kernel/net/ipv6/anycast.c, branch 0x221E-v0.0.1-v6.19

ipv6: start using dst_dev_rcu()

2025-08-30T02:36:32Z

Refactor icmpv6_xrlim_allow() and ip6_dst_hoplimit() so that we acquire rcu_read_lock() a bit longer to be able to use dst_dev_rcu() instead of dst_dev(). __ip6_rt_update_pmtu() and rt6_do_redirect can directly use dst_dev_rcu() in sections already holding rcu_read_lock(). Small changes to use dst_dev_net_rcu() in ip6_default_advmss(), ipv6_sock_ac_join(), ip6_mc_find_dev() and ndisc_send_skb(). Fixes: 4a6ce2b6f2ec ("net: introduce a new function dst_dev_put()") Signed-off-by: Eric Dumazet Reviewed-by: David Ahern Link: https://patch.msgid.link/20250828195823.3958522-3-edumazet@google.com Signed-off-by: Jakub Kicinski

dev: Pass netdevice_tracker to dev_get_by_flags_rcu().

2025-07-15T00:11:14Z

This is a follow-up for commit eb1ac9ff6c4a5 ("ipv6: anycast: Don't hold RTNL for IPV6_JOIN_ANYCAST."). We should not add a new device lookup API without netdevice_tracker. Let's pass netdevice_tracker to dev_get_by_flags_rcu() and rename it with netdev_ prefix to match other newer APIs. Note that we always use GFP_ATOMIC for netdev_hold() as it's expected to be called under RCU. Suggested-by: Jakub Kicinski Link: https://lore.kernel.org/netdev/20250708184053.102109f6@kernel.org/ Signed-off-by: Kuniyuki Iwashima Reviewed-by: Simon Horman Link: https://patch.msgid.link/20250711051120.2866855-1-kuniyu@google.com Signed-off-by: Jakub Kicinski

ipv6: anycast: Don't hold RTNL for IPV6_JOIN_ANYCAST.

2025-07-09T01:32:39Z

inet6_sk(sk)->ipv6_ac_list is protected by lock_sock(). In ipv6_sock_ac_join(), only __dev_get_by_index(), __dev_get_by_flags(), and __in6_dev_get() require RTNL. __dev_get_by_flags() is only used by ipv6_sock_ac_join() and can be converted to RCU version. Let's replace RCU version helper and drop RTNL from IPV6_JOIN_ANYCAST. setsockopt_needs_rtnl() will be removed in the next patch. Signed-off-by: Kuniyuki Iwashima Reviewed-by: Eric Dumazet Link: https://patch.msgid.link/20250702230210.3115355-15-kuni1840@gmail.com Signed-off-by: Jakub Kicinski

ipv6: anycast: Unify two error paths in ipv6_sock_ac_join().

2025-07-09T01:32:39Z

The next patch will replace __dev_get_by_index() and __dev_get_by_flags() to RCU + refcount version. Then, we will need to call dev_put() in some error paths. Let's unify two error paths to make the next patch cleaner. Note that we add READ_ONCE() for net->ipv6.devconf_all->forwarding and idev->conf.forwarding as we will drop RTNL that protects them. Signed-off-by: Kuniyuki Iwashima Reviewed-by: Eric Dumazet Link: https://patch.msgid.link/20250702230210.3115355-14-kuni1840@gmail.com Signed-off-by: Jakub Kicinski

ipv6: anycast: Don't hold RTNL for IPV6_LEAVE_ANYCAST and IPV6_ADDRFORM.

2025-07-09T01:32:39Z

inet6_sk(sk)->ipv6_ac_list is protected by lock_sock(). In ipv6_sock_ac_drop() and ipv6_sock_ac_close(), only __dev_get_by_index() and __in6_dev_get() requrie RTNL. Let's replace them with dev_get_by_index() and in6_dev_get() and drop RTNL from IPV6_LEAVE_ANYCAST and IPV6_ADDRFORM. Signed-off-by: Kuniyuki Iwashima Reviewed-by: Eric Dumazet Link: https://patch.msgid.link/20250702230210.3115355-13-kuni1840@gmail.com Signed-off-by: Jakub Kicinski

ipv6: anycast: Don't use rtnl_dereference().

