routing cache related crashes with v6-mapped IPv4 addresses

[Matthias Drochner]

Hi -
I've enabled v4-to-v6-mapped addresses on my system
(by setting the "v6only" sysctl to 0), and not it crashes
from kernel page faults occasionally.
The stackframe is:
in6_pcbrtentry+0x60()
tcp_segsize+0xbf()
tcp_output+0x153()
tcp_usrreq()
sosend()

The crash happens within the v6 address comparision in
netinet6/in6_pcb.c (-current, rev. 1.89), line 916.
Looking deeper, the "cdst" pointer returned by
rtcache_getdst() was 0xc1bc8ff0. 0xc1bc9000 was an
invalid address.
The sockaddr at *cdst was actually an IPv4 sockaddr_in
for which the 16 bytes are just enough.

So the case of an IPv4 route needs to be handled
explicitely, otherwise the IPv6 address comparision
will compare random junk. (and the cache will have
little effect)

best regards
Matthias




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Forschungszentrum Juelich GmbH
52425 Juelich

Sitz der Gesellschaft: Juelich
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Vorsitzende des Aufsichtsrats: MinDirig'in Baerbel Brumme-Bothe
Geschaeftsfuehrung: Prof. Dr. Achim Bachem (Vorsitzender), Dr. Ulrich Krafft (stellv.
Vorsitzender)
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[Matthias Drochner]

the case of an IPv4 route needs to be handled explicitely

The appended patch seems to dtrt. Not that clean yet, just
wanted to show what I mean.

best regards
Matthias





-----------------------------------------------------------------------------------------
-----------------------------------------------------------------------------------------
Forschungszentrum Juelich GmbH
52425 Juelich

Sitz der Gesellschaft: Juelich
Eingetragen im Handelsregister des Amtsgerichts Dueren Nr. HR B 3498
Vorsitzende des Aufsichtsrats: MinDirig'in Baerbel Brumme-Bothe
Geschaeftsfuehrung: Prof. Dr. Achim Bachem (Vorsitzender), Dr. Ulrich Krafft (stellv.
Vorsitzender)
-----------------------------------------------------------------------------------------
-----------------------------------------------------------------------------------------

[Joerg Sonnenberger]

Post by Matthias Drochner

the case of an IPv4 route needs to be handled explicitely

The appended patch seems to dtrt. Not that clean yet, just
wanted to show what I mean.

I think this is correct. You said it -- not pretty, but needed. Note
that this was broken before, but we didn't bother to check the route.

Joerg

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