diff --git a/dll/windivert.c b/dll/windivert.c
index 32a4da4..eb4fd28 100644
--- a/dll/windivert.c
+++ b/dll/windivert.c
@@ -51,19 +51,6 @@
 #define WINDIVERT_DRIVER32_SYS          L"\\" WINDIVERT_DRIVER_NAME L"32.sys"
 #define WINDIVERT_DRIVER64_SYS          L"\\" WINDIVERT_DRIVER_NAME L"64.sys"
 
-/*
- * Definitions to remove (some) external dependencies:
- */
-#define BYTESWAP16(x)                   \
-    ((((x) >> 8) & 0x00FF) | (((x) << 8) & 0xFF00))
-#define BYTESWAP32(x)                   \
-    ((((x) >> 24) & 0x000000FF) | (((x) >> 8) & 0x0000FF00) | \
-     (((x) << 8) & 0x00FF0000) | (((x) << 24) & 0xFF000000))
-#define ntohs(x)                        BYTESWAP16(x)
-#define htons(x)                        BYTESWAP16(x)
-#define ntohl(x)                        BYTESWAP32(x)
-#define htonl(x)                        BYTESWAP32(x)
-
 static BOOLEAN WinDivertIsXDigit(char c);
 static BOOLEAN WinDivertIsSpace(char c);
 static BOOLEAN WinDivertIsAlNum(char c);
@@ -532,41 +519,6 @@ extern HANDLE WinDivertOpen(const char *filter, WINDIVERT_LAYER layer,
     return handle;
 }
 
-/*
- * Workaround for #134
- */
-static void WinDivertFixChecksums(PVOID pPacket, UINT packetLen,
-    PWINDIVERT_ADDRESS addr)
-{
-    UINT64 flags =
-        WINDIVERT_HELPER_NO_IP_CHECKSUM |
-        WINDIVERT_HELPER_NO_TCP_CHECKSUM |
-        WINDIVERT_HELPER_NO_UDP_CHECKSUM;
-    BOOL calc = FALSE;
-    if (addr->PseudoIPChecksum != 0)
-    {
-        addr->PseudoIPChecksum = 0;
-        flags &= ~WINDIVERT_HELPER_NO_IP_CHECKSUM;
-        calc = TRUE;
-    }
-    if (addr->PseudoTCPChecksum != 0)
-    {
-        addr->PseudoTCPChecksum = 0;
-        flags &= ~WINDIVERT_HELPER_NO_TCP_CHECKSUM;
-        calc = TRUE;
-    }
-    if (addr->PseudoUDPChecksum != 0)
-    {
-        addr->PseudoUDPChecksum = 0;
-        flags &= ~WINDIVERT_HELPER_NO_UDP_CHECKSUM;
-        calc = TRUE;
-    }
-    if (calc)
-    {
-        WinDivertHelperCalcChecksums(pPacket, packetLen, addr, flags);
-    }
-}
-
 /*
  * Receive a WinDivert packet.
  */
@@ -612,7 +564,6 @@ extern BOOL WinDivertSend(HANDLE handle, PVOID pPacket, UINT packetLen,
         SetLastError(ERROR_INVALID_PARAMETER);
         return FALSE;
     }
-    WinDivertFixChecksums(pPacket, packetLen, addr);
     return WinDivertIoControl(handle, IOCTL_WINDIVERT_SEND, 0, (UINT64)addr,
         pPacket, packetLen, writelen);
 }
@@ -629,7 +580,6 @@ extern BOOL WinDivertSendEx(HANDLE handle, PVOID pPacket, UINT packetLen,
         SetLastError(ERROR_INVALID_PARAMETER);
         return FALSE;
     }
-    WinDivertFixChecksums(pPacket, packetLen, addr);
     if (overlapped == NULL)
     {
         return WinDivertIoControl(handle, IOCTL_WINDIVERT_SEND, 0,
diff --git a/dll/windivert_helper.c b/dll/windivert_helper.c
index 06976a6..0ffc158 100644
--- a/dll/windivert_helper.c
+++ b/dll/windivert_helper.c
@@ -252,8 +252,6 @@ typedef UINT64 ERROR, *PERROR;
 #define IS_ERROR(err)                           \
     (GET_CODE(err) != WINDIVERT_ERROR_NONE)
 
