Implement TCP fragmentation for HTTP Persistent (keep-alive) sessions.

New option `-k` splits HTTP request into two segments, and either
send only the first one (Windows would retransmit the other one
based on ACK number in ACK reply) or both (with `-n` enabled).

This fixes behaviour on some DPI which trace persistent sessions
but do not reassemble packages.

Makefile

@@ -1,13 +1,17 @@
-CPREFIX = x86_64-w64-mingw32
+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 -I $(WINDIVERTHEADERS) -L $(WINDIVERTLIBS) \
-         -O2 -fPIE -Wformat -Werror=format-security -D_FORTIFY_SOURCE=2
+LIBS = -L$(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
 
@@ -26,7 +30,7 @@ manifest:
 .PRECIOUS: $(TARGET) $(OBJECTS)
 
 $(TARGET): $(OBJECTS)
-	$(CC) $(OBJECTS) -Wall $(LIBS) -s -o $@
+	$(CC) $(OBJECTS) -Wall $(LDFLAGS) $(LIBS) -s -o $@
 
 clean:
 	-rm -f *.o

README.md

@@ -16,16 +16,29 @@ Usage: goodbyedpi.exe [OPTION...]
  -p          block passive DPI
  -r          replace Host with hoSt
  -s          remove space between host header and its value
+ -m          mix Host header case (test.com -> tEsT.cOm)
  -f [value]  set HTTP fragmentation to value
+ -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
+ -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.
 
- -1          enables all options, -f 2 -e 2 (most compatible mode, default)
- -2          enables all options, -f 2 -e 40 (better speed yet still compatible)
- -3          all options except HTTP fragmentation, -e 40 (even better speed)
- -4          all options except fragmentation (best speed)
+ -1          -p -r -s -f 2 -k 2 -n -e 2 (most compatible mode, default)
+ -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)
 ```
 
-Try to run `goodbyedpi.exe` without any arguments first. If you can open blocked websites it means your ISP has DPI which can be circumvented. This is the slowest mode.
+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.
+
+Try `goodbyedpi -1` to see if it works too.
 
 Then try `goodbyedpi.exe -2`. It should be faster for HTTPS sites. Mode `-3` speed ups HTTP websites.
 
@@ -35,17 +48,20 @@ Use `goodbyedpi.exe -4` if it works for your ISP's DPI. This is the fastest mode
 
 ### Passive DPI
 
-Most Passive DPI send HTTP 301 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 have always have IP Identification field equal to `0x0000` or `0x0001`, as seen with Russian providers. These packets 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 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.
 
 ### Active DPI
 
-Active DPI is more tricky to fool. Currently the software uses 3 methods to circumvent Active DPI:
+Active DPI is more tricky to fool. Currently the software uses 4 methods to circumvent Active DPI:
 
 * TCP-level fragmentation for first data packet
+* TCP-level fragmentation for persistent (keep-alive) HTTP sessions
 * Replacing `Host` header with `hoSt`
 * Removing space between header name and value in `Host` header
+* Adding additional space between HTTP Method (GET, POST etc) and URI
+* Mixing case of Host header value
 
-These methods do not break any website as are fully compatible with TCP and HTTP standards, yet it's sufficient to prevent DPI data classification and to circumvent censorship.
+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).
 
 The program loads WinDivert driver which uses Windows Filtering Platform to set filters and redirect packets to the userspace. It's running as long as console window is visible and terminates when you close the window.
 
@@ -55,11 +71,34 @@ This project can be build using **GNU Make** and [**mingw**](https://mingw-w64.o
 
 To build x86 exe run:
 
-`make CPREFIX=i686-w64-mingw32 WINDIVERTHEADERS=/path/to/windivert/include WINDIVERTLIBS=/path/to/windivert/x86`
+`make CPREFIX=i686-w64-mingw32- WINDIVERTHEADERS=/path/to/windivert/include WINDIVERTLIBS=/path/to/windivert/x86`
 
 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- WINDIVERTHEADERS=/path/to/windivert/include WINDIVERTLIBS=/path/to/windivert/amd64`
+
+# 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.
 
 # Similar projects
 

blackwhitelist.c

@@ -0,0 +1,110 @@
+/*
+ * Blacklist for GoodbyeDPI HTTP DPI circumvention tricks
+ *
+ * This is a simple domain hash table.
+ * Domain records are added from a text file, where every
+ * domain is separated with a new line.
