LSP packet modify
- by kellogs
Hello,
anybody care to share some insights on how to use LSP for packet modifying ?
I am using the non IFS subtype and I can see how (pseudo?) packets first enter WSPRecv. But how do I modify them ? My inquiry is about one single HTTP response that causes WSPRecv to be called 3 times :((. I need to modify several parts of this response, but since it comes in 3 slices, it is pretty hard to modify it accordingly. And, maybe on other machines or under different conditions (such as high traffic) there would only be one sole WSPRecv call, or maybe 10 calls. What is the best way to work arround this (please no NDIS :D), and how to properly change the buffer (lpBuffers-buf) by increasing it ?
int WSPAPI
WSPRecv(
SOCKET s,
LPWSABUF lpBuffers,
DWORD dwBufferCount,
LPDWORD lpNumberOfBytesRecvd,
LPDWORD lpFlags,
LPWSAOVERLAPPED lpOverlapped,
LPWSAOVERLAPPED_COMPLETION_ROUTINE lpCompletionRoutine,
LPWSATHREADID lpThreadId,
LPINT lpErrno
)
{
LPWSAOVERLAPPEDPLUS ProviderOverlapped = NULL;
SOCK_INFO *SocketContext = NULL;
int ret = SOCKET_ERROR;
*lpErrno = NO_ERROR;
//
// Find our provider socket corresponding to this one
//
SocketContext = FindAndRefSocketContext(s, lpErrno);
if ( NULL == SocketContext )
{
dbgprint( "WSPRecv: FindAndRefSocketContext failed!" );
goto cleanup;
}
//
// Check for overlapped I/O
//
if ( NULL != lpOverlapped )
{
/*bla bla .. not interesting in my case*/
}
else
{
ASSERT( SocketContext->Provider->NextProcTable.lpWSPRecv );
SetBlockingProvider(SocketContext->Provider);
ret = SocketContext->Provider->NextProcTable.lpWSPRecv(
SocketContext->ProviderSocket,
lpBuffers,
dwBufferCount,
lpNumberOfBytesRecvd,
lpFlags,
lpOverlapped,
lpCompletionRoutine,
lpThreadId,
lpErrno);
SetBlockingProvider(NULL);
//is this the place to modify packet length and contents ?
if (strstr(lpBuffers->buf, "var mapObj = null;"))
{
int nLen = strlen(lpBuffers->buf) + 200;
/*CHAR *szNewBuf = new CHAR[];
CHAR *pIndex;
pIndex = strstr(lpBuffers->buf, "var mapObj = null;");
nLen = strlen(strncpy(szNewBuf, lpBuffers->buf, (pIndex - lpBuffers->buf) * sizeof (CHAR)));
nLen = strlen(strncpy(szNewBuf + nLen * sizeof(CHAR), "var com = null;\r\n", 17 * sizeof(CHAR)));
pIndex += 18 * sizeof(CHAR);
nLen = strlen(strncpy(szNewBuf + nLen * sizeof(CHAR), pIndex, 1330 * sizeof (CHAR)));
nLen = strlen(strncpy(szNewBuf + nLen * sizeof(CHAR), "if (com == null)\r\n" \
"com = new ActiveXObject(\"InterCommJS.Gateway\");\r\n" \
"com.lat = latitude;\r\n" \
"com.lon = longitude;\r\n}", 111 * sizeof (CHAR)));
pIndex = strstr(szNewBuf, "Content-Length:");
pIndex += 16 * sizeof(CHAR);
strncpy(pIndex, "1465", 4 * sizeof(CHAR));
lpBuffers->buf = szNewBuf;
lpBuffers->len += 128;*/
}
if ( SOCKET_ERROR != ret )
{
SocketContext->BytesRecv += *lpNumberOfBytesRecvd;
}
}
cleanup:
if ( NULL != SocketContext )
DerefSocketContext( SocketContext, lpErrno );
return ret;
}
Thank you
