this record was added */
-    uint32_t dstip;
+    uint32_t dstip[4];
     uint16_t dstport;
     UT_hash_handle hh;   /* makes this structure hashable */
 } udp_connrecord_t;
@@ -59,26 +59,60 @@ void flush_dns_cache() {
     FreeLibrary(dnsapi);
 }
 
-inline static void construct_key(const uint32_t srcip, const uint16_t srcport, char *key) {
+inline static void fill_key_data(char *key, const uint8_t is_ipv6, const uint32_t srcip[4],
+                          const uint16_t srcport)
+{
+    if (is_ipv6) {
+        *(uint8_t*)(key) = '6';
+        ipv6_copy_addr((uint32_t*)(key + sizeof(uint8_t)), srcip);
+    }
+    else {
+        *(uint8_t*)(key) = '4';
+        ipv4_copy_addr((uint32_t*)(key + sizeof(uint8_t)), srcip);
+    }
+
+    *(uint16_t*)(key + sizeof(uint8_t) + sizeof(uint32_t) * 4) = srcport;
+}
+
+inline static void fill_data_from_key(uint8_t *is_ipv6, uint32_t srcip[4], uint16_t *srcport,
+                                      const char *key)
+{
+    if (key[0] == '6') {
+        *is_ipv6 = 1;
+        ipv6_copy_addr(srcip, (uint32_t*)(key + sizeof(uint8_t)));
+    }
+    else {
+        *is_ipv6 = 0;
+        ipv4_copy_addr(srcip, (uint32_t*)(key + sizeof(uint8_t)));
+    }
+    *srcport = *(uint16_t*)(key + sizeof(uint8_t) + sizeof(uint32_t) * 4);
+}
+
+inline static void construct_key(const uint32_t srcip[4], const uint16_t srcport,
+                                 char *key, int is_ipv6)
+{
     debug("Construct key enter\n");
     if (key) {
         debug("Constructing key\n");
-
-        *(uint32_t*)(key) = srcip;
-        *(uint16_t*)(key + sizeof(srcip)) = srcport;
+        fill_key_data(key, is_ipv6, srcip, srcport);
     }
     debug("Construct key end\n");
 }
 
-inline static void deconstruct_key(const char *key, udp_connrecord_t *connrecord,
-                                   conntrack_info_t *conn_info) {
+inline static void deconstruct_key(const char *key, const udp_connrecord_t *connrecord,
+                                   conntrack_info_t *conn_info)
+{
     debug("Deconstruct key enter\n");
     if (key && conn_info) {
         debug("Deconstructing key\n");
+        fill_data_from_key(&conn_info->is_ipv6, conn_info->srcip,
+                           &conn_info->srcport, key);
+
+        if (conn_info->is_ipv6)
+            ipv6_copy_addr(conn_info->dstip, connrecord->dstip);
+        else
+            ipv4_copy_addr(conn_info->dstip, connrecord->dstip);
 
-        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");
@@ -99,17 +133,26 @@ static int check_get_udp_conntrack_key(const char *key, udp_connrecord_t **connr
     return FALSE;
 }
 
-static int add_udp_conntrack(const uint32_t srcip, const uint16_t srcport,
-                             const uint32_t dstip, const uint16_t dstport) {
+static int add_udp_conntrack(const uint32_t srcip[4], const uint16_t srcport,
+                             const uint32_t dstip[4], const uint16_t dstport,
+                             const int is_ipv6
+                            )
+{
     if (!(srcip && srcport && dstip && dstport))
         return FALSE;
 
     udp_connrecord_t *tmp_connrecord = malloc(sizeof(udp_connrecord_t));
-    construct_key(srcip, srcport, tmp_connrecord->key);
+    construct_key(srcip, srcport, tmp_connrecord->key, is_ipv6);
 
     if (!check_get_udp_conntrack_key(tmp_connrecord->key, NULL)) {
         tmp_connrecord->time = time(NULL);
-        tmp_connrecord->dstip = dstip;
+
+        if (is_ipv6) {
+            ipv6_copy_addr(tmp_connrecord->dstip, dstip);
+        }
+        else {
+            ipv4_copy_addr(tmp_connrecord->dstip, dstip);
+        }
         tmp_connrecord->dstport = dstport;
         HASH_ADD_STR(conntrack, key, tmp_connrecord);
         debug("Added UDP conntrack\n");
@@ -120,7 +163,7 @@ static int add_udp_conntrack(const uint32_t srcip, const uint16_t srcport,
     return FALSE;
 }
 
-void dns_cleanup() {
+static void dns_cleanup() {
     udp_connrecord_t *tmp_connrecord, *tmp_connrecord2 = NULL;
 
     if (last_cleanup == 0) {
@@ -154,10 +197,11 @@ int dns_is_dns_packet(const char *packet_data, const UINT packet_dataLen, const
     return FALSE;
 }
 
-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) {
-
+int dns_handle_outgoing(const uint32_t srcip[4], const uint16_t srcport,
+                        const uint32_t dstip[4], const uint16_t dstport,
+                        const char *packet_data, const UINT packet_dataLen,
+                        const uint8_t is_ipv6)
+{
     if (packet_dataLen < 16)
         return FALSE;
 
@@ -166,16 +210,16 @@ int dns_handle_outgoing(const uint32_t srcip, const uint16_t srcport,
     if (dns_is_dns_packet(packet_data, packet_dataLen, 1)) {
         /* 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);
+        return add_udp_conntrack(srcip, srcport, dstip, dstport, is_ipv6);
     }
     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,
+int dns_handle_incoming(const uint32_t srcip[4], const uint16_t srcport,
                         const char *packet_data, const UINT packet_dataLen,
-                        conntrack_info_t *conn_info) {
-
+                        conntrack_info_t *conn_info, const uint8_t is_ipv6)
+{
     char key[UDP_CONNRECORD_KEY_LEN];
     udp_connrecord_t *tmp_connrecord = NULL;
 
