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Basically, removing an IPv6 route does not require RTNL because the IPv6 routing tables are protected by per table lock. inet6_rtm_delroute() calls nexthop_find_by_id() to check if the nexthop specified by RTA_NH_ID exists. nexthop uses rbtree and the top-down walk can be safely performed under RCU. ip6_route_del() already relies on RCU and the table lock, but we need to extend the RCU critical section a bit more to cover __ip6_del_rt(). For example, nexthop_for_each_fib6_nh() and inet6_rt_notify() needs RCU. Let's call nexthop_find_by_id() and __ip6_del_rt() under RCU and get rid of RTNL from inet6_rtm_delroute() and SIOCDELRT. Even if the nexthop is removed after rcu_read_unlock() in inet6_rtm_delroute(), __remove_nexthop_fib() cleans up the routes tied to the nexthop, and ip6_route_del() returns -ESRCH. So the request was at least valid as of nexthop_find_by_id(), and it's just a matter of timing. Note that we need to pass false to lwtunnel_valid_encap_type_attr(). The following patches also use the newroute bool. Note also that fib6_get_table() does not require RCU because once allocated fib6_table is not freed until netns dismantle. I will post a follow-up series to convert such callers to RCU-lockless version. [0] Link: https://lore.kernel.org/netdev/20250417174557.65721-1-kuniyu@amazon.com/ #[0] Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com> Link: https://patch.msgid.link/20250418000443.43734-3-kuniyu@amazon.com Signed-off-by: Paolo Abeni <pabeni@redhat.com>
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 reStructuredText markup notation.
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.