-#define MAX(a, b)                               ((a) > (b)? (a): (b))
-                                
 /*
  * Prototypes.
  */
@@ -261,233 +259,11 @@ static PEXPR WinDivertParseFilter(HANDLE pool, TOKEN *toks, UINT *i,
     INT depth, BOOL and, PERROR error);
 static BOOL WinDivertCondExecFilter(PWINDIVERT_FILTER filter, UINT length,
     UINT8 field, UINT32 arg);
-static UINT16 WinDivertInitPseudoHeader(PWINDIVERT_IPHDR ip_header,
-    PWINDIVERT_IPV6HDR ipv6_header, UINT8 protocol, UINT len,
-    void *pseudo_header);
-static UINT16 WinDivertHelperCalcChecksum(PVOID pseudo_header,
-    UINT16 pseudo_header_len, PVOID data, UINT len);
 static BOOL WinDivertDeserializeFilter(PWINDIVERT_STREAM stream,
     PWINDIVERT_FILTER filter, UINT *length);
 static void WinDivertFormatExpr(PWINDIVERT_STREAM stream, PEXPR expr,
     BOOL top_level, BOOL and);
 
-/*
- * Skip well-known IPv6 extension headers.
- */
-static UINT8 WinDivertSkipExtHeaders(UINT8 proto, UINT8 **header, UINT *len)
-{
-    UINT hdrlen;
-
-    while (TRUE)
-    {
-        if (*len <= 2)
-        {
-            return IPPROTO_NONE;
-        }
-
-        hdrlen = (UINT)*(*header + 1);
-        switch (proto)
-        {
-            case IPPROTO_FRAGMENT:
-                hdrlen = 8;
-                break;
-            case IPPROTO_AH:
-                hdrlen += 2;
-                hdrlen *= 4;
-                break;
-            case IPPROTO_HOPOPTS:
-            case IPPROTO_DSTOPTS:
-            case IPPROTO_ROUTING:
-                hdrlen++;
-                hdrlen *= 8;
-                break;
-            case IPPROTO_NONE:
-                return proto;
-            default:
-                return proto;
-        }
-
-        if (hdrlen >= *len)
-        {
-            return IPPROTO_NONE;
-        }
-
-        proto = **header;
-        *header += hdrlen;
-        *len -= hdrlen;
-    }
-}
-
-/*
- * Parse IPv4/IPv6/ICMP/ICMPv6/TCP/UDP headers from a raw packet.
- */
-static BOOL WinDivertHelperParsePacket_2(PVOID pPacket, UINT packetLen,
-    PWINDIVERT_IPHDR *ppIpHdr, PWINDIVERT_IPV6HDR *ppIpv6Hdr,
-    PWINDIVERT_ICMPHDR *ppIcmpHdr, PWINDIVERT_ICMPV6HDR *ppIcmpv6Hdr,
-    PWINDIVERT_TCPHDR *ppTcpHdr, PWINDIVERT_UDPHDR *ppUdpHdr, UINT8 *pProto,
-    PVOID *ppData, UINT *pDataLen)
-{
-    PWINDIVERT_IPHDR ip_header = NULL;
-    PWINDIVERT_IPV6HDR ipv6_header = NULL;
-    PWINDIVERT_ICMPHDR icmp_header = NULL;
-    PWINDIVERT_ICMPV6HDR icmpv6_header = NULL;
-    PWINDIVERT_TCPHDR tcp_header = NULL;
-    PWINDIVERT_UDPHDR udp_header = NULL;
-    UINT16 header_len;
-    UINT8 trans_proto = 0;
-    PVOID data = NULL;
-    UINT data_len = 0;
-    BOOL success;
-
-    if (pPacket == NULL || packetLen < sizeof(UINT8))
-    {
-        goto WinDivertHelperParsePacketExit;
-    }
-    data = pPacket;
-    data_len = packetLen;
-
-    ip_header = (PWINDIVERT_IPHDR)data;
-    switch (ip_header->Version)
-    {
-        case 4:
-            if (data_len < sizeof(WINDIVERT_IPHDR) ||
-                ip_header->HdrLength < 5 ||
-                data_len < ip_header->HdrLength*sizeof(UINT32) ||
-                ntohs(ip_header->Length) != data_len)
-            {
-                ip_header = NULL;
-                goto WinDivertHelperParsePacketExit;
-            }
-            trans_proto = ip_header->Protocol;
-            header_len = ip_header->HdrLength*sizeof(UINT32);
-            data = (PVOID)((UINT8 *)data + header_len);
-            data_len -= header_len;