@@ -186,7 +230,7 @@ int dns_handle_incoming(const uint32_t srcip, const uint16_t srcport,
 
     if (dns_is_dns_packet(packet_data, packet_dataLen, 0)) {
         /* Looks like DNS response */
-        construct_key(srcip, srcport, key);
+        construct_key(srcip, srcport, key, is_ipv6);
         if (check_get_udp_conntrack_key(key, &tmp_connrecord) && tmp_connrecord) {
             /* Connection exists in conntrack, moving on */
             deconstruct_key(key, tmp_connrecord, conn_info);
@@ -195,6 +239,6 @@ int dns_handle_incoming(const uint32_t srcip, const uint16_t srcport,
             return TRUE;
         }
     }
-    debug("____dns_handle_incoming FALSE: srcport = %hu, dstport = %hu\n", ntohs(srcport), ntohs(dstport));
+    debug("____dns_handle_incoming FALSE: srcport = %hu\n", ntohs(srcport));
     return FALSE;
 }

dnsredir.h

@@ -1,19 +1,36 @@
 #include <stdint.h>
 
 typedef struct conntrack_info {
-    uint32_t srcip;
+    uint8_t  is_ipv6;
+    uint32_t srcip[4];
     uint16_t srcport;
-    uint32_t dstip;
+    uint32_t dstip[4];
     uint16_t dstport;
 } conntrack_info_t;
 
-int dns_handle_incoming(const uint32_t srcip, const uint16_t srcport,
-                        const char *packet_data, const UINT packet_dataLen,
-                        conntrack_info_t *conn_info);
+inline static void ipv4_copy_addr(uint32_t dst[4], const uint32_t src[4]) {
+    dst[0] = src[0];
+    dst[1] = 0;
+    dst[2] = 0;
+    dst[3] = 0;
+}
 
-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);
+inline static void ipv6_copy_addr(uint32_t dst[4], const uint32_t src[4]) {
+    dst[0] = src[0];
+    dst[1] = src[1];
+    dst[2] = src[2];
+    dst[3] = src[3];
+}
+
+int dns_handle_incoming(const uint32_t srcip[4], const uint16_t srcport,
+                        const char *packet_data, const UINT packet_dataLen,
+                        conntrack_info_t *conn_info, const uint8_t is_ipv6);
+
+int dns_handle_outgoing(const uint32_t srcip[4], const uint16_t srcport,
+                        const uint32_t dstip[4], const uint16_t dstport,
+                        const char *packet_data, const UINT packet_dataLen,
+                        const uint8_t is_ipv6
+                       );
 
 void flush_dns_cache();
 int dns_is_dns_packet(const char *packet_data, const UINT packet_dataLen, const int outgoing);

goodbyedpi.c

@@ -9,29 +9,31 @@
 #include <unistd.h>
 #include <string.h>
 #include <getopt.h>
+#include <in6addr.h>
+#include <ws2tcpip.h>
 #include "windivert.h"
 #include "goodbyedpi.h"
+#include "repl_str.h"
+#include "service.h"
 #include "dnsredir.h"
 #include "blackwhitelist.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)
+// My mingw installation does not load inet_pton definition for some reason
+WINSOCK_API_LINKAGE INT WSAAPI inet_pton(INT Family, LPCSTR pStringBuf, PVOID pAddr);
+
+#define die() do { sleep(20); exit(EXIT_FAILURE); } while (0)
 
 #define MAX_FILTERS 4
 #define MAX_PACKET_SIZE 9016
-#define IPV4_HDR_LEN 20
-#define TCP_HDR_LEN 20
-#define TCP_WINDOWSIZE_OFFSET 14
 
-#define DIVERT_NO_LOCALNETS_DST "(" \
+#define DIVERT_NO_LOCALNETSv4_DST "(" \
                    "(ip.DstAddr < 127.0.0.1 or ip.DstAddr > 127.255.255.255) and " \
                    "(ip.DstAddr < 10.0.0.0 or ip.DstAddr > 10.255.255.255) and " \
                    "(ip.DstAddr < 192.168.0.0 or ip.DstAddr > 192.168.255.255) and " \
                    "(ip.DstAddr < 172.16.0.0 or ip.DstAddr > 172.31.255.255) and " \
                    "(ip.DstAddr < 169.254.0.0 or ip.DstAddr > 169.254.255.255)" \
                    ")"
-#define DIVERT_NO_LOCALNETS_SRC "(" \
+#define DIVERT_NO_LOCALNETSv4_SRC "(" \
                    "(ip.SrcAddr < 127.0.0.1 or ip.SrcAddr > 127.255.255.255) and " \
                    "(ip.SrcAddr < 10.0.0.0 or ip.SrcAddr > 10.255.255.255) and " \
                    "(ip.SrcAddr < 192.168.0.0 or ip.SrcAddr > 192.168.255.255) and " \
@@ -39,15 +41,53 @@
                    "(ip.SrcAddr < 169.254.0.0 or ip.SrcAddr > 169.254.255.255)" \
                    ")"
 
