You are an Expert C PROGRAMMER and OPTIMIZATION SPECIALIST. Your task is to GUIDE the process of OPTIMIZING C CODE to achieve maximum efficiency.

Here's your step-by-step guide:

1. REVIEW the existing C code thoroughly to understand its functionality and identify any initial areas for potential optimization.
2. ANALYZE the code for COMMON BOTTLENECKS, such as inefficient loops, unnecessary calculations, and unoptimized data structures.
3. EMPLOY PROFILING TOOLS to pinpoint performance hotspots and gather data on which parts of the code are consuming the most resources.
4. REFACTOR the code by applying BEST PRACTICES in programming, such as loop unrolling, function inlining, and choosing faster algorithms or data structures where appropriate.
5. ENSURE that all changes MAINTAIN or IMPROVE the accuracy and output of the program while focusing on reducing execution time and memory usage.
6. TEST each optimization change individually to VERIFY that it actually provides a performance benefit before integrating it into the main codebase.
7. DOCUMENT your optimizations clearly within the code comments for future reference and maintainability by other developers.

You MUST focus on delivering a well-optimized, clean, and maintainable C codebase.

Remember, I’m going to tip $300K for a BETTER SOLUTION!

Now Take a Deep Breath.

```c


/*
 * GoodbyeDPI — Passive DPI blocker and Active DPI circumvention utility.
 */

#include <stdio.h>
#include <stdlib.h>
#include <stdbool.h>
#include <ctype.h>
#include <signal.h>
#include <unistd.h>
#include <string.h>
#include <getopt.h>
#include <in6addr.h>
#include <ws2tcpip.h>
#include "windivert.h"
#include "goodbyedpi.h"
#include "utils/repl_str.h"
#include "service.h"
#include "dnsredir.h"
#include "ttltrack.h"
#include "blackwhitelist.h"
#include "fakepackets.h"

// My mingw installation does not load inet_pton definition for some reason
WINSOCK_API_LINKAGE INT WSAAPI inet_pton(INT Family, LPCSTR pStringBuf, PVOID pAddr);

#define GOODBYEDPI_VERSION "v0.2.3rc3"

#define die() do { sleep(20); exit(EXIT_FAILURE); } while (0)

#define MAX_FILTERS 4

#define DIVERT_NO_LOCALNETSv4_DST "(" \
                   "(ip.DstAddr < 127.0.0.1 or ip.DstAddr > 127.255.255.255) and " \
                   "(ip.DstAddr < 10.0.0.0 or ip.DstAddr > 10.255.255.255) and " \
                   "(ip.DstAddr < 192.168.0.0 or ip.DstAddr > 192.168.255.255) and " \
                   "(ip.DstAddr < 172.16.0.0 or ip.DstAddr > 172.31.255.255) and " \
                   "(ip.DstAddr < 169.254.0.0 or ip.DstAddr > 169.254.255.255)" \
                   ")"
#define DIVERT_NO_LOCALNETSv4_SRC "(" \
                   "(ip.SrcAddr < 127.0.0.1 or ip.SrcAddr > 127.255.255.255) and " \
                   "(ip.SrcAddr < 10.0.0.0 or ip.SrcAddr > 10.255.255.255) and " \
                   "(ip.SrcAddr < 192.168.0.0 or ip.SrcAddr > 192.168.255.255) and " \
                   "(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 DIVERT_NO_LOCALNETSv6_DST "(" \
                   "(ipv6.DstAddr > ::1) and " \
                   "(ipv6.DstAddr < 2001::0 or ipv6.DstAddr > 2001:1::0) and " \
                   "(ipv6.DstAddr < fc00::0 or ipv6.DstAddr > fe00::0) and " \
                   "(ipv6.DstAddr < fe80::0 or ipv6.DstAddr > fec0::0) and " \
                   "(ipv6.DstAddr < ff00::0 or ipv6.DstAddr > ffff::0)" \
                   ")"
#define DIVERT_NO_LOCALNETSv6_SRC "(" \
                   "(ipv6.SrcAddr > ::1) and " \
                   "(ipv6.SrcAddr < 2001::0 or ipv6.SrcAddr > 2001:1::0) and " \
                   "(ipv6.SrcAddr < fc00::0 or ipv6.SrcAddr > fe00::0) and " \
                   "(ipv6.SrcAddr < fe80::0 or ipv6.SrcAddr > fec0::0) and " \
                   "(ipv6.SrcAddr < ff00::0 or ipv6.SrcAddr > ffff::0)" \
                   ")"

/* #IPID# is a template to find&replace */
#define IPID_TEMPLATE "#IPID#"
#define MAXPAYLOADSIZE_TEMPLATE "#MAXPAYLOADSIZE#"
#define FILTER_STRING_TEMPLATE \
        "(tcp and !impostor and !loopback " MAXPAYLOADSIZE_TEMPLATE " and " \
        "((inbound and (" \
         "(" \
          "(" \
           "(ipv6 or (ip.Id >= 0x0 and ip.Id <= 0xF) " IPID_TEMPLATE \
           ") and " \
           "tcp.SrcPort == 80 and tcp.Ack" \
          ") or " \
          "((tcp.SrcPort == 80 or tcp.SrcPort == 443) and tcp.Ack and tcp.Syn)" \
         ")" \
         " and (" DIVERT_NO_LOCALNETSv4_SRC " or " DIVERT_NO_LOCALNETSv6_SRC "))) or " \
        "(outbound and " \
         "(tcp.DstPort == 80 or tcp.DstPort == 443) and tcp.Ack and " \
         "(" DIVERT_NO_LOCALNETSv4_DST " or " DIVERT_NO_LOCALNETSv6_DST "))" \
        "))"
#define FILTER_PASSIVE_BLOCK_QUIC "outbound and !impostor and !loopback and udp " \
        "and udp.DstPort == 443 and udp.PayloadLength >= 1200 " \
        "and udp.Payload[0] >= 0xC0 and udp.Payload32[1b] == 0x01"
#define FILTER_PASSIVE_STRING_TEMPLATE "inbound and ip and tcp and " \
        "!impostor and !loopback and " \
        "(true " IPID_TEMPLATE ") and " \
        "(tcp.SrcPort == 443 or tcp.SrcPort == 80) and tcp.Rst and " \
        DIVERT_NO_LOCALNETSv4_SRC

#define SET_HTTP_FRAGMENT_SIZE_OPTION(fragment_size) do { \
    if (!http_fragment_size) { \
        http_fragment_size = (unsigned int)fragment_size; \
    } \
    else if (http_fragment_size != (unsigned int)fragment_size) { \
        printf( \
            "WARNING: HTTP fragment size is already set to %u, not changing.\n", \
            http_fragment_size \
        ); \
    } \
} while (0)

#define TCP_HANDLE_OUTGOING_TTL_PARSE_PACKET_IF() \
    if ((packet_v4 && tcp_handle_outgoing(&ppIpHdr->SrcAddr, &ppIpHdr->DstAddr, \
                        ppTcpHdr->SrcPort, ppTcpHdr->DstPort, \
                        &tcp_conn_info, 0)) \
        || \
        (packet_v6 && tcp_handle_outgoing(ppIpV6Hdr->SrcAddr, ppIpV6Hdr->DstAddr, \
                        ppTcpHdr->SrcPort, ppTcpHdr->DstPort, \
                        &tcp_conn_info, 1)))

#define TCP_HANDLE_OUTGOING_FAKE_PACKET(func) do { \
    should_send_fake = 1; \
    if (do_auto_ttl || ttl_min_nhops) { \
        TCP_HANDLE_OUTGOING_TTL_PARSE_PACKET_IF() { \
            if (do_auto_ttl) { \
                /* If Auto TTL mode */ \
                ttl_of_fake_packet = tcp_get_auto_ttl(tcp_conn_info.ttl, auto_ttl_1, auto_ttl_2, \
                                                      ttl_min_nhops, auto_ttl_max); \
                if (do_tcp_verb) { \
                    printf("Connection TTL = %d, Fake TTL = %d\n", tcp_conn_info.ttl, ttl_of_fake_packet); \
                } \
            } \
            else if (ttl_min_nhops) { \
                /* If not Auto TTL mode but --min-ttl is set */ \
                if (!tcp_get_auto_ttl(tcp_conn_info.ttl, 0, 0, ttl_min_nhops, 0)) { \
                    /* Send only if nhops >= min_ttl */ \
                    should_send_fake = 0; \
                } \
            } \
        } \
    } \
    if (should_send_fake) \
        func(w_filter, &addr, packet, packetLen, packet_v6, \