-            break;
-        case 6:
-            ip_header = NULL;
-            ipv6_header = (PWINDIVERT_IPV6HDR)data;
-            if (data_len < sizeof(WINDIVERT_IPV6HDR) ||
-                ntohs(ipv6_header->Length) !=
-                    data_len - sizeof(WINDIVERT_IPV6HDR))
-            {
-                ipv6_header = NULL;
-                goto WinDivertHelperParsePacketExit;
-            }
-            trans_proto = ipv6_header->NextHdr;
-            data = (PVOID)((UINT8 *)data + sizeof(WINDIVERT_IPV6HDR));
-            data_len -= sizeof(WINDIVERT_IPV6HDR);
-            trans_proto = WinDivertSkipExtHeaders(trans_proto, (UINT8 **)&data,
-                &data_len);
-            break;
-        default:
-            ip_header = NULL;
-            goto WinDivertHelperParsePacketExit;
-    }
-    switch (trans_proto)
-    {
-        case IPPROTO_TCP:
-            tcp_header = (PWINDIVERT_TCPHDR)data;
-            if (data_len < sizeof(WINDIVERT_TCPHDR) ||
-                tcp_header->HdrLength < 5 ||
-                data_len < tcp_header->HdrLength*sizeof(UINT32))
-            {
-                tcp_header = NULL;
-                goto WinDivertHelperParsePacketExit;
-            }
-            header_len = tcp_header->HdrLength*sizeof(UINT32);
-            data = ((UINT8 *)data + header_len);
-            data_len -= header_len;
-            break;
-        case IPPROTO_UDP:
-            udp_header = (PWINDIVERT_UDPHDR)data;
-            if (data_len < sizeof(WINDIVERT_UDPHDR) ||
-                ntohs(udp_header->Length) != data_len)
-            {
-                udp_header = NULL;
-                goto WinDivertHelperParsePacketExit;
-            }
-            data = ((UINT8 *)data + sizeof(WINDIVERT_UDPHDR));
-            data_len -= sizeof(WINDIVERT_UDPHDR);
-            break;
-        case IPPROTO_ICMP:
-            icmp_header = (PWINDIVERT_ICMPHDR)data;
-            if (ip_header == NULL ||
-                data_len < sizeof(WINDIVERT_ICMPHDR))
-            {
-                icmp_header = NULL;
-                goto WinDivertHelperParsePacketExit;
-            }
-            data = ((UINT8 *)data + sizeof(WINDIVERT_ICMPHDR));
-            data_len -= sizeof(WINDIVERT_ICMPHDR);
-            break;
-        case IPPROTO_ICMPV6:
-            icmpv6_header = (PWINDIVERT_ICMPV6HDR)data;
-            if (ipv6_header == NULL ||
-                data_len < sizeof(WINDIVERT_ICMPV6HDR))
-            {
-                icmpv6_header = NULL;
-                goto WinDivertHelperParsePacketExit;
-            }
-            data = ((UINT8 *)data + sizeof(WINDIVERT_ICMPV6HDR));
-            data_len -= sizeof(WINDIVERT_ICMPV6HDR);
-            break;
-        default:
-            break;
-    }
-
-    if (data_len == 0)
-    {
-        data = NULL;
-    }
-
-WinDivertHelperParsePacketExit:
-    success = TRUE;
-    if (ppIpHdr != NULL)
-    {
-        *ppIpHdr = ip_header;
-        success = success && (ip_header != NULL);
-    }
-    if (ppIpv6Hdr != NULL)
-    {
-        *ppIpv6Hdr = ipv6_header;
-        success = success && (ipv6_header != NULL);
-    }
-    if (ppIcmpHdr != NULL)
-    {
-        *ppIcmpHdr = icmp_header;
-        success = success && (icmp_header != NULL);
-    }
-    if (ppIcmpv6Hdr != NULL)
-    {
-        *ppIcmpv6Hdr = icmpv6_header;
-        success = success && (icmpv6_header != NULL);
-    }
-    if (ppTcpHdr != NULL)
-    {
-        *ppTcpHdr = tcp_header;
-        success = success && (tcp_header != NULL);
