GoodbyeDPI v0.1.8

Previous value of 2 caused issues with the services connected via
very different uplink/downlink routing links.

.editorconfig

@@ -0,0 +1,8 @@
+root = true
+
+[*]
+charset = utf-8
+indent_style = space
+indent_size = 4
+insert_final_newline = true
+end_of_line = lf

.github/ISSUE_TEMPLATE/bug.yml

@@ -0,0 +1,47 @@
+name: Bug Report / Сообщение об ошибке
+description: File a bug report / Сообщить об ошибке в проекте
+
+body:
+  - type: markdown
+    attributes:
+      value: |
+        Please pay some attention!
+        GoodbyeDPI does not guarantee to work on your ISP on 100% or at all. If GoodbyeDPI can't unblock some or any websites, this is most likely not a software bug, and you should not report it.
+        Please report software bugs, such as: website incompatibility (if the website works without GoodbyeDPI but breaks with GoobyeDPI enabled), antivirus incompatibility, DNS redirection problems, incorrect packet handling, and other software issues.
+        Please make sure to check other opened and closed issues, it could be your question or issue has been already discussed.
+
+        Пожалуйста, прочтите!
+        GoodbyeDPI не гарантирует ни 100% работу с вашим провайдером, ни работу вообще. Если GoodbyeDPI не разблокирует доступ к некоторым или всем веб-сайтам, вероятнее всего, это не программная ошибка, и не стоит о ней сообщать здесь.
+        Сообщайте только об ошибках в программе, таких как: некорректная работа с веб-сайтами (когда веб-сайт работает без GoodbyeDPI, но ломается с GoodbyeDPI), несовместимость с антивирусами, проблемы с перенаправлением DNS, некорректная обработка пакетов, и другие проблемы.
+        Также посмотрите другие открытые и закрытые баги. Возможно, ваш вопрос или проблема уже обсуждались.
+  - type: input
+    id: os
+    attributes:
+      label: Operating system / операционная система
+      description: Enter your Windows version. For Windows 10 and 11 include build/update number.
+      placeholder: ex. Windows 10 20H2
+    validations:
+      required: true
+  - type: dropdown
+    id: is-svc
+    attributes:
+      label: Running as service / Запуск программы как сервис
+      description: Do you use GoodbyeDPI as a Windows Service?
+      options:
+        - I run it as a regular program / Запускаю программу обычным образом
+        - I installed it as a service / Установил как сервис Windows
+    validations:
+      required: true
+  - type: textarea
+    id: what-happened
+    attributes:
+      label: Describe the issue / Опишите проблему
+      description: A clear and concise description of what the bug is / Подробно опишите, в чём заключается проблема
+      placeholder: Attach the screenshots for clarity / При необходимости приложите скриншоты
+    validations:
+      required: true
+  - type: textarea
+    id: additional-info
+    attributes:
+      label: Additional information / Дополнительная информация
+      description: If you have a hints on why this bug happens, you can express it here / Если у вас есть предположения об источнике бага, вы можете изложить их здесь

.github/ISSUE_TEMPLATE/config.yml

@@ -0,0 +1,5 @@
+blank_issues_enabled: false
+contact_links:
+  - name: Questions about the program / Вопросы по програме
+    url: https://ntc.party/c/community-software/goodbyedpi/8
+    about: Please ask and answer questions on forum / Пожалуйста, задавайте вопросы только на форуме

.github/ISSUE_TEMPLATE/feature.yml

@@ -0,0 +1,15 @@
+name:  Feature request / Предложить новую функциональность 
+description:  Suggest an idea or function for this project / Предложить новую идею или функциональность в программе
+
+body:
+  - type: markdown
+    attributes:
+      value: |
+        If you think of a great function or circumvention method which is missing from the program, go ahead and suggest it here.
+        Если вы придумали новую функцию или метод обхода, которого еще нет в программе, напишите о нем подробнее здесь.
+  - type: textarea
+    id: description
+    attributes:
+      label: Describe your feature / Опишите ваше предложение
+    validations:
+      required: true

.github/workflows/build.yml

@@ -0,0 +1,75 @@
+name: Build GoodbyeDPI
+
+on:
+  push:
+    paths:
+      - 'src/**'
+
+env:
+  WINDIVERT_URL: https://www.reqrypt.org/download/WinDivert-1.4.3-A.zip
+  WINDIVERT_NAME: WinDivert-1.4.3-A.zip
+  WINDIVERT_SHA256: 4084bc3931f31546d375ed89e3f842776efa46f321ed0adcd32d3972a7d02566
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v2
+
+      - name: Declare short commit variable
+        id: vars
+        run: |
+          echo "::set-output name=sha_short::$(git rev-parse --short HEAD)"
+
+      - name: Install MinGW-w64
+        run: >
+          sudo DEBIAN_FRONTEND=noninteractive XZ_DEFAULTS="-T0" XZ_OPT="-T0" eatmydata
+          apt install -y --no-install-recommends gcc-mingw-w64
+
+      - name: Download WinDivert from cache
+        id: windivert-cache
+        uses: actions/cache@v2
+        with:
+          path: ${{ env. WINDIVERT_NAME }}
+          key: ${{ env. WINDIVERT_SHA256 }}
+
+      - name: Download WinDivert from the website
+        if: steps.windivert-cache.outputs.cache-hit != 'true'
+        run: >
+          wget ${{ env. WINDIVERT_URL }} &&
+          (echo ${{ env. WINDIVERT_SHA256 }} ${{ env. WINDIVERT_NAME }} | sha256sum -c)
+
+      - name: Unpack WinDivert
+        run: unzip ${{ env. WINDIVERT_NAME }}
+
+      - name: Compile x86_64
+        run: >
+          cd src && make clean &&
+          make CPREFIX=x86_64-w64-mingw32- BIT64=1 WINDIVERTHEADERS=../WinDivert-1.4.3-A/include WINDIVERTLIBS=../WinDivert-1.4.3-A/x86_64 -j4
+      
+      - name: Prepare x86_64 directory
+        run: |
+          mkdir goodbyedpi_x86_64_${{ steps.vars.outputs.sha_short }}
+          cp src/goodbyedpi.exe WinDivert-1.4.3-A/x86_64/*.{dll,sys} goodbyedpi_x86_64_${{ steps.vars.outputs.sha_short }}
+
+      - name: Upload output file x86_64 (64 bit)
+        uses: actions/upload-artifact@v2
+        with:
+          name: goodbyedpi_x86_64_${{ steps.vars.outputs.sha_short }}
+          path: goodbyedpi_x86_64_${{ steps.vars.outputs.sha_short }}
+
+      - name: Compile i686
+        run: >
+          cd src && make clean &&
+          make CPREFIX=i686-w64-mingw32- WINDIVERTHEADERS=../WinDivert-1.4.3-A/include WINDIVERTLIBS=../WinDivert-1.4.3-A/x86 -j4
+
+      - name: Prepare x86 directory
+        run: |
+          mkdir goodbyedpi_x86_${{ steps.vars.outputs.sha_short }}
+          cp src/goodbyedpi.exe WinDivert-1.4.3-A/x86/*.{dll,sys} goodbyedpi_x86_${{ steps.vars.outputs.sha_short }}
+
+      - name: Upload output file x86
+        uses: actions/upload-artifact@v2
+        with:
+          name: goodbyedpi_x86_${{ steps.vars.outputs.sha_short }}
+          path: goodbyedpi_x86_${{ steps.vars.outputs.sha_short }}