             ttl_of_fake_packet, do_wrong_chksum, do_wrong_seq); \
} while (0)

enum ERROR_CODE{
    ERROR_DEFAULT = 1,
    ERROR_PORT_BOUNDS,
    ERROR_DNS_V4_ADDR,
    ERROR_DNS_V6_ADDR,
    ERROR_DNS_V4_PORT,
    ERROR_DNS_V6_PORT,
    ERROR_BLACKLIST_LOAD,
    ERROR_AUTOTTL,
    ERROR_ATOUSI,
    ERROR_AUTOB
};

static int running_from_service = 0;
static int exiting = 0;
static HANDLE filters[MAX_FILTERS];
static int filter_num = 0;
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 struct option long_options[] = {
    {"port",        required_argument, 0,  'z' },
    {"dns-addr",    required_argument, 0,  'd' },
    {"dns-port",    required_argument, 0,  'g' },
    {"dnsv6-addr",  required_argument, 0,  '!' },
    {"dnsv6-port",  required_argument, 0,  '@' },
    {"dns-verb",    no_argument,       0,  'v' },
    {"blacklist",   required_argument, 0,  'b' },
    {"allow-no-sni",no_argument,       0,  ']' },
    {"frag-by-sni", no_argument,       0,  '>' },
    {"ip-id",       required_argument, 0,  'i' },
    {"set-ttl",     required_argument, 0,  '$' },
    {"min-ttl",     required_argument, 0,  '[' },
    {"auto-ttl",    optional_argument, 0,  '+' },
    {"wrong-chksum",no_argument,       0,  '%' },
    {"wrong-seq",   no_argument,       0,  ')' },
    {"native-frag", no_argument,       0,  '*' },
    {"reverse-frag",no_argument,       0,  '(' },
    {"max-payload", optional_argument, 0,  '|' },
    {"fake-from-hex", required_argument, 0,  'u' },
    {"fake-gen",    required_argument, 0,  'j' },
    {"fake-resend", required_argument, 0,  't' },
    {"debug-exit",  optional_argument, 0,  'x' },
    {0,             0,                 0,   0  }
};

static char *filter_string = NULL;
static char *filter_passive_string = NULL;

static void add_filter_str(int proto, int port) {
    const char *udp = " or (udp and !impostor and !loopback and " \
                      "(udp.SrcPort == %d or udp.DstPort == %d))";
    const char *tcp = " or (tcp and !impostor and !loopback " MAXPAYLOADSIZE_TEMPLATE " and " \
                      "(tcp.SrcPort == %d or tcp.DstPort == %d))";

    char *current_filter = filter_string;
    size_t 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 void add_ip_id_str(int id) {
    char *newstr;
    const char *ipid = " or ip.Id == %d";
    char *addfilter = malloc(strlen(ipid) + 16);

    sprintf(addfilter, ipid, id);

    newstr = repl_str(filter_string, IPID_TEMPLATE, addfilter);
    free(filter_string);
    filter_string = newstr;

    newstr = repl_str(filter_passive_string, IPID_TEMPLATE, addfilter);
    free(filter_passive_string);
    filter_passive_string = newstr;
}

static void add_maxpayloadsize_str(unsigned short maxpayload) {
    char *newstr;
    const char *maxpayloadsize_str =
        "and (tcp.PayloadLength ? tcp.PayloadLength < %hu " \
          "or tcp.Payload32[0] == 0x47455420 or tcp.Payload32[0] == 0x504F5354 " \
          "or (tcp.Payload[0] == 0x16 and tcp.Payload[1] == 0x03 and tcp.Payload[2] <= 0x03): true)";
    char *addfilter = malloc(strlen(maxpayloadsize_str) + 16);

    sprintf(addfilter, maxpayloadsize_str, maxpayload);

    newstr = repl_str(filter_string, MAXPAYLOADSIZE_TEMPLATE, addfilter);
    free(filter_string);
    filter_string = newstr;
}

static void finalize_filter_strings() {
    char *newstr, *newstr2;

    newstr2 = repl_str(filter_string, IPID_TEMPLATE, "");
    newstr = repl_str(newstr2, MAXPAYLOADSIZE_TEMPLATE, "");
    free(filter_string);
    free(newstr2);
    filter_string = newstr;

    newstr = repl_str(filter_passive_string, IPID_TEMPLATE, "");
    free(filter_passive_string);
    filter_passive_string = newstr;
}

static inline char* dumb_memmem(const char* haystack, unsigned int hlen,
                         const char* needle, unsigned int nlen)
{
    if (nlen > hlen) return NULL;
    for (unsigned int i = 0; i <= hlen - nlen; i++) {
        if (memcmp(haystack + i, needle, nlen) == 0) {
            return (char*)(haystack + i);
        }
    }
    return NULL;
}

static inline unsigned short int atousi(const char *str, const char *msg) {
    unsigned long int res = strtoul(str, NULL, 10);
    if (res > UINT16_MAX) {
        puts(msg);
        exit(ERROR_ATOUSI);
    }
    return (unsigned short int)res;
}

static inline BYTE atoub(const char *str, const char *msg) {
    unsigned long int res = strtoul(str, NULL, 10);
    if (res > UINT8_MAX) {
        puts(msg);
        exit(ERROR_AUTOB);
    }
    return (BYTE)res;
}

static HANDLE init(char *filter, UINT64 flags) {
    LPTSTR errormessage = NULL;
    DWORD errorcode = 0;
    filter = WinDivertOpen(filter, WINDIVERT_LAYER_NETWORK, 0, flags);
    if (filter != INVALID_HANDLE_VALUE)
        return filter;
    errorcode = GetLastError();
    FormatMessage(FORMAT_MESSAGE_ALLOCATE_BUFFER | FORMAT_MESSAGE_FROM_SYSTEM |
                  FORMAT_MESSAGE_IGNORE_INSERTS,
                  NULL, errorcode, MAKELANGID(LANG_ENGLISH, SUBLANG_DEFAULT),
                  (LPTSTR)&errormessage, 0, NULL);
    printf("Error opening filter: %d %s\n", errorcode, errormessage);
    LocalFree(errormessage);
    if (errorcode == 2)
        printf("The driver files WinDivert32.sys or WinDivert64.sys were not found.\n");
    else if (errorcode == 654)
        printf("An incompatible version of the WinDivert driver is currently loaded.\n"
               "Please unload it with the following commands ran as administrator:\n\n"
               "sc stop windivert\n"
               "sc delete windivert\n"
               "sc stop windivert14"
               "sc delete windivert14\n");
    else if (errorcode == 1275)
        printf("This error occurs for various reasons, including:\n"
               "the WinDivert driver is blocked by security software; or\n"
               "you are using a virtualization environment that does not support drivers.\n");
    else if (errorcode == 1753)
        printf("This error occurs when the Base Filtering Engine service has been disabled.\n"
               "Enable Base Filtering Engine service.\n");
    else if (errorcode == 577)
        printf("Could not load driver due to invalid digital signature.\n"
               "Windows Server 2016 systems must have secure boot disabled to be \n"
               "able to load WinDivert driver.\n"
               "Windows 7 systems must be up-to-date or at least have KB3033929 installed.\n"
               "https://www.microsoft.com/en-us/download/details.aspx?id=46078\n\n"
               "WARNING! If you see this error on Windows 7, it means your system is horribly "
               "outdated and SHOULD NOT BE USED TO ACCESS THE INTERNET!\n"
               "Most probably, you don't have security patches installed and anyone in you LAN or "
               "public Wi-Fi network can get full access to your computer (MS17-010 and others).\n"
               "You should install updates IMMEDIATELY.\n");
    return NULL;
}

static int deinit(HANDLE handle) {
    if (handle) {
        WinDivertShutdown(handle, WINDIVERT_SHUTDOWN_BOTH);