-    }
-    if (ppUdpHdr != NULL)
-    {
-        *ppUdpHdr = udp_header;
-        success = success && (udp_header != NULL);
-    }
-    if (pProto != NULL)
-    {
-        *pProto = trans_proto;
-    }
-    if (ppData != NULL)
-    {
-        *ppData = data;
-        success = success && (data != NULL);
-    }
-    if (pDataLen != NULL)
-    {
-        *pDataLen = data_len;
-    }
-    return success;
-}
-
 /*
  * Parse IPv4/IPv6/ICMP/ICMPv6/TCP/UDP headers from a raw packet.
  */
@@ -497,196 +273,8 @@ extern BOOL WinDivertHelperParsePacket(PVOID pPacket, UINT packetLen,
     PWINDIVERT_TCPHDR *ppTcpHdr, PWINDIVERT_UDPHDR *ppUdpHdr, PVOID *ppData,
     UINT *pDataLen)
 {
-    return WinDivertHelperParsePacket_2(pPacket, packetLen, ppIpHdr,
-        ppIpv6Hdr, ppIcmpHdr, ppIcmpv6Hdr, ppTcpHdr, ppUdpHdr, NULL,
-        ppData, pDataLen);
-}
-
-/*
- * Calculate IPv4/IPv6/ICMP/ICMPv6/TCP/UDP checksums.
- */
-extern UINT WinDivertHelperCalcChecksums(PVOID pPacket, UINT packetLen,
-    PWINDIVERT_ADDRESS pAddr, UINT64 flags)
-{
-    UINT8 pseudo_header[
-        MAX(sizeof(WINDIVERT_PSEUDOHDR), sizeof(WINDIVERT_PSEUDOV6HDR))];
-    UINT16 pseudo_header_len;
-    PWINDIVERT_IPHDR ip_header;
-    PWINDIVERT_IPV6HDR ipv6_header;
-    PWINDIVERT_ICMPHDR icmp_header;
-    PWINDIVERT_ICMPV6HDR icmpv6_header;
-    PWINDIVERT_TCPHDR tcp_header;
-    PWINDIVERT_UDPHDR udp_header;
-    UINT payload_len, checksum_len;
-    UINT count = 0;
-
-    WinDivertHelperParsePacket_2(pPacket, packetLen, &ip_header, &ipv6_header,
-        &icmp_header, &icmpv6_header, &tcp_header, &udp_header, NULL, NULL,
-        &payload_len);
-
-    if (ip_header != NULL && !(flags & WINDIVERT_HELPER_NO_IP_CHECKSUM))
-    {
-        ip_header->Checksum = 0;
-        if (pAddr == NULL || pAddr->PseudoIPChecksum == 0)
-        {
-            ip_header->Checksum = WinDivertHelperCalcChecksum(NULL, 0,
-                ip_header, ip_header->HdrLength*sizeof(UINT32));
-        }
-        count++;
-    }
-
-    if (icmp_header != NULL)
-    {
-        if ((flags & WINDIVERT_HELPER_NO_ICMP_CHECKSUM) != 0)
-        {
-            return count;
-        }
-        icmp_header->Checksum = 0;
-        icmp_header->Checksum = WinDivertHelperCalcChecksum(NULL, 0,
-            icmp_header, payload_len + sizeof(WINDIVERT_ICMPHDR));
-        count++;
-        return count;
-    }
-
-    if (icmpv6_header != NULL)
-    {
-        if ((flags & WINDIVERT_HELPER_NO_ICMPV6_CHECKSUM) != 0)
-        {
-            return count;
-        }
-        checksum_len = payload_len + sizeof(WINDIVERT_ICMPV6HDR);
-        pseudo_header_len = WinDivertInitPseudoHeader(NULL, ipv6_header, 
-            IPPROTO_ICMPV6, checksum_len, pseudo_header);
-        icmpv6_header->Checksum = 0;
-        icmpv6_header->Checksum = WinDivertHelperCalcChecksum(pseudo_header,
-            pseudo_header_len, icmpv6_header, checksum_len);
-        count++;
-        return count;
-    }
-
-    if (tcp_header != NULL)
-    {
-        if ((flags & WINDIVERT_HELPER_NO_TCP_CHECKSUM) != 0)
-        {
-            return count;
-        }
-        if (pAddr == NULL || pAddr->PseudoTCPChecksum == 0)
-        {
-            // Full TCP checksum
-            checksum_len = payload_len + tcp_header->HdrLength*sizeof(UINT32);
-            pseudo_header_len = WinDivertInitPseudoHeader(ip_header,
-                ipv6_header, IPPROTO_TCP, checksum_len, pseudo_header);
-            tcp_header->Checksum = 0;