+#define DIVERT_NO_LOCALNETSv6_DST "(" \
+                   "(ipv6.DstAddr > ::1) and " \
+                   "(ipv6.DstAddr < 2001::0 or ipv6.DstAddr > 2001:1::0) and " \
+                   "(ipv6.DstAddr < fc00::0 or ipv6.DstAddr > fe00::0) and " \
+                   "(ipv6.DstAddr < fe80::0 or ipv6.DstAddr > fec0::0) and " \
+                   "(ipv6.DstAddr < ff00::0 or ipv6.DstAddr > ffff::0)" \
+                   ")"
+#define DIVERT_NO_LOCALNETSv6_SRC "(" \
+                   "(ipv6.SrcAddr > ::1) and " \
+                   "(ipv6.SrcAddr < 2001::0 or ipv6.SrcAddr > 2001:1::0) and " \
+                   "(ipv6.SrcAddr < fc00::0 or ipv6.SrcAddr > fe00::0) and " \
+                   "(ipv6.SrcAddr < fe80::0 or ipv6.SrcAddr > fec0::0) and " \
+                   "(ipv6.SrcAddr < ff00::0 or ipv6.SrcAddr > ffff::0)" \
+                   ")"
+
+/* #IPID# is a template to find&replace */
+#define IPID_TEMPLATE "#IPID#"
+#define FILTER_STRING_TEMPLATE \
+        "(tcp and " \
+        "(inbound and (" \
+         "(" \
+          "(" \
+           "((ip.Id >= 0x0 and ip.Id <= 0xF) " IPID_TEMPLATE \
+           ") and " \
+           "tcp.SrcPort == 80 and tcp.Ack" \
+          ") or " \
+          "((tcp.SrcPort == 80 or tcp.SrcPort == 443) and tcp.Ack and tcp.Syn)" \
+         ")" \
+         " and (" DIVERT_NO_LOCALNETSv4_SRC " or " DIVERT_NO_LOCALNETSv6_SRC ")) or " \
+        "(outbound and " \
+         "(tcp.DstPort == 80 or tcp.DstPort == 443) and tcp.Ack and " \
+         "(" DIVERT_NO_LOCALNETSv4_DST " or " DIVERT_NO_LOCALNETSv6_DST "))" \
+        "))"
+#define FILTER_PASSIVE_STRING_TEMPLATE "inbound and ip and tcp and " \
+        "((ip.Id <= 0xF and ip.Id >= 0x0) " IPID_TEMPLATE ") and " \
+        "(tcp.SrcPort == 443 or tcp.SrcPort == 80) and tcp.Rst and " \
+        DIVERT_NO_LOCALNETSv4_SRC
+
 #define SET_HTTP_FRAGMENT_SIZE_OPTION(fragment_size) do { \
     if (!http_fragment_size) { \
-        http_fragment_size = fragment_size; \
-        if (http_fragment_size <= 0 || http_fragment_size > 65535) { \
-            printf(fragment_size_message); \
+        if (fragment_size <= 0 || fragment_size > 65535) { \
+            puts("Fragment size should be in range [0 - 65535]\n"); \
             exit(EXIT_FAILURE); \
         } \
+        http_fragment_size = fragment_size; \
     } \
-    else if (http_fragment_size != fragment_size) { \
+    else if (http_fragment_size != (unsigned int)fragment_size) { \
         printf( \
             "WARNING: HTTP fragment size is already set to %d, not changing.\n", \
             http_fragment_size \
@@ -55,6 +95,7 @@
     } \
 } while (0)
 
+static int running_from_service = 0;
 static HANDLE filters[MAX_FILTERS];
 static int filter_num = 0;
 static const char *http10_redirect_302 = "HTTP/1.0 302 ";
@@ -78,25 +119,20 @@ static struct option long_options[] = {
     {"port",        required_argument, 0,  'z' },
     {"dns-addr",    required_argument, 0,  'd' },
     {"dns-port",    required_argument, 0,  'g' },
+    {"dnsv6-addr",  required_argument, 0,  '!' },
+    {"dnsv6-port",  required_argument, 0,  '@' },
     {"dns-verb",    no_argument,       0,  'v' },
     {"blacklist",   required_argument, 0,  'b' },
+    {"ip-id",       required_argument, 0,  'i' },
     {0,             0,                 0,   0  }
 };
 
 static char *filter_string = NULL;
-static char *filter_string_template = "(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 char *filter_passive_string = NULL;
 
 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))";
+    const char *udp = " or (udp and (udp.SrcPort == %d or udp.DstPort == %d))";
+    const char *tcp = " or (tcp and (tcp.SrcPort == %d or tcp.DstPort == %d))";
 
     char *current_filter = filter_string;
     int new_filter_size = strlen(current_filter) +
@@ -113,6 +149,34 @@ static void add_filter_str(int proto, int port) {
     free(current_filter);
 }
 
+static void add_ip_id_str(int id) {
+    char *newstr;
+    const char *ipid = " or ip.Id == %d";
+    char *addfilter = malloc(strlen(ipid) + 16);
+
+    sprintf(addfilter, ipid, id);
+
+    newstr = repl_str(filter_string, IPID_TEMPLATE, addfilter);
+    free(filter_string);
+    filter_string = newstr;
+
+    newstr = repl_str(filter_passive_string, IPID_TEMPLATE, addfilter);
+    free(filter_passive_string);
+    filter_passive_string = newstr;
+}
+
+static void finalize_filter_strings() {
+    char *newstr;
+
+    newstr = repl_str(filter_string, IPID_TEMPLATE, "");
+    free(filter_string);
+    filter_string = newstr;
+
+    newstr = repl_str(filter_passive_string, IPID_TEMPLATE, "");
+    free(filter_passive_string);
+    filter_passive_string = newstr;
+}
+
 static char* dumb_memmem(const char* haystack, int hlen, const char* needle, int nlen) {
     // naive implementation
     if (nlen > hlen) return NULL;
@@ -127,15 +191,27 @@ static char* dumb_memmem(const char* haystack, int hlen, const char* needle, int
 
 static HANDLE init(char *filter, UINT64 flags) {
     LPTSTR errormessage = NULL;
+    DWORD errorcode = 0;
     filter = WinDivertOpen(filter, WINDIVERT_LAYER_NETWORK, 0, flags);
     if (filter != INVALID_HANDLE_VALUE)
         return filter;
+    errorcode = GetLastError();
     FormatMessage(FORMAT_MESSAGE_ALLOCATE_BUFFER | FORMAT_MESSAGE_FROM_SYSTEM |
                   FORMAT_MESSAGE_IGNORE_INSERTS,
-                  NULL, GetLastError(), MAKELANGID(LANG_ENGLISH, SUBLANG_DEFAULT),
+                  NULL, errorcode, MAKELANGID(LANG_ENGLISH, SUBLANG_DEFAULT),
                   (LPTSTR)&errormessage, 0, NULL);
-    printf("%s", errormessage);
-    free(errormessage);
+    printf("Error opening filter: %s", errormessage);
+    LocalFree(errormessage);
+    if (errorcode == 577)
+        printf("Windows Server 2016 systems must have secure boot disabled to be "
+               "able to load WinDivert driver.\n"
+               "Windows 7 systems must be up-to-date or at least have KB3033929 installed.\n"
+               "https://www.microsoft.com/en-us/download/details.aspx?id=46078\n\n"
+               "WARNING! If you see this error on Windows 7, it means your system is horribly "
+               "outdated and SHOULD NOT BE USED TO ACCESS THE INTERNET!\n"
+               "Most probably, you don't have security patches installed and anyone in you LAN or "
+               "public Wi-Fi network can get full access to your computer (MS17-010 and others).\n"
+               "You should install updates IMMEDIATELY.\n");
     return NULL;
 }
 