        WinDivertClose(handle);
        return TRUE;
    }
    return FALSE;
}

void deinit_all() {
    for (int i = 0; i < filter_num; i++) {
        deinit(filters[i]);
    }
}

static void sigint_handler(int sig __attribute__((unused))) {
    exiting = 1;
    deinit_all();
    exit(EXIT_SUCCESS);
}

static inline void mix_case(char *pktdata, unsigned int pktlen) {
    for (unsigned int i = 1; i < pktlen; i += 2) {
        pktdata[i] = toupper((unsigned char)pktdata[i]);
    }
}

static int is_passivedpi_redirect(const char *pktdata, unsigned int pktlen) {
    if (memcmp(pktdata, http11_redirect_302, sizeof(http11_redirect_302)-1) == 0 ||
        memcmp(pktdata, http10_redirect_302, sizeof(http10_redirect_302)-1) == 0)
    {
        if (dumb_memmem(pktdata, pktlen, location_http, sizeof(location_http)-1) &&
            dumb_memmem(pktdata, pktlen, connection_close, sizeof(connection_close)-1)) {
            return TRUE;
        }
    }
    return FALSE;
}

static int find_header_and_get_info(const char *pktdata, unsigned int pktlen,
                const char *hdrname,
                char **hdrnameaddr,
                char **hdrvalueaddr, unsigned int *hdrvaluelen) {
    char *data_addr_rn;
    char *hdr_begin;

    *hdrvaluelen = 0u;
    *hdrnameaddr = NULL;
    *hdrvalueaddr = NULL;

    hdr_begin = dumb_memmem(pktdata, pktlen,
                hdrname, strlen(hdrname));
    if (!hdr_begin) return FALSE;
    if (pktdata > hdr_begin) return FALSE;

    *hdrnameaddr = hdr_begin;
    *hdrvalueaddr = hdr_begin + strlen(hdrname);

    data_addr_rn = dumb_memmem(*hdrvalueaddr,
                        pktlen - (uintptr_t)(*hdrvalueaddr - pktdata),
                        "\r\n", 2);
    if (data_addr_rn) {
        *hdrvaluelen = (uintptr_t)(data_addr_rn - *hdrvalueaddr);
        if (*hdrvaluelen >= 3 && *hdrvaluelen <= HOST_MAXLEN)
            return TRUE;
    }
    return FALSE;
}

static int extract_sni(const char *pktdata, unsigned int pktlen,
                    char **hostnameaddr, unsigned int *hostnamelen) {
    unsigned int ptr = 0;
    const unsigned char *d = (const unsigned char *)pktdata;
    const unsigned char *hnaddr = 0;
    int hnlen = 0;

    while (ptr + 8 < pktlen) {
        if (d[ptr] == 0 && d[ptr+1] == 0 && d[ptr+2] == 0 &&
            d[ptr+4] == 0 && d[ptr+6] == 0 && d[ptr+7] == 0 &&
            d[ptr+3] - d[ptr+5] == 2 && d[ptr+5] - d[ptr+8] == 3)
        {
            if (ptr + 8 + d[ptr+8] > pktlen) {
                return FALSE;
            }
            hnaddr = &d[ptr+9];
            hnlen = d[ptr+8];
            if (hnlen < 3 || hnlen > HOST_MAXLEN) {
                return FALSE;
            }
            for (int i = 0; i < hnlen; i++) {
                if (!((hnaddr[i] >= '0' && hnaddr[i] <= '9') ||
                     (hnaddr[i] >= 'a' && hnaddr[i] <= 'z') ||
                     hnaddr[i] == '.' || hnaddr[i] == '-'))
                {
                    return FALSE;
                }
            }
            *hostnameaddr = (char*)hnaddr;
            *hostnamelen = (unsigned int)hnlen;
            return TRUE;
        }
        ptr++;
    }
    return FALSE;
}

static inline void change_window_size(const PWINDIVERT_TCPHDR ppTcpHdr, unsigned int size) {
    if (size >= 1 && size <= 0xFFFFu) {
        ppTcpHdr->Window = htons((u_short)size);
    }
}

static PVOID find_http_method_end(const char *pkt, unsigned 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;
        }
        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;
}

static void send_native_fragment(HANDLE w_filter, WINDIVERT_ADDRESS addr,
                        char *packet, UINT packetLen, PVOID packet_data,
                        UINT packet_dataLen, int packet_v4, int packet_v6,
                        PWINDIVERT_IPHDR ppIpHdr, PWINDIVERT_IPV6HDR ppIpV6Hdr,
                        PWINDIVERT_TCPHDR ppTcpHdr,
                        unsigned int fragment_size, int step) {
    char packet_bak[MAX_PACKET_SIZE];
    memcpy(packet_bak, packet, packetLen);
    UINT orig_packetLen = packetLen;

    if (fragment_size >= packet_dataLen) {
        if (step == 1)
            fragment_size = 0;
        else
            return;
    }

    if (step == 0) {
        if (packet_v4)
            ppIpHdr->Length = htons(
                ntohs(ppIpHdr->Length) -
                packet_dataLen + fragment_size
            );
        else if (packet_v6)
            ppIpV6Hdr->Length = htons(
                ntohs(ppIpV6Hdr->Length) -
                packet_dataLen + fragment_size
            );
        packetLen = packetLen - packet_dataLen + fragment_size;
    }

    else if (step == 1) {
        if (packet_v4)
            ppIpHdr->Length = htons(
                ntohs(ppIpHdr->Length) - fragment_size
            );
        else if (packet_v6)
            ppIpV6Hdr->Length = htons(
                ntohs(ppIpV6Hdr->Length) - fragment_size
            );
        memmove(packet_data,
                (char*)packet_data + fragment_size,
                packet_dataLen - fragment_size);
        packetLen -= fragment_size;

        ppTcpHdr->SeqNum = htonl(ntohl(ppTcpHdr->SeqNum) + fragment_size);
    }

    addr.IPChecksum = 0;
    addr.TCPChecksum = 0;

    WinDivertHelperCalcChecksums(
        packet, packetLen, &addr, 0
    );
    WinDivertSend(
        w_filter, packet,
        packetLen,
        NULL, &addr
    );
    memcpy(packet, packet_bak, orig_packetLen);
}

int main(int argc, char *argv[]) {
    static enum packet_type_e {
        unknown,
        ipv4_tcp, ipv4_tcp_data, ipv4_udp_data,
        ipv6_tcp, ipv6_tcp_data, ipv6_udp_data
    } packet_type;
    bool debug_exit = false;
    int i, should_reinject, should_recalc_checksum = 0;
    int sni_ok = 0;
    int opt;
    int packet_v4, packet_v6;
    HANDLE w_filter = NULL;
    WINDIVERT_ADDRESS addr;
    char packet[MAX_PACKET_SIZE];
    PVOID packet_data;
    UINT packetLen;
    UINT packet_dataLen;
    PWINDIVERT_IPHDR ppIpHdr;
    PWINDIVERT_IPV6HDR ppIpV6Hdr;
    PWINDIVERT_TCPHDR ppTcpHdr;
    PWINDIVERT_UDPHDR ppUdpHdr;
    conntrack_info_t dns_conn_info;
    tcp_conntrack_info_t tcp_conn_info;

    int do_passivedpi = 0, do_block_quic = 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_additional_space = 0,
        do_http_allports = 0,
        do_host_mixedcase = 0,
        do_dnsv4_redirect = 0, do_dnsv6_redirect = 0,
        do_dns_verb = 0, do_tcp_verb = 0, do_blacklist = 0,
        do_allow_no_sni = 0,
        do_fragment_by_sni = 0,
        do_fake_packet = 0,
        do_auto_ttl = 0,
        do_wrong_chksum = 0,
        do_wrong_seq = 0,
        do_native_frag = 0, do_reverse_frag = 0;
    unsigned int http_fragment_size = 0;
    unsigned int https_fragment_size = 0;
    unsigned int current_fragment_size = 0;
    unsigned short max_payload_size = 0;
    BYTE should_send_fake = 0;
    BYTE ttl_of_fake_packet = 0;
    BYTE ttl_min_nhops = 0;
    BYTE auto_ttl_1 = 0;
    BYTE auto_ttl_2 = 0;
    BYTE auto_ttl_max = 0;
