Let's register inet6_rtm_deladdr() with RTNL_FLAG_DOIT_PERNET and
hold rtnl_net_lock() before inet6_addr_del().

Now that inet6_addr_del() is always called under per-netns RTNL.

Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Link: https://patch.msgid.link/20250115080608.28127-12-kuniyu@amazon.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

Let's register inet6_rtm_newaddr() with RTNL_FLAG_DOIT_PERNET
and hold rtnl_net_lock() before __dev_get_by_index().

Now that inet6_addr_add() and inet6_addr_modify() are always
called under per-netns RTNL.

Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Link: https://patch.msgid.link/20250115080608.28127-11-kuniyu@amazon.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

inet6_addr_add() and inet6_addr_modify() have the same code to validate
IPv6 lifetime that is done under RTNL.

Let's factorise it out to inet6_rtm_newaddr() so that we can validate
the lifetime without RTNL later.

Note that inet6_addr_add() is called from addrconf_add_ifaddr(), but the
lifetime is INFINITY_LIFE_TIME in the path, so expires and flags are 0.

Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Link: https://patch.msgid.link/20250115080608.28127-10-kuniyu@amazon.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

We will convert inet6_rtm_newaddr() to per-netns RTNL.

Except for IFA_F_OPTIMISTIC, cfg.ifa_flags can be set before
__dev_get_by_index().

Let's move ifa_flags setup before __dev_get_by_index() so that
we can set ifa_flags without RTNL.

Also, now it's moved before tb[IFA_CACHEINFO] in preparing for
the next patch.

Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Link: https://patch.msgid.link/20250115080608.28127-9-kuniyu@amazon.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

inet6_addr_add() is called from inet6_rtm_newaddr() and
addrconf_add_ifaddr().

inet6_addr_add() looks up dev by __dev_get_by_index(), but
it's already done in inet6_rtm_newaddr().

Let's move the 2nd lookup to addrconf_add_ifaddr() and pass
dev to inet6_addr_add().

Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Link: https://patch.msgid.link/20250115080608.28127-8-kuniyu@amazon.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

These functions are called from inet6_ioctl() with a socket's netns
and hold RTNL.

  * SIOCSIFADDR    : addrconf_add_ifaddr()
  * SIOCDIFADDR    : addrconf_del_ifaddr()
  * SIOCSIFDSTADDR : addrconf_set_dstaddr()

Let's use rtnl_net_lock().

Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Link: https://patch.msgid.link/20250115080608.28127-7-kuniyu@amazon.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

addrconf_init() holds RTNL for blackhole_netdev, which is the global
device in init_net.

addrconf_cleanup() holds RTNL to clean up devices in init_net too.

Let's use rtnl_net_lock(&init_net) there.

Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Link: https://patch.msgid.link/20250115080608.28127-6-kuniyu@amazon.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

addrconf_dad_work() is per-address work and holds RTNL internally.

We can fetch netns as dev_net(ifp->idev->dev).

Let's use rtnl_net_lock().

Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Link: https://patch.msgid.link/20250115080608.28127-5-kuniyu@amazon.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

addrconf_verify_work() is per-netns work to call addrconf_verify_rtnl()
under RTNL.

Let's use rtnl_net_lock().

Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Link: https://patch.msgid.link/20250115080608.28127-4-kuniyu@amazon.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

net.ipv6.conf.${DEV}.XXX sysctl are changed under RTNL:

  * forwarding
  * ignore_routes_with_linkdown
  * disable_ipv6
  * proxy_ndp
  * addr_gen_mode
  * stable_secret
  * disable_policy

Let's use rtnl_net_lock() there.

Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Link: https://patch.msgid.link/20250115080608.28127-3-kuniyu@amazon.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>