Method and apparatus for blind checksum and correction for network transmissions

Abstract

Method and apparatus for providing a checksum in a network transmission. In one aspect of the invention, a checksum for a packet to be transmitted on a network is determined by retrieving packet information from a storage device, the packet information to be included in the packet to be transmitted. A blind checksum value is determined based on the retrieved packet information, and the blind checksum value is adjusted to a protocol checksum based on descriptor information describing the structure of the packet. The protocol checksum is inserted in the packet before the packet is transmitted.

1 . A method for determining a checksum for a packet to be transmitted on a network, the method comprising: 
 retrieving packet information from a storage device, the packet information to be included in the packet to be transmitted;    determining a blind checksum value based on the retrieved packet information; and    adjusting the blind checksum value to a protocol checksum based on descriptor information describing the structure of the packet, wherein the protocol checksum is inserted in the packet before the packet is transmitted.    
   
   
       2 . The method of  claim 1  wherein the blind checksum value is determined by summing all the retrieved packet information.  
   
   
       3 . The method of  claim 1  wherein adjusting the blind checksum value includes adding or subtracting at least one halfword value of the packet information to or from the blind checksum value.  
   
   
       4 . The method of  claim 3  wherein the packet to be transmitted is a TCP/IP packet, and wherein adjusting the blind checksum value includes adding a halfword value to the blind checksum value if the halfword value is an IP header field required to determine a TCP checksum value and the halfword value was not included in the blind checksum.  
   
   
       5 . The method of  claim 3  wherein the packet to be transmitted is a TCP/IP packet, and wherein adjusting the blind checksum value includes subtracting a halfword value from the blind checksum value if the halfword value is an IP header field not required to determine a TCP checksum value and the halfword value was included in the blind checksum.  
   
   
       6 . The method of  claim 1  wherein the retrieved packet information includes a header and a body of the packet.  
   
   
       7 . The method of  claim 1  wherein the retrieved packet information includes a body of the packet and no header of the packet, and further comprising retrieving the header of the packet with the descriptor information.  
   
   
       8 . The method of  claim 7  further comprising merging the header with the body of the packet after the blind checksum is determined for the body.  
   
   
       9 . The method of  claim 1  further comprising sending the packet information to a data buffer after the blind checksum has been determined, wherein the packet information is retrieved from the data buffer for the adjusting of the blind checksum.  
   
   
       10 . The method of  claim 1  further comprising retrieving the descriptor information from the storage device.  
   
   
       11 . The method of  claim 10  wherein the blind checksum value is determined when at a portion of the packet information is stored separately from the descriptor in memory, and further comprising: 
 determining the protocol checksum based on descriptor information describing the structure of the packet, if the packet information is stored with and retrieved with the descriptor information.    
   
   
       12 . The method of  claim 1  further comprising determining the descriptor information by parsing the packet information.  
   
   
       13 . The method of  claim 1  wherein the packet is provided according to the TCP/IP protocol.  
   
   
       14 . The method of  claim 3  wherein adjusting the blind checksum value includes subtracting out bytes of an IP header portion of the packet information and leaving in bytes of the IP header portion that are needed for a pseudo header to create a TCP checksum.  
   
   
       15 . The method of  claim 14  wherein adjusting the blind checksum value includes subtracting out one byte of a halfword and keeping the other byte of the halfword for fields in the IP header portion in which only one byte of the field is needed in the pseudo header.  
   
   
       16 . The method of  claim 3  wherein adjusting the blind checksum value includes subtracting out one byte of a halfword and keeping the other byte of the halfword if the halfword is positioned on a boundary between a portion of the packet information already included in the blind checksum value and a portion not included in the blind checksum value.  
   
   
       17 . An apparatus for determining a checksum for a packet to be transmitted on a network, the apparatus comprising: 
 a memory access unit that retrieves packet information from a storage device, the packet information to be included in the packet to be transmitted;    an accumulator that determines a blind checksum value based on the retrieved packet information; and    a transmission unit that receives the packet information and the blind checksum value and adjusts the blind checksum value to a protocol checksum based on descriptor information describing the structure of the packet, wherein the transmission unit inserts the protocol checksum in the packet and outputs the packet for transmission on the network.    
   
   
       18 . The apparatus of  claim 17  wherein the accumulator determines the blind checksum value by summing retrieved packet information as it is loaded.  
   
   
       19 . The apparatus of  claim 17  further comprising a transmission processor, wherein the transmission processor retrieves the descriptor information from the storage device and provides the descriptor information to the transmission unit.  
   
   
       20 . The apparatus of  claim 19  wherein the transmission processor receives the blind checksum value from the accumulator and provides the blind checksum value to the transmission unit.  
   
   
       21 . The apparatus of  claim 17  further comprising a data buffer coupled to the memory access unit, wherein the data buffer receives the packet information from the memory access unit, and wherein the packet information is sent from the data buffer to the transmission unit.  
   
   
       22 . The apparatus of  claim 17  wherein the retrieved packet information includes a header and a body of the packet.  
   
   
       23 . The apparatus of  claim 17  wherein the retrieved packet information includes a body of the packet and no header of the packet, and wherein the memory access unit retrieves the header of the packet with the descriptor information.  
   
   
       24 . The apparatus of  claim 23  further comprising a merge unit that merges the header with the body of the packet after the accumulator determines the blind checksum for the body and wherein the transmission unit receives the merged packet information from the merge unit.  
   
   
       25 . The apparatus of  claim 17  wherein the transmission unit adjusts the blind checksum value includes adding or subtracting at least one halfword value of the packet information to or from the blind checksum value.  
   
   
       26 . The apparatus of  claim 25  wherein the packet to be transmitted is a TCP/IP packet, and wherein the transmission unit adjusts the blind checksum value by adding a halfword value to the blind checksum value if the halfword value is an IP header field required to determine a TCP checksum value and the halfword value was not included in the blind checksum.  
   
   
       27 . The apparatus of  claim 25  wherein the packet to be transmitted is a TCP/IP packet, and wherein the transmission unit adjusts the blind checksum value by subtracting a halfword value from the blind checksum value if the halfword value is an IP header field not required to determine a TCP checksum value and the halfword value was included in the blind checksum.  
   
   
       28 . The apparatus of  claim 19  wherein the transmission processor also retrieves the packet information with the descriptor information from storage device and provides the packet information to the transmission unit, wherein the transmission unit creates the protocol checksum based on the descriptor information.