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From: Jacques Gelinas (jack_at_solucorp.qc.ca)
Date: Sat 08 Feb 2003 - 06:08:44 GMT

I am trying to figure that bug. I have withness the bug twice on
a server although I am using ctx-15 and ctx-16 on many servers.

The big difference between ctx-15 and the previous is the way
the struct iproot_info is used. In previous kernel, only struct task
was referencing struct iproot pointers. A reference count was maintained
when a new process was created and when a process was ending. Easy.

In ctx-15, sockets also reference those pointers, so have to handle
the reference count. The big issue when debugging ctx-15 was to
realised that sockets (struct sock) were copied to other struct such
as tcp_tw_bucket and that some common routine were use
to handle both struct sock and struct tcp_tw_bucket. Anyway, the
reference count stuff, while trivial (one line of core here and there) took
some time to get right (one line of code here and there, but where :-) ).

Now, I realise that ipv6 is sharing much of the code of ipv4. It does
share the socket initialisation code, but it use the same
cleanup function: inet_sock_destruct. This function does the reference
count stuff on iproot_info using a non initialised pointer. Oops.

So I did the following in net/ipv6/af_inet6.c

*** af_inet6.bak 2001-10-31 15:32:46.000000000 -0500
--- af_inet6.c 2003-02-08 00:50:28.000000000 -0500
*** 183,188 ****
--- 183,191 ----
        sk->protinfo.af_inet.mc_index = 0;
        sk->protinfo.af_inet.mc_list = NULL;

+ sk->s_context = current->s_context;
+ sk->ip_info = NULL;
        if (ipv4_config.no_pmtu_disc)
                sk->protinfo.af_inet.pmtudisc = IP_PMTUDISC_DONT;

Now, I suspect this is not all. But just to make sure:

Aare there some people out there having crash with ctx-15 or 16,
not using ipv6 at all ?

Those using ipv6, can you try this patch ?

(for sure it does not make the kernel vserver/ipv6 aware).

Jacques Gelinas <jack_at_solucorp.qc.ca>
vserver: run general purpose virtual servers on one box, full speed!

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