Remove STRUIO_IP support from ip_cksum.c
The dblk STRUIOP_IP flag was introduced in 1994 as a consolidation private interface to speed up FDDI processing.
It is not used anywhere in illumos-gate, it is consolidation private, and from the information available, appears to only work with Synchronous STREAMS compatible drivers, and it makes the ip_cksum() source an largely unreadable complicated mess. Removing the support allows for a substantial simplification of the function.
Updated by Jason King about 2 years ago
As part of the testing, the attached mblk.tar code was created. It extracts both the new and old ip_cksum() code and runs it against a contrived mblk_t chain of random data to compare the results (to make sure the new code returns the same checksum as the existing code). It was tested on both x86 and sparc successfully.