Nework Emulation with UML, bug 8895

[clowncoder <vincent-perrier@club-internet.fr>]

Hello,
You can have a configured and running network inside a single linux machine,
only one script command is enough. After the start of all the machine, a
graphical representation of your topology helps your interactions with
the network. This virtual network can be downloaded at http://clownix.net,
I must warn you, it is a 350mega bz2 file-system that needs 4 giga on 
the host.
Very usefull for networking development in kernel as proved by bug 8895
that has been found with the above tool:

The uncorrected bug 8895:

file:  /usr/src/linux-2.6.24.2/net/ipv6/ip6_fib.c  line  796:   
"dst_free(&rt->u.dst);"

------- /Comment From qmiao <mailto:qmiao@centecnetworks.com> 2007-08-29 
23:33:07 /---

        fib6_add
                ...

                if (fn->leaf == NULL) {
                        fn->leaf = rt;    <--**-- rt is assigned to fn->leaf
                        atomic_inc(&rt->rt6i_ref);
                }
                ...
                err = fib6_add_rt2node(fn, rt, info); <-**- return -EEXIST
                ...
(Here err was not null)
                ...
                if (err) {
                        ...
                        dst_free(&rt->u.dst); <--**-- Actually rt is still in
tree (fn->leaf = rt /* see above */)
                        ...
                        }