building openafs-modules for 2.4.21 fails

[Anders Lennartsson <anders.lennartsson@foi.se>]

building modules for openafs based on openafs-source-modules 1.2.9-2 at
the same time as building kernel 2.4.21 fails on a recently updated sid
system.
the build stops where net/sock.h cannot be found and included during
compilation of ../rx/rx_knet.c

this file should be included from the kernel sources include files, but
I think somehow the links made during configuring openafs-modules are
suspicious. Building with 2.4.20 works fine though.

Any ideas?

Anders