Bug 14427
Summary: | ipv6 forward cause strange route | ||
---|---|---|---|
Product: | Networking | Reporter: | Alexander Zubkov (zubkov318) |
Component: | IPV6 | Assignee: | Hideaki YOSHIFUJI (yoshfuji) |
Status: | RESOLVED CODE_FIX | ||
Severity: | normal | CC: | alan, hannes, higuita |
Priority: | P1 | ||
Hardware: | All | ||
OS: | Linux | ||
Kernel Version: | - | Subsystem: | |
Regression: | No | Bisected commit-id: |
Description
Alexander Zubkov
2009-10-17 10:41:58 UTC
(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). > 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
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at http://vger.kernel.org/majordomo-info.html
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
Reply-To: pekkas@netcore.fi 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. >> RFC 3627: Use of /127 Prefix Length Between Routers Considered Harmful
Consider reopening bug. Because it is not more INVALID.
Request for Comments: 6547
RFC 3627 to Historic Status
Request for Comments: 6164
Using 127-Bit IPv6 Prefixes on Inter-Router Links
Can you verify the problem still exists on 3.2 or later ? Sorry, missed last comment. Tested now on Arch linux 3.10.2-1 kernel. Looks like nothing is changed. Hmpf, I thought that had been fixed with https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=2bda8a0c8af5294b869da1efd2c2b9a562f50dcf. I'll have a look. Oh, shit! I have tested on other prefix length. /127 is OK now. Thank you! No problem! ;) I tested on net-next and really wondered why 3.10 should behave differently. |