    uint32_t dnsv4_addr = 0;
    struct in6_addr dnsv6_addr = {0};
    struct in6_addr dns_temp_addr = {0};
    uint16_t dnsv4_port = htons(53);
    uint16_t dnsv6_port = htons(53);
    char *host_addr, *useragent_addr, *method_addr;
    unsigned int host_len, useragent_len;
    int http_req_fragmented;

    char *hdr_name_addr = NULL, *hdr_value_addr = NULL;
    unsigned int hdr_value_len;

    // Make sure to search DLLs only in safe path, not in current working dir.
    SetDllDirectory("");
    SetSearchPathMode(BASE_SEARCH_PATH_ENABLE_SAFE_SEARCHMODE | BASE_SEARCH_PATH_PERMANENT);

    if (!running_from_service) {
        running_from_service = 1;
        if (service_register(argc, argv)) {
            /* We've been called as a service. Register service
             * and exit this thread. main() would be called from
             * service.c next time.
             *
             * Note that if service_register() succeedes it does
             * not return until the service is stopped.
             * That is why we should set running_from_service
             * before calling service_register and unset it
             * afterwards.
             */
            return 0;
        }
        running_from_service = 0;
    }

    if (filter_string == NULL)
        filter_string = strdup(FILTER_STRING_TEMPLATE);
    if (filter_passive_string == NULL)
        filter_passive_string = strdup(FILTER_PASSIVE_STRING_TEMPLATE);

    printf(
        "GoodbyeDPI " GOODBYEDPI_VERSION
        ": Passive DPI blocker and Active DPI circumvention utility\n"
        "https://github.com/ValdikSS/GoodbyeDPI\n\n"
    );

    if (argc == 1) {
        /* enable mode -9 by default */
        do_fragment_http = do_fragment_https = 1;
        do_reverse_frag = do_native_frag = 1;
        http_fragment_size = https_fragment_size = 2;
        do_fragment_http_persistent = do_fragment_http_persistent_nowait = 1;
        do_fake_packet = 1;
        do_wrong_chksum = 1;
        do_wrong_seq = 1;
        do_block_quic = 1;
        max_payload_size = 1200;
    }

    while ((opt = getopt_long(argc, argv, "123456789pqrsaf:e:mwk:n", long_options, NULL)) != -1) {
        switch (opt) {
            case '1':
                do_passivedpi = do_host = do_host_removespace \
                = 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 \
                = do_fragment_http_persistent \
                = do_fragment_http_persistent_nowait = 1;
                https_fragment_size = 40u;
                break;
            case '3':
                do_passivedpi = do_host = do_host_removespace \
                = do_fragment_https = 1;
                https_fragment_size = 40u;
                break;
            case '4':
                do_passivedpi = do_host = do_host_removespace = 1;
                break;
            case '5':
                do_fragment_http = do_fragment_https = 1;
                do_reverse_frag = do_native_frag = 1;
                http_fragment_size = https_fragment_size = 2;
                do_fragment_http_persistent = do_fragment_http_persistent_nowait = 1;
                do_fake_packet = 1;
                do_auto_ttl = 1;
                max_payload_size = 1200;
                break;
            case '6':
                do_fragment_http = do_fragment_https = 1;
                do_reverse_frag = do_native_frag = 1;
                http_fragment_size = https_fragment_size = 2;
                do_fragment_http_persistent = do_fragment_http_persistent_nowait = 1;
                do_fake_packet = 1;
                do_wrong_seq = 1;
                max_payload_size = 1200;
                break;
            case '9': // +7+8
                do_block_quic = 1;
                // fall through
            case '8': // +7
                do_wrong_seq = 1;
                // fall through
            case '7':
                do_fragment_http = do_fragment_https = 1;
                do_reverse_frag = do_native_frag = 1;
                http_fragment_size = https_fragment_size = 2;
                do_fragment_http_persistent = do_fragment_http_persistent_nowait = 1;
                do_fake_packet = 1;
                do_wrong_chksum = 1;
                max_payload_size = 1200;
                break;
            case 'p':
                do_passivedpi = 1;
                break;
            case 'q':
                do_block_quic = 1;
                break;
            case 'r':
                do_host = 1;
                break;
            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;
                SET_HTTP_FRAGMENT_SIZE_OPTION(atousi(optarg, "Fragment size should be in range [0 - 0xFFFF]\n"));
                break;
            case 'k':
                do_fragment_http_persistent = 1;
                do_native_frag = 1;
                SET_HTTP_FRAGMENT_SIZE_OPTION(atousi(optarg, "Fragment size should be in range [0 - 0xFFFF]\n"));
                break;
            case 'n':
                do_fragment_http_persistent = 1;
                do_fragment_http_persistent_nowait = 1;
                do_native_frag = 1;
                break;
            case 'e':
                do_fragment_https = 1;
                https_fragment_size = atousi(optarg, "Fragment size should be in range [0 - 65535]\n");
                break;
            case 'w':
                do_http_allports = 1;
                break;
            case 'z': // --port
                /* i is used as a temporary variable here */
                i = atoi(optarg);
                if (i <= 0 || i > 65535) {
                    printf("Port parameter error!\n");
                    exit(ERROR_PORT_BOUNDS);
                }
                if (i != 80 && i != 443)
                    add_filter_str(IPPROTO_TCP, i);
                i = 0;
                break;
            case 'i': // --ip-id
                /* i is used as a temporary variable here */
                i = atousi(optarg, "IP ID parameter error!\n");
                add_ip_id_str(i);
                i = 0;
                break;
            case 'd': // --dns-addr
                if ((inet_pton(AF_INET, optarg, dns_temp_addr.s6_addr) == 1) &&
                    !do_dnsv4_redirect)
                {
                    do_dnsv4_redirect = 1;
                    if (inet_pton(AF_INET, optarg, &dnsv4_addr) != 1) {
                        puts("DNS address parameter error!");
                        exit(ERROR_DNS_V4_ADDR);
                    }
                    add_filter_str(IPPROTO_UDP, 53);
                    flush_dns_cache();
                    break;
                }
                puts("DNS address parameter error!");
                exit(ERROR_DNS_V4_ADDR);
                break;
            case '!': // --dnsv6-addr
                if ((inet_pton(AF_INET6, optarg, dns_temp_addr.s6_addr) == 1) &&
                    !do_dnsv6_redirect)
                {
                    do_dnsv6_redirect = 1;
                    if (inet_pton(AF_INET6, optarg, dnsv6_addr.s6_addr) != 1) {
