Add workaround for #134

For some reason pseudo checksums do not work on
some systems.  The workaround is to modify
WinDivertSend() so that it calculates the full
checksums before forwarding the packet to the
driver.

CHANGELOG

@@ -123,3 +123,5 @@ WinDivert 1.4.0-rc
       for unmodified packets.
 WinDivert 1.4.1
     - Dual license WinDivert under LGPLv3 and GPLv2.
+WinDivert 1.4.2
+    - Add workaround for pseudo checksum issue (see #134).

VERSION

@@ -1 +1 @@
-1.4.1
+1.4.2

dll/windivert.c

@@ -514,6 +514,41 @@ 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.
  */
@@ -554,6 +589,12 @@ extern BOOL WinDivertRecvEx(HANDLE handle, PVOID pPacket, UINT packetLen,
 extern BOOL WinDivertSend(HANDLE handle, PVOID pPacket, UINT packetLen,
     PWINDIVERT_ADDRESS addr, UINT *writelen)
 {
+    if (addr == NULL)
+    {
+        SetLastError(ERROR_INVALID_PARAMETER);
+        return FALSE;
+    }
+    WinDivertFixChecksums(pPacket, packetLen, addr);
     return WinDivertIoControl(handle, IOCTL_WINDIVERT_SEND, 0, (UINT64)addr,
         pPacket, packetLen, writelen);
 }
@@ -565,11 +606,12 @@ extern BOOL WinDivertSendEx(HANDLE handle, PVOID pPacket, UINT packetLen,
     UINT64 flags, PWINDIVERT_ADDRESS addr, UINT *writelen,
     LPOVERLAPPED overlapped)
 {
-    if (flags != 0)
+    if (flags != 0 || addr == NULL)
     {
         SetLastError(ERROR_INVALID_PARAMETER);
         return FALSE;
     }
+    WinDivertFixChecksums(pPacket, packetLen, addr);
     if (overlapped == NULL)
     {
         return WinDivertIoControl(handle, IOCTL_WINDIVERT_SEND, 0,