Makefile

@@ -1,37 +0,0 @@
-ifndef MSYSTEM
-	CPREFIX = x86_64-w64-mingw32-
-endif
-
-WINDIVERTHEADERS = ../../include
-WINDIVERTLIBS = ../binary
-
-TARGET = goodbyedpi.exe
-LIBS = -L$(WINDIVERTLIBS) -lWinDivert -lws2_32
-CC = $(CPREFIX)gcc
-CCWINDRES = $(CPREFIX)windres
-CFLAGS = -Wall -Wextra -I$(WINDIVERTHEADERS) -L$(WINDIVERTLIBS) \
-         -O2 -pie -fPIE -Wformat -Werror=format-security -D_FORTIFY_SOURCE=2
-LDFLAGS = -Wl,-O1,--sort-common,--as-needed
-
-.PHONY: default all clean
-
-default: manifest $(TARGET)
-all: default
-
-OBJECTS = $(patsubst %.c, %.o, $(wildcard *.c)) goodbyedpi-rc.o
-HEADERS = $(wildcard *.h)
-
-%.o: %.c $(HEADERS)
-	$(CC) $(CFLAGS) -c $< -o $@
-
-manifest:
-	$(CCWINDRES) goodbyedpi-rc.rc goodbyedpi-rc.o
-
-.PRECIOUS: $(TARGET) $(OBJECTS)
-
-$(TARGET): $(OBJECTS)
-	$(CC) $(OBJECTS) -Wall $(LDFLAGS) $(LIBS) -s -o $@
-
-clean:
-	-rm -f *.o
-	-rm -f $(TARGET)

README.md

@@ -17,42 +17,69 @@ Usage: goodbyedpi.exe [OPTION...]
  -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
- -k [value]  enable HTTP persistent (keep-alive) fragmentation and set it to value
+ -f <value>  set HTTP fragmentation to value
+ -k <value>  enable HTTP persistent (keep-alive) fragmentation and set it to value
  -n          do not wait for first segment ACK when -k is enabled
- -e [value]  set HTTPS 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      [value]    additional TCP port to perform fragmentation on (and HTTP tricks with -w)
- --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
- --blacklist [txtfile]  perform HTTP tricks only to host names and subdomains from
-                        supplied text file. This option can be supplied multiple times.
+ --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)
+ --dnsv6-addr  <value>    redirect UDPv6 DNS requests to the supplied IPv6 address (experimental)
+ --dnsv6-port  <value>    redirect UDPv6 DNS requests to the supplied port (53 by default)
+ --dns-verb               print verbose DNS redirection messages
+ --blacklist   <txtfile>  perform circumvention tricks only to host names and subdomains from
+                          supplied text file (HTTP Host/TLS SNI).
+                          This option can be supplied multiple times.
+ --set-ttl     <value>    activate Fake Request Mode and send it with supplied TTL value.
+                          DANGEROUS! May break websites in unexpected ways. Use with care.
+ --auto-ttl    [decttl]   activate Fake Request Mode, automatically detect TTL and decrease
+                          it from standard 64 or 128 by decttl (128/64 - TTL - 4 by default).
+ --wrong-chksum           activate Fake Request Mode and send it with incorrect TCP checksum.
+                          May not work in a VM or with some routers, but is safer than set-ttl.
+ --wrong-seq              activate Fake Request Mode and send it with TCP SEQ/ACK in the past.
+ --native-frag            fragment (split) the packets by sending them in smaller packets, without
+                          shrinking the Window Size. Works faster (does not slow down the connection)
+                          and better.
+ --reverse-frag           fragment (split) the packets just as --native-frag, but send them in the
+                          reversed order. Works with the websites which could not handle segmented
+                          HTTPS TLS ClientHello (because they receive the TCP flow "combined").
 