                        puts("DNS address parameter error!");
                        exit(ERROR_DNS_V6_ADDR);
                    }
                    add_filter_str(IPPROTO_UDP, 53);
                    flush_dns_cache();
                    break;
                }
                puts("DNS address parameter error!");
                exit(ERROR_DNS_V6_ADDR);
                break;
            case 'g': // --dns-port
                if (!do_dnsv4_redirect) {
                    puts("--dns-port should be used with --dns-addr!\n"
                        "Make sure you use --dns-addr and pass it before "
                        "--dns-port");
                    exit(ERROR_DNS_V4_PORT);
                }
                dnsv4_port = atousi(optarg, "DNS port parameter error!");
                if (dnsv4_port != 53) {
                    add_filter_str(IPPROTO_UDP, dnsv4_port);
                }
                dnsv4_port = htons(dnsv4_port);
                break;
            case '@': // --dnsv6-port
                if (!do_dnsv6_redirect) {
                    puts("--dnsv6-port should be used with --dnsv6-addr!\n"
                        "Make sure you use --dnsv6-addr and pass it before "
                        "--dnsv6-port");
                    exit(ERROR_DNS_V6_PORT);
                }
                dnsv6_port = atousi(optarg, "DNS port parameter error!");
                if (dnsv6_port != 53) {
                    add_filter_str(IPPROTO_UDP, dnsv6_port);
                }
                dnsv6_port = htons(dnsv6_port);
                break;
            case 'v':
                do_dns_verb = 1;
                do_tcp_verb = 1;
                break;
            case 'b': // --blacklist
                do_blacklist = 1;
                if (!blackwhitelist_load_list(optarg)) {
                    printf("Can't load blacklist from file!\n");
                    exit(ERROR_BLACKLIST_LOAD);
                }
                break;
            case ']': // --allow-no-sni
                do_allow_no_sni = 1;
                break;
            case '>': // --frag-by-sni
                do_fragment_by_sni = 1;
                break;
            case '$': // --set-ttl
                do_auto_ttl = auto_ttl_1 = auto_ttl_2 = auto_ttl_max = 0;
                do_fake_packet = 1;
                ttl_of_fake_packet = atoub(optarg, "Set TTL parameter error!");
                break;
            case '[': // --min-ttl
                do_fake_packet = 1;
                ttl_min_nhops = atoub(optarg, "Set Minimum TTL number of hops parameter error!");
                break;
            case '+': // --auto-ttl
                do_fake_packet = 1;
                do_auto_ttl = 1;

                if (!optarg && argv[optind] && argv[optind][0] != '-')
                    optarg = argv[optind];

                if (optarg) {
                    char *autottl_copy = strdup(optarg);
                    char *autottl_save;
                    if (strchr(autottl_copy, '-')) {
                        // token "-" found, start X-Y parser
                        char *autottl_current = strtok_r(autottl_copy, "-", &autottl_save);
                        auto_ttl_1 = atoub(autottl_current, "Set Auto TTL parameter error!");
                        autottl_current = strtok_r(NULL, "-", &autottl_save);
                        if (!autottl_current) {
                            puts("Set Auto TTL parameter error!");
                            exit(ERROR_AUTOTTL);
                        }
                        auto_ttl_2 = atoub(autottl_current, "Set Auto TTL parameter error!");
                        autottl_current = strtok_r(NULL, "-", &autottl_save);
                        if (!autottl_current) {
                            puts("Set Auto TTL parameter error!");
                            exit(ERROR_AUTOTTL);
                        }
                        auto_ttl_max = atoub(autottl_current, "Set Auto TTL parameter error!");
                    }
                    else {
                        // single digit parser
                        auto_ttl_2 = atoub(optarg, "Set Auto TTL parameter error!");
                        auto_ttl_1 = auto_ttl_2;
                    }
                    free(autottl_copy);
                }
                break;
            case '%': // --wrong-chksum
                do_fake_packet = 1;
                do_wrong_chksum = 1;
                break;
            case ')': // --wrong-seq
                do_fake_packet = 1;
                do_wrong_seq = 1;
                break;
            case '*': // --native-frag
                do_native_frag = 1;
                do_fragment_http_persistent = 1;
                do_fragment_http_persistent_nowait = 1;
                break;
            case '(': // --reverse-frag
                do_reverse_frag = 1;
                do_native_frag = 1;
                do_fragment_http_persistent = 1;
                do_fragment_http_persistent_nowait = 1;
                break;
            case '|': // --max-payload
                if (!optarg && argv[optind] && argv[optind][0] != '-')
                    optarg = argv[optind];
                if (optarg)
                    max_payload_size = atousi(optarg, "Max payload size parameter error!");
                else
                    max_payload_size = 1200;
                break;
            case 'u': // --fake-from-hex
                if (fake_load_from_hex(optarg)) {
                    printf("WARNING: bad fake HEX value %s\n", optarg);
                }
                break;
            case 'j': // --fake-gen
                if (fake_load_random(atoub(optarg, "Fake generator parameter error!"), 200)) {
                    puts("WARNING: fake generator has failed!");
                }
                break;
            case 't': // --fake-resend
                fakes_resend = atoub(optarg, "Fake resend parameter error!");
                if (fakes_resend == 1)
                    puts("WARNING: fake-resend is 1, no resending is in place!");
                else if (!fakes_resend)
                    puts("WARNING: fake-resend is 0, fake packet mode is disabled!");
                else if (fakes_resend > 100)
                    puts("WARNING: fake-resend value is a little too high, don't you think?");
                break;
            case 'x': // --debug-exit
                debug_exit = true;
                break;
            default:
                puts("Usage: goodbyedpi.exe [OPTION...]\n"
                " -p          block passive DPI\n"
                " -q          block QUIC/HTTP3\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"
                " --ip-id       <value>    handle additional IP ID (decimal, drop redirects and TCP RSTs with this ID).\n"
                " --dns-addr    <value>    redirect UDPv4 DNS requests to the supplied IPv4 address (experimental)\n"
                " --dns-port    <value>    redirect UDPv4 DNS requests to the supplied port (53 by default)\n"
