Things became much better when I replaced drivers/net/de4x5.c and
drivers/net/de4x5.h with the same ones from kernel 2.1.72. I sent a bug
report with a complete kernel oops to the de4x5.c author.
By the way, I found the origin of my strange messages: the portmap daemon
is needed on both machines (server and client). Also, the redhat portmap
daemon has some bugs (it segfaulted when I ran it in debug mode...)
so I began to write my own portmap. During the process, I isolated my
"'Exception at' infinite loop" to a call to openlog(). This I will investigate
further tomorrow.
Good night folks.
--Thomas Pornin