+ */
+#include <windows.h>
+#include <stdio.h>
+#include "goodbyedpi.h"
+#include "uthash.h"
+#include "getline.h"
+
+typedef struct blackwhitelist_record {
+    const char *host;
+    UT_hash_handle hh;   /* makes this structure hashable */
+} blackwhitelist_record_t;
+
+static blackwhitelist_record_t *blackwhitelist = NULL;
+
+static int check_get_hostname(const char *host) {
+    blackwhitelist_record_t *tmp_record = NULL;
+    if (!blackwhitelist) return FALSE;
+
+    HASH_FIND_STR(blackwhitelist, host, tmp_record);
+    if (tmp_record) {
+        debug("check_get_hostname found host\n");
+        return TRUE;
+    }
+    debug("check_get_hostname host not found\n");
+    return FALSE;
+}
+
+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);
+
+    if (!check_get_hostname(host)) {
+        strncpy(host_c, host, host_len);
+        host_c[host_len] = '\0';
+        tmp_record->host = host_c;
+        HASH_ADD_KEYPTR(hh, blackwhitelist, tmp_record->host,
+                        strlen(tmp_record->host), tmp_record);
+        debug("Added host %s\n", host_c);
+        return TRUE;
+    }
+    debug("Not added host %s\n", host);
+    free(tmp_record);
+    free(host_c);
+    return FALSE;
+}
+
+int blackwhitelist_load_list(const char *filename) {
+    char *line = malloc(HOST_MAXLEN + 1);
+    size_t linelen = HOST_MAXLEN + 1;
+    int cnt = 0;
+    ssize_t read;
+
+    FILE *fp = fopen(filename, "r");
+    if (!fp) return FALSE;
+
+    while ((read = getline(&line, &linelen, fp)) != -1) {
+        /* works with both \n and \r\n */
+        line[strcspn(line, "\r\n")] = '\0';
+        if (strlen(line) > HOST_MAXLEN) {
+            printf("WARNING: host %s exceeds maximum host length and has not been added\n",
+                line);
+            continue;
+        }
+        if (strlen(line) < 4)
+            continue;
+        if (add_hostname(line))
+            cnt++;
+    }
+    free(line);
+    if (!blackwhitelist) return FALSE;
+    printf("Loaded %d hosts from file %s\n", cnt, filename);
+    fclose(fp);
+    return TRUE;
+}
+
+int blackwhitelist_check_hostname(const char *host_addr, int host_len) {
+    char current_host[HOST_MAXLEN + 1];
+    char *tokenized_host = NULL;
+
+    if (host_len > HOST_MAXLEN) return FALSE;
+    if (host_addr && host_len) {
+        memcpy(current_host, host_addr, host_len);
+        current_host[host_len] = '\0';
+    }
+
+    if (check_get_hostname(current_host))
+            return TRUE;
+
+    tokenized_host = strchr(current_host, '.');
+    while (tokenized_host != NULL && tokenized_host < (current_host + HOST_MAXLEN)) {
+        /* Search hostname only if there is next token */
+        if (strchr(tokenized_host + 1, '.') && check_get_hostname(tokenized_host + 1))
+            return TRUE;
+        tokenized_host = strchr(tokenized_host + 1, '.');
+    }
+
+    debug("____blackwhitelist_check_hostname FALSE: host %s\n", current_host);
+    return FALSE;
+}

blackwhitelist.h

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

dnsredir.c

@@ -0,0 +1,200 @@
+/*
+ * DNS UDP Connection Tracker for GoodbyeDPI
+ *
+ * This is a simple connection tracker for DNS UDP data.
+ * It's not a proper one. The caveats as follows:
+ *    * Uses only source IP address and port as a hash key;
+ *    * One-shot only. Removes conntrack record as soon as gets the reply;
+ *    * Does not properly parse DNS request and response, only checks some bytes;
+ *
+ * But anyway, it works fine for DNS.
+ */
+
+#include <windows.h>
+#include <time.h>
+#include <stdio.h>
+#include "goodbyedpi.h"
+#include "dnsredir.h"
+#include "uthash.h"
+
+// IPv6 incompatible!
+#define UDP_CONNRECORD_KEY_LEN 6
+
+#define DNS_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 UDP_CONNRECORD_KEY_LEN bytes long,
+ * we don't need to use any string function to determine length.
+ */
+#undef uthash_strlen
+#define uthash_strlen(s) UDP_CONNRECORD_KEY_LEN
+
+typedef struct udp_connrecord {
+    /* key (srcip[4] + srcport[2]) */
+    char key[UDP_CONNRECORD_KEY_LEN];
+    time_t time;         /* time when this record was added */
+    uint32_t dstip;
+    uint16_t dstport;
+    UT_hash_handle hh;   /* makes this structure hashable */
+} udp_connrecord_t;
+
+static time_t last_cleanup = 0;
+static udp_connrecord_t *conntrack = NULL;
+
+void flush_dns_cache() {
+    BOOL WINAPI (*DnsFlushResolverCache)();
+
+    HMODULE dnsapi = LoadLibrary("dnsapi.dll");
+    if (dnsapi == NULL)
+    {
+        printf("Can't load dnsapi.dll to flush DNS cache!\n");
+        exit(EXIT_FAILURE);
+    }
+
+    DnsFlushResolverCache = (void*)GetProcAddress(dnsapi, "DnsFlushResolverCache");
+    if (DnsFlushResolverCache == NULL || !DnsFlushResolverCache())
+        printf("Can't flush DNS cache!");
+    FreeLibrary(dnsapi);
+}
+
+inline static void construct_key(const uint32_t srcip, const uint16_t srcport, char *key) {
+    debug("Construct key enter\n");
+    if (key) {
+        debug("Constructing key\n");
+
+        *(uint32_t*)(key) = srcip;
+        *(uint16_t*)(key + sizeof(srcip)) = srcport;
+    }
+    debug("Construct key end\n");
+}
+
+inline static void deconstruct_key(const char *key, udp_connrecord_t *connrecord,
+                                   conntrack_info_t *conn_info) {
+    debug("Deconstruct key enter\n");
+    if (key && conn_info) {
+        debug("Deconstructing key\n");
+
+        conn_info->srcip = *(uint32_t*)(key);
+        conn_info->srcport = *(uint16_t*)(key + sizeof(conn_info->srcip));
+        conn_info->dstip = connrecord->dstip;
+        conn_info->dstport = connrecord->dstport;
+    }
+    debug("Deconstruct key end\n");
+}
+
+static int check_get_udp_conntrack_key(const char *key, udp_connrecord_t **connrecord) {
+    udp_connrecord_t *tmp_connrecord = NULL;
+    if (!conntrack) return FALSE;
+
+    HASH_FIND_STR(conntrack, key, tmp_connrecord);
+    if (tmp_connrecord) {
+        if (connrecord)
+            *connrecord = tmp_connrecord;
+        debug("check_get_udp_conntrack_key found key\n");
+        return TRUE;
+    }
+    debug("check_get_udp_conntrack_key key not found\n");
+    return FALSE;
+}
+
+static int add_udp_conntrack(const uint32_t srcip, const uint16_t srcport,
+                             const uint32_t dstip, const uint16_t dstport) {
