On Tue, 11 Dec 2012, Simon Wilkinson wrote:
On 11 Dec 2012, at 20:05, Michael Meffie wrote:
The Checksum field allows for an optional packet checksum. A zero
checksum field value means that checksums are not being computed. An
Rx security protocol (identified by the security field, described
below) may choose to use this field to transport some checksum of the
packet that is computed and verified by it (for example, rxkad uses
this field for a cryptographic header checksum). Rx itself makes no
use of the checksum field.
Technically, this is a "spare" field that rxkad hijacked to use for
checksums. I don't think there's any particular problem with rxgk
assigning it a different meaning. One possible consideration is that the
OpenAFS RX stack notes the presence of non-zero values here, and the
rx_IsUsingPktCksum() function will return true if it has seen any in the
life of the connection. However, the only caller of this function in the
OpenAFS code is rxkad, and I don't think it makes much sense outside of
rxkad itself.
Thanks for adding the confirmation. I was pretty sure that we didn't
care, but explicitly discussing the issue on-list seems preferable to
silently making assumptions.
-Ben
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