-            tcp_header->Checksum = WinDivertHelperCalcChecksum(
-                pseudo_header, pseudo_header_len, tcp_header, checksum_len);
-        }
-        else if (pAddr->Outbound)
-        {
-            // Pseudo TCP checksum
-            tcp_header->Checksum = 0;
-        }
-        count++;
-        return count;
-    }
-
-    if (udp_header != NULL)
-    {
-        if ((flags & WINDIVERT_HELPER_NO_UDP_CHECKSUM) != 0)
-        {
-            return count;
-        }
-        if (pAddr == NULL || pAddr->PseudoUDPChecksum == 0)
-        {
-            // Full UDP checksum
-            checksum_len = payload_len + sizeof(WINDIVERT_UDPHDR);
-            pseudo_header_len = WinDivertInitPseudoHeader(ip_header,
-                ipv6_header, IPPROTO_UDP, checksum_len, pseudo_header);
-            udp_header->Checksum = 0;
-            udp_header->Checksum = WinDivertHelperCalcChecksum(
-                pseudo_header, pseudo_header_len, udp_header, checksum_len);
-            if (udp_header->Checksum == 0)
-            {
-                udp_header->Checksum = 0xFFFF;
-            }
-        }
-        else if (pAddr->Outbound)
-        {
-            // Pseudo UDP checksum
-            udp_header->Checksum = 0;
-        }
-        count++;
-    }
-    return count;
-}
-
-/*
- * Initialize the IP/IPv6 pseudo header.
- */
-static UINT16 WinDivertInitPseudoHeader(PWINDIVERT_IPHDR ip_header,
-    PWINDIVERT_IPV6HDR ipv6_header, UINT8 protocol, UINT len,
-    void *pseudo_header)
-{
-    if (ip_header != NULL)
-    {
-        PWINDIVERT_PSEUDOHDR pseudo_header_v4 =
-            (PWINDIVERT_PSEUDOHDR)pseudo_header;
-        pseudo_header_v4->SrcAddr  = ip_header->SrcAddr;
-        pseudo_header_v4->DstAddr  = ip_header->DstAddr;
-        pseudo_header_v4->Zero     = 0;
-        pseudo_header_v4->Protocol = protocol;
-        pseudo_header_v4->Length   = htons((UINT16)len);
-        return sizeof(WINDIVERT_PSEUDOHDR);
-    }
-    else
-    {
-        PWINDIVERT_PSEUDOV6HDR pseudo_header_v6 =
-            (PWINDIVERT_PSEUDOV6HDR)pseudo_header;
-        memcpy(pseudo_header_v6->SrcAddr, ipv6_header->SrcAddr,
-            sizeof(pseudo_header_v6->SrcAddr));
-        memcpy(pseudo_header_v6->DstAddr, ipv6_header->DstAddr,
-            sizeof(pseudo_header_v6->DstAddr));
-        pseudo_header_v6->Length  = htonl((UINT32)len);
-        pseudo_header_v6->NextHdr = protocol;
-        pseudo_header_v6->Zero    = 0;
-        return sizeof(WINDIVERT_PSEUDOV6HDR);
-    }
-}
-
-/*
- * Generic checksum computation.
- */
-static UINT16 WinDivertHelperCalcChecksum(PVOID pseudo_header,
-    UINT16 pseudo_header_len, PVOID data, UINT len)
-{
-    register const UINT16 *data16 = (const UINT16 *)pseudo_header;
-    register size_t len16 = pseudo_header_len >> 1;
-    register UINT32 sum = 0;
-    size_t i;
-
-    // Pseudo header:
-    for (i = 0; i < len16; i++)
-    {
-        sum += (UINT32)data16[i];
-    }
-
-    // Main data:
-    data16 = (const UINT16 *)data;
-    len16 = len >> 1;
-    for (i = 0; i < len16; i++)
-    {
-        sum += (UINT32)data16[i];
-    }
-
-    if (len & 0x1)
-    {
-        const UINT8 *data8 = (const UINT8 *)data;
-        sum += (UINT16)data8[len-1];
-    }
-
-    sum = (sum & 0xFFFF) + (sum >> 16);
-    sum += (sum >> 16);
-    sum = ~sum;
-    return (UINT16)sum;
+    return WinDivertParsePacket(pPacket, packetLen, ppIpHdr, ppIpv6Hdr,
+        ppIcmpHdr, ppIcmpv6Hdr, ppTcpHdr, ppUdpHdr, NULL, ppData, pDataLen);
 }
 