+    if (!(srcip && srcport && dstip && dstport))
+        return FALSE;
+
+    udp_connrecord_t *tmp_connrecord = malloc(sizeof(udp_connrecord_t));
+    construct_key(srcip, srcport, tmp_connrecord->key);
+
+    if (!check_get_udp_conntrack_key(tmp_connrecord->key, NULL)) {
+        tmp_connrecord->time = time(NULL);
+        tmp_connrecord->dstip = dstip;
+        tmp_connrecord->dstport = dstport;
+        HASH_ADD_STR(conntrack, key, tmp_connrecord);
+        debug("Added UDP conntrack\n");
+        return TRUE;
+    }
+    debug("Not added UDP conntrack\n");
+    free(tmp_connrecord);
+    return FALSE;
+}
+
+void dns_cleanup() {
+    udp_connrecord_t *tmp_connrecord, *tmp_connrecord2 = NULL;
+
+    if (last_cleanup == 0) {
+        last_cleanup = time(NULL);
+        return;
+    }
+
+    if (difftime(time(NULL), last_cleanup) >= DNS_CLEANUP_INTERVAL_SEC) {
+        last_cleanup = time(NULL);
+
+        HASH_ITER(hh, conntrack, tmp_connrecord, tmp_connrecord2) {
+            if (difftime(last_cleanup, tmp_connrecord->time) >= DNS_CLEANUP_INTERVAL_SEC) {
+                HASH_DEL(conntrack, tmp_connrecord);
+                free(tmp_connrecord);
+            }
+        }
+    }
+}
+
+int dns_is_dns_packet(const char *packet_data, const UINT packet_dataLen, const int outgoing) {
+    if (packet_dataLen < 16) return FALSE;
+
+    if (outgoing && (ntohs(*(const uint16_t*)(packet_data + 2)) & 0xFA00) == 0 &&
+        (ntohs(*(const uint32_t*)(packet_data + 6))) == 0) {
+        return TRUE;
+    }
+    else if (!outgoing &&
+        (ntohs(*(const uint16_t*)(packet_data + 2)) & 0xF800) == 0x8000) {
+        return TRUE;
+    }
+    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) {
+
+    if (packet_dataLen < 16)
+        return FALSE;
+
+    dns_cleanup();
+
+    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);
+    }
+    debug("____dns_handle_outgoing FALSE: srcport = %hu, dstport = %hu\n", ntohs(srcport), ntohs(dstport));
+    return FALSE;
+}
+
+int dns_handle_incoming(const uint32_t srcip, const uint16_t srcport,
+                        const char *packet_data, const UINT packet_dataLen,
+                        conntrack_info_t *conn_info) {
+
+    char key[UDP_CONNRECORD_KEY_LEN];
+    udp_connrecord_t *tmp_connrecord = NULL;
+
+    if (packet_dataLen < 16 || !conn_info)
+        return FALSE;
+
+    dns_cleanup();
+
+    if (dns_is_dns_packet(packet_data, packet_dataLen, 0)) {
+        /* Looks like DNS response */
+        construct_key(srcip, srcport, key);
+        if (check_get_udp_conntrack_key(key, &tmp_connrecord) && tmp_connrecord) {
+            /* Connection exists in conntrack, moving on */
+            deconstruct_key(key, tmp_connrecord, conn_info);
+            HASH_DEL(conntrack, tmp_connrecord);
+            free(tmp_connrecord);
+            return TRUE;
+        }
+    }
+    debug("____dns_handle_incoming FALSE: srcport = %hu, dstport = %hu\n", ntohs(srcport), ntohs(dstport));
+    return FALSE;
+}

dnsredir.h

@@ -0,0 +1,19 @@
+#include <stdint.h>
+
+typedef struct conntrack_info {
+    uint32_t srcip;
+    uint16_t srcport;
+    uint32_t dstip;
+    uint16_t dstport;
+} conntrack_info_t;
+
+int dns_handle_incoming(const uint32_t srcip, const uint16_t srcport,
+                        const char *packet_data, const UINT packet_dataLen,
+                        conntrack_info_t *conn_info);
+
+int dns_handle_outgoing(const uint32_t srcip, const uint16_t srcport,
+                        const uint32_t dstip, const uint16_t dstport,
+                        const char *packet_data, const UINT packet_dataLen);
+
+void flush_dns_cache();
+int dns_is_dns_packet(const char *packet_data, const UINT packet_dataLen, const int outgoing);

getline.c

@@ -0,0 +1,92 @@
+/*	$NetBSD: getdelim.c,v 1.2 2015/12/25 20:12:46 joerg Exp $	*/
+/*	NetBSD-src: getline.c,v 1.2 2014/09/16 17:23:50 christos Exp 	*/
+
+/*-
+ * Copyright (c) 2011 The NetBSD Foundation, Inc.
+ * All rights reserved.
+ *
+ * This code is derived from software contributed to The NetBSD Foundation
+ * by Christos Zoulas.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
+ * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
+ * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+ * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
+ * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include "getline.h"
+
+#if !HAVE_GETDELIM
+
+ssize_t
+getdelim(char **buf, size_t *bufsiz, int delimiter, FILE *fp)
+{
+	char *ptr, *eptr;
+
+
+	if (*buf == NULL || *bufsiz == 0) {
+		*bufsiz = BUFSIZ;
+		if ((*buf = malloc(*bufsiz)) == NULL)
+			return -1;
+	}
+
+	for (ptr = *buf, eptr = *buf + *bufsiz;;) {
+		int c = fgetc(fp);
+		if (c == -1) {
+			if (feof(fp)) {
+				ssize_t diff = (ssize_t)(ptr - *buf);
+				if (diff != 0) {
+					*ptr = '\0';
+					return diff;
+				}
+			}
+			return -1;
+		}
+		*ptr++ = c;
+		if (c == delimiter) {
+			*ptr = '\0';
+			return ptr - *buf;
+		}
+		if (ptr + 2 >= eptr) {
+			char *nbuf;
+			size_t nbufsiz = *bufsiz * 2;
+			ssize_t d = ptr - *buf;
+			if ((nbuf = realloc(*buf, nbufsiz)) == NULL)
+				return -1;
+			*buf = nbuf;
+			*bufsiz = nbufsiz;
+			eptr = nbuf + nbufsiz;
+			ptr = nbuf + d;
+		}
+	}
+}
+
+#endif
+
+#if !HAVE_GETLINE
+
+ssize_t
+getline(char **buf, size_t *bufsiz, FILE *fp)
+{
+	return getdelim(buf, bufsiz, '\n', fp);
+}
+
+#endif

getline.h

@@ -0,0 +1,7 @@
+#if !HAVE_GETDELIM
+ssize_t	getdelim(char **, size_t *, int, FILE *);
+#endif
+
+#if !HAVE_GETLINE
+ssize_t	getline(char **, size_t *, FILE *);
+#endif

goodbyedpi.c

@@ -4,55 +4,147 @@
 
 #include <stdio.h>
 #include <stdlib.h>
+#include <ctype.h>
 #include <signal.h>
 #include <unistd.h>
 #include <string.h>
-#include <winsock2.h>
+#include <getopt.h>
 #include "windivert.h"
+#include "goodbyedpi.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)
 
 #define MAX_FILTERS 4
-#define MAX_PACKET_SIZE 1516
+#define MAX_PACKET_SIZE 9016
 #define IPV4_HDR_LEN 20
 #define TCP_HDR_LEN 20
-#define IPV4_TOTALLEN_OFFSET 2
 #define TCP_WINDOWSIZE_OFFSET 14
 
+#define DIVERT_NO_LOCALNETS_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 "(" \
+                   "(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 " \
+                   "(ip.SrcAddr < 172.16.0.0 or ip.SrcAddr > 172.31.255.255) and " \
