* Re: [Bugme-new] [Bug 14427] New: ipv6 forward cause strange route
[not found] <bug-14427-10286@http.bugzilla.kernel.org/>
@ 2009-11-03 6:32 ` Andrew Morton
2009-11-03 11:06 ` YOSHIFUJI Hideaki
0 siblings, 1 reply; 4+ messages in thread
From: Andrew Morton @ 2009-11-03 6:32 UTC (permalink / raw)
To: netdev; +Cc: bugzilla-daemon, bugme-daemon, green
(switched to email. Please respond via emailed reply-to-all, not via the
bugzilla web interface).
On Sat, 17 Oct 2009 10:42:01 GMT bugzilla-daemon@bugzilla.kernel.org wrote:
> http://bugzilla.kernel.org/show_bug.cgi?id=14427
>
> Summary: ipv6 forward cause strange route
> 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: green@msu.ru
> Regression: No
>
>
> When enabling forwarding for IPv6 on interface, in the routing table local
> appears new route. It like route to local ip but with all host bits set to 0.
> Example:
> --------------------------------------------------
> # cat /proc/sys/net/ipv6/conf/eth0/forwarding
> 0
> # ip -6 addr add 2001:db8:1:1::5/64 dev eth0
> # ip -6 route show table local
> ...
> local 2001:db8:1:1::5 via :: dev lo proto none metric 0 mtu 16436 advmss
> 16376 hoplimit 4294967295
> ...
> # echo 1 > /proc/sys/net/ipv6/conf/eth0/forwarding
> # ip -6 route show table local
> ...
> local 2001:db8:1:1:: via :: dev lo proto none metric 0 mtu 16436 advmss
> 16376 hoplimit 4294967295
> local 2001:db8:1:1::5 via :: dev lo proto none metric 0 mtu 16436 advmss
> 16376 hoplimit 4294967295
> ...
> --------------------------------------------------
> After enabling forwarding, route "2001:db8:1:1:: via :: dev lo" is added. No
> matter, forwarding is enabled before or after adding of address, this route is
> "on" with forwarding and "off" without it.
> Such behavior causes problems with /127 network masks. For example:
> --------------------------------------------------
> # echo 1 > /proc/sys/net/ipv6/conf/eth0/forwarding
> # ip -6 addr add 2001:db8:1:1::5/127 dev eth0
> # ip -6 route add default via 2001:db8:1:1::4
> RTNETLINK answers: Invalid argument
> --------------------------------------------------
> But if we disable forwarding (and strange route) when adding needed route, we
> will succeed.
> --------------------------------------------------
> # echo 0 > /proc/sys/net/ipv6/conf/eth0/forwarding
> # ip -6 route add default via 2001:db8:1:1::4
> # echo 1 > /proc/sys/net/ipv6/conf/eth0/forwarding
> --------------------------------------------------
> Default route remains in the table after enabling forwarding and it is doing in
> work. But in this case we still can not access 2001:db8:1:1::4, because it is
> routed to loopback:
> --------------------------------------------------
> # ping6 -c 1 2001:db8:1:1::4
> PING 2001:db8:1:1::4(2001:db8:1:1::4) 56 data bytes
> 64 bytes from 2001:db8:1:1::5: icmp_seq=1 ttl=64 time=0.114 ms
> --------------------------------------------------
> We get reply from self interface.
>
> This was tested on x86 and x86_64 with 2.6.30 kernel and some previous versions
> on ArchLinux (2.6.30 x86 and x86_64), Ubuntu (2.6.28-15-generic x86_64) and
> gentoo (2.6.30-gentoo-r5 x86_64).
>
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [Bugme-new] [Bug 14427] New: ipv6 forward cause strange route
2009-11-03 6:32 ` [Bugme-new] [Bug 14427] New: ipv6 forward cause strange route Andrew Morton
@ 2009-11-03 11:06 ` YOSHIFUJI Hideaki
2009-11-03 11:19 ` YOSHIFUJI Hideaki
0 siblings, 1 reply; 4+ messages in thread
From: YOSHIFUJI Hideaki @ 2009-11-03 11:06 UTC (permalink / raw)
To: Andrew Morton, green
Cc: netdev, bugzilla-daemon, bugme-daemon, yoshfuji, Pekka Savola, davem
Hello.
This is not a bug but a feature of IPv6 called "subnet anycast
address." The address is automatically assigned on routers.
References:
RFC 2526: Reserved IPv6 Subnet Anycast Addresses
RFC 3627: Use of /127 Prefix Length Between Routers Considered Harmful
--yoshfuji
Andrew Morton wrote:
> (switched to email. Please respond via emailed reply-to-all, not via the
> bugzilla web interface).
>
> On Sat, 17 Oct 2009 10:42:01 GMT bugzilla-daemon@bugzilla.kernel.org wrote:
>
>> http://bugzilla.kernel.org/show_bug.cgi?id=14427
>>
>> Summary: ipv6 forward cause strange route
>> 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: green@msu.ru
>> Regression: No
>>
>>
>> When enabling forwarding for IPv6 on interface, in the routing table local
>> appears new route. It like route to local ip but with all host bits set to 0.
>> Example:
>> --------------------------------------------------
>> # cat /proc/sys/net/ipv6/conf/eth0/forwarding
>> 0
>> # ip -6 addr add 2001:db8:1:1::5/64 dev eth0
>> # ip -6 route show table local
>> ...