- -1          -p -r -s -f 2 -k 2 -n -e 2 (most compatible mode, default)
+
+LEGACY modesets:
+ -1          -p -r -s -f 2 -k 2 -n -e 2 (most compatible mode)
  -2          -p -r -s -f 2 -k 2 -n -e 40 (better speed for HTTPS yet still compatible)
  -3          -p -r -s -e 40 (better speed for HTTP and HTTPS)
  -4          -p -r -s (best speed)
+
+Modern modesets (more stable, more compatible, faster):
+ -5          -f 2 -e 2 --auto-ttl --reverse-frag (this is the default)
+ -6          -f 2 -e 2 --wrong-seq --reverse-frag
 ```
 
-To check if your ISP's DPI could be circumvented, run `3_all_dnsredir_hardcore.cmd` first. This is the most hardcore mode which will show if this program is suitable for your ISP and DPI vendor at all. If you can open blocked websites with this mode, 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.
+To check if your ISP's DPI could be circumvented, first make sure that your provider does not poison DNS answers by enabling "Secure DNS (DNS over HTTPS)" option in your browser.
 
-Try `goodbyedpi -1` to see if it works too.
+* **Chrome**: Settings → [Privacy and security](chrome://settings/security) > Use secure DNS → With: NextDNS
+* **Firefox**: [Settings](about:preferences) → Network Settings → Enable DNS over HTTPS → Use provider: NextDNS
 
-Then try `goodbyedpi.exe -2`. It should be faster for HTTPS sites. Mode `-3` speed ups HTTP websites.
+Then run the `goodbyedpi.exe` executable without any options. If it works — congratulations! You can use it as-is or configure further, for example by using `--blacklist` option if the list of blocked websites is known and available for your country.
 
-Use `goodbyedpi.exe -4` if it works for your ISP's DPI. This is the fastest mode but not compatible with every DPI.
+If your provider intercepts DNS requests, you may want to use `--dns-addr` option to a public DNS resover running on non-standard port (such as Yandex DNS `77.88.8.8:1253`) or configure DNS over HTTPS/TLS using third-party applications.
+
+Check the .cmd scripts and modify it according to your preference and network conditions.
 
 # How does it work
 
 ### 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 7 methods to circumvent Active DPI:
 
 * TCP-level fragmentation for first data packet
 * TCP-level fragmentation for persistent (keep-alive) HTTP sessions
@@ -60,6 +87,7 @@ Active DPI is more tricky to fool. Currently the software uses 4 methods to circ
 * 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
+* Sending fake HTTP/HTTPS packets with low Time-To-Live value, incorrect checksum or incorrect TCP Sequence/Acknowledgement numbers to fool DPI and prevent delivering them to the destination
 
 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).
 
@@ -75,16 +103,28 @@ To build x86 exe run:
 
 And for x86_64:
 
-`make CPREFIX=x86_64-w64-mingw32- WINDIVERTHEADERS=/path/to/windivert/include WINDIVERTLIBS=/path/to/windivert/amd64`
+`make CPREFIX=x86_64-w64-mingw32- BIT64=1 WINDIVERTHEADERS=/path/to/windivert/include WINDIVERTLIBS=/path/to/windivert/amd64`
 
 # How to install as Windows Service
 
-Use `service_install_russia_blacklist.cmd`, `service_install_russia_blacklist_dnsredir.cmd` and `service_remove.cmd` scripts.  
+Check examples in `service_install_russia_blacklist.cmd`, `service_install_russia_blacklist_dnsredir.cmd` and `service_remove.cmd` scripts.
+
 Modify them according to your own needs.
 
+# Known issues
+
+* Horribly outdated Windows 7 installations are not able to load WinDivert driver due to missing support for SHA256 digital signatures. Install KB3033929 [x86](https://www.microsoft.com/en-us/download/details.aspx?id=46078)/[x64](https://www.microsoft.com/en-us/download/details.aspx?id=46148), or better, update the whole system using Windows Update.
+* ~~Some SSL/TLS stacks unable to process fragmented ClientHello packets, and HTTPS websites won't open. Bug: [#4](https://github.com/ValdikSS/GoodbyeDPI/issues/4), [#64](https://github.com/ValdikSS/GoodbyeDPI/issues/64).~~ Fragmentation issues are fixed in v0.1.7.
+* ~~ESET Antivirus is incompatible with WinDivert driver [#91](https://github.com/ValdikSS/GoodbyeDPI/issues/91). This is most probably antivirus bug, not WinDivert.~~
+
+
 # Similar projects
 
-[zapret](https://github.com/bol-van/zapret) by @bol-van (for Linux).
+- **[zapret](https://github.com/bol-van/zapret)** by @bol-van (for Linux).
+- **[Green Tunnel](https://github.com/SadeghHayeri/GreenTunnel)** by @SadeghHayeri (for MacOS, Linux and Windows).
+- **[DPITunnel](https://github.com/zhenyolka/DPITunnel)** by @zhenyolka (for Android).
+- **[PowerTunnel](https://github.com/krlvm/PowerTunnel)** by @krlvm (for Windows, MacOS and Linux).
+- **[PowerTunnel for Android](https://github.com/krlvm/PowerTunnel-Android)** by @krlvm (for Android).
 
 # Kudos
 

blackwhitelist.h

@@ -1,2 +0,0 @@
-int blackwhitelist_load_list(const char *filename);
-int blackwhitelist_check_hostname(const char *host_addr, int host_len);

src/Makefile

@@ -0,0 +1,51 @@
+ifndef MSYSTEM
+	CPREFIX = x86_64-w64-mingw32-
+endif
+
+WINDIVERTHEADERS = ../../../include