 /*
@@ -2563,7 +2151,7 @@ extern BOOL WinDivertHelperEvalFilter(const char *filter, PVOID packet,
                 SetLastError(ERROR_INVALID_PARAMETER);
                 return FALSE;
             }
-            WinDivertHelperParsePacket_2(packet, packet_len, &iphdr, &ipv6hdr,
+            WinDivertParsePacket(packet, packet_len, &iphdr, &ipv6hdr,
                 &icmphdr, &icmpv6hdr, &tcphdr, &udphdr, &protocol, NULL,
                 &payload_len);
             if ((addr->IPv6 && ipv6hdr == NULL) ||
diff --git a/include/windivert.h b/include/windivert.h
index dfe341d..2c8249f 100644
--- a/include/windivert.h
+++ b/include/windivert.h
@@ -413,8 +413,6 @@ typedef struct
     UINT16 Checksum;
 } WINDIVERT_UDPHDR, *PWINDIVERT_UDPHDR;
 
-#ifndef WINDIVERT_KERNEL
-
 /*
  * Flags for WinDivertHelperCalcChecksums()
  */
@@ -424,6 +422,8 @@ typedef struct
 #define WINDIVERT_HELPER_NO_TCP_CHECKSUM                    8
 #define WINDIVERT_HELPER_NO_UDP_CHECKSUM                    16
 