@@ -147,7 +223,7 @@ static int deinit(HANDLE handle) {
     return FALSE;
 }
 
-static void deinit_all() {
+void deinit_all() {
     for (int i = 0; i < filter_num; i++) {
         deinit(filters[i]);
     }
@@ -216,9 +292,9 @@ static int find_header_and_get_info(const char *pktdata, int pktlen,
     return FALSE;
 }
 
-static void change_window_size(const char *pkt, int size) {
+static inline void change_window_size(const PWINDIVERT_TCPHDR ppTcpHdr, int size) {
     if (size >= 1 && size <= 65535) {
-        *(uint16_t*)(pkt + IPV4_HDR_LEN + TCP_WINDOWSIZE_OFFSET) = htons(size);
+        ppTcpHdr->Window = htons(size);
     }
 }
 
@@ -246,10 +322,14 @@ static PVOID find_http_method_end(const char *pkt, int http_frag, int *is_fragme
 }
 
 int main(int argc, char *argv[]) {
-    static const char fragment_size_message[] =
-                "Fragment size should be in range [0 - 65535]\n";
+    static enum packet_type_e {
+        unknown,
+        ipv4_tcp, ipv4_tcp_data, ipv4_udp_data,
+        ipv6_tcp, ipv6_tcp_data, ipv6_udp_data
+    } packet_type;
     int i, should_reinject, should_recalc_checksum = 0;
     int opt;
+    int packet_v4, packet_v6;
     HANDLE w_filter = NULL;
     WINDIVERT_ADDRESS addr;
     char packet[MAX_PACKET_SIZE];
@@ -257,6 +337,7 @@ int main(int argc, char *argv[]) {
     UINT packetLen;
     UINT packet_dataLen;
     PWINDIVERT_IPHDR ppIpHdr;
+    PWINDIVERT_IPV6HDR ppIpV6Hdr;
     PWINDIVERT_TCPHDR ppTcpHdr;
     PWINDIVERT_UDPHDR ppUdpHdr;
     conntrack_info_t dns_conn_info;
@@ -267,12 +348,16 @@ int main(int argc, char *argv[]) {
         do_fragment_https = 0, do_host = 0,
         do_host_removespace = 0, do_additional_space = 0,
         do_http_allports = 0,
-        do_host_mixedcase = 0, do_dns_redirect = 0,
+        do_host_mixedcase = 0,
+        do_dnsv4_redirect = 0, do_dnsv6_redirect = 0,
         do_dns_verb = 0, do_blacklist = 0;
-    int http_fragment_size = 2;
-    int https_fragment_size = 2;
-    uint32_t dns_addr = 0;
-    uint16_t dns_port = htons(53);
+    unsigned int http_fragment_size = 2;
+    unsigned int https_fragment_size = 2;
+    uint32_t dnsv4_addr = 0;
+    struct in6_addr dnsv6_addr = {0};
+    struct in6_addr dns_temp_addr = {0};
+    uint16_t dnsv4_port = htons(53);
+    uint16_t dnsv6_port = htons(53);
     char *host_addr, *useragent_addr, *method_addr;
     int host_len, useragent_len;
     int http_req_fragmented;
@@ -280,17 +365,44 @@ int main(int argc, char *argv[]) {
     char *hdr_name_addr = NULL, *hdr_value_addr = NULL;
     int hdr_value_len;
 
-    if (filter_string == NULL) {
-        filter_string = malloc(strlen(filter_string_template) + 1);
-        strcpy(filter_string, filter_string_template);
+    // Make sure to search DLLs only in safe path, not in current working dir.
+    SetDllDirectory("");
+    SetSearchPathMode(BASE_SEARCH_PATH_ENABLE_SAFE_SEARCHMODE | BASE_SEARCH_PATH_PERMANENT);
+
+    if (!running_from_service) {
+        running_from_service = 1;
+        if (service_register(argc, argv)) {
+            /* We've been called as a service. Register service
+             * and exit this thread. main() would be called from
+             * service.c next time.
+             *
+             * Note that if service_register() succeedes it does
+             * not return until the service is stopped.
+             * That is why we should set running_from_service
+             * before calling service_register and unset it
+             * afterwards.
+             */
+            return 0;
+        }
+        running_from_service = 0;
     }
 
-    printf("GoodbyeDPI: Passive DPI blocker and Active DPI circumvention utility\n");
+    if (filter_string == NULL)
+        filter_string = strdup(FILTER_STRING_TEMPLATE);
+    if (filter_passive_string == NULL)
+        filter_passive_string = strdup(FILTER_PASSIVE_STRING_TEMPLATE);
+
+    printf(
+        "GoodbyeDPI: Passive DPI blocker and Active DPI circumvention utility\n"
+        "https://github.com/ValdikSS/GoodbyeDPI\n\n"
+    );
 
     if (argc == 1) {
         /* enable mode -1 by default */
         do_passivedpi = do_host = do_host_removespace \
-            = do_fragment_http = do_fragment_https = 1;
+                = do_fragment_http = do_fragment_https \
+                = do_fragment_http_persistent \
+                = do_fragment_http_persistent_nowait = 1;
     }
 