+WINDIVERTLIBS = ../../binary
+MINGWLIB = /usr/x86_64-w64-mingw32/lib/
+
+TARGET = goodbyedpi.exe
+# Linking SSP does not work for some reason, the executable doesn't start.
+#LIBS = -L$(WINDIVERTLIBS) -Wl,-Bstatic -lssp -Wl,-Bdynamic -lWinDivert -lws2_32
+LIBS = -L$(WINDIVERTLIBS) -lWinDivert -lws2_32 -l:libssp.a
+CC = $(CPREFIX)gcc
+CCWINDRES = $(CPREFIX)windres
+CFLAGS = -std=c99 -pie -fPIE -pipe -I$(WINDIVERTHEADERS) -L$(WINDIVERTLIBS) \
+         -O2 -D_FORTIFY_SOURCE=2 -fstack-protector \
+         -Wall -Wextra -Wpedantic -Wformat=2 -Wno-format-nonliteral -Wshadow -Wstrict-aliasing=1 -Werror=format-security \
+         -Wfloat-equal -Wcast-align -Wsign-conversion \
+         #-fstack-protector-strong
+LDFLAGS = -fstack-protector -Wl,-O1,-pie,--dynamicbase,--nxcompat,--sort-common,--as-needed \
+-Wl,--image-base,0x140000000 -Wl,--disable-auto-image-base
+
+ifdef BIT64
+	LDFLAGS += -Wl,--high-entropy-va -Wl,--pic-executable,-e,mainCRTStartup
+else
+	CFLAGS += -m32
+	LDFLAGS += -Wl,--pic-executable,-e,_mainCRTStartup -m32
+endif
+
+.PHONY: default all clean
+
+default: manifest $(TARGET)
+all: default
+
+OBJECTS = $(patsubst %.c, %.o, $(wildcard *.c utils/*.c)) goodbyedpi-rc.o
+HEADERS = $(wildcard *.h utils/*.h)
+
+%.o: %.c $(HEADERS)
+	$(CC) $(CFLAGS) -c $< -o $@
+
+manifest:
+	$(CCWINDRES) goodbyedpi-rc.rc goodbyedpi-rc.o
+
+.PRECIOUS: $(TARGET) $(OBJECTS)
+
+$(TARGET): $(OBJECTS)
+	$(CC) $(OBJECTS) $(LDFLAGS) $(LIBS) -s -o $@
+
+clean:
+	-rm -f *.o utils/*.o
+	-rm -f $(TARGET)

src/blackwhitelist.c

@@ -8,8 +8,8 @@
 #include <windows.h>
 #include <stdio.h>
 #include "goodbyedpi.h"
-#include "uthash.h"
-#include "getline.h"
+#include "utils/uthash.h"
+#include "utils/getline.h"
 
 typedef struct blackwhitelist_record {
     const char *host;
@@ -35,14 +35,11 @@ static int add_hostname(const char *host) {
     if (!host)
         return FALSE;
 
-    int host_len = strlen(host);
-
     blackwhitelist_record_t *tmp_record = malloc(sizeof(blackwhitelist_record_t));
-    char *host_c = malloc(host_len + 1);
+    char *host_c = NULL;
 
     if (!check_get_hostname(host)) {
-        strncpy(host_c, host, host_len);
-        host_c[host_len] = '\0';
+        host_c = strdup(host);
         tmp_record->host = host_c;
         HASH_ADD_KEYPTR(hh, blackwhitelist, tmp_record->host,
                         strlen(tmp_record->host), tmp_record);
@@ -51,7 +48,8 @@ static int add_hostname(const char *host) {
     }
     debug("Not added host %s\n", host);
     free(tmp_record);
-    free(host_c);
+    if (host_c)
+        free(host_c);
     return FALSE;
 }
 
@@ -84,7 +82,7 @@ int blackwhitelist_load_list(const char *filename) {
     return TRUE;
 }
 
-int blackwhitelist_check_hostname(const char *host_addr, int host_len) {
+int blackwhitelist_check_hostname(const char *host_addr, size_t host_len) {
     char current_host[HOST_MAXLEN + 1];
     char *tokenized_host = NULL;
 

src/blackwhitelist.h

@@ -0,0 +1,2 @@
+int blackwhitelist_load_list(const char *filename);
+int blackwhitelist_check_hostname(const char *host_addr, size_t host_len);

src/dnsredir.c

@@ -15,7 +15,7 @@
 #include <stdio.h>
 #include "goodbyedpi.h"
 #include "dnsredir.h"
-#include "uthash.h"
+#include "utils/uthash.h"
 
 /* key ('4' for IPv4 or '6' for IPv6 + srcip[16] + srcport[2]) */
 #define UDP_CONNRECORD_KEY_LEN 19
@@ -44,7 +44,7 @@ static time_t last_cleanup = 0;
 static udp_connrecord_t *conntrack = NULL;
 
 void flush_dns_cache() {
-    BOOL WINAPI (*DnsFlushResolverCache)();
+    long long int WINAPI (*DnsFlushResolverCache)();
 
     HMODULE dnsapi = LoadLibrary("dnsapi.dll");
     if (dnsapi == NULL)
@@ -53,7 +53,7 @@ void flush_dns_cache() {
         exit(EXIT_FAILURE);
     }
 
-    DnsFlushResolverCache = (void*)GetProcAddress(dnsapi, "DnsFlushResolverCache");
+    DnsFlushResolverCache = GetProcAddress(dnsapi, "DnsFlushResolverCache");
     if (DnsFlushResolverCache == NULL || !DnsFlushResolverCache())
         printf("Can't flush DNS cache!");
     FreeLibrary(dnsapi);
@@ -89,7 +89,7 @@ inline static void fill_data_from_key(uint8_t *is_ipv6, uint32_t srcip[4], uint1
 }
 
 inline static void construct_key(const uint32_t srcip[4], const uint16_t srcport,
-                                 char *key, int is_ipv6)
+                                 char *key, const uint8_t is_ipv6)
 {
     debug("Construct key enter\n");
     if (key) {
@@ -135,7 +135,7 @@ static int check_get_udp_conntrack_key(const char *key, udp_connrecord_t **connr
 
 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
+                             const uint8_t is_ipv6
                             )
 {
     if (!(srcip && srcport && dstip && dstport))
@@ -239,6 +239,6 @@ int dns_handle_incoming(const uint32_t srcip[4], 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;
 }

src/dnsredir.h

@@ -1,3 +1,5 @@
+#ifndef _DNSREDIR_H
+#define _DNSREDIR_H
 #include <stdint.h>
 
 typedef struct conntrack_info {
@@ -34,3 +36,4 @@ int dns_handle_outgoing(const uint32_t srcip[4], const uint16_t srcport,
 
 void flush_dns_cache();