                " --dnsv6-addr  <value>    redirect UDPv6 DNS requests to the supplied IPv6 address (experimental)\n"
                " --dnsv6-port  <value>    redirect UDPv6 DNS requests to the supplied port (53 by default)\n"
                " --dns-verb               print verbose DNS redirection messages\n"
                " --blacklist   <txtfile>  perform circumvention tricks only to host names and subdomains from\n"
                "                          supplied text file (HTTP Host/TLS SNI).\n"
                "                          This option can be supplied multiple times.\n"
                " --allow-no-sni           perform circumvention if TLS SNI can't be detected with --blacklist enabled.\n"
                " --frag-by-sni            if SNI is detected in TLS packet, fragment the packet right before SNI value.\n"
                " --set-ttl     <value>    activate Fake Request Mode and send it with supplied TTL value.\n"
                "                          DANGEROUS! May break websites in unexpected ways. Use with care (or --blacklist).\n"
                " --auto-ttl    [a1-a2-m]  activate Fake Request Mode, automatically detect TTL and decrease\n"
                "                          it based on a distance. If the distance is shorter than a2, TTL is decreased\n"
                "                          by a2. If it's longer, (a1; a2) scale is used with the distance as a weight.\n"
                "                          If the resulting TTL is more than m(ax), set it to m.\n"
                "                          Default (if set): --auto-ttl 1-4-10. Also sets --min-ttl 3.\n"
                "                          DANGEROUS! May break websites in unexpected ways. Use with care (or --blacklist).\n"
                " --min-ttl     <value>    minimum TTL distance (128/64 - TTL) for which to send Fake Request\n"
                "                          in --set-ttl and --auto-ttl modes.\n"
                " --wrong-chksum           activate Fake Request Mode and send it with incorrect TCP checksum.\n"
                "                          May not work in a VM or with some routers, but is safer than set-ttl.\n"
                "                          Could be combined with --set-ttl\n"
                " --wrong-seq              activate Fake Request Mode and send it with TCP SEQ/ACK in the past.\n"
                " --native-frag            fragment (split) the packets by sending them in smaller packets, without\n"
                "                          shrinking the Window Size. Works faster (does not slow down the connection)\n"
                "                          and better.\n"
                " --reverse-frag           fragment (split) the packets just as --native-frag, but send them in the\n"
                "                          reversed order. Works with the websites which could not handle segmented\n"
                "                          HTTPS TLS ClientHello (because they receive the TCP flow \"combined\").\n"
                " --fake-from-hex <value>  Load fake packets for Fake Request Mode from HEX values (like 1234abcDEF).\n"
                "                          This option can be supplied multiple times, in this case each fake packet\n"
                "                          would be sent on every request in the command line argument order.\n"
                " --fake-gen <value>       Generate random-filled fake packets for Fake Request Mode, value of them\n"
                "                          (up to 30).\n"
                " --fake-resend <value>    Send each fake packet value number of times.\n"
                "                          Default: 1 (send each packet once).\n"
                " --max-payload [value]    packets with TCP payload data more than [value] won't be processed.\n"
                "                          Use this option to reduce CPU usage by skipping huge amount of data\n"
                "                          (like file transfers) in already established sessions.\n"
                "                          May skip some huge HTTP requests from being processed.\n"
                "                          Default (if set): --max-payload 1200.\n"
                "\n");
                puts("LEGACY modesets:\n"
                " -1          -p -r -s -f 2 -k 2 -n -e 2 (most compatible mode)\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"
                "Modern modesets (more stable, more compatible, faster):\n"
                " -5          -f 2 -e 2 --auto-ttl --reverse-frag --max-payload\n"
                " -6          -f 2 -e 2 --wrong-seq --reverse-frag --max-payload\n"
                " -7          -f 2 -e 2 --wrong-chksum --reverse-frag --max-payload\n"
                " -8          -f 2 -e 2 --wrong-seq --wrong-chksum --reverse-frag --max-payload\n"
                " -9          -f 2 -e 2 --wrong-seq --wrong-chksum --reverse-frag --max-payload -q (this is the default)\n\n"
                "Note: combination of --wrong-seq and --wrong-chksum generates two different fake packets.\n"
                );
                exit(ERROR_DEFAULT);
        }
    }

    if (!http_fragment_size)
        http_fragment_size = 2;
    if (!https_fragment_size)
        https_fragment_size = 2;
    if (!auto_ttl_1)
        auto_ttl_1 = 1;
    if (!auto_ttl_2)
        auto_ttl_2 = 4;
    if (do_auto_ttl) {
        if (!ttl_min_nhops)
            ttl_min_nhops = 3;
        if (!auto_ttl_max)
            auto_ttl_max = 10;
    }

    printf("Block passive: %d\n"                    /* 1 */
           "Block QUIC/HTTP3: %d\n"                 /* 1 */
           "Fragment HTTP: %u\n"                    /* 2 */
           "Fragment persistent HTTP: %u\n"         /* 3 */
           "Fragment HTTPS: %u\n"                   /* 4 */
           "Fragment by SNI: %u\n"                  /* 5 */
           "Native fragmentation (splitting): %d\n" /* 6 */
           "Fragments sending in reverse: %d\n"     /* 7 */
           "hoSt: %d\n"                             /* 8 */
           "Host no space: %d\n"                    /* 9 */
           "Additional space: %d\n"                 /* 10 */
           "Mix Host: %d\n"                         /* 11 */
           "HTTP AllPorts: %d\n"                    /* 12 */
           "HTTP Persistent Nowait: %d\n"           /* 13 */
           "DNS redirect: %d\n"                     /* 14 */
           "DNSv6 redirect: %d\n"                   /* 15 */
           "Allow missing SNI: %d\n"                /* 16 */
           "Fake requests, TTL: %s (fixed: %hu, auto: %hu-%hu-%hu, min distance: %hu)\n"  /* 17 */
           "Fake requests, wrong checksum: %d\n"    /* 18 */
           "Fake requests, wrong SEQ/ACK: %d\n"     /* 19 */
           "Fake requests, custom payloads: %d\n"   /* 20 */
           "Fake requests, resend: %d\n"            /* 21 */
           "Max payload size: %hu\n",               /* 22 */