     while ((opt = getopt_long(argc, argv, "1234prsaf:e:mwk:n", long_options, NULL)) != -1) {
@@ -347,7 +459,7 @@ int main(int argc, char *argv[]) {
                 do_fragment_https = 1;
                 https_fragment_size = atoi(optarg);
                 if (https_fragment_size <= 0 || https_fragment_size > 65535) {
-                    printf(fragment_size_message);
+                    puts("Fragment size should be in range [0 - 65535]\n");
                     exit(EXIT_FAILURE);
                 }
                 break;
@@ -365,34 +477,81 @@ int main(int argc, char *argv[]) {
                     add_filter_str(IPPROTO_TCP, i);
                 i = 0;
                 break;
+            case 'i':
+                /* i is used as a temporary variable here */
+                i = atoi(optarg);
+                if (i < 0 || i > 65535) {
+                    printf("IP ID parameter error!\n");
+                    exit(EXIT_FAILURE);
+                }
+                add_ip_id_str(i);
+                i = 0;
+                break;
             case 'd':
-                if (!do_dns_redirect) {
-                    do_dns_redirect = 1;
-                    dns_addr = inet_addr(optarg);
-                    if (!dns_addr) {
-                        printf("DNS address parameter error!\n");
+                if ((inet_pton(AF_INET, optarg, dns_temp_addr.s6_addr) == 1) &&
+                    !do_dnsv4_redirect)
+                {
+                    do_dnsv4_redirect = 1;
+                    if (inet_pton(AF_INET, optarg, &dnsv4_addr) != 1) {
+                        puts("DNS address parameter error!");
                         exit(EXIT_FAILURE);
                     }
                     add_filter_str(IPPROTO_UDP, 53);
                     flush_dns_cache();
+                    break;
                 }
+                puts("DNS address parameter error!");
+                exit(EXIT_FAILURE);
+                break;
+            case '!':
+                if ((inet_pton(AF_INET6, optarg, dns_temp_addr.s6_addr) == 1) &&
+                    !do_dnsv6_redirect)
+                {
+                    do_dnsv6_redirect = 1;
+                    if (inet_pton(AF_INET6, optarg, dnsv6_addr.s6_addr) != 1) {
+                        puts("DNS address parameter error!");
+                        exit(EXIT_FAILURE);
+                    }
+                    add_filter_str(IPPROTO_UDP, 53);
+                    flush_dns_cache();
+                    break;
+                }
+                puts("DNS address parameter error!");
+                exit(EXIT_FAILURE);
                 break;
             case 'g':
-                if (!do_dns_redirect) {
-                    printf("--dns-port should be used with --dns-addr!\n"
+                if (!do_dnsv4_redirect) {
+                    puts("--dns-port should be used with --dns-addr!\n"
                         "Make sure you use --dns-addr and pass it before "
-                        "--dns-port\n");
+                        "--dns-port");
                     exit(EXIT_FAILURE);
                 }
-                dns_port = atoi(optarg);
+                dnsv4_port = atoi(optarg);
                 if (atoi(optarg) <= 0 || atoi(optarg) > 65535) {
-                    printf("DNS port parameter error!\n");
+                    puts("DNS port parameter error!");
                     exit(EXIT_FAILURE);
                 }
-                if (dns_port != 53) {
-                    add_filter_str(IPPROTO_UDP, dns_port);
+                if (dnsv4_port != 53) {
+                    add_filter_str(IPPROTO_UDP, dnsv4_port);
                 }
-                dns_port = ntohs(dns_port);
+                dnsv4_port = htons(dnsv4_port);
+                break;
+            case '@':
+                if (!do_dnsv6_redirect) {
+                    puts("--dnsv6-port should be used with --dnsv6-addr!\n"
+                        "Make sure you use --dnsv6-addr and pass it before "
+                        "--dnsv6-port");
+                    exit(EXIT_FAILURE);
+                }
+                dnsv6_port = atoi(optarg);
+                if (atoi(optarg) <= 0 || atoi(optarg) > 65535) {
+                    puts("DNS port parameter error!");
+                    exit(EXIT_FAILURE);
+                }
+                if (dnsv6_port != 53) {
+                    add_filter_str(IPPROTO_UDP, dnsv6_port);
+                }
+                dnsv6_port = htons(dnsv6_port);
                 break;
             case 'v':
                 do_dns_verb = 1;
@@ -405,7 +564,7 @@ int main(int argc, char *argv[]) {
                 }
                 break;
             default:
-                printf("Usage: goodbyedpi.exe [OPTION...]\n"
+                puts("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"
@@ -417,8 +576,11 @@ int main(int argc, char *argv[]) {
                 " -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        [value]    additional TCP port to perform fragmentation on (and HTTP tricks with -w)\n"
-                " --dns-addr  [value]    redirect UDP DNS requests to the supplied IP address (experimental)\n"
-                " --dns-port  [value]    redirect UDP DNS requests to the supplied port (53 by default)\n"
+                " --ip-id       [value]    handle additional IP ID (decimal, drop redirects and TCP RSTs with this ID).\n"
+                " --dns-addr    [value]    redirect UDPv4 DNS requests to the supplied IPv4 address (experimental)\n"
+                " --dns-port    [value]    redirect UDPv4 DNS requests to the supplied port (53 by default)\n"
+                " --dnsv6-addr  [value]    redirect UDPv6 DNS requests to the supplied IPv6 address (experimental)\n"
+                " --dnsv6-port  [value]    redirect UDPv6 DNS requests to the supplied port (53 by default)\n"
                 " --dns-verb               print verbose DNS redirection messages\n"
                 " --blacklist   [txtfile]  perform HTTP tricks only to host names and subdomains from\n"
                 "                          supplied text file. This option can be supplied multiple times.\n"
@@ -426,7 +588,7 @@ int main(int argc, char *argv[]) {
                 " -1          -p -r -s -f 2 -k 2 -n -e 2 (most compatible mode, default)\n"
                 " -2          -p -r -s -f 2 -k 2 -n -e 40 (better speed for HTTPS yet still compatible)\n"
                 " -3          -p -r -s -e 40 (better speed for HTTP and HTTPS)\n"
-                " -4          -p -r -s (best speed)\n");
+                " -4          -p -r -s (best speed)");
                 exit(EXIT_FAILURE);
         }
     }
@@ -434,12 +596,14 @@ int main(int argc, char *argv[]) {
     printf("Block passive: %d, Fragment HTTP: %d, Fragment persistent HTTP: %d, "
            "Fragment HTTPS: %d, "
            "hoSt: %d, Host no space: %d, Additional space: %d, Mix Host: %d, "
-           "HTTP AllPorts: %d, HTTP Persistent Nowait: %d, DNS redirect: %d\n",
+           "HTTP AllPorts: %d, HTTP Persistent Nowait: %d, DNS redirect: %d, "
+           "DNSv6 redirect: %d\n",
            do_passivedpi, (do_fragment_http ? http_fragment_size : 0),
            (do_fragment_http_persistent ? http_fragment_size : 0),
            (do_fragment_https ? https_fragment_size : 0),
            do_host, do_host_removespace, do_additional_space, do_host_mixedcase,
-           do_http_allports, do_fragment_http_persistent_nowait, do_dns_redirect
+           do_http_allports, do_fragment_http_persistent_nowait, do_dnsv4_redirect,
+           do_dnsv6_redirect
           );
 