+                   "(ip.SrcAddr < 169.254.0.0 or ip.SrcAddr > 169.254.255.255)" \
+                   ")"
+
+#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); \
+            exit(EXIT_FAILURE); \
+        } \
+    } \
+    else if (http_fragment_size != fragment_size) { \
+        printf( \
+            "WARNING: HTTP fragment size is already set to %d, not changing.\n", \
+            http_fragment_size \
+        ); \
+    } \
+} while (0)
+
 static HANDLE filters[MAX_FILTERS];
 static int filter_num = 0;
-static const char *http_redirect_10 = "HTTP/1.0 30";
-static const char *http_redirect_11 = "HTTP/1.1 30";
+static const char *http10_redirect_302 = "HTTP/1.0 302 ";
+static const char *http11_redirect_302 = "HTTP/1.1 302 ";
 static const char *http_host_find = "\r\nHost: ";
 static const char *http_host_replace = "\r\nhoSt: ";
+static const char *http_useragent_find = "\r\nUser-Agent: ";
+static const char *location_http = "\r\nLocation: http://";
+static const char *connection_close = "\r\nConnection: close";
+static const char *http_methods[] = {
+    "GET ",
+    "HEAD ",
+    "POST ",
+    "PUT ",
+    "DELETE ",
+    "CONNECT ",
+    "OPTIONS ",
+};
 
-static char* dumb_memmem(char* haystack, int hlen, char* needle, int nlen) {
+static struct option long_options[] = {
+    {"port",      required_argument, 0,  'z' },
+    {"dns-addr",  required_argument, 0,  'd' },
+    {"dns-port",  required_argument, 0,  'g' },
+    {"dns-verb",  no_argument,       0,  'v' },
+    {"blacklist", required_argument, 0,  'b' },
+    {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 void add_filter_str(int proto, int port) {
+    const char *udp = " or (ip and udp and (udp.SrcPort == %d or udp.DstPort == %d))";
+    const char *tcp = " or (ip and tcp and (tcp.SrcPort == %d or tcp.DstPort == %d))";
+
+    char *current_filter = filter_string;
+    int new_filter_size = strlen(current_filter) +
+            (proto == IPPROTO_UDP ? strlen(udp) : strlen(tcp)) + 16;
+    char *new_filter = malloc(new_filter_size);
+
+    strcpy(new_filter, current_filter);
+    if (proto == IPPROTO_UDP)
+        sprintf(&(new_filter[strlen(new_filter)]), udp, port, port);
+    else
+        sprintf(&(new_filter[strlen(new_filter)]), tcp, port, port);
+
+    filter_string = new_filter;
+    free(current_filter);
+}
+
+static char* dumb_memmem(const char* haystack, int hlen, const char* needle, int nlen) {
     // naive implementation
-    if (nlen > hlen) return 0;
+    if (nlen > hlen) return NULL;
     int i;
     for (i=0; i<hlen-nlen+1; i++) {
         if (memcmp(haystack+i,needle,nlen)==0) {
-            return haystack+i;
+            return (char*)(haystack+i);
         }
     }
     return NULL;
 }
 
 static HANDLE init(char *filter, UINT64 flags) {
+    LPTSTR errormessage = NULL;
     filter = WinDivertOpen(filter, WINDIVERT_LAYER_NETWORK, 0, flags);
     if (filter != INVALID_HANDLE_VALUE)
         return filter;
+    FormatMessage(FORMAT_MESSAGE_ALLOCATE_BUFFER | FORMAT_MESSAGE_FROM_SYSTEM |
+                  FORMAT_MESSAGE_IGNORE_INSERTS,
+                  NULL, GetLastError(), MAKELANGID(LANG_ENGLISH, SUBLANG_DEFAULT),
+                  (LPTSTR)&errormessage, 0, NULL);
+    printf("%s", errormessage);
+    free(errormessage);
     return NULL;
 }
 
 static int deinit(HANDLE handle) {
     if (handle) {
         WinDivertClose(handle);
-        return 1;
+        return TRUE;
     }
-    return 0;
+    return FALSE;
 }
 
 static void deinit_all() {
@@ -61,33 +153,102 @@ static void deinit_all() {
     }
 }
 
-static void sigint_handler(int sig) {
+static void sigint_handler(int sig __attribute__((unused))) {
     deinit_all();
     exit(EXIT_SUCCESS);
 }
 
-static int find_passivedpi_redirect(char *pktdata) {
-    if (memcmp(pktdata, http_redirect_11, strlen(http_redirect_11)) == 0
-        || memcmp(pktdata, http_redirect_10, strlen(http_redirect_10)) == 0) {
-        return 1;
+static void mix_case(char *pktdata, int pktlen) {
+    int i;
+
+    if (pktlen <= 0) return;
+    for (i = 0; i < pktlen; i++) {
+        if (i % 2) {
+            pktdata[i] = toupper(pktdata[i]);
+        }
     }
-    return 0;
 }
 
-/* Finds Host header with \r\n before it */
-static PVOID find_host_header(char *pktdata, int pktlen) {
-    return dumb_memmem(pktdata, pktlen,
-                (char*)http_host_find, strlen(http_host_find));
+static int is_passivedpi_redirect(const char *pktdata, int pktlen) {
+    /* First check if this is HTTP 302 redirect */
+    if (memcmp(pktdata, http11_redirect_302, strlen(http11_redirect_302)) == 0 ||
+        memcmp(pktdata, http10_redirect_302, strlen(http10_redirect_302)) == 0)
+    {
+        /* Then check if this is a redirect to new http site with Connection: close */
+        if (dumb_memmem(pktdata, pktlen, location_http, strlen(location_http)) &&
+            dumb_memmem(pktdata, pktlen, connection_close, strlen(connection_close))) {
+            return TRUE;
+        }
+    }
+    return FALSE;
 }
 
-static void change_window_size(char *pkt, int size) {
-    *(uint16_t*)(pkt + IPV4_HDR_LEN + TCP_WINDOWSIZE_OFFSET) = htons(size);
+static int find_header_and_get_info(const char *pktdata, int pktlen,
+                const char *hdrname,
+                char **hdrnameaddr,
+                char **hdrvalueaddr, int *hdrvaluelen) {
+    char *data_addr_rn;
+    char *hdr_begin;
+
+    *hdrvaluelen = 0;
+    *hdrnameaddr = NULL;
+    *hdrvalueaddr = NULL;
+
+    /* Search for the header */
+    hdr_begin = dumb_memmem(pktdata, pktlen,
+                hdrname, strlen(hdrname));
+    if (!hdr_begin) return FALSE;
+    if ((PVOID)pktdata > (PVOID)hdr_begin) return FALSE;
+
+    /* Set header address */
+    *hdrnameaddr = hdr_begin;
+    *hdrvalueaddr = (PVOID)hdr_begin + strlen(hdrname);
+
+    /* Search for header end (\r\n) */
+    data_addr_rn = dumb_memmem(*hdrvalueaddr,
+                        pktlen - ((PVOID)*hdrvalueaddr - (PVOID)pktdata),
+                        "\r\n", 2);
+    if (data_addr_rn) {
+        *hdrvaluelen = (PVOID)data_addr_rn - (PVOID)*hdrvalueaddr;
+        if (*hdrvaluelen > 0 && *hdrvaluelen <= 512)
+            return TRUE;
+    }
+    return FALSE;
+}
+
+static void change_window_size(const char *pkt, int size) {
