Re: Are "skb->data" physically continuous?

[Nick Patavalis (npat@inaccessnetworks.com)]

On Tue, Sep 16, 2003 at 12:27:21PM +0100, Jamie Lokier wrote:
> Nick Patavalis wrote:
> > How should the kernel be notified if the calculation of a checksum
> > failed (checksum does not match). Reading the e100 source, I see that
> > if the checksums (any of the checksums, I presume) of a packet are
> > invalid, then the driver sets "skb->ip_summed" to CHECKSUM_NONE; but
> 
> I'm reading the 2.6.0-test5 e100 source, and I don't see anywhere
> where it's set to CHECKSUM_NONE if the checksum is known to be
> invalid.  I see CHECKSUM_UNNECESSARY in those cases.
> 

Reading e100_main.c, from 2.6.0-test2 (the latest version I have
readily available), I see (sory for the ugly line-numbers):

2052     /* set the checksum info */
2053     if (bdp->flags & DF_CSUM_OFFLOAD) {
2054             if (bdp->rev_id >= D102_REV_ID) {
2055                     skb->ip_summed = e100_D102_check_checksum(rfd);
2056             } else {
2057                     skb->ip_summed = e100_D101M_checksum(bdp, skb);
2058             }
2059     } else {
2060             skb->ip_summed = CHECKSUM_NONE;
2061     }

2914 e100_D102_check_checksum(rfd_t *rfd)
2915 {
2916         if (((le16_to_cpu(rfd->rfd_header.cb_status)) & RFD_PARSE_BIT)
2917             && (((rfd->rcvparserstatus & CHECKSUM_PROTOCOL_MASK) ==
2918                  RFD_TCP_PACKET)
2919                 || ((rfd->rcvparserstatus & CHECKSUM_PROTOCOL_MASK) ==
2920                     RFD_UDP_PACKET))
2921             && (rfd->checksumstatus & TCPUDP_CHECKSUM_BIT_VALID)
2922             && (rfd->checksumstatus & TCPUDP_CHECKSUM_VALID)) {
2923                 return CHECKSUM_UNNECESSARY;
2924         }
2925         return CHECKSUM_NONE;
2926 }

the function "e100_D101M_checksum(bdp, skb)" is similar.

Am I wrong to interpret this as:

  if HW checksuming supported, then
      if checksum is valid
          skb->ip_summed = CHECKSUM_UNNECESSARY
      else
          skb->ip_summed = CHECKSUM_NONE
  else
      skb->ip_summed = CHECKSUM_NONE

I don't know if sommething changed from test2 to test5

/npat

-- 
Perilous to us all are the devices of an art deeper than we possess 
ourselves.
  -- Gandalf, in J.R.R. Tolkien's The Lord of the Rings
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