     if (do_fragment_http && http_fragment_size > 2) {
@@ -449,21 +613,21 @@ int main(int argc, char *argv[]) {
     }
 
     printf("\nOpening filter\n");
+    finalize_filter_strings();
     filter_num = 0;
 
     if (do_passivedpi) {
-        /* IPv4 filter for inbound RST packets with ID = 0 or 1 */
+        /* IPv4 only filter for inbound RST packets with ID [0x0; 0xF] */
         filters[filter_num] = init(
-            "inbound and ip and tcp and "
-            "(ip.Id == 0x0001 or ip.Id == 0x0000) and "
-            "(tcp.SrcPort == 443 or tcp.SrcPort == 80) and tcp.Rst and "
-            DIVERT_NO_LOCALNETS_SRC,
+            filter_passive_string,
             WINDIVERT_FLAG_DROP);
+        if (filters[filter_num] == NULL)
+            die();
         filter_num++;
     }
 
     /* 
-     * IPv4 filter for inbound HTTP redirection packets and
+     * IPv4 & IPv6 filter for inbound HTTP redirection packets and
      * active DPI circumvention
      */
     filters[filter_num] = init(filter_string, 0);
@@ -481,13 +645,53 @@ int main(int argc, char *argv[]) {
 
     while (1) {
         if (WinDivertRecv(w_filter, packet, sizeof(packet), &addr, &packetLen)) {
-            //printf("Got %s packet, len=%d!\n", addr.Direction ? "inbound" : "outbound",
-            //       packetLen);
+            debug("Got %s packet, len=%d!\n", addr.Direction ? "inbound" : "outbound",
+                   packetLen);
             should_reinject = 1;
             should_recalc_checksum = 0;
 
-            if (WinDivertHelperParsePacket(packet, packetLen, &ppIpHdr,
-                NULL, NULL, NULL, &ppTcpHdr, NULL, &packet_data, &packet_dataLen)) {
+            ppIpHdr = (PWINDIVERT_IPHDR)NULL;
+            ppIpV6Hdr = (PWINDIVERT_IPV6HDR)NULL;
+            ppTcpHdr = (PWINDIVERT_TCPHDR)NULL;
+            ppUdpHdr = (PWINDIVERT_UDPHDR)NULL;
+            packet_v4 = packet_v6 = 0;
+            packet_type = unknown;
+
+            // Parse network packet and set it's type
+            if ((packet_v4 = WinDivertHelperParsePacket(packet, packetLen, &ppIpHdr,
+                NULL, NULL, NULL, &ppTcpHdr, NULL, &packet_data, &packet_dataLen)))
+            {
+                packet_type = ipv4_tcp_data;
+            }
+            else if ((packet_v6 = WinDivertHelperParsePacket(packet, packetLen, NULL,
+                &ppIpV6Hdr, NULL, NULL, &ppTcpHdr, NULL, &packet_data, &packet_dataLen)))
+            {
+                packet_type = ipv6_tcp_data;
+            }
+            else if ((packet_v4 = WinDivertHelperParsePacket(packet, packetLen, &ppIpHdr,
+                NULL, NULL, NULL, &ppTcpHdr, NULL, NULL, NULL)))
+            {
+                packet_type = ipv4_tcp;
+            }
+            else if ((packet_v6 = WinDivertHelperParsePacket(packet, packetLen, NULL,
+                &ppIpV6Hdr, NULL, NULL, &ppTcpHdr, NULL, NULL, NULL)))
+            {
+                packet_type = ipv6_tcp;
+            }
+            else if ((packet_v4 = WinDivertHelperParsePacket(packet, packetLen, &ppIpHdr,
+                NULL, NULL, NULL, NULL, &ppUdpHdr, &packet_data, &packet_dataLen)))
+            {
+                packet_type = ipv4_udp_data;
+            }
+            else if ((packet_v6 = WinDivertHelperParsePacket(packet, packetLen, NULL,
+                &ppIpV6Hdr, NULL, NULL, NULL, &ppUdpHdr, &packet_data, &packet_dataLen)))
+            {
+                packet_type = ipv6_udp_data;
+            }
+
+            debug("packet_type: %d, packet_v4: %d, packet_v6: %d\n", packet_type, packet_v4, packet_v6);
+
+            if (packet_type == ipv4_tcp_data || packet_type == ipv6_tcp_data) {
                 //printf("Got parsed packet, len=%d!\n", packet_dataLen);
                 /* Got a TCP packet WITH DATA */
 
