* 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 > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html ^ 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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