>> local 2001:db8:1:1::5 via :: dev lo proto none metric 0 mtu 16436 advmss
>> 16376 hoplimit 4294967295
>> ...
>> # echo 1 > /proc/sys/net/ipv6/conf/eth0/forwarding
>> # ip -6 route show table local
>> ...
>> local 2001:db8:1:1:: via :: dev lo proto none metric 0 mtu 16436 advmss
>> 16376 hoplimit 4294967295
>> local 2001:db8:1:1::5 via :: dev lo proto none metric 0 mtu 16436 advmss
>> 16376 hoplimit 4294967295
>> ...
>> --------------------------------------------------
>> After enabling forwarding, route "2001:db8:1:1:: via :: dev lo" is added. No
>> matter, forwarding is enabled before or after adding of address, this route is
>> "on" with forwarding and "off" without it.
>> Such behavior causes problems with /127 network masks. For example:
>> --------------------------------------------------
>> # echo 1 > /proc/sys/net/ipv6/conf/eth0/forwarding
>> # ip -6 addr add 2001:db8:1:1::5/127 dev eth0
>> # ip -6 route add default via 2001:db8:1:1::4
>> RTNETLINK answers: Invalid argument
>> --------------------------------------------------
>> But if we disable forwarding (and strange route) when adding needed route, we
>> will succeed.
>> --------------------------------------------------
>> # echo 0 > /proc/sys/net/ipv6/conf/eth0/forwarding
>> # ip -6 route add default via 2001:db8:1:1::4
>> # echo 1 > /proc/sys/net/ipv6/conf/eth0/forwarding
>> --------------------------------------------------
>> Default route remains in the table after enabling forwarding and it is doing in
>> work. But in this case we still can not access 2001:db8:1:1::4, because it is
>> routed to loopback:
>> --------------------------------------------------
>> # ping6 -c 1 2001:db8:1:1::4
>> PING 2001:db8:1:1::4(2001:db8:1:1::4) 56 data bytes
>> 64 bytes from 2001:db8:1:1::5: icmp_seq=1 ttl=64 time=0.114 ms
>> --------------------------------------------------
>> We get reply from self interface.
>>
>> This was tested on x86 and x86_64 with 2.6.30 kernel and some previous versions
>> on ArchLinux (2.6.30 x86 and x86_64), Ubuntu (2.6.28-15-generic x86_64) and
>> gentoo (2.6.30-gentoo-r5 x86_64).
>>
>
> --
> To unsubscribe from this list: send the line "unsubscribe netdev" in
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^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [Bugme-new] [Bug 14427] New: ipv6 forward cause strange route
2009-11-03 11:06 ` YOSHIFUJI Hideaki
@ 2009-11-03 11:19 ` YOSHIFUJI Hideaki
2009-11-04 8:01 ` Pekka Savola
0 siblings, 1 reply; 4+ messages in thread
From: YOSHIFUJI Hideaki @ 2009-11-03 11:19 UTC (permalink / raw)
To: Andrew Morton, green
Cc: netdev, bugzilla-daemon, bugme-daemon, Pekka Savola, davem
I wrote:
> This is not a bug but a feature of IPv6 called "subnet anycast
> address." The address is automatically assigned on routers.
>
> References:
> RFC 2526: Reserved IPv6 Subnet Anycast Addresses
> RFC 3627: Use of /127 Prefix Length Between Routers Considered Harmful
I should say "Subnet-router anycast address" and
RFC3513: Internet Protocol Version 6 (IPv6) Addressing
Architecture".
Sorry for confusion.
--yoshfuji
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [Bugme-new] [Bug 14427] New: ipv6 forward cause strange route
2009-11-03 11:19 ` YOSHIFUJI Hideaki
@ 2009-11-04 8:01 ` Pekka Savola
0 siblings, 0 replies; 4+ messages in thread
From: Pekka Savola @ 2009-11-04 8:01 UTC (permalink / raw)
To: YOSHIFUJI Hideaki
Cc: Andrew Morton, green, netdev, bugzilla-daemon, bugme-daemon, davem
On Tue, 3 Nov 2009, YOSHIFUJI Hideaki wrote:
>> RFC 2526: Reserved IPv6 Subnet Anycast Addresses
>> RFC 3627: Use of /127 Prefix Length Between Routers Considered Harmful
>
> I should say "Subnet-router anycast address" and
> RFC3513: Internet Protocol Version 6 (IPv6) Addressing
> Architecture".
FWIW, please note that commercial vendors haven't implemented this
very extensively, and there's also some recent activity arguing this
is not very useful:
http://tools.ietf.org/html/draft-kohno-ipv6-prefixlen-p2p-00
We'll likely get better idea how folks react to this during the next
week's IETF.
--
Pekka Savola "You each name yourselves king, yet the
Netcore Oy kingdom bleeds."
Systems. Networks. Security. -- George R.R. Martin: A Clash of Kings
^ permalink raw reply [flat|nested] 4+ messages in thread
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[not found] <bug-14427-10286@http.bugzilla.kernel.org/>
2009-11-03 6:32 ` [Bugme-new] [Bug 14427] New: ipv6 forward cause strange route Andrew Morton
2009-11-03 11:06 ` YOSHIFUJI Hideaki
2009-11-03 11:19 ` YOSHIFUJI Hideaki
2009-11-04 8:01 ` Pekka Savola
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