Pull a fix from hme.c rev 1.73 (to #if 0'ed out part):
> Fix a bug in calculation of checksum deduction:
> - To get 16 bit one's complement value from uint32_t variable,
>  higher 16 bits should be ignored.
> - RFC 1624 describes methods to recalculate checksum field in headers,
>  i.e. one's complement of one's complement sum that could be 0x0000,
>  but we don't have to use the strategy to deduct one's complement sum
>  itself which won't be zero but should be 0xffff.

(tsutsui)