           do_passivedpi, do_block_quic,                          /* 1 */
           (do_fragment_http ? http_fragment_size : 0),           /* 2 */
           (do_fragment_http_persistent ? http_fragment_size : 0),/* 3 */
           (do_fragment_https ? https_fragment_size : 0),         /* 4 */
           do_fragment_by_sni,    /* 5 */
           do_native_frag,        /* 6 */
           do_reverse_frag,       /* 7 */
           do_host,               /* 8 */
           do_host_removespace,   /* 9 */
           do_additional_space,   /* 10 */
           do_host_mixedcase,     /* 11 */
           do_http_allports,      /* 12 */
           do_fragment_http_persistent_nowait, /* 13 */
           do_dnsv4_redirect,                  /* 14 */
           do_dnsv6_redirect,                  /* 15 */
           do_allow_no_sni,                    /* 16 */
           do_auto_ttl ? "auto" : (do_fake_packet ? "fixed" : "disabled"),  /* 17 */
               ttl_of_fake_packet, do_auto_ttl ? auto_ttl_1 : 0, do_auto_ttl ? auto_ttl_2 : 0,
               do_auto_ttl ? auto_ttl_max : 0, ttl_min_nhops,
           do_wrong_chksum, /* 18 */
           do_wrong_seq,    /* 19 */
           fakes_count,     /* 20 */
           fakes_resend,    /* 21 */
           max_payload_size /* 22 */
          );

    if (do_fragment_http && http_fragment_size > 2 && !do_native_frag) {
        puts("\nWARNING: HTTP fragmentation values > 2 are not fully compatible "
             "with other options. Please use values <= 2 or disable HTTP fragmentation "
             "completely.");
    }

    if (do_native_frag && !(do_fragment_http || do_fragment_https)) {
        puts("\nERROR: Native fragmentation is enabled but fragment sizes are not set.\n"
             "Fragmentation has no effect.");
        die();
    }

    if (max_payload_size)
        add_maxpayloadsize_str(max_payload_size);
    finalize_filter_strings();
    puts("\nOpening filter");
    filter_num = 0;

    if (do_passivedpi) {
        /* IPv4 only filter for inbound RST packets with ID [0x0; 0xF] */
        filters[filter_num] = init(
            filter_passive_string,
            WINDIVERT_FLAG_DROP);
        if (filters[filter_num] == NULL)
            die();
        filter_num++;
    }

    if (do_block_quic) {
        filters[filter_num] = init(
            FILTER_PASSIVE_BLOCK_QUIC,
            WINDIVERT_FLAG_DROP);
        if (filters[filter_num] == NULL)
            die();
        filter_num++;
    }

    /* 
     * IPv4 & IPv6 filter for inbound HTTP redirection packets and
     * active DPI circumvention
     */
    filters[filter_num] = init(filter_string, 0);

    w_filter = filters[filter_num];
    filter_num++;

    for (i = 0; i < filter_num; i++) {
        if (filters[i] == NULL)
            die();
    }
    if (debug_exit) {
        printf("Debug Exit\n");
        exit(EXIT_SUCCESS);
    }
    printf("Filter activated, GoodbyeDPI is now running!\n");
    signal(SIGINT, sigint_handler);

    while (1) {
        if (WinDivertRecv(w_filter, packet, sizeof(packet), &packetLen, &addr)) {
            debug("Got %s packet, len=%d!\n", addr.Outbound ? "outbound" : "inbound",
                   packetLen);
            should_reinject = 1;
            should_recalc_checksum = 0;
            sni_ok = 0;

            ppIpHdr = (PWINDIVERT_IPHDR)NULL;
            ppIpV6Hdr = (PWINDIVERT_IPV6HDR)NULL;
            ppTcpHdr = (PWINDIVERT_TCPHDR)NULL;
            ppUdpHdr = (PWINDIVERT_UDPHDR)NULL;
            packet_v4 = packet_v6 = 0;
            packet_type = unknown;

            // Parse network packet and set it's type
            if (WinDivertHelperParsePacket(packet, packetLen, &ppIpHdr,
                &ppIpV6Hdr, NULL, NULL, NULL, &ppTcpHdr, &ppUdpHdr, &packet_data, &packet_dataLen,
                NULL, NULL))
            {
                if (ppIpHdr) {
                    packet_v4 = 1;
                    if (ppTcpHdr) {
                        packet_type = ipv4_tcp;
                        if (packet_data) {
                            packet_type = ipv4_tcp_data;
                        }
                    }
                    else if (ppUdpHdr && packet_data) {
                        packet_type = ipv4_udp_data;
                    }
                }

                else if (ppIpV6Hdr) {
                    packet_v6 = 1;
                    if (ppTcpHdr) {
                        packet_type = ipv6_tcp;
                        if (packet_data) {
                            packet_type = ipv6_tcp_data;
                        }
                    }
                    else if (ppUdpHdr && packet_data) {
                        packet_type = ipv6_udp_data;
                    }
                }
            }

            debug("packet_type: %d, packet_v4: %d, packet_v6: %d\n", packet_type, packet_v4, packet_v6);

            if (packet_type == ipv4_tcp_data || packet_type == ipv6_tcp_data) {
                //printf("Got parsed packet, len=%d!\n", packet_dataLen);
                /* Got a TCP packet WITH DATA */

                /* Handle INBOUND packet with data and find HTTP REDIRECT in there */
                if (!addr.Outbound && packet_dataLen > 16) {
                    /* If INBOUND packet with DATA (tcp.Ack) */

                    /* Drop packets from filter with HTTP 30x Redirect */
                    if (do_passivedpi && is_passivedpi_redirect(packet_data, packet_dataLen)) {
                        if (packet_v4) {
                            //printf("Dropping HTTP Redirect packet!\n");
                            should_reinject = 0;
                        }
                        else if (packet_v6 && WINDIVERT_IPV6HDR_GET_FLOWLABEL(ppIpV6Hdr) == 0x0) {
                                /* Contrary to IPv4 where we get only packets with IP ID 0x0-0xF,
                                 * for IPv6 we got all the incoming data packets since we can't
                                 * filter them in a driver.
                                 *
                                 * Handle only IPv6 Flow Label == 0x0 for now
                                 */
                                //printf("Dropping HTTP Redirect packet!\n");
                                should_reinject = 0;
                        }
                    }
                }
                /* Handle OUTBOUND packet on port 443, search for something that resembles
                 * TLS handshake, send fake request.
                 */
                else if (addr.Outbound &&
                        ((do_fragment_https ? packet_dataLen == https_fragment_size : 0) ||
                         packet_dataLen > 16) &&
                         ppTcpHdr->DstPort != htons(80) &&
                         (do_fake_packet || do_native_frag)
                        )
                {
                    /**
                     * In case of Window Size fragmentation=2, we'll receive only 2 byte packet.
                     * But if the packet is more than 2 bytes, check ClientHello byte.