2025-07-09T01:32:39Z

inet6_dev->ac_list is protected by inet6_dev->lock, so rtnl_dereference() is a bit rough annotation. As done in mcast.c, we can use ac_dereference() that checks if inet6_dev->lock is held. Let's replace rtnl_dereference() with a new helper ac_dereference(). Note that now addrconf_join_solict() / addrconf_leave_solict() in __ipv6_dev_ac_inc() / __ipv6_dev_ac_dec() does not need RTNL, so we can remove ASSERT_RTNL() there. Signed-off-by: Kuniyuki Iwashima Reviewed-by: Eric Dumazet Link: https://patch.msgid.link/20250702230210.3115355-12-kuni1840@gmail.com Signed-off-by: Jakub Kicinski

netlink: add IPv6 anycast join/leave notifications

2025-01-09T11:54:45Z

This change introduces a mechanism for notifying userspace applications about changes to IPv6 anycast addresses via netlink. It includes: * Addition and deletion of IPv6 anycast addresses are reported using RTM_NEWANYCAST and RTM_DELANYCAST. * A new netlink group (RTNLGRP_IPV6_ACADDR) for subscribing to these notifications. This enables user space applications(e.g. ip monitor) to efficiently track anycast addresses through netlink messages, improving metrics collection and system monitoring. It also unlocks the potential for advanced anycast management in user space, such as hardware offload control and fine grained network control. Cc: Maciej Żenczykowski Cc: Lorenzo Colitti Signed-off-by: Yuyang Huang Reviewed-by: David Ahern Link: https://patch.msgid.link/20250107114355.1766086-1-yuyanghuang@google.com Signed-off-by: Paolo Abeni

ipv6: switch inet6_acaddr_hash() to less predictable hash

2024-10-10T02:33:57Z

commit 2384d02520ff ("net/ipv6: Add anycast addresses to a global hashtable") added inet6_acaddr_hash(), using ipv6_addr_hash() and net_hash_mix() to get hash spreading for typical users. However ipv6_addr_hash() is highly predictable and a malicious user could abuse a specific hash bucket. Switch to __ipv6_addr_jhash(). We could use a dedicated secret, or reuse net_hash_mix() as I did in this patch. Signed-off-by: Eric Dumazet Reviewed-by: David Ahern Reviewed-by: Kuniyuki Iwashima Link: https://patch.msgid.link/20241008121307.800040-1-edumazet@google.com Signed-off-by: Jakub Kicinski

ipv6: anycast: use call_rcu_hurry() in aca_put()

2024-05-01T10:46:21Z

This is a followup of commit b5327b9a300e ("ipv6: use call_rcu_hurry() in fib6_info_release()"). I had another pmtu.sh failure, and found another lazy call_rcu() causing this failure. aca_free_rcu() calls fib6_info_release() which releases devices references. We must not delay it too much or risk unregister_netdevice/ref_tracker traces because references to netdev are not released in time. This should speedup device/netns dismantles when CONFIG_RCU_LAZY=y Signed-off-by: Eric Dumazet Reviewed-by: David Ahern Signed-off-by: David S. Miller

ipv6: anycast: complete RCU handling of struct ifacaddr6

2024-02-27T02:40:34Z

struct ifacaddr6 are already freed after RCU grace period. Add __rcu qualifier to aca_next pointer, and idev->ac_list Add relevant rcu_assign_pointer() and dereference accessors. ipv6_chk_acast_dev() no longer needs to acquire idev->lock. /proc/net/anycast6 is now purely RCU protected, it no longer acquires idev->lock. Similarly in6_dump_addrs() can use RCU protection to iterate through anycast addresses. It was relying on a mixture of RCU and RTNL but next patches will get rid of RTNL there. Signed-off-by: Eric Dumazet Reviewed-by: Jiri Pirko Link: https://lore.kernel.org/r/20240223201054.220534-1-edumazet@google.com Signed-off-by: Jakub Kicinski