+    if (size >= 1 && size <= 65535) {
+        *(uint16_t*)(pkt + IPV4_HDR_LEN + TCP_WINDOWSIZE_OFFSET) = htons(size);
+    }
+}
+
+/* HTTP method end without trailing space */
+static PVOID find_http_method_end(const char *pkt, int http_frag, int *is_fragmented) {
+    unsigned int i;
+    for (i = 0; i<(sizeof(http_methods) / sizeof(*http_methods)); i++) {
+        if (memcmp(pkt, http_methods[i], strlen(http_methods[i])) == 0) {
+            if (is_fragmented)
+                *is_fragmented = 0;
+            return (char*)pkt + strlen(http_methods[i]) - 1;
+        }
+        /* Try to find HTTP method in a second part of fragmented packet */
+        if ((http_frag == 1 || http_frag == 2) &&
+            memcmp(pkt, http_methods[i] + http_frag,
+                   strlen(http_methods[i]) - http_frag) == 0
+           )
+        {
+            if (is_fragmented)
+                *is_fragmented = 1;
+            return (char*)pkt + strlen(http_methods[i]) - http_frag - 1;
+        }
+    }
+    return NULL;
 }
 
 int main(int argc, char *argv[]) {
     static const char fragment_size_message[] =
                 "Fragment size should be in range [0 - 65535]\n";
-    int i, should_reinject = 0;
+    int i, should_reinject, should_recalc_checksum = 0;
     int opt;
     HANDLE w_filter = NULL;
     WINDIVERT_ADDRESS addr;
@@ -97,14 +258,32 @@ int main(int argc, char *argv[]) {
     UINT packet_dataLen;
     PWINDIVERT_IPHDR ppIpHdr;
     PWINDIVERT_TCPHDR ppTcpHdr;
+    PWINDIVERT_UDPHDR ppUdpHdr;
+    conntrack_info_t dns_conn_info;
 
     int do_passivedpi = 0, do_fragment_http = 0,
+        do_fragment_http_persistent = 0,
+        do_fragment_http_persistent_nowait = 0,
         do_fragment_https = 0, do_host = 0,
-        do_host_removespace = 0;
+        do_host_removespace = 0, do_additional_space = 0,
+        do_http_allports = 0,
+        do_host_mixedcase = 0, do_dns_redirect = 0,
+        do_dns_verb = 0, do_blacklist = 0;
     int http_fragment_size = 2;
     int https_fragment_size = 2;
-    char *data_addr, *data_addr_rn, *host_addr;
-    int host_len, fromhost_uptoend_len;
+    uint32_t dns_addr = 0;
+    uint16_t dns_port = htons(53);
+    char *host_addr, *useragent_addr, *method_addr;
+    int host_len, useragent_len;
+    int http_req_fragmented;
+
+    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);
+    }
 
     printf("GoodbyeDPI: Passive DPI blocker and Active DPI circumvention utility\n");
 
@@ -114,21 +293,26 @@ int main(int argc, char *argv[]) {
             = do_fragment_http = do_fragment_https = 1;
     }
 
-    while ((opt = getopt(argc, argv, "1234prsf:e:")) != -1) {
+    while ((opt = getopt_long(argc, argv, "1234prsaf:e:mwk:n", long_options, NULL)) != -1) {
         switch (opt) {
             case '1':
                 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;
                 break;
             case '2':
                 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;
                 https_fragment_size = 40;
                 break;
             case '3':
                 do_passivedpi = do_host = do_host_removespace \
                 = do_fragment_https = 1;
                 https_fragment_size = 40;
+                break;
             case '4':
                 do_passivedpi = do_host = do_host_removespace = 1;
                 break;
@@ -141,13 +325,23 @@ int main(int argc, char *argv[]) {
             case 's':
                 do_host_removespace = 1;
                 break;
+            case 'a':
+                do_additional_space = 1;
+                do_host_removespace = 1;
+                break;
+            case 'm':
+                do_host_mixedcase = 1;
+                break;
             case 'f':
                 do_fragment_http = 1;
-                http_fragment_size = atoi(optarg);
-                if (http_fragment_size <= 0 || http_fragment_size > 65535) {
-                    printf(fragment_size_message);
-                    exit(EXIT_FAILURE);
-                }
+                SET_HTTP_FRAGMENT_SIZE_OPTION(atoi(optarg));
+                break;
+            case 'k':
+                do_fragment_http_persistent = 1;
+                SET_HTTP_FRAGMENT_SIZE_OPTION(atoi(optarg));
+                break;
+            case 'n':
+                do_fragment_http_persistent_nowait = 1;
                 break;
             case 'e':
                 do_fragment_https = 1;
@@ -157,47 +351,122 @@ int main(int argc, char *argv[]) {
                     exit(EXIT_FAILURE);
                 }
                 break;
+            case 'w':
+                do_http_allports = 1;
+                break;
+            case 'z':
+                /* i is used as a temporary variable here */
+                i = atoi(optarg);
+                if (i <= 0 || i > 65535) {
+                    printf("Port parameter error!\n");
+                    exit(EXIT_FAILURE);
+                }
+                if (i != 80 && i != 443)
+                    add_filter_str(IPPROTO_TCP, 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");
+                        exit(EXIT_FAILURE);
+                    }
+                    add_filter_str(IPPROTO_UDP, 53);
+                    flush_dns_cache();
+                }
+                break;
+            case 'g':
+                if (!do_dns_redirect) {
+                    printf("--dns-port should be used with --dns-addr!\n"
+                        "Make sure you use --dns-addr and pass it before "
+                        "--dns-port\n");
+                    exit(EXIT_FAILURE);
+                }
+                dns_port = atoi(optarg);
+                if (atoi(optarg) <= 0 || atoi(optarg) > 65535) {
+                    printf("DNS port parameter error!\n");
+                    exit(EXIT_FAILURE);
+                }
+                if (dns_port != 53) {
+                    add_filter_str(IPPROTO_UDP, dns_port);
+                }
+                dns_port = ntohs(dns_port);
+                break;
+            case 'v':
+                do_dns_verb = 1;
+                break;
+            case 'b':
+                do_blacklist = 1;
+                if (!blackwhitelist_load_list(optarg)) {
+                    printf("Can't load blacklist from file!\n");