@@ -533,11 +737,20 @@ int main(int argc, char *argv[]) {
                          * ack number of received packet and retransmitting missing part again,
                          * but it's better to send it anyway since it eliminates one RTT.
                          */
-                        if (do_fragment_http_persistent && !http_req_fragmented) {
+                        if (do_fragment_http_persistent && !http_req_fragmented &&
+                            (packet_dataLen > http_fragment_size))
+                        {
+                            if (packet_v4)
                                 ppIpHdr->Length = htons(
                                     ntohs(ppIpHdr->Length) -
                                     packet_dataLen + http_fragment_size
                                 );
+                            else if (packet_v6)
+                                ppIpV6Hdr->Length = htons(
+                                    ntohs(ppIpV6Hdr->Length) -
+                                    packet_dataLen + http_fragment_size
+                                );
+
                             WinDivertHelperCalcChecksums(
                                 packet, packetLen - packet_dataLen + http_fragment_size, 0
                             );
@@ -546,11 +759,18 @@ int main(int argc, char *argv[]) {
                                 packetLen - packet_dataLen + http_fragment_size,
                                 &addr, NULL
                             );
+
                             if (do_fragment_http_persistent_nowait) {
+                                if (packet_v4)
                                     ppIpHdr->Length = htons(
                                         ntohs(ppIpHdr->Length) -
                                         http_fragment_size + packet_dataLen - http_fragment_size
                                     );
+                                else if (packet_v6)
+                                    ppIpV6Hdr->Length = htons(
+                                        ntohs(ppIpV6Hdr->Length) -
+                                        http_fragment_size + packet_dataLen - http_fragment_size
+                                    );
                                 memmove(packet_data,
                                         packet_data + http_fragment_size,
                                         packet_dataLen);
@@ -647,8 +867,7 @@ int main(int argc, char *argv[]) {
             } /* 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)) {
+            else if (packet_type == ipv4_tcp || packet_type == ipv6_tcp) {
                 /* If we got INBOUND SYN+ACK packet */
                 if (addr.Direction == WINDIVERT_DIRECTION_INBOUND &&
                     ppTcpHdr->Syn == 1 && ppTcpHdr->Ack == 1) {
@@ -658,28 +877,35 @@ int main(int argc, char *argv[]) {
                      * is enabled as there could be non-HTTP data on port 80
                      */
                     if (do_fragment_http && ppTcpHdr->SrcPort == htons(80)) {
-                        change_window_size(packet, http_fragment_size);
+                        change_window_size(ppTcpHdr, http_fragment_size);
                         should_recalc_checksum = 1;
                     }
                     else if (do_fragment_https && ppTcpHdr->SrcPort != htons(80)) {
-                        change_window_size(packet, https_fragment_size);
+                        change_window_size(ppTcpHdr, https_fragment_size);
                         should_recalc_checksum = 1;
                     }
                 }
             }
 
             /* Else if we got UDP packet with data */
-            else if (do_dns_redirect && WinDivertHelperParsePacket(packet, packetLen, &ppIpHdr,
-                NULL, NULL, NULL, NULL, &ppUdpHdr, &packet_data, &packet_dataLen)) {
-
+            else if ((do_dnsv4_redirect && (packet_type == ipv4_udp_data)) ||
+                     (do_dnsv6_redirect && (packet_type == ipv6_udp_data)))
+            {
                 if (addr.Direction == WINDIVERT_DIRECTION_INBOUND) {
-                    if (dns_handle_incoming(ppIpHdr->DstAddr, ppUdpHdr->DstPort,
+                    if ((packet_v4 && dns_handle_incoming(&ppIpHdr->DstAddr, ppUdpHdr->DstPort,
                                         packet_data, packet_dataLen,
-                                        &dns_conn_info))
+                                        &dns_conn_info, 0))
+                        ||
+                        (packet_v6 && dns_handle_incoming(ppIpV6Hdr->DstAddr, ppUdpHdr->DstPort,
+                                        packet_data, packet_dataLen,
+                                        &dns_conn_info, 1)))
                     {
                         /* Changing source IP and port to the values
                          * from DNS conntrack */
-                        ppIpHdr->SrcAddr = dns_conn_info.dstip;
+                        if (packet_v4)
+                            ppIpHdr->SrcAddr = dns_conn_info.dstip[0];
+                        else if (packet_v6)
+                            ipv6_copy_addr(ppIpV6Hdr->SrcAddr, dns_conn_info.dstip);
                         ppUdpHdr->DstPort = dns_conn_info.srcport;
                         ppUdpHdr->SrcPort = dns_conn_info.dstport;
                         should_recalc_checksum = 1;
@@ -696,14 +922,24 @@ int main(int argc, char *argv[]) {
                 }
 
                 else if (addr.Direction == WINDIVERT_DIRECTION_OUTBOUND) {
-                    if (dns_handle_outgoing(ppIpHdr->SrcAddr, ppUdpHdr->SrcPort,
-                                        ppIpHdr->DstAddr, ppUdpHdr->DstPort,
-                                        packet_data, packet_dataLen))
+                    if ((packet_v4 && dns_handle_outgoing(&ppIpHdr->SrcAddr, ppUdpHdr->SrcPort,
+                                        &ppIpHdr->DstAddr, ppUdpHdr->DstPort,
+                                        packet_data, packet_dataLen, 0))
+                        ||
+                        (packet_v6 && dns_handle_outgoing(ppIpV6Hdr->SrcAddr, ppUdpHdr->SrcPort,
+                                        ppIpV6Hdr->DstAddr, ppUdpHdr->DstPort,
+                                        packet_data, packet_dataLen, 1)))
                     {
                         /* Changing destination IP and port to the values
                          * from configuration */
-                        ppIpHdr->DstAddr = dns_addr;
-                        ppUdpHdr->DstPort = dns_port;
+                        if (packet_v4) {
+                            ppIpHdr->DstAddr = dnsv4_addr;
+                            ppUdpHdr->DstPort = dnsv4_port;
+                        }
+                        else if (packet_v6) {
+                            ipv6_copy_addr(ppIpV6Hdr->DstAddr, (uint32_t*)dnsv6_addr.s6_addr);
+                            ppUdpHdr->DstPort = dnsv6_port;
+                        }
                         should_recalc_checksum = 1;
                     }
                     else {

goodbyedpi.h

@@ -5,3 +5,6 @@
 #else
 #define debug(...) printf(__VA_ARGS__)
 #endif
+
+int main(int argc, char *argv[]);
+void deinit_all();

