2a4b742e6a
external storage. Highlights: - additional "void *" argument to (*ext_free)(), an opaque cookie for use by the free function. - MCLALLOC() and MCLFREE() calls are gone. They are replaced by MEXTADD() (add external storage to mbuf), MEXTMALLOC() (malloc() external storage and attach to mbuf), and MEXTREMOVE() (remove external storage from mbuf). - completely new external storage reference counting mechanism; mclrefcnt[] is gone. These changes will eventually be used to pass driver DMA buffers up the network stack, and reduce/eliminate copies in certain code paths (e.g. NFS writes). From Matt Thomas <matt@3am-software.com> and myself <thorpej@nas.nasa.gov>, with some input from Chris Demetriou <cgd@cs.cmu.edu> and review by Charles Hannum <mycroft@mit.edu>.