+                    exit(EXIT_FAILURE);
+                }
+                break;
             default:
                 printf("Usage: goodbyedpi.exe [OPTION...]\n"
                 " -p          block passive DPI\n"
                 " -r          replace Host with hoSt\n"
                 " -s          remove space between host header and its value\n"
+                " -a          additional space between Method and Request-URI (enables -s, may break sites)\n"
+                " -m          mix Host header case (test.com -> tEsT.cOm)\n"
                 " -f [value]  set HTTP fragmentation to value\n"
+                " -k [value]  enable HTTP persistent (keep-alive) fragmentation and set it to value\n"
+                " -n          do not wait for first segment ACK when -k is enabled\n"
                 " -e [value]  set HTTPS fragmentation to value\n"
+                " -w          try to find and parse HTTP traffic on all processed ports (not only on port 80)\n"
+                " --port      [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"
+                " --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"
                 "\n"
-                " -1          enables all options, -f 2 -e 2 (most compatible mode, default)\n"
-                " -2          enables all options, -f 2 -e 40 (better speed yet still compatible)\n"
-                " -3          all options except HTTP fragmentation, -e 40 (even better speed)\n"
-                " -4          all options except fragmentation (best speed)\n");
+                " -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");
                 exit(EXIT_FAILURE);
         }
     }
 
-    printf("Block passive: %d, Fragment HTTP: %d, Fragment HTTPS: %d, "
-           "hoSt: %d, Host no space: %d\n",
+    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",
            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_host, do_host_removespace, do_additional_space, do_host_mixedcase,
+           do_http_allports, do_fragment_http_persistent_nowait, do_dns_redirect
+          );
+
+    if (do_fragment_http && http_fragment_size > 2) {
+        printf("WARNING: HTTP fragmentation values > 2 are not fully compatible "
+               "with other options. Please use values <= 2 or disable HTTP fragmentation "
+               "completely.\n");
+    }
 
     printf("\nOpening filter\n");
     filter_num = 0;
 
     if (do_passivedpi) {
-        /* Filter for inbound RST packets with ID = 0 or 1 */
-        filters[filter_num] = init("inbound and (ip.Id == 0x0001 or ip.Id == 0x0000) and "
-                        "(tcp.SrcPort == 443 or tcp.SrcPort == 80) and tcp.Rst",
-                        WINDIVERT_FLAG_DROP);
+        /* IPv4 filter for inbound RST packets with ID = 0 or 1 */
+        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,
+            WINDIVERT_FLAG_DROP);
         filter_num++;
     }
 
     /* 
-     * Filter for inbound HTTP redirection packets and
+     * IPv4 filter for inbound HTTP redirection packets and
      * active DPI circumvention
      */
-    filters[filter_num] = init("(inbound and (ip.Id == 0x0001 or ip.Id == 0x0000) and tcp.SrcPort == 80 and tcp.Ack) "
-                      "or (inbound and (tcp.SrcPort == 80 or tcp.SrcPort == 443) and tcp.Ack and tcp.Syn) "
-                      "or (outbound and (tcp.DstPort == 80 or tcp.DstPort == 443) and tcp.Ack)",
-                      0);
+    filters[filter_num] = init(filter_string, 0);
 
     w_filter = filters[filter_num];
     filter_num++;
@@ -215,79 +484,249 @@ int main(int argc, char *argv[]) {
             //printf("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)) {
                 //printf("Got parsed packet, len=%d!\n", packet_dataLen);
-                /* Got a packet WITH DATA */
+                /* Got a TCP packet WITH DATA */
 
                 /* Handle INBOUND packet with data and find HTTP REDIRECT in there */
                 if (addr.Direction == WINDIVERT_DIRECTION_INBOUND && packet_dataLen > 16) {
                     /* If INBOUND packet with DATA (tcp.Ack) */
 
                     /* Drop packets from filter with HTTP 30x Redirect */
-                    if (do_passivedpi && find_passivedpi_redirect(packet_data)) {
+                    if (do_passivedpi && is_passivedpi_redirect(packet_data, packet_dataLen)) {
                         //printf("Dropping HTTP Redirect packet!\n");
                         should_reinject = 0;
                     }
                 }
-                /* Handle OUTBOUND packet, search for Host header */
+                /* Handle OUTBOUND packet on port 80, search for Host header */
                 else if (addr.Direction == WINDIVERT_DIRECTION_OUTBOUND && 
-                         packet_dataLen > 16 && ppTcpHdr->DstPort == htons(80) &&
-                        (do_host || do_host_removespace)) {
+                        packet_dataLen > 16 &&
+                        (do_http_allports ? 1 : (ppTcpHdr->DstPort == htons(80))) &&
+                        find_http_method_end(packet_data,
+                                             (do_fragment_http ? http_fragment_size : 0),
+                                             &http_req_fragmented) &&
+                        (do_host || do_host_removespace ||
+                        do_host_mixedcase || do_fragment_http_persistent))
+                {
 
-                    data_addr = find_host_header(packet_data, packet_dataLen);
+                    /* Find Host header */
+                    if (find_header_and_get_info(packet_data, packet_dataLen,
+                        http_host_find, &hdr_name_addr, &hdr_value_addr, &hdr_value_len) &&
+                        hdr_value_len > 0 && hdr_value_len <= HOST_MAXLEN &&
+                        (do_blacklist ? blackwhitelist_check_hostname(hdr_value_addr, hdr_value_len) : 1))
+                    {
+                        host_addr = hdr_value_addr;
+                        host_len = hdr_value_len;
 
-                    if (do_host && data_addr) {
-                        /* Replace "Host: " with "hoSt: " */
-                        memcpy(data_addr, http_host_replace, strlen(http_host_replace));
-                        //printf("Replaced Host header!\n");
-                    }