 int dns_is_dns_packet(const char *packet_data, const UINT packet_dataLen, const int outgoing);
+#endif

src/fakepackets.c

@@ -0,0 +1,195 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <ctype.h>
+#include <unistd.h>
+#include <in6addr.h>
+#include <ws2tcpip.h>
+#include "windivert.h"
+#include "goodbyedpi.h"
+
+static const unsigned char fake_http_request[] = "GET / HTTP/1.1\r\nHost: www.w3.org\r\n"
+                                                 "User-Agent: curl/7.65.3\r\nAccept: */*\r\n"
+                                                 "Accept-Encoding: deflate, gzip, br\r\n\r\n";
+static const unsigned char fake_https_request[] = {
+    0x16, 0x03, 0x01, 0x02, 0x00, 0x01, 0x00, 0x01, 0xfc, 0x03, 0x03, 0x9a, 0x8f, 0xa7, 0x6a, 0x5d,
+    0x57, 0xf3, 0x62, 0x19, 0xbe, 0x46, 0x82, 0x45, 0xe2, 0x59, 0x5c, 0xb4, 0x48, 0x31, 0x12, 0x15,
+    0x14, 0x79, 0x2c, 0xaa, 0xcd, 0xea, 0xda, 0xf0, 0xe1, 0xfd, 0xbb, 0x20, 0xf4, 0x83, 0x2a, 0x94,
+    0xf1, 0x48, 0x3b, 0x9d, 0xb6, 0x74, 0xba, 0x3c, 0x81, 0x63, 0xbc, 0x18, 0xcc, 0x14, 0x45, 0x57,
+    0x6c, 0x80, 0xf9, 0x25, 0xcf, 0x9c, 0x86, 0x60, 0x50, 0x31, 0x2e, 0xe9, 0x00, 0x22, 0x13, 0x01,
+    0x13, 0x03, 0x13, 0x02, 0xc0, 0x2b, 0xc0, 0x2f, 0xcc, 0xa9, 0xcc, 0xa8, 0xc0, 0x2c, 0xc0, 0x30,
+    0xc0, 0x0a, 0xc0, 0x09, 0xc0, 0x13, 0xc0, 0x14, 0x00, 0x33, 0x00, 0x39, 0x00, 0x2f, 0x00, 0x35,
+    0x01, 0x00, 0x01, 0x91, 0x00, 0x00, 0x00, 0x0f, 0x00, 0x0d, 0x00, 0x00, 0x0a, 0x77, 0x77, 0x77,
+    0x2e, 0x77, 0x33, 0x2e, 0x6f, 0x72, 0x67, 0x00, 0x17, 0x00, 0x00, 0xff, 0x01, 0x00, 0x01, 0x00,
+    0x00, 0x0a, 0x00, 0x0e, 0x00, 0x0c, 0x00, 0x1d, 0x00, 0x17, 0x00, 0x18, 0x00, 0x19, 0x01, 0x00,
+    0x01, 0x01, 0x00, 0x0b, 0x00, 0x02, 0x01, 0x00, 0x00, 0x23, 0x00, 0x00, 0x00, 0x10, 0x00, 0x0e,
+    0x00, 0x0c, 0x02, 0x68, 0x32, 0x08, 0x68, 0x74, 0x74, 0x70, 0x2f, 0x31, 0x2e, 0x31, 0x00, 0x05,
+    0x00, 0x05, 0x01, 0x00, 0x00, 0x00, 0x00, 0x00, 0x33, 0x00, 0x6b, 0x00, 0x69, 0x00, 0x1d, 0x00,
+    0x20, 0xb0, 0xe4, 0xda, 0x34, 0xb4, 0x29, 0x8d, 0xd3, 0x5c, 0x70, 0xd3, 0xbe, 0xe8, 0xa7, 0x2a,
+    0x6b, 0xe4, 0x11, 0x19, 0x8b, 0x18, 0x9d, 0x83, 0x9a, 0x49, 0x7c, 0x83, 0x7f, 0xa9, 0x03, 0x8c,
+    0x3c, 0x00, 0x17, 0x00, 0x41, 0x04, 0x4c, 0x04, 0xa4, 0x71, 0x4c, 0x49, 0x75, 0x55, 0xd1, 0x18,
+    0x1e, 0x22, 0x62, 0x19, 0x53, 0x00, 0xde, 0x74, 0x2f, 0xb3, 0xde, 0x13, 0x54, 0xe6, 0x78, 0x07,
+    0x94, 0x55, 0x0e, 0xb2, 0x6c, 0xb0, 0x03, 0xee, 0x79, 0xa9, 0x96, 0x1e, 0x0e, 0x98, 0x17, 0x78,
+    0x24, 0x44, 0x0c, 0x88, 0x80, 0x06, 0x8b, 0xd4, 0x80, 0xbf, 0x67, 0x7c, 0x37, 0x6a, 0x5b, 0x46,
+    0x4c, 0xa7, 0x98, 0x6f, 0xb9, 0x22, 0x00, 0x2b, 0x00, 0x09, 0x08, 0x03, 0x04, 0x03, 0x03, 0x03,
+    0x02, 0x03, 0x01, 0x00, 0x0d, 0x00, 0x18, 0x00, 0x16, 0x04, 0x03, 0x05, 0x03, 0x06, 0x03, 0x08,
+    0x04, 0x08, 0x05, 0x08, 0x06, 0x04, 0x01, 0x05, 0x01, 0x06, 0x01, 0x02, 0x03, 0x02, 0x01, 0x00,
+    0x2d, 0x00, 0x02, 0x01, 0x01, 0x00, 0x1c, 0x00, 0x02, 0x40, 0x01, 0x00, 0x15, 0x00, 0x96, 0x00,
+    0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+    0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+    0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+    0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+    0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+    0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+    0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+    0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+    0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+    0x00, 0x00, 0x00, 0x00, 0x00
+};
+
+static int send_fake_data(const HANDLE w_filter,
+                          const PWINDIVERT_ADDRESS addr,
+                          const char *pkt,
+                          const UINT packetLen,
+                          const BOOL is_ipv6,
+                          const BOOL is_https,
+                          const BYTE set_ttl,
+                          const BYTE set_checksum,
+                          const BYTE set_seq
+                         ) {
+    char packet_fake[MAX_PACKET_SIZE];
+    WINDIVERT_ADDRESS addr_new;
+    PVOID packet_data;
+    UINT packet_dataLen;
+    UINT packetLen_new;
+    PWINDIVERT_IPHDR ppIpHdr;
+    PWINDIVERT_IPV6HDR ppIpV6Hdr;
+    PWINDIVERT_TCPHDR ppTcpHdr;
+    unsigned const char *fake_request_data = is_https ? fake_https_request : fake_http_request;
+    UINT fake_request_size = is_https ? sizeof(fake_https_request) : sizeof(fake_http_request) - 1;
+
+    memcpy(&addr_new, addr, sizeof(WINDIVERT_ADDRESS));
+    memcpy(packet_fake, pkt, packetLen);
+
+    addr_new.PseudoTCPChecksum = 0;
+    addr_new.PseudoIPChecksum = 0;
+
+    if (!is_ipv6) {
+        // IPv4 TCP Data packet
+        if (!WinDivertHelperParsePacket(packet_fake, packetLen, &ppIpHdr,
+            NULL, NULL, NULL, &ppTcpHdr, NULL, &packet_data, &packet_dataLen))
+            return 1;
+    }
+    else {
+        // IPv6 TCP Data packet
+        if (!WinDivertHelperParsePacket(packet_fake, packetLen, NULL,
+            &ppIpV6Hdr, NULL, NULL, &ppTcpHdr, NULL, &packet_data, &packet_dataLen))
+            return 1;
+    }
+
+    if (packetLen + fake_request_size + 1 > MAX_PACKET_SIZE)