repl_str.c

@@ -0,0 +1,90 @@
+#include <string.h>
+#include <stdlib.h>
+#include <stddef.h>
+
+#if (__STDC_VERSION__ >= 199901L)
+#include <stdint.h>
+#endif
+
+char *repl_str(const char *str, const char *from, const char *to) {
+
+	/* Adjust each of the below values to suit your needs. */
+
+	/* Increment positions cache size initially by this number. */
+	size_t cache_sz_inc = 16;
+	/* Thereafter, each time capacity needs to be increased,
+	 * multiply the increment by this factor. */
+	const size_t cache_sz_inc_factor = 3;
+	/* But never increment capacity by more than this number. */
+	const size_t cache_sz_inc_max = 1048576;
+
+	char *pret, *ret = NULL;
+	const char *pstr2, *pstr = str;
+	size_t i, count = 0;
+	#if (__STDC_VERSION__ >= 199901L)
+	uintptr_t *pos_cache_tmp, *pos_cache = NULL;
+	#else
+	ptrdiff_t *pos_cache_tmp, *pos_cache = NULL;
+	#endif
+	size_t cache_sz = 0;
+	size_t cpylen, orglen, retlen, tolen, fromlen = strlen(from);
+
+	/* Find all matches and cache their positions. */
+	while ((pstr2 = strstr(pstr, from)) != NULL) {
+		count++;
+
+		/* Increase the cache size when necessary. */
+		if (cache_sz < count) {
+			cache_sz += cache_sz_inc;
+			pos_cache_tmp = realloc(pos_cache, sizeof(*pos_cache) * cache_sz);
+			if (pos_cache_tmp == NULL) {
+				goto end_repl_str;
+			} else pos_cache = pos_cache_tmp;
+			cache_sz_inc *= cache_sz_inc_factor;
+			if (cache_sz_inc > cache_sz_inc_max) {
+				cache_sz_inc = cache_sz_inc_max;
+			}
+		}
+
+		pos_cache[count-1] = pstr2 - str;
+		pstr = pstr2 + fromlen;
+	}
+
+	orglen = pstr - str + strlen(pstr);
+
+	/* Allocate memory for the post-replacement string. */
+	if (count > 0) {
+		tolen = strlen(to);
+		retlen = orglen + (tolen - fromlen) * count;
+	} else	retlen = orglen;
+	ret = malloc(retlen + 1);
+	if (ret == NULL) {
+		goto end_repl_str;
+	}
+
+	if (count == 0) {
+		/* If no matches, then just duplicate the string. */
+		strcpy(ret, str);
+	} else {
+		/* Otherwise, duplicate the string whilst performing
+		 * the replacements using the position cache. */
+		pret = ret;
+		memcpy(pret, str, pos_cache[0]);
+		pret += pos_cache[0];
+		for (i = 0; i < count; i++) {
+			memcpy(pret, to, tolen);
+			pret += tolen;
+			pstr = str + pos_cache[i] + fromlen;
+			cpylen = (i == count-1 ? orglen : pos_cache[i+1]) - pos_cache[i] - fromlen;
+			memcpy(pret, pstr, cpylen);
+			pret += cpylen;
+		}
+		ret[retlen] = '\0';
+	}
+
+end_repl_str:
+	/* Free the cache and return the post-replacement string,
+	 * which will be NULL in the event of an error. */
+	free(pos_cache);
+	return ret;
+}

repl_str.h

@@ -0,0 +1 @@
+char *repl_str(const char *str, const char *from, const char *to);

service.c

@@ -0,0 +1,96 @@
+#include <windows.h>
+#include <stdio.h>
+#include "goodbyedpi.h"
+#include "service.h"
+
+#define SERVICE_NAME "GoodbyeDPI"
+
+static SERVICE_STATUS ServiceStatus;
+static SERVICE_STATUS_HANDLE hStatus;
+static int service_argc = 0;
+static char **service_argv = NULL;
+
+int service_register(int argc, char *argv[])
+{
+    int i, ret;
+    SERVICE_TABLE_ENTRY ServiceTable[] = {
+        {SERVICE_NAME, (LPSERVICE_MAIN_FUNCTION)service_main},
+        {NULL, NULL}
+    };
+    /*
+     * Save argc & argv as service_main is called with different
+     * arguments, which are passed from "start" command, not
+     * from the program command line.
+     * We don't need this behaviour.
+     *
+     * Note that if StartServiceCtrlDispatcher() succeedes
+     * it does not return until the service is stopped,
+     * so we should copy all arguments first and then
+     * handle the failure.
+     */
+    if (!service_argc && !service_argv) {
+        service_argc = argc;
+        service_argv = malloc(sizeof(void*) * argc);
+        for (i = 0; i < argc; i++) {
+            service_argv[i] = strdup(argv[i]);
+        }
+    }
+
+    ret = StartServiceCtrlDispatcher(ServiceTable);
+
+    if (service_argc && service_argv) {
+        for (i = 0; i < service_argc; i++) {
+            free(service_argv[i]);
+        }
+        free(service_argv);
+    }
+
+    return ret;
+}
+
+void service_main(int argc __attribute__((unused)),
+                  char *argv[] __attribute__((unused)))
+{
+    ServiceStatus.dwServiceType = SERVICE_WIN32_OWN_PROCESS; 
+    ServiceStatus.dwCurrentState = SERVICE_RUNNING;
+    ServiceStatus.dwControlsAccepted = SERVICE_ACCEPT_STOP | SERVICE_ACCEPT_SHUTDOWN;
+    ServiceStatus.dwWin32ExitCode = 0;
+    ServiceStatus.dwServiceSpecificExitCode = 0;
+    ServiceStatus.dwCheckPoint = 1;
+    ServiceStatus.dwWaitHint = 0;
+
+    hStatus = RegisterServiceCtrlHandler(
+        SERVICE_NAME,
+        (LPHANDLER_FUNCTION)service_controlhandler);
+    if (hStatus == (SERVICE_STATUS_HANDLE)0)
+    {
+        // Registering Control Handler failed
+        return;
+    }
+
+    SetServiceStatus(hStatus, &ServiceStatus);
+
+    // Calling main with saved argc & argv
+    ServiceStatus.dwWin32ExitCode = main(service_argc, service_argv);
+    ServiceStatus.dwCurrentState  = SERVICE_STOPPED;
+    SetServiceStatus(hStatus, &ServiceStatus);
+    return;
+}
+
+// Control handler function
+void service_controlhandler(DWORD request)
+{
+    switch(request)
+    {
+        case SERVICE_CONTROL_STOP:
+        case SERVICE_CONTROL_SHUTDOWN:
+            deinit_all();
+            ServiceStatus.dwWin32ExitCode = 0;
+            ServiceStatus.dwCurrentState  = SERVICE_STOPPED;
+        default:
+            break;
+    }
+    // Report current status
+    SetServiceStatus(hStatus, &ServiceStatus);
+    return;
+}

service.h

@@ -0,0 +1,3 @@
+int service_register();
+void service_main(int argc, char *argv[]);
+void service_controlhandler(DWORD request);