+                        /*
+                         * Handle new HTTP request in new
+                         * connection (when Window Size modification disabled)
+                         * or already established connection (keep-alive).
+                         * We split HTTP request into two packets: one of http_fragment_size length
+                         * and another of original_size - http_fragment_size length.
+                         *
+                         * The second packet of a splitted part is not really needed to be sent
+                         * as Windows understand that is hasn't been sent by checking
+                         * 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) {
+                            ppIpHdr->Length = htons(
+                                ntohs(ppIpHdr->Length) -
+                                packet_dataLen + http_fragment_size
+                            );
+                            WinDivertHelperCalcChecksums(
+                                packet, packetLen - packet_dataLen + http_fragment_size, 0
+                            );
+                            WinDivertSend(
+                                w_filter, packet,
+                                packetLen - packet_dataLen + http_fragment_size,
+                                &addr, NULL
+                            );
+                            if (do_fragment_http_persistent_nowait) {
+                                ppIpHdr->Length = htons(
+                                    ntohs(ppIpHdr->Length) -
+                                    http_fragment_size + packet_dataLen - http_fragment_size
+                                );
+                                memmove(packet_data,
+                                        packet_data + http_fragment_size,
+                                        packet_dataLen);
+                                packet_dataLen -= http_fragment_size;
+                                packetLen -= http_fragment_size;
+                                hdr_value_addr -= http_fragment_size;
+                                hdr_name_addr -= http_fragment_size;
+                                host_addr = hdr_value_addr;
 
-                    if (do_host_removespace && data_addr) {
-                        host_addr = data_addr + strlen(http_host_find);
-
-                        fromhost_uptoend_len = packet_dataLen - ((PVOID)host_addr - packet_data);
-                        data_addr_rn = dumb_memmem(host_addr,
-                                                    fromhost_uptoend_len,
-                                                    "\r\n", 2);
-                        if (data_addr_rn) {
-                            host_len = data_addr_rn - host_addr;
-                            if (host_len <= 64) {
-                                /* Move memory left by 1 byte and reduce packet size for 1 byte */
-                                memmove(host_addr - 1, host_addr, fromhost_uptoend_len);
-                                /* Reduce "Total Length" in IP header by 1 byte */
-                                *(uint16_t*)(packet + IPV4_TOTALLEN_OFFSET) = ntohs(
-                                     htons(*(uint16_t*)(packet + IPV4_TOTALLEN_OFFSET)) - 1);
-                                /* Reduce packetLen by 1 byte */
-                                packetLen--;
-                                //printf("Replaced Host header!\n");
+                                ppTcpHdr->SeqNum = htonl(ntohl(ppTcpHdr->SeqNum) + http_fragment_size);
+                                should_recalc_checksum = 1;
+                            }
+                            else {
+                                continue;
                             }
                         }
-                    }
-                    WinDivertHelperCalcChecksums(packet, packetLen, 0);
-                }
-            }
+
+                        if (do_host_mixedcase) {
+                            mix_case(host_addr, host_len);
+                            should_recalc_checksum = 1;
+                        }
+
+                        if (do_host) {
+                            /* Replace "Host: " with "hoSt: " */
+                            memcpy(hdr_name_addr, http_host_replace, strlen(http_host_replace));
+                            should_recalc_checksum = 1;
+                            //printf("Replaced Host header!\n");
+                        }
+
+                        /* If removing space between host header and its value
+                         * and adding additional space between Method and Request-URI */
+                        if (do_additional_space && do_host_removespace) {
+                            /* End of "Host:" without trailing space */
+                            method_addr = find_http_method_end(packet_data,
+                                                            (do_fragment_http ? http_fragment_size : 0),
+                                                            NULL);
+
+                            if (method_addr) {
+                                memmove(method_addr + 1, method_addr,
+                                        (PVOID)host_addr - (PVOID)method_addr - 1);
+                                should_recalc_checksum = 1;
+                            }
+                        }
+                        /* If just removing space between host header and its value */
+                        else if (do_host_removespace) {
+                            if (find_header_and_get_info(packet_data, packet_dataLen,
+                                                        http_useragent_find, &hdr_name_addr,
+                                                         &hdr_value_addr, &hdr_value_len))
+                            {
+                                useragent_addr = hdr_value_addr;
+                                useragent_len = hdr_value_len;
+
+                                /* We move Host header value by one byte to the left and then
+                                 * "insert" stolen space to the end of User-Agent value because
+                                 * some web servers are not tolerant to additional space in the
+                                 * end of Host header.
