* Re: [Bugme-new] [Bug 8754] New: Kernel addrconf modifies MTU of non-kernel routes
[not found] <bug-8754-10286@http.bugzilla.kernel.org/>
@ 2007-07-14 22:09 ` Andrew Morton
2007-07-15 9:29 ` Simon Arlott
0 siblings, 1 reply; 3+ messages in thread
From: Andrew Morton @ 2007-07-14 22:09 UTC (permalink / raw)
To: bugme-daemon@kernel-bugs.osdl.org; +Cc: netdev, bugzilla
On Sat, 14 Jul 2007 14:54:32 -0700 (PDT) bugme-daemon@bugzilla.kernel.org wrote:
> http://bugzilla.kernel.org/show_bug.cgi?id=8754
>
> Summary: Kernel addrconf modifies MTU of non-kernel routes
> Product: Networking
> Version: 2.5
> Platform: All
> OS/Version: Linux
> Tree: Mainline
> Status: NEW
> Severity: normal
> Priority: P1
> Component: IPV6
> AssignedTo: yoshfuji@linux-ipv6.org
> ReportedBy: bugzilla@fire.lp0.eu
>
>
> I have an MTU of 16110 set on eth0 on a network where the MTU is 1500 as set by
> RAs. One of the other hosts on the network has an MRU/MTU of 7200 so I have a
> specific route to it with this MTU.
>
> If I add the route early (i.e. on startup) before address autoconfiguration
> takes place, when the first RA is received the kernel changes the MTU on my
> route - this should not happen.
>
^ permalink raw reply [flat|nested] 3+ messages in thread* Re: [Bugme-new] [Bug 8754] New: Kernel addrconf modifies MTU of non-kernel routes
2007-07-14 22:09 ` [Bugme-new] [Bug 8754] New: Kernel addrconf modifies MTU of non-kernel routes Andrew Morton
@ 2007-07-15 9:29 ` Simon Arlott
2007-07-31 20:32 ` Simon Arlott
0 siblings, 1 reply; 3+ messages in thread
From: Simon Arlott @ 2007-07-15 9:29 UTC (permalink / raw)
To: netdev; +Cc: Andrew Morton, bugme-daemon@kernel-bugs.osdl.org
On 14/07/07 23:09, Andrew Morton wrote:
> On Sat, 14 Jul 2007 14:54:32 -0700 (PDT) bugme-daemon@bugzilla.kernel.org wrote:
>> http://bugzilla.kernel.org/show_bug.cgi?id=8754
>>
>> I have an MTU of 16110 set on eth0 on a network where the MTU is 1500 as set by
>> RAs. One of the other hosts on the network has an MRU/MTU of 7200 so I have a
>> specific route to it with this MTU.
>>
>> If I add the route early (i.e. on startup) before address autoconfiguration
>> takes place, when the first RA is received the kernel changes the MTU on my
>> route - this should not happen.
This also happens whenever I change the MTU on eth0 - it will alter the
MTU on routes *I* have added too. While this is valid behaviour for a
new MTU that is too low for the route it is not for an MTU above the route.
Changing the MTU also allows the "next RA with MTU set changes
non-kernel routes too" problem to occur again.
--
Simon Arlott
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [Bugme-new] [Bug 8754] New: Kernel addrconf modifies MTU of non-kernel routes
2007-07-15 9:29 ` Simon Arlott
@ 2007-07-31 20:32 ` Simon Arlott
0 siblings, 0 replies; 3+ messages in thread
From: Simon Arlott @ 2007-07-31 20:32 UTC (permalink / raw)
To: netdev; +Cc: bugme-daemon
On 15/07/07 10:29, Simon Arlott wrote:
> On 14/07/07 23:09, Andrew Morton wrote:
>> On Sat, 14 Jul 2007 14:54:32 -0700 (PDT) bugme-daemon@bugzilla.kernel.org wrote:
>>> http://bugzilla.kernel.org/show_bug.cgi?id=8754
>>>
>>> I have an MTU of 16110 set on eth0 on a network where the MTU is 1500 as set by
>>> RAs. One of the other hosts on the network has an MRU/MTU of 7200 so I have a
>>> specific route to it with this MTU.
>>>
>>> If I add the route early (i.e. on startup) before address autoconfiguration
>>> takes place, when the first RA is received the kernel changes the MTU on my
>>> route - this should not happen.
>
> This also happens whenever I change the MTU on eth0 - it will alter the
> MTU on routes *I* have added too. While this is valid behaviour for a
> new MTU that is too low for the route it is not for an MTU above the route.
>
> Changing the MTU also allows the "next RA with MTU set changes
> non-kernel routes too" problem to occur again.
The problem seems to be that because the IPv6 code maintains its own MTU for
each interface, which is set from RAs (router advertisements) and when the
interface MTU is set (it's also improperly modifiable via sysctl when it
shouldn't be, but that's another bug), it uses that to limit the MTU of every
route.
I propose that it should use the real interface MTU as the limit for non-kernel
routes and the RA MTU for kernel routes.
Since IPv6 routes (appear to) always have an MTU (IPv4 routes don't and hence
inherit from the interface) this would have the side effect that a user-added
route's automatically set MTU would not be lowered by the RA MTU.
New user IPv6 routes without an explicit MTU should not have one set and use
the RA MTU automatically.
Is this ok? I'll send a patch to do this some time this week when I get around
to it.
--
Simon Arlott
^ permalink raw reply [flat|nested] 3+ messages in thread
end of thread, other threads:[~2007-07-31 20:32 UTC | newest]
Thread overview: 3+ messages (download: mbox.gz follow: Atom feed
-- links below jump to the message on this page --
[not found] <bug-8754-10286@http.bugzilla.kernel.org/>
2007-07-14 22:09 ` [Bugme-new] [Bug 8754] New: Kernel addrconf modifies MTU of non-kernel routes Andrew Morton
2007-07-15 9:29 ` Simon Arlott
2007-07-31 20:32 ` Simon Arlott
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).