Method and system for supporting read operations with CRC for iSCSI and iSCSI chimney

• US 20060015655A1
• Filed: 06/17/2005
• Published: 01/19/2006
• Est. Priority Date: 08/30/2002
• Status: Active Grant

• Current Assignee: Avago Technologies International Sales Pte Limited (Broadcom, Inc.)
• Original Assignee: Broadcom Corporation (Broadcom, Inc.)
• Inventors: Fan, Kan Frankie, McDaniel, Scott, Zur, Uri El
• Granted Patent: US 8,180,928 B2
• Time in Patent Office: Days
• US Class Current: 710/5
• CPC Class Codes: H04L 69/16 Implementation or adaptation of Internet protocol [IP], of transmission control protocol [TCP] or of user datagram protocol [UDP]
• CPC Class Codes: H04L 69/168 specially adapted for link layer protocols, e.g. asynchronous transfer mode [ATM], synchronous optical network [SONET] or point-to-point protocol [PPP]
• CPC Class Codes: H04L 69/169 Special adaptations of TCP, UDP or IP for interworking of IP based networks with other networks protocols for interworking, protocol conversion H04L69/08

Abstract

Certain embodiments of the invention may be found in a method and system for performing SCSI read operations with a CRC via a TCP offload engine. Aspects of the method may comprise receiving an iSCSI read command from an initiator. Data may be fetched from a buffer based on the received iSCSI read command. The fetched data may be zero copied from the buffer to the initiator and a TCP sequence may be retransmitted to the initiator. A digest value may be calculated, which may be communicated to the initiator. An accumulated digest value stored in a temporary buffer may be utilized to calculate a final digest value, if the buffer is posted. The retransmitted TCP sequence may be processed and the fetched data may be zero copied into an iSCSI buffer, if the buffer is posted. The calculated final digest value may be communicated to the initiator.

Claims

1. A method for performing a SCSI read operation via a TCP offload engine, the method comprising:

receiving an iSCSI read command from an initiator;

fetching data from a buffer based on said received iSCSI read command;

zero copying said fetched data from said buffer to said initiator; and

communicating a calculated digest value to said initiator.

2. The method according to claim 1, further comprising:

utilizing an accumulated digest value stored in a temporary buffer for calculating a final digest value, if said buffer is posted;

processing a retransmitted TCP sequence retransmitted to said initiator and zero copying said fetched data into an iSCSI buffer, if said buffer is posted;

communicating said calculated final digest value to said initiator; and

processing said retransmitted TCP sequence retransmitted to said initiator, if said buffer is not posted.

3. The method according to claim 1, further comprising:

parsing an iSCSI protocol data unit to identify additional header and a base header;

calculating said digest value for a header of said iSCSI protocol data unit; and

placing said communicated calculated digest value of said header of said iSCSI protocol data unit in a temporary buffer.

4. The method according to claim 1, further comprising placing said zero copied fetched data into said buffer.

5. The method according to claim 1, further comprising invoking a recovery procedure if said calculated digest value of said header of an iSCSI protocol data unit has failed.

6. The method according to claim 5, further comprising stripping said header from said iSCSI protocol data unit and placing said zero copied fetched data in an iSCSI buffer, if said calculated digest value of said header of said iSCSI protocol data unit has not failed.

7. The method according to claim 6, further comprising allocating said iSCSI buffer for a next frame of said zero copied fetched data in said iSCSI protocol data unit.

8. The method according to claim 6, further comprising posting said iSCSI buffer to hardware.

9. The method according to claim 1, further comprising generating an out of order message, if frames of said zero copied fetched data are not in order.

10. The method according to claim 1, further comprising communicating said calculated digest value to said initiator, if frames of said zero copied fetched data are not in order.

12. The system according to claim 1, wherein:

said at least one driver utilizes an accumulated digest value stored in a temporary buffer for calculating a final digest value, if said buffer is posted;

said at least one driver processes a retransmitted TCP sequence retransmitted to said initiator and zero copying said fetched data into an iSCSI buffer, if said buffer is posted;

said at least one driver communicates said calculated final digest value to said initiator; and

said at least one driver processes said retransmitted TCP sequence retransmitted to said initiator, if said buffer is not posted.

14. The system according to claim 1, wherein said at least one driver places said zero copied fetched data into said buffer.

15. The system according to claim 1, wherein said at least one driver invokes a recovery procedure if said calculated digest value of said header of an iSCSI protocol data unit has failed.

16. The system according to claim 15, wherein said at least one driver strips said header from said iSCSI protocol data unit and placing said zero copied fetched data in an iSCSI buffer, if said calculated digest value of said header of said iSCSI protocol data unit has not failed.

17. The system according to claim 16, wherein said at least one driver allocates said iSCSI buffer for a next frame of said zero copied fetched data in said iSCSI protocol data unit.

18. The system according to claim 16, wherein said at least one driver posts said iSCSI buffer to hardware.

11. A system for performing a SCSI read operation via a TCP offload engine, the system comprising:

a target that receives an iSCSI read command from an initiator;

at least one driver that fetches data from a buffer based on said received iSCSI read command;

said at least one driver zero copies said fetched data from said buffer to said initiator; and

said at least one driver calculates a digest value, which is communicated to said initiator.

13. The system according to claim 11, wherein:

said at least one driver parses an iSCSI protocol data unit to identify additional header and a base header;

said at least one driver calculates said digest value for a header of said iSCSI protocol data unit; and

said at least one driver places said communicated calculated digest value of said header of said iSCSI protocol data unit in a temporary buffer.

19. The system according to claim 11, wherein said at least one driver generates an out of order message, if frames of said zero copied fetched data are not in order.

20. The system according to claim 11, wherein said at least one driver communicates said calculated digest value to said initiator, if frames of said zero copied fetched data are not in order.