+        return 2;
+
+    memcpy(packet_data, fake_request_data, fake_request_size);
+    packetLen_new = packetLen - packet_dataLen + fake_request_size;
+
+    if (!is_ipv6) {
+        ppIpHdr->Length = htons(
+            ntohs(ppIpHdr->Length) -
+            packet_dataLen + fake_request_size
+        );
+
+        if (set_ttl)
+            ppIpHdr->TTL = set_ttl;
+    }
+    else {
+        ppIpV6Hdr->Length = htons(
+            ntohs(ppIpV6Hdr->Length) -
+            packet_dataLen + fake_request_size
+        );
+
+        if (set_ttl)
+            ppIpV6Hdr->HopLimit = set_ttl;
+    }
+
+    if (set_seq) {
+        // This is the smallest ACK drift Linux can't handle already, since at least v2.6.18.
+        // https://github.com/torvalds/linux/blob/v2.6.18/net/netfilter/nf_conntrack_proto_tcp.c#L395
+        ppTcpHdr->AckNum = htonl(ntohl(ppTcpHdr->AckNum) - 66000);
+        // This is just random, no specifics about this value.
+        ppTcpHdr->SeqNum = htonl(ntohl(ppTcpHdr->SeqNum) - 10000);
+    }
+
+    // Recalculate the checksum
+    WinDivertHelperCalcChecksums(packet_fake, packetLen_new, &addr_new, (UINT64)NULL);
+
+    if (set_checksum) {
+        // ...and damage it
+        ppTcpHdr->Checksum = htons(ntohs(ppTcpHdr->Checksum) - 1);
+    }
+    //printf("Pseudo checksum: %d\n", addr_new.PseudoTCPChecksum);
+
+    WinDivertSend(
+        w_filter, packet_fake,
+        packetLen_new,
+        &addr_new, NULL
+    );
+    debug("Fake packet: OK");
+
+    return 0;
+}
+
+static int send_fake_request(const HANDLE w_filter,
+                                  const PWINDIVERT_ADDRESS addr,
+                                  const char *pkt,
+                                  const UINT packetLen,
+                                  const BOOL is_ipv6,
+                                  const BOOL is_https,
+                                  const BYTE set_ttl,
+                                  const BYTE set_checksum,
+                                  const BYTE set_seq
+                                 ) {
+    if (set_ttl) {
+        send_fake_data(w_filter, addr, pkt, packetLen,
+                          is_ipv6, is_https,
+                          set_ttl, FALSE, FALSE);
+    }
+    if (set_checksum) {
+        send_fake_data(w_filter, addr, pkt, packetLen,
+                          is_ipv6, is_https,
+                          FALSE, set_checksum, FALSE);
+    }
+    if (set_seq) {
+        send_fake_data(w_filter, addr, pkt, packetLen,
+                          is_ipv6, is_https,
+                          FALSE, FALSE, set_seq);
+    }
+    return 0;
+}
+
+int send_fake_http_request(const HANDLE w_filter,
+                                  const PWINDIVERT_ADDRESS addr,
+                                  const char *pkt,
+                                  const UINT packetLen,
+                                  const BOOL is_ipv6,
+                                  const BYTE set_ttl,
+                                  const BYTE set_checksum,
+                                  const BYTE set_seq
+                                 ) {
+    return send_fake_request(w_filter, addr, pkt, packetLen,
+                          is_ipv6, FALSE,
+                          set_ttl, set_checksum, set_seq);
+}
+
+int send_fake_https_request(const HANDLE w_filter,
+                                   const PWINDIVERT_ADDRESS addr,
+                                   const char *pkt,
+                                   const UINT packetLen,
+                                   const BOOL is_ipv6,
+                                   const BYTE set_ttl,
+                                   const BYTE set_checksum,
+                                   const BYTE set_seq
+                                 ) {
+    return send_fake_request(w_filter, addr, pkt, packetLen,
+                          is_ipv6, TRUE,
+                          set_ttl, set_checksum, set_seq);
+}

src/fakepackets.h

@@ -0,0 +1,18 @@
+int send_fake_http_request(const HANDLE w_filter,
+                                  const PWINDIVERT_ADDRESS addr,
+                                  const char *pkt,
+                                  const UINT packetLen,
+                                  const BOOL is_ipv6,
+                                  const BYTE set_ttl,
+                                  const BYTE set_checksum,
+                                  const BYTE set_seq
+                                 );
+int send_fake_https_request(const HANDLE w_filter,
+                                   const PWINDIVERT_ADDRESS addr,
+                                   const char *pkt,
+                                   const UINT packetLen,
+                                   const BOOL is_ipv6,
+                                   const BYTE set_ttl,
+                                   const BYTE set_checksum,
+                                   const BYTE set_seq
+                                 );

src/goodbyedpi.exe.manifest

@@ -1,7 +1,7 @@
 <?xml version="1.0" encoding="UTF-8" standalone="yes"?>
