Kernel Functions for Drivers                         mac_hcksum_get(9F)

NAME

     mac_hcksum_set, mac_hcksum_get -- Hardware checksumming offload
     routines

SYNOPSIS

     #include <sys/mac_provider.h>

     void mac_hcksum_get(mblk_t *mp, uint32_t *start, uint32_t *stuff,
         uint32_t *end, uint32_t *value, uint32_t *flags);

     void mac_hcksum_set(mblk_t *mp, uint32_t start, uint32_t stuff,
         uint32_t end, uint32_t value, uint32_t *flags);

INTERFACE LEVEL

     Solaris architecture specific (Solaris DDI).

PARAMETER

     mp		Pointer to a message block.

     start 	Offset, in bytes, from the start of the IP header to the 	
		start of the checksum span.
	
     end   	Offset, in bytes, from the start of the IP header to the 	
		end of the checksum span.
	
     stuff	Offset, in bytes, from the start of the IP header to the
		checksum field in the protocol header.
	
     value	Hardware computed checksum value
	
     flags	Per-packet flags indicating the hardware checksumming
     		to be performed on outbound packets, or the hardware
		checksumming performed on inbound packet.

DESCRIPTION

     Hardware checksumming allows the checksum computation to be
     offloaded to the network device hardware for lower CPU
     utilization. Hardware checksumming capabilities are advertised
     from the driver's mc_getcapab(9E) entry point. The description of
     mc_getcapab(9E) also includes more information about the expected
     behavior of drivers for full and partial checksumming offload.

     For received traffic, the hardware can enable hardware
     checksumming, and the network stack will know how to handle
     packets for which checksum computation or verification has been
     performed.  The mac_hcksum_set() routine can be used by a device
     driver to associate information related to the hardware
     checksumming performed on the packet.  The flags argument can be
     a combination of the following:

     HCK_FULLCKSUM		The full checksum was computed, and is
				passed through the value argument.

     HCK_FULLCKSUM_OK		The full checksum was verified in
     				hardware and is correct.

     HCK_PARTIALCKSUM		Partial checksum computed and passed
     				through the value argument. The start
				and end arguments specify the
				checksum span.

     HCK_IPV4_HDRCKSUM_OK	IP header checksum was verified in
     				hardware and is correct

     The HCK_FULLCKSUM and HCK_FULLCKSUM_OK are mutually
     exclusive, i.e. if the HCK_FULLCKSUM is set, the network
     stack will use the specified checksum value to verify that it
     matches the checksum found in the packet. If the
     HCK_FULLCKSUM_OK is specified, the stack will assume that the
     hardware checksum was verified in hardware.

     HCK_PARTIALCKSUM is mutually exclusive with the
     HCK_FULLCKSUM and HCK_FULLCKSUM flags.

     For outbound packets, hardware checksumming capabilities are
     queried via the mc_getcapab(9E) entry point. Hardware
     checksumming is enabled by the network stack based on the
     MAC_CAPAB_HCKSUM capability. A device driver which advertised
     support for this capability can subsequently received outbound
     packets which may not have a fully computed checksum. It is the
     responsibility of the driver to invoke mac_hcksum_get() to
     retrieve the per-packet hardware checksumming meta-data.

     HCK_FULLCKSUM		Compute full checksum for this
     				packet.

     HCK_PARTIALCKSUM		Compute partial 1's complement
     				checksum based on the
				start, stuff, and offset.

     HCK_IPV4_HDRCKSUM		Compute the IP header checksum.

     HCK_PARTIALCKSUM is mutually exclusive with HCK_FULLCKSUM.

NOTES

     Note that the flags HCK_FULLCKSUM, HCK_FULLCKSUM_OK, and
     HCK_PARTIALCKSUM, are used for both IPv4 and IPv6
     packets. The driver advertises support for IPv4 and/or IPv6 full
     checksumming during capability negotiation, see mc_getcapab(9E).

ATTRIBUTES

     See attributes(5) for descriptions of the  following  attri-
     butes:

     ____________________________________________________________
    |       ATTRIBUTE TYPE        |       ATTRIBUTE VALUE       |
    |_____________________________|_____________________________|
    | Availability                | SUNWhea                     |
    |_____________________________|_____________________________|
    | Interface Stability         | Committed                   |
    |_____________________________|_____________________________|


SEE ALSO

     mac(9E), attributes(5)