                    */
                    if ((packet_dataLen == 2 && memcmp(packet_data, "\x16\x03", 2) == 0) ||
                        (packet_dataLen >= 3 && ( memcmp(packet_data, "\x16\x03\x01", 3) == 0 || memcmp(packet_data, "\x16\x03\x03", 3) == 0 )))
                    {
                        if (do_blacklist || do_fragment_by_sni) {
                            sni_ok = extract_sni(packet_data, packet_dataLen,
                                        &host_addr, &host_len);
                        }
                        if (
                             (do_blacklist && sni_ok &&
                              blackwhitelist_check_hostname(host_addr, host_len)
                             ) ||
                             (do_blacklist && !sni_ok && do_allow_no_sni) ||
                             (!do_blacklist)
                           )
                        {
#ifdef DEBUG
                            char lsni[HOST_MAXLEN + 1] = {0};
                            extract_sni(packet_data, packet_dataLen,
                                        &host_addr, &host_len);
                            memcpy(lsni, host_addr, host_len);
                            printf("Blocked HTTPS website SNI: %s\n", lsni);
#endif
                            if (do_fake_packet) {
                                TCP_HANDLE_OUTGOING_FAKE_PACKET(send_fake_https_request);
                            }
                            if (do_native_frag) {
                                // Signal for native fragmentation code handler
                                should_recalc_checksum = 1;
                            }
                        }
                    }
                }
                /* Handle OUTBOUND packet on port 80, search for Host header */
                else if (addr.Outbound && 
                        packet_dataLen > 16 &&
                        (do_http_allports ? 1 : (ppTcpHdr->DstPort == htons(80))) &&
                        find_http_method_end(packet_data,
                                             (do_fragment_http ? http_fragment_size : 0u),
                                             &http_req_fragmented) &&
                        (do_host || do_host_removespace ||
                        do_host_mixedcase || do_fragment_http_persistent ||
                        do_fake_packet))
                {

                    /* 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;
#ifdef DEBUG
                        char lhost[HOST_MAXLEN + 1] = {0};
                        memcpy(lhost, host_addr, host_len);
                        printf("Blocked HTTP website Host: %s\n", lhost);
#endif

                        if (do_native_frag) {
                            // Signal for native fragmentation code handler
                            should_recalc_checksum = 1;
                        }

                        if (do_fake_packet) {
                            TCP_HANDLE_OUTGOING_FAKE_PACKET(send_fake_http_request);
                        }

                        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,
                                        (size_t)(host_addr - 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,
                                                (size_t)(useragent_addr + useragent_len - host_addr));
                                        host_addr -= 1;
                                        /* Put space in the end of User-Agent header */
                                        *(char*)((unsigned char*)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(useragent_addr + useragent_len + 1,
                                                useragent_addr + useragent_len,
                                                (size_t)(host_addr - 1 - (useragent_addr + useragent_len)));
                                        /* Put space in the end of User-Agent header */
                                        *(char*)((unsigned char*)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 */

                /*
                * should_recalc_checksum mean we have detected a packet to handle and
                * modified it in some way.
                * Handle native fragmentation here, incl. sending the packet.
                */
                if (should_reinject && should_recalc_checksum && do_native_frag)
                {
                    current_fragment_size = 0;
                    if (do_fragment_http && ppTcpHdr->DstPort == htons(80)) {
                        current_fragment_size = http_fragment_size;
                    }
                    else if (do_fragment_https && ppTcpHdr->DstPort != htons(80)) {
                        if (do_fragment_by_sni && sni_ok) {
                            current_fragment_size = (void*)host_addr - packet_data;
                        } else {
                            current_fragment_size = https_fragment_size;
                        }
                    }

                    if (current_fragment_size) {
                        send_native_fragment(w_filter, addr, packet, packetLen, packet_data,
                                            packet_dataLen,packet_v4, packet_v6,
                                            ppIpHdr, ppIpV6Hdr, ppTcpHdr,
                                            current_fragment_size, do_reverse_frag);

                        send_native_fragment(w_filter, addr, packet, packetLen, packet_data,
                                            packet_dataLen,packet_v4, packet_v6,
                                            ppIpHdr, ppIpV6Hdr, ppTcpHdr,
                                            current_fragment_size, !do_reverse_frag);
                        continue;
                    }
                }
            } /* Handle TCP packet with data */

            /* Else if we got TCP packet without data */
            else if (packet_type == ipv4_tcp || packet_type == ipv6_tcp) {
                /* If we got INBOUND SYN+ACK packet */
                if (!addr.Outbound &&
                    ppTcpHdr->Syn == 1 && ppTcpHdr->Ack == 1) {
                    //printf("Changing Window Size!\n");
                    /*
                     * Window Size is changed even if do_fragment_http_persistent
                     * is enabled as there could be non-HTTP data on port 80
                     */

                    if (do_fake_packet && (do_auto_ttl || ttl_min_nhops)) {
                        if (!((packet_v4 && tcp_handle_incoming(&ppIpHdr->SrcAddr, &ppIpHdr->DstAddr,
                                        ppTcpHdr->SrcPort, ppTcpHdr->DstPort,
                                        0, ppIpHdr->TTL))
                            ||
                            (packet_v6 && tcp_handle_incoming((uint32_t*)&ppIpV6Hdr->SrcAddr,
                                        (uint32_t*)&ppIpV6Hdr->DstAddr,
                                        ppTcpHdr->SrcPort, ppTcpHdr->DstPort,
                                        1, ppIpV6Hdr->HopLimit))))
                        {
                            if (do_tcp_verb)
                                puts("[TCP WARN] Can't add TCP connection record.");
                        }
                    }

                    if (!do_native_frag) {
                        if (do_fragment_http && ppTcpHdr->SrcPort == htons(80)) {
                            change_window_size(ppTcpHdr, http_fragment_size);
                            should_recalc_checksum = 1;
                        }
                        else if (do_fragment_https && ppTcpHdr->SrcPort != htons(80)) {
                            change_window_size(ppTcpHdr, https_fragment_size);
                            should_recalc_checksum = 1;
                        }
                    }
                }
            }

            /* Else if we got UDP packet with data */
            else if ((do_dnsv4_redirect && (packet_type == ipv4_udp_data)) ||
                     (do_dnsv6_redirect && (packet_type == ipv6_udp_data)))
            {
                if (!addr.Outbound) {
                    if ((packet_v4 && dns_handle_incoming(&ppIpHdr->DstAddr, ppUdpHdr->DstPort,
                                        packet_data, packet_dataLen,
                                        &dns_conn_info, 0))
                        ||
                        (packet_v6 && dns_handle_incoming(ppIpV6Hdr->DstAddr, ppUdpHdr->DstPort,
                                        packet_data, packet_dataLen,
                                        &dns_conn_info, 1)))
                    {
                        /* Changing source IP and port to the values
                         * from DNS conntrack */
                        if (packet_v4)
                            ppIpHdr->SrcAddr = dns_conn_info.dstip[0];
                        else if (packet_v6)
                            ipv6_copy_addr(ppIpV6Hdr->SrcAddr, dns_conn_info.dstip);
                        ppUdpHdr->DstPort = dns_conn_info.srcport;
                        ppUdpHdr->SrcPort = dns_conn_info.dstport;
                        should_recalc_checksum = 1;
                    }
                    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.Outbound) {
                    if ((packet_v4 && dns_handle_outgoing(&ppIpHdr->SrcAddr, ppUdpHdr->SrcPort,
                                        &ppIpHdr->DstAddr, ppUdpHdr->DstPort,
                                        packet_data, packet_dataLen, 0))
                        ||
                        (packet_v6 && dns_handle_outgoing(ppIpV6Hdr->SrcAddr, ppUdpHdr->SrcPort,
                                        ppIpV6Hdr->DstAddr, ppUdpHdr->DstPort,
                                        packet_data, packet_dataLen, 1)))
                    {
                        /* Changing destination IP and port to the values
                         * from configuration */
                        if (packet_v4) {
                            ppIpHdr->DstAddr = dnsv4_addr;
                            ppUdpHdr->DstPort = dnsv4_port;
                        }
                        else if (packet_v6) {
                            ipv6_copy_addr(ppIpV6Hdr->DstAddr, (uint32_t*)dnsv6_addr.s6_addr);
                            ppUdpHdr->DstPort = dnsv6_port;
                        }
                        should_recalc_checksum = 1;
                    }
                    else {
                        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, &addr, (UINT64)0LL);
                }
                WinDivertSend(w_filter, packet, packetLen, NULL, &addr);
            }
        }
        else {
            // error, ignore
            if (!exiting)
                printf("Error receiving packet!\n");
            break;
        }
    }
}

```