Hello, I'm upgrading my machines from kernel 4.14 to the 5.4 series, and noticed quite a significant behavior change, so I was wondering if this was intentional or a side effect of something, or a bug. It already broke my network connectivity for a while and required troubleshooting, to figure out that a certain script that I had, used to set up all routes before, and only then putting the interface up. On 4.14.170 this works: # ip link add dummy100 type dummy # ip route add fd99::/128 dev dummy100 # ip -6 route | grep dummy fd99:: dev dummy100 metric 1024 linkdown pref medium # On 5.4.19 however: # ip link add dummy100 type dummy # ip route add fd99::/128 dev dummy100 RTNETLINK answers: Network is down # ip -6 route | grep dummy # Sorry for not narrowing it down more precisely between 4.14 and 5.4, but I'm sure for the right people this will be easily either an "oh shit" or "yeah, that", even without any more precise version information :)
Linux networking does not use bugzilla, so this bug was ignored. See this change that was done to make IPv6 behave like IPv4 commit 955ec4cb3b54c7c389a9f830be7d3ae2056b9212 Author: David Ahern <dsahern@gmail.com> Date: Wed Jan 24 19:45:29 2018 -0800 net/ipv6: Do not allow route add with a device that is down IPv6 allows routes to be installed when the device is not up (admin up). Worse, it does not mark it as LINKDOWN. IPv4 does not allow it and really there is no reason for IPv6 to allow it, so check the flags and deny if device is admin down. Signed-off-by: David Ahern <dsahern@gmail.com> Reviewed-by: Ido Schimmel <idosch@mellanox.com> Reviewed-by: Roopa Prabhu <roopa@cumulusnetworks.com> Signed-off-by: David S. Miller <davem@davemloft.net>