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[ Upstream commitf5b51fe804] When a netdevice is unregistered, we flush the relevant exception via rt6_sync_down_dev() -> fib6_ifdown() -> fib6_del() -> fib6_del_route(). Finally, we end-up calling rt6_remove_exception(), where we release the relevant dst, while we keep the references to the related fib6_info and dev. Such references should be released later when the dst will be destroyed. There are a number of caches that can keep the exception around for an unlimited amount of time - namely dst_cache, possibly even socket cache. As a result device registration may hang, as demonstrated by this script: ip netns add cl ip netns add rt ip netns add srv ip netns exec rt sysctl -w net.ipv6.conf.all.forwarding=1 ip link add name cl_veth type veth peer name cl_rt_veth ip link set dev cl_veth netns cl ip -n cl link set dev cl_veth up ip -n cl addr add dev cl_veth 2001::2/64 ip -n cl route add default via 2001::1 ip -n cl link add tunv6 type ip6tnl mode ip6ip6 local 2001::2 remote 2002::1 hoplimit 64 dev cl_veth ip -n cl link set tunv6 up ip -n cl addr add 2013::2/64 dev tunv6 ip link set dev cl_rt_veth netns rt ip -n rt link set dev cl_rt_veth up ip -n rt addr add dev cl_rt_veth 2001::1/64 ip link add name rt_srv_veth type veth peer name srv_veth ip link set dev srv_veth netns srv ip -n srv link set dev srv_veth up ip -n srv addr add dev srv_veth 2002::1/64 ip -n srv route add default via 2002::2 ip -n srv link add tunv6 type ip6tnl mode ip6ip6 local 2002::1 remote 2001::2 hoplimit 64 dev srv_veth ip -n srv link set tunv6 up ip -n srv addr add 2013::1/64 dev tunv6 ip link set dev rt_srv_veth netns rt ip -n rt link set dev rt_srv_veth up ip -n rt addr add dev rt_srv_veth 2002::2/64 ip netns exec srv netserver & sleep 0.1 ip netns exec cl ping6 -c 4 2013::1 ip netns exec cl netperf -H 2013::1 -t TCP_STREAM -l 3 & sleep 1 ip -n rt link set dev rt_srv_veth mtu 1400 wait %2 ip -n cl link del cl_veth This commit addresses the issue purging all the references held by the exception at time, as we currently do for e.g. ipv6 pcpu dst entries. v1 -> v2: - re-order the code to avoid accessing dst and net after dst_dev_put() Fixes:93531c6743("net/ipv6: separate handling of FIB entries from dst based routes") Signed-off-by: Paolo Abeni <pabeni@redhat.com> Reviewed-by: David Ahern <dsahern@gmail.com> Signed-off-by: David S. Miller <davem@davemloft.net> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
See Documentation/00-INDEX for a list of what is contained in each file.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.