 <assembly xmlns="urn:schemas-microsoft-com:asm.v1" manifestVersion="1.0">
-    <assemblyIdentity version="1.0.0.0" processorArchitecture="X86" name="GoodbyeDPI" type="win32"/> 
-    <description>Divert</description> 
+    <assemblyIdentity version="1.0.0.0" processorArchitecture="X86" name="GoodbyeDPI" type="win32"/>
+    <description>GoodbyeDPI</description>
     <trustInfo xmlns="urn:schemas-microsoft-com:asm.v2">
         <security>
             <requestedPrivileges>
@@ -9,4 +9,4 @@
             </requestedPrivileges>
         </security>
     </trustInfo>
-</assembly> 
+</assembly>

src/goodbyedpi.h

@@ -1,4 +1,5 @@
 #define HOST_MAXLEN 253
+#define MAX_PACKET_SIZE 9016
 
 #ifndef DEBUG
 #define debug(...) do {} while (0)

src/service.c

@@ -30,7 +30,7 @@ int service_register(int argc, char *argv[])
      */
     if (!service_argc && !service_argv) {
         service_argc = argc;
-        service_argv = malloc(sizeof(void*) * argc);
+        service_argv = malloc(sizeof(void*) * (size_t)argc);
         for (i = 0; i < argc; i++) {
             service_argv[i] = strdup(argv[i]);
         }
@@ -71,7 +71,7 @@ void service_main(int argc __attribute__((unused)),
     SetServiceStatus(hStatus, &ServiceStatus);
 
     // Calling main with saved argc & argv
-    ServiceStatus.dwWin32ExitCode = main(service_argc, service_argv);
+    ServiceStatus.dwWin32ExitCode = (DWORD)main(service_argc, service_argv);
     ServiceStatus.dwCurrentState  = SERVICE_STOPPED;
     SetServiceStatus(hStatus, &ServiceStatus);
     return;

src/ttltrack.c

@@ -0,0 +1,241 @@
+/**
+ * TCP (TTL) Connection Tracker for GoodbyeDPI
+ *
+ * Monitors SYN/ACK only, to extract the TTL value of the remote server.
+ *
+ */
+
+#include <windows.h>
+#include <time.h>
+#include <stdio.h>
+#include "goodbyedpi.h"
+#include "ttltrack.h"
+#include "utils/uthash.h"
+
+
+/* key ('4' for IPv4 or '6' for IPv6 + srcip[16] + dstip[16] + srcport[2] + dstport[2]) */
+#define TCP_CONNRECORD_KEY_LEN 37
+
+#define TCP_CLEANUP_INTERVAL_SEC 30
+
+/* 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 TCP_CONNRECORD_KEY_LEN bytes long,
+ * we don't need to use any string function to determine length.
+ */
+#undef uthash_strlen
+#define uthash_strlen(s) TCP_CONNRECORD_KEY_LEN
+
+typedef struct tcp_connrecord {
+    /* key ('4' for IPv4 or '6' for IPv6 + srcip[16] + dstip[16] + srcport[2] + dstport[2]) */
+    char key[TCP_CONNRECORD_KEY_LEN];
+    time_t time;         /* time when this record was added */
+    uint16_t ttl;
+    UT_hash_handle hh;   /* makes this structure hashable */
+} tcp_connrecord_t;
+
+static time_t last_cleanup = 0;
+static tcp_connrecord_t *conntrack = NULL;
+
+inline static void fill_key_data(char *key, const uint8_t is_ipv6, const uint32_t srcip[4],
+                    const uint32_t dstip[4], const uint16_t srcport, const uint16_t dstport)
+{
+    unsigned int offset = 0;
+
+    if (is_ipv6) {
+        *(uint8_t*)(key) = '6';
+        offset += sizeof(uint8_t);
+        ipv6_copy_addr((uint32_t*)(key + offset), srcip);
+        offset += sizeof(uint32_t) * 4;
+        ipv6_copy_addr((uint32_t*)(key + offset), dstip);
+        offset += sizeof(uint32_t) * 4;
+    }
+    else {
+        *(uint8_t*)(key) = '4';
+        offset += sizeof(uint8_t);
+        ipv4_copy_addr((uint32_t*)(key + offset), srcip);
+        offset += sizeof(uint32_t) * 4;
+        ipv4_copy_addr((uint32_t*)(key + offset), dstip);
+        offset += sizeof(uint32_t) * 4;
+    }
+
+    *(uint16_t*)(key + offset) = srcport;
+    offset += sizeof(srcport);
+    *(uint16_t*)(key + offset) = dstport;
+    offset += sizeof(dstport);
+}
+
+inline static void fill_data_from_key(uint8_t *is_ipv6, uint32_t srcip[4], uint32_t dstip[4],
+                                     uint16_t *srcport, uint16_t *dstport, const char *key)
+{
+    unsigned int offset = 0;
+
+    if (key[0] == '6') {
+        *is_ipv6 = 1;
+        offset += sizeof(uint8_t);
+        ipv6_copy_addr(srcip, (uint32_t*)(key + offset));
+        offset += sizeof(uint32_t) * 4;
+        ipv6_copy_addr(dstip, (uint32_t*)(key + offset));
+        offset += sizeof(uint32_t) * 4;
+    }
+    else {
+        *is_ipv6 = 0;
+        offset += sizeof(uint8_t);
+        ipv4_copy_addr(srcip, (uint32_t*)(key + offset));
+        offset += sizeof(uint32_t) * 4;
+        ipv4_copy_addr(dstip, (uint32_t*)(key + offset));
+        offset += sizeof(uint32_t) * 4;
+    }
+    *srcport = *(uint16_t*)(key + offset);
+    offset += sizeof(*srcport);
+    *dstport = *(uint16_t*)(key + offset);
+    offset += sizeof(*dstport);
+}
+
+inline static void construct_key(const uint32_t srcip[4], const uint32_t dstip[4],
+                                 const uint16_t srcport, const uint16_t dstport,
+                                 char *key, const uint8_t is_ipv6)
+{
+    debug("Construct key enter\n");
+    if (key) {
+        debug("Constructing key\n");
+        fill_key_data(key, is_ipv6, srcip, dstip, srcport, dstport);
+    }
+    debug("Construct key end\n");
+}
+
+inline static void deconstruct_key(const char *key, const tcp_connrecord_t *connrecord,