+#ifndef WINDIVERT_KERNEL
+
 /*
  * Parse IPv4/IPv6/ICMP/ICMPv6/TCP/UDP headers from a raw packet.
  */
diff --git a/sys/windivert.c b/sys/windivert.c
index 47dacac..2706043 100644
--- a/sys/windivert.c
+++ b/sys/windivert.c
@@ -663,7 +663,7 @@ static struct layer_s layer_resource_assignment_ipv4_0 =
     0
 };
 static layer_t layer_resource_assignment_ipv4 =
-	&layer_resource_assignment_ipv4_0;
+    &layer_resource_assignment_ipv4_0;
 
 static struct layer_s layer_resource_assignment_ipv6_0 =
 {
@@ -680,7 +680,7 @@ static struct layer_s layer_resource_assignment_ipv6_0 =
     0
 };
 static layer_t layer_resource_assignment_ipv6 =
-	&layer_resource_assignment_ipv6_0;
+    &layer_resource_assignment_ipv6_0;
 
 static struct layer_s layer_auth_connect_ipv4_0 =
 {
@@ -810,6 +810,11 @@ static struct layer_s layer_flow_established_ipv6_0 =
 };
 static layer_t layer_flow_established_ipv6 = &layer_flow_established_ipv6_0;
 
+/*
+ * Shared functions.
+ */
+#include "windivert_shared.c"
+
 /*
  * WinDivert malloc/free.
  */
@@ -887,18 +892,18 @@ extern NTSTATUS DriverEntry(IN PDRIVER_OBJECT driver_obj,
         FWPM_LAYER_ALE_FLOW_ESTABLISHED_V4;
     layer_flow_established_ipv6->layer_guid =
         FWPM_LAYER_ALE_FLOW_ESTABLISHED_V6;
-	layer_resource_assignment_ipv4->layer_guid =
+    layer_resource_assignment_ipv4->layer_guid =
         FWPM_LAYER_ALE_RESOURCE_ASSIGNMENT_V4;
-	layer_resource_assignment_ipv6->layer_guid =
+    layer_resource_assignment_ipv6->layer_guid =
         FWPM_LAYER_ALE_RESOURCE_ASSIGNMENT_V6;
     layer_auth_connect_ipv4->layer_guid = FWPM_LAYER_ALE_AUTH_CONNECT_V4;
     layer_auth_connect_ipv6->layer_guid = FWPM_LAYER_ALE_AUTH_CONNECT_V6;
     layer_auth_listen_ipv4->layer_guid = FWPM_LAYER_ALE_AUTH_LISTEN_V4;
     layer_auth_listen_ipv6->layer_guid = FWPM_LAYER_ALE_AUTH_LISTEN_V6;
     layer_auth_recv_accept_ipv4->layer_guid =
-		FWPM_LAYER_ALE_AUTH_RECV_ACCEPT_V4;
+        FWPM_LAYER_ALE_AUTH_RECV_ACCEPT_V4;
     layer_auth_recv_accept_ipv6->layer_guid =
-		FWPM_LAYER_ALE_AUTH_RECV_ACCEPT_V6;
+        FWPM_LAYER_ALE_AUTH_RECV_ACCEPT_V6;
     layer_inbound_network_ipv4->sublayer_guid =
         WINDIVERT_SUBLAYER_INBOUND_IPV4_GUID;
     layer_outbound_network_ipv4->sublayer_guid = 
@@ -2119,7 +2124,7 @@ static NTSTATUS windivert_write(context_t context, WDFREQUEST request,
     BOOL ipv4;
     UINT8 layer;
     UINT32 priority;
-    UINT64 flags;
+    UINT64 flags, checksums;
     HANDLE handle, compl_handle;
     PNET_BUFFER_LIST buffers = NULL;
     NTSTATUS status = STATUS_SUCCESS;
@@ -2183,6 +2188,7 @@ windivert_write_bad_packet:
         goto windivert_write_exit;
     }
 
+    // Copy packet data:
     data_copy = windivert_malloc(data_len, FALSE);
     if (data_copy == NULL)
     {
@@ -2191,7 +2197,6 @@ windivert_write_bad_packet:
             status);
         goto windivert_write_exit;
     }
-
     RtlCopyMemory(data_copy, data, sizeof(WINDIVERT_IPHDR));
     ip_header = (PWINDIVERT_IPHDR)data_copy;
     switch (ip_header->Version)
@@ -2225,6 +2230,19 @@ windivert_write_bad_packet:
             (char *)data + sizeof(WINDIVERT_IPHDR),
             data_len - sizeof(WINDIVERT_IPHDR));
     }
+
+    // Fix checksums:
+    if (addr->PseudoIPChecksum != 0 || addr->PseudoTCPChecksum != 0 ||
+        addr->PseudoUDPChecksum != 0)
+    {
+        checksums = 
+            (addr->PseudoIPChecksum?  0: WINDIVERT_HELPER_NO_IP_CHECKSUM) |
+            (addr->PseudoTCPChecksum? 0: WINDIVERT_HELPER_NO_TCP_CHECKSUM) |
+            (addr->PseudoUDPChecksum? 0: WINDIVERT_HELPER_NO_UDP_CHECKSUM);
+        WinDivertHelperCalcChecksums(data_copy, data_len, NULL, checksums);
+    }
+
+    // Decrement TTL for impostor packets:
     if (addr->Impostor && !windivert_decrement_ttl(data_copy, ipv4,
             (addr->PseudoIPChecksum == 0)))
     {
@@ -2232,6 +2250,7 @@ windivert_write_bad_packet:
         goto windivert_write_exit;
     }
 
