//Copy the packet into a buffer
  while (CurrentMdl && DataLength > 0)
    {
      NdisQueryMdl(CurrentMdl, &pSrc, &CurrLength, NormalPagePriority);
      if (pSrc == NULL)
        {
	  bytesCopied = 0;
	  break;
        }
        
      //
      //  Current buffer length is greater than the offset to the buffer
      //
      
      if (CurrLength > Offset)
        {
	  pSrc += Offset;
	  CurrLength -= Offset;
	  
	  if (CurrLength > DataLength)
            {
	      CurrLength = DataLength;
            }
	  DataLength -= CurrLength;
	  NdisMoveMemory(pDest, pSrc, CurrLength);
	  bytesCopied += CurrLength;
            
	  pDest += CurrLength;
	  Offset = 0;
        }
      else
        {
	  Offset -= CurrLength;
        }
      NdisGetNextMdl(CurrentMdl, &CurrentMdl);
      
    }
  

?

這段代碼就是拷貝數據到緩沖區。其中CurrMDL,offset和dataLength來自Net_Buffer:

    pNetBuffer = NET_BUFFER_LIST_FIRST_NB(pNetBufferList);
  
  //
  // Try to get the 1p data from OOB data
  //
  if(NET_BUFFER_LIST_INFO(pNetBufferList, Ieee8021QNetBufferListInfo) != 0)
    {
      Ndis8021QInfo.Value = NET_BUFFER_LIST_INFO(pNetBufferList, Ieee8021QNetBufferListInfo);
      UserPriority  = (UCHAR)Ndis8021QInfo.TagHeader.UserPriority;
    }     
  
  //copy the packet into a buffer
  pDest = packetBuffer;
  
  CurrentMdl = pNetBuffer->MdlChain;
  Offset = pNetBuffer->DataOffset;
  DataLength = pNetBuffer->DataLength;
  

?其中NET_BUFFER_LIST_FIRST_NB返回的是第一個Net_Buffer.? CurrentMDL指向MDL的list.現在來看看如何拷貝數據的。其中NdisQueryMdl返回MDL虛擬地址的基地址Psrc，和對應的緩沖區長度CurrLength


?
?1、如果CurrLenght >?offset,那么把Psrc+offset,指向used data.同樣，CurrLength-offset，表示當前的MDL中有用的數據長度。然后執行NdisMoveMemory的拷貝操作.緊接著把，dataLength-CurrLength,因為已經拷貝好了一部分，然后再把offset置零，因為現在指針已經到了可用數據區。

2、當再次得到下一個MDL的Psrc,和CurrLength時，因為offset已經=0，所以CurrLength肯定大于0，所以即使執行PSrc+=offset, CurrLength-=offset.最后拷貝整個長度的空間(以圖為例，不都是這樣！！)，dataLength-CurrLength.

3、最后第三次得到pSrc,和CurrLength,但是CurrLength,已經大于dataLength，所以只拷貝dataLength的長度數據。就完成了所有數據拷貝。

4、但是如果第一次的時候offset>CurrLength,那么就是比如圖中第一個MDL為unused data區，執行offset-=CurrLength.如下圖：

?

?這樣之后又回到了前面所說的CurrLength>offset了。

這就是拷貝數據到緩沖區的過程。不知有何疏漏，或者錯誤，見諒~
?

拷貝MDL中數據到緩沖區