+                                   tcp_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->dstip,
+                           &conn_info->srcport, &conn_info->dstport,
+                           key);
+
+        conn_info->ttl = connrecord->ttl;
+    }
+    debug("Deconstruct key end\n");
+}
+
+static int check_get_tcp_conntrack_key(const char *key, tcp_connrecord_t **connrecord) {
+    tcp_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_tcp_conntrack_key found key\n");
+        return TRUE;
+    }
+    debug("check_get_tcp_conntrack_key key not found\n");
+    return FALSE;
+}
+
+static int add_tcp_conntrack(const uint32_t srcip[4], const uint32_t dstip[4],
+                             const uint16_t srcport, const uint16_t dstport,
+                             const uint8_t is_ipv6, const uint8_t ttl
+                            )
+{
+    if (!(srcip && srcport && dstip && dstport))
+        return FALSE;
+
+    tcp_connrecord_t *tmp_connrecord = malloc(sizeof(tcp_connrecord_t));
+    construct_key(srcip, dstip, srcport, dstport, tmp_connrecord->key, is_ipv6);
+
+    if (!check_get_tcp_conntrack_key(tmp_connrecord->key, NULL)) {
+        tmp_connrecord->time = time(NULL);
+        tmp_connrecord->ttl = ttl;
+        HASH_ADD_STR(conntrack, key, tmp_connrecord);
+        debug("Added TCP conntrack %u:%hu - %u:%hu\n", srcip[0], ntohs(srcport), dstip[0], ntohs(dstport));
+        return TRUE;
+    }
+    debug("Not added TCP conntrack %u:%hu - %u:%hu\n", srcip[0], ntohs(srcport), dstip[0], ntohs(dstport));
+    free(tmp_connrecord);
+    return FALSE;
+}
+
+static void tcp_cleanup() {
+    tcp_connrecord_t *tmp_connrecord, *tmp_connrecord2 = NULL;
+
+    if (last_cleanup == 0) {
+        last_cleanup = time(NULL);
+        return;
+    }
+
+    if (difftime(time(NULL), last_cleanup) >= TCP_CLEANUP_INTERVAL_SEC) {
+        last_cleanup = time(NULL);
+
+        HASH_ITER(hh, conntrack, tmp_connrecord, tmp_connrecord2) {
+            if (difftime(last_cleanup, tmp_connrecord->time) >= TCP_CLEANUP_INTERVAL_SEC) {
+                HASH_DEL(conntrack, tmp_connrecord);
+                free(tmp_connrecord);
+            }
+        }
+    }
+}
+
+int tcp_handle_incoming(uint32_t srcip[4], uint32_t dstip[4],
+                        uint16_t srcport, uint16_t dstport,
+                        uint8_t is_ipv6, uint8_t ttl)
+{
+    tcp_cleanup();
+
+    debug("trying to add TCP srcport = %hu, dstport = %hu\n", ntohs(srcport), ntohs(dstport));
+    return add_tcp_conntrack(srcip, dstip, srcport, dstport, is_ipv6, ttl);
+
+    debug("____tcp_handle_incoming FALSE: srcport = %hu, dstport = %hu\n", ntohs(srcport), ntohs(dstport));
+    return FALSE;
+}
+
+int tcp_handle_outgoing(uint32_t srcip[4], uint32_t dstip[4],
+                        uint16_t srcport, uint16_t dstport,
+                        tcp_conntrack_info_t *conn_info,
+                        uint8_t is_ipv6)
+{
+    char key[TCP_CONNRECORD_KEY_LEN];
+    tcp_connrecord_t *tmp_connrecord = NULL;
+
+    if (!conn_info)
+        return FALSE;
+
+    tcp_cleanup();
+    construct_key(dstip, srcip, dstport, srcport, key, is_ipv6);
+    if (check_get_tcp_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);
+        debug("____tcp_handle_outgoing TRUE: srcport = %hu\n", ntohs(srcport));
+        return TRUE;
+    }
+
+    debug("____tcp_handle_outgoing FALSE: srcport = %hu\n", ntohs(srcport));
+    return FALSE;
+}
+
+int tcp_get_auto_ttl(const uint8_t ttl, const uint8_t decrease_for) {
+    uint8_t ttl_of_fake_packet = 0;
+
+    if (ttl > 98 && ttl < 128) {
+        /* Safekeeping */
+        if (128 - ttl > decrease_for + 1) {
+            ttl_of_fake_packet = 128 - ttl - decrease_for;
+        }
+    }
+    else if (ttl > 34 && ttl < 64) {
+        /* Safekeeping */
+        if (64 - ttl > decrease_for + 1) {
+            ttl_of_fake_packet = 64 - ttl - decrease_for;
+        }
+    }
+    else {
+        ttl_of_fake_packet = 0;
+    }
+
+    return ttl_of_fake_packet;
+}

src/ttltrack.h

@@ -0,0 +1,25 @@
+#ifndef _TTLTRACK_H
+#define _TTLTRACK_H
+#include <stdint.h>
+#include "dnsredir.h"
+
+typedef struct tcp_conntrack_info {
+    uint8_t  is_ipv6;
+    uint8_t  ttl;
+    uint32_t srcip[4];
+    uint16_t srcport;
+    uint32_t dstip[4];
+    uint16_t dstport;
+} tcp_conntrack_info_t;
+
+int tcp_handle_incoming(uint32_t srcip[4], uint32_t dstip[4],
+                        uint16_t srcport, uint16_t dstport,
+                        uint8_t is_ipv6, uint8_t ttl);
+
+int tcp_handle_outgoing(uint32_t srcip[4], uint32_t dstip[4],
+                        uint16_t srcport, uint16_t dstport,
+                        tcp_conntrack_info_t *conn_info,
+                        uint8_t is_ipv6);
+
+int tcp_get_auto_ttl(uint8_t ttl, uint8_t decrease_for);
+#endif

src/utils/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] = (uintptr_t)(pstr2 - str);
+		pstr = pstr2 + fromlen;
+	}
+
+	orglen = (size_t)(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;
+}

src/utils/repl_str.h

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