+    // Allocate packet:
     mdl_copy = IoAllocateMdl(data_copy, data_len, FALSE, FALSE, NULL);
     if (mdl_copy == NULL)
     {
@@ -2239,7 +2258,6 @@ windivert_write_bad_packet:
         DEBUG_ERROR("failed to allocate MDL for injected packet", status);
         goto windivert_write_exit;
     }
-
     MmBuildMdlForNonPagedPool(mdl_copy);
     status = FwpsAllocateNetBufferAndNetBufferList0(nbl_pool_handle, 0, 0,
         mdl_copy, 0, data_len, &buffers);
@@ -2250,6 +2268,7 @@ windivert_write_bad_packet:
         goto windivert_write_exit;
     }
 
+    // Inject packet:
     handle = (ipv4? inject_handle: injectv6_handle);
     compl_handle = ((flags & WINDIVERT_FLAG_DEBUG) != 0? (HANDLE)request: NULL);
     if (layer == WINDIVERT_LAYER_NETWORK_FORWARD)
@@ -3521,7 +3540,7 @@ static void windivert_resource_assignment_v4_classify(
     socket_data.RemoteAddr[2] = 0;
     socket_data.RemoteAddr[3] = 0;
     value = fixed_vals->incomingValue[
-		FWPS_FIELD_ALE_RESOURCE_ASSIGNMENT_V4_IP_LOCAL_PORT].value;
+        FWPS_FIELD_ALE_RESOURCE_ASSIGNMENT_V4_IP_LOCAL_PORT].value;
     socket_data.LocalPort = (value.type == FWP_UINT16? value.uint16: 0);
     socket_data.RemotePort = 0;
     socket_data.Protocol = fixed_vals->incomingValue[
@@ -3575,7 +3594,7 @@ static void windivert_resource_assignment_v6_classify(
     socket_data.RemoteAddr[2] = 0;
     socket_data.RemoteAddr[3] = 0;
     value = fixed_vals->incomingValue[
-		FWPS_FIELD_ALE_RESOURCE_ASSIGNMENT_V6_IP_LOCAL_PORT].value;
+        FWPS_FIELD_ALE_RESOURCE_ASSIGNMENT_V6_IP_LOCAL_PORT].value;
     socket_data.LocalPort = (value.type == FWP_UINT16? value.uint16: 0);
     socket_data.RemotePort = 0;
     socket_data.Protocol = fixed_vals->incomingValue[
@@ -3697,7 +3716,7 @@ static void windivert_auth_listen_v4_classify(
     socket_data.RemoteAddr[2] = 0;
     socket_data.RemoteAddr[3] = 0;
     socket_data.LocalPort = fixed_vals->incomingValue[
-		FWPS_FIELD_ALE_AUTH_LISTEN_V4_IP_LOCAL_PORT].value.uint16;
+        FWPS_FIELD_ALE_AUTH_LISTEN_V4_IP_LOCAL_PORT].value.uint16;
     socket_data.RemotePort = 0;
     socket_data.Protocol = IPPROTO_TCP;
 
@@ -3737,7 +3756,7 @@ static void windivert_auth_listen_v6_classify(
     socket_data.RemoteAddr[2] = 0;
     socket_data.RemoteAddr[3] = 0;
     socket_data.LocalPort = fixed_vals->incomingValue[
-		FWPS_FIELD_ALE_AUTH_LISTEN_V6_IP_LOCAL_PORT].value.uint16;
+        FWPS_FIELD_ALE_AUTH_LISTEN_V6_IP_LOCAL_PORT].value.uint16;
     socket_data.RemotePort = 0;
     socket_data.Protocol = IPPROTO_TCP;
 
@@ -5456,8 +5475,6 @@ windivert_filter_compile_error:
 /* WINDIVERT REFLECT MANAGER IMPLEMENTATION                                 */
 /****************************************************************************/
 
-#include "windivert_shared.c"
-
 /*
  * WinDivert reflect state.
  */