Bug 112751
| Summary: | learns IPv6 default route and IP address from its own announcement on wrong interface | ||
|---|---|---|---|
| Product: | Networking | Reporter: | Marc Haber (mh+kernel-bugzilla) |
| Component: | IPV6 | Assignee: | Hideaki YOSHIFUJI (yoshfuji) |
| Status: | RESOLVED INVALID | ||
| Severity: | normal | CC: | hannes |
| Priority: | P1 | ||
| Hardware: | x86-64 | ||
| OS: | Linux | ||
| Kernel Version: | 4.4.2 | Subsystem: | |
| Regression: | Yes | Bisected commit-id: | |
Did I understood correctly, eth0 is part of br0? Hi Hannes, no, there is no connection between eth0 and br0. VMs connect to br0, the host routes between eth0 and br0.
[2/502]mh@fan:~$ sudo brctl show
bridge name bridge id STP enabled interfaces
br0 8000.c6f498dc5e21 no dummy0
vnet0
vnet1
vnet2
[3/502]mh@fan:~$
Sorry for being unclear.
Greetings
Marc
The issue seems to be that /proc/sys/net/ipv6/conf/eth0/accept_ra_from_local is 1. This is the case because the default gateway visible on eth0 has the link local address fe80::1 while the local box has also fe80::1 on br0 to be default gateway to its VMs. This is a bug in accept_ra_from_local. The kernel should never set a default route on a different interface than the one that an RA was received. The RA comes in on br0, which has accept_ra_from_local 0. Hence, the RA should be ignored. If /proc/sys/net/ipv6/conf/br0/accept_ra_from_local were 1, the RA should be accepted and the route should be configured on br0, not on eth0. This is not a kernel issue. systemd 229 decided to handle incoming router announcements itself. And of course, the NIH implementation is flawed. This issue can be closed. I apologize. Should I have done things wrong when closing this, its caused by my unfamiliarity with bugzilla. |
Hi, I have a box with an eth0 interface pointing to the Internet. There is a router which sends out router announcements. These are properly learned. On my boxes' br0, there is a radvd advertising the box itself as a router to the internet, for VMs running on the machine. accept_ra on eth0 is set to 2, accept_ra on br0 is set to 1. When the radvd on br0 sends out its announcement, the kernel on the local box sees the announcement and adds a default route, pointing to br0's link local IPv6 address, but with the interface set to eth0. It also adds an IP address for the network visible on br0 to eth0. This makes IPv6 communication kind of hard. [1/501]mh@fan:~$ ip addr 1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00 inet 127.0.0.1/8 scope host lo valid_lft forever preferred_lft forever inet6 ::1/128 scope host valid_lft forever preferred_lft forever 2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP group default qlen 1000 link/ether 54:04:a6:82:21:00 brd ff:ff:ff:ff:ff:ff inet 192.168.182.250/32 brd 192.168.182.250 scope global eth0 valid_lft forever preferred_lft forever inet 192.168.182.29/24 brd 192.168.182.255 scope global dynamic eth0 valid_lft 13861sec preferred_lft 13861sec inet6 2a01:238:4071:328d:5604:a6ff:fe82:2100/64 scope global mngtmpaddr noprefixroute dynamic valid_lft 86101sec preferred_lft 14101sec inet6 2a01:238:4071:3282:5604:a6ff:fe82:2100/64 scope global mngtmpaddr noprefixroute dynamic valid_lft 86086sec preferred_lft 14086sec inet6 2a01:238:4071:3282::1d:250/128 scope global valid_lft forever preferred_lft forever inet6 2a01:238:4071:3282::1d:100/64 scope global valid_lft forever preferred_lft forever inet6 fe80::5604:a6ff:fe82:2100/64 scope link valid_lft forever preferred_lft forever 3: br0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP group default qlen 1000 link/ether c6:f4:98:dc:5e:21 brd ff:ff:ff:ff:ff:ff inet 192.168.29.254/24 brd 192.168.29.255 scope global br0 valid_lft forever preferred_lft forever inet6 2a01:238:4071:328d::1d:153/64 scope global valid_lft forever preferred_lft forever inet6 2a01:238:4071:328d::1d:100/64 scope global valid_lft forever preferred_lft forever inet6 fec0:0:0:ffff::3/128 scope site valid_lft forever preferred_lft forever inet6 fec0:0:0:ffff::2/128 scope site valid_lft forever preferred_lft forever inet6 fec0:0:0:ffff::1/128 scope site valid_lft forever preferred_lft forever inet6 fe80::c4f4:98ff:fedc:5e21/64 scope link valid_lft forever preferred_lft forever 4: dummy0: <BROADCAST,NOARP,UP,LOWER_UP> mtu 1500 qdisc noqueue master br0 state UNKNOWN group default qlen 1000 link/ether 72:6f:a6:b6:30:e2 brd ff:ff:ff:ff:ff:ff inet6 fe80::706f:a6ff:feb6:30e2/64 scope link valid_lft forever preferred_lft forever [2/502]mh@fan:~$ The network on eth0 is 2a01:238:4071:3282::/64, the one on br0 is 2a01:238:4071:328d::/64 [6/506]mh@fan:~$ sudo tcpdump -i br0 -npe icmp6 21:01:31.358957 c6:f4:98:dc:5e:21 > 33:33:00:00:00:01, ethertype IPv6 (0x86dd), length 134: fe80::c4f4:98ff:fedc:5e21 > ff02::1: ICMP6, router advertisement, length 80 [5/505]mh@fan:~$ while sleep 2; do date; ip -6 r show default; done Sa 20. Feb 21:01:29 CET 2016 default via fe80::1 dev eth0 proto ra metric 1024 pref medium Sa 20. Feb 21:01:31 CET 2016 default via fe80::1 dev eth0 proto ra metric 1024 pref medium default via fe80::c4f4:98ff:fedc:5e21 dev eth0 proto ra metric 1024 pref medium I guess this broke with kernel 4.4. Greetings Marc