+                                 *
+                                 * Nothing is done if User-Agent header is missing.
+                                 */
+                                if (useragent_addr && useragent_len > 0) {
+                                    /* useragent_addr is in the beginning of User-Agent value */
+
+                                    if (useragent_addr > host_addr) {
+                                        /* Move one byte to the LEFT from "Host:"
+                                        * to the end of User-Agent
+                                        */
+                                        memmove(host_addr - 1, host_addr,
+                                                (PVOID)useragent_addr + useragent_len - (PVOID)host_addr);
+                                        host_addr -= 1;
+                                        /* Put space in the end of User-Agent header */
+                                        *(char*)((PVOID)useragent_addr + useragent_len - 1) = ' ';
+                                        should_recalc_checksum = 1;
+                                        //printf("Replaced Host header!\n");
+                                    }
+                                    else {
+                                        /* User-Agent goes BEFORE Host header */
+
+                                        /* Move one byte to the RIGHT from the end of User-Agent
+                                        * to the "Host:"
+                                        */
+                                        memmove((PVOID)useragent_addr + useragent_len + 1,
+                                                (PVOID)useragent_addr + useragent_len,
+                                                (PVOID)host_addr - 1 - ((PVOID)useragent_addr + useragent_len));
+                                        /* Put space in the end of User-Agent header */
+                                        *(char*)((PVOID)useragent_addr + useragent_len) = ' ';
+                                        should_recalc_checksum = 1;
+                                        //printf("Replaced Host header!\n");
+                                    }
+                                } /* if (host_len <= HOST_MAXLEN && useragent_addr) */
+                            } /* if (find_header_and_get_info http_useragent) */
+                        } /* else if (do_host_removespace) */
+                    } /* if (find_header_and_get_info http_host) */
+                } /* Handle OUTBOUND packet with data */
+            } /* Handle TCP packet with data */
+
             /* Else if we got TCP packet without data */
             else if (WinDivertHelperParsePacket(packet, packetLen, &ppIpHdr,
                 NULL, NULL, NULL, &ppTcpHdr, NULL, NULL, NULL)) {
-                /* If we got SYN+ACK packet */
+                /* If we got INBOUND SYN+ACK packet */
                 if (addr.Direction == WINDIVERT_DIRECTION_INBOUND &&
-                    ppTcpHdr->Syn == 1) {
+                    ppTcpHdr->Syn == 1 && ppTcpHdr->Ack == 1) {
                     //printf("Changing Window Size!\n");
-                    if (do_fragment_http && ppTcpHdr->DstPort == htons(80)) {
+                    /*
+                     * Window Size is changed even if do_fragment_http_persistent
+                     * 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);
-                        WinDivertHelperCalcChecksums(packet, packetLen, 0);
+                        should_recalc_checksum = 1;
                     }
-                    else if (do_fragment_https && ppTcpHdr->DstPort != htons(80)) {
+                    else if (do_fragment_https && ppTcpHdr->SrcPort != htons(80)) {
                         change_window_size(packet, https_fragment_size);
-                        WinDivertHelperCalcChecksums(packet, packetLen, 0);
+                        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)) {
+
+                if (addr.Direction == WINDIVERT_DIRECTION_INBOUND) {
+                    if (dns_handle_incoming(ppIpHdr->DstAddr, ppUdpHdr->DstPort,
+                                        packet_data, packet_dataLen,
+                                        &dns_conn_info))
+                    {
+                        /* Changing source IP and port to the values
+                         * from DNS conntrack */
+                        ppIpHdr->SrcAddr = dns_conn_info.dstip;
+                        ppUdpHdr->DstPort = dns_conn_info.srcport;
+                        ppUdpHdr->SrcPort = dns_conn_info.dstport;
+                        should_recalc_checksum = 1;
+                    }
+                    else {
+                        if (dns_is_dns_packet(packet_data, packet_dataLen, 0))
+                            should_reinject = 0;
+
+                        if (do_dns_verb && !should_reinject) {
+                            printf("[DNS] Error handling incoming packet: srcport = %hu, dstport = %hu\n",
+                               ntohs(ppUdpHdr->SrcPort), ntohs(ppUdpHdr->DstPort));
+                        }
+                    }
+                }
+
+                else if (addr.Direction == WINDIVERT_DIRECTION_OUTBOUND) {
+                    if (dns_handle_outgoing(ppIpHdr->SrcAddr, ppUdpHdr->SrcPort,
+                                        ppIpHdr->DstAddr, ppUdpHdr->DstPort,
+                                        packet_data, packet_dataLen))
+                    {
+                        /* Changing destination IP and port to the values
+                         * from configuration */
+                        ppIpHdr->DstAddr = dns_addr;
+                        ppUdpHdr->DstPort = dns_port;
+                        should_recalc_checksum = 1;
+                    }
+                    else {
+                        if (dns_is_dns_packet(packet_data, packet_dataLen, 1))
+                            should_reinject = 0;
+
+                        if (do_dns_verb && !should_reinject) {
+                            printf("[DNS] Error handling outgoing packet: srcport = %hu, dstport = %hu\n",
+                               ntohs(ppUdpHdr->SrcPort), ntohs(ppUdpHdr->DstPort));
+                        }
                     }
                 }
             }
 
             if (should_reinject) {
                 //printf("Re-injecting!\n");
+                if (should_recalc_checksum) {
+                    WinDivertHelperCalcChecksums(packet, packetLen, 0);
+                }
+                else {
+                    WinDivertHelperCalcChecksums(packet, packetLen,
+                                                 WINDIVERT_HELPER_NO_REPLACE);
+                }
                 WinDivertSend(w_filter, packet, packetLen, &addr, NULL);
             }
         }

goodbyedpi.h

@@ -0,0 +1,7 @@
+#define HOST_MAXLEN 253
+
+#ifndef DEBUG
+#define debug(...) do {} while (0)
+#else
+#define debug(...) printf(__VA_ARGS__)
+#endif