IPv6 can't be a module anymore, we no longer need to export:
- neigh_changeaddr
- neigh_carrier_down
- neigh_ifdown
- neigh_connected_output
- neigh_direct_output
- neigh_table_init
- neigh_table_clear
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: David Ahern <dsahern@kernel.org>
Link: https://patch.msgid.link/20260605073426.2922242-1-edumazet@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
neigh_xmit always releases the skb, except when no neighbour table is
found. But even the first added user of neigh_xmit (mpls) relied on
neigh_xmit to release the skb (or queue it for tx).
sashiko reported:
If neigh_xmit() is called with an uninitialized neighbor table (for
example, NEIGH_ND_TABLE when IPv6 is disabled), it returns -EAFNOSUPPORT
and bypasses its internal out_kfree_skb error path. Because the return
value of neigh_xmit() is ignored here, does this leak the SKB?
Assume full ownership and remove the last code path that doesn't
xmit or free skb.
Fixes: 4fd3d7d9e8 ("neigh: Add helper function neigh_xmit")
Signed-off-by: Florian Westphal <fw@strlen.de>
Reviewed-by: Kuniyuki Iwashima <kuniyu@google.com>
Reviewed-by: Ido Schimmel <idosch@nvidia.com>
Link: https://patch.msgid.link/20260424145843.74055-1-fw@strlen.de
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
As IPv6 is built-in only, the macro is always evaluating to an empty
one. Remove it completely from the code.
Signed-off-by: Fernando Fernandez Mancera <fmancera@suse.de>
Link: https://patch.msgid.link/20260325120928.15848-3-fmancera@suse.de
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Prior to commit dc2a27e524 ("neighbour: Update pneigh_entry in
pneigh_create()."), a pneigh's protocol was updated only when the
value of the NDA_PROTOCOL attribute was non-0. While moving the code,
that check was removed. This is a small change of user-visible
behavior, and inconsistent with the (non-proxy) neighbour behavior.
Fixes: dc2a27e524 ("neighbour: Update pneigh_entry in pneigh_create().")
Signed-off-by: Sabrina Dubroca <sd@queasysnail.net>
Reviewed-by: David Ahern <dsahern@kernel.org>
Reviewed-by: Kuniyuki Iwashima <kuniyu@google.com>
Link: https://patch.msgid.link/38c61de1bb032871a886aff9b9b52fe1cdd4cada.1772894876.git.sd@queasysnail.net
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
This is the result of running the Coccinelle script from
scripts/coccinelle/api/kmalloc_objs.cocci. The script is designed to
avoid scalar types (which need careful case-by-case checking), and
instead replace kmalloc-family calls that allocate struct or union
object instances:
Single allocations: kmalloc(sizeof(TYPE), ...)
are replaced with: kmalloc_obj(TYPE, ...)
Array allocations: kmalloc_array(COUNT, sizeof(TYPE), ...)
are replaced with: kmalloc_objs(TYPE, COUNT, ...)
Flex array allocations: kmalloc(struct_size(PTR, FAM, COUNT), ...)
are replaced with: kmalloc_flex(*PTR, FAM, COUNT, ...)
(where TYPE may also be *VAR)
The resulting allocations no longer return "void *", instead returning
"TYPE *".
Signed-off-by: Kees Cook <kees@kernel.org>
Similarly to the issue from the previous patch, neigh_timer_handler() also
updates the neighbor separately from formatting and sending the netlink
notification message. We have not seen reports to the effect of this
causing trouble, but in theory, the same sort of issues could have come up:
neigh_timer_handler() would make changes as necessary, but before
formatting and sending a notification, is interrupted before sending by
another thread, which makes a parallel change and sends its own message.
The message send that is prompted by an earlier change thus contains
information that does not reflect the change having been made.
To solve this, the netlink notification needs to be in the same critical
section that updates the neighbor. The critical section is ended by the
neigh_probe() call which drops the lock before calling solicit. Stretching
the critical section over the solicit call is problematic, because that can
then involved all sorts of forwarding callbacks. Therefore, like in the
previous patch, split the netlink notification away from the internal one
and move it ahead of the probe call.
Signed-off-by: Petr Machata <petrm@nvidia.com>
Reviewed-by: Ido Schimmel <idosch@nvidia.com>
Reviewed-by: Simon Horman <horms@kernel.org>
Link: https://patch.msgid.link/e440118511cbdbe1d88eb0d71c9047116feb96e0.1769012464.git.petrm@nvidia.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
As noted in a previous patch, one race remains in the current code. A
kernel thread might interrupt a userspace thread after the change is done,
but before formatting and sending the message. Then what we would see is
two messages with the same contents:
userspace thread kernel thread
================ =============
neigh_update
write_lock_bh(n->lock)
n->nud_state = STALE
write_unlock_bh(n->lock)
-------------------------->
neigh:update
write_lock_bh(n->lock)
n->nud_state = REACHABLE
write_unlock_bh(n->lock)
neigh_notify
read_lock_bh(n->lock)
__neigh_fill_info
ndm->nud_state = REACHABLE
rtnl_notify
read_unlock_bh(n->lock)
RTNL REACHABLE sent
<--------
neigh_notify
read_lock_bh(n->lock)
__neigh_fill_info
ndm->nud_state = REACHABLE
rtnl_notify
read_unlock_bh(n->lock)
RTNL REACHABLE sent again
The solution is to send the netlink message inside the critical section
where the neighbor is changed, so that it reflects the notified-upon
neighbor state.
To that end, in __neigh_update(), move the current neigh_notify() call up
to said critical section, and convert it to __neigh_notify(), because the
lock is held. This motion crosses calls to neigh_update_managed_list(),
neigh_update_gc_list() and neigh_update_process_arp_queue(), all of which
potentially unlock and give an opportunity for the above race.
This also crosses a call to neigh_update_process_arp_queue() which calls
neigh->output(), which might be neigh_resolve_output() calls
neigh_event_send() calls neigh_event_send_probe() calls
__neigh_event_send() calls neigh_probe(), which touches neigh->probes,
an update which will now not be visible in the notification.
However, there is indication that there is no promise that these changes
will be accurately projected to notifications: fib6_table_lookup()
indirectly calls route.c's find_match() calls rt6_probe(), which looks up a
neighbor and call __neigh_set_probe_once(), which sets neigh->probes to 0,
but neither this nor the caller seems to send a notification.
Additionally, the neighbor object that the neigh_probe() mentioned above is
called on, might be the alternative neighbor looked up for the ARP queue
packet destination. If that is the case, the changed value of n1->probes is
not notified anywhere.
So at least in some circumstances, the reported number of probes needs to
be assumed to change without notification.
Signed-off-by: Petr Machata <petrm@nvidia.com>
Reviewed-by: Ido Schimmel <idosch@nvidia.com>
Reviewed-by: Simon Horman <horms@kernel.org>
Link: https://patch.msgid.link/ceb44995498eb52375cb2d46c3245bdb9e74b355.1769012464.git.petrm@nvidia.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
The netlink message needs to be send inside the critical section where the
neighbor is changed, so that it reflects the notified-upon neighbor state.
On the other hand, there is no such need in case of notifier chain: the
listeners do not assume lock, and often in fact just schedule a delayed
work to act on the neighbor later. At least one in fact also takes the
neighbor lock.
This requires that the netlink notification be done before the internal
notifier chain message is sent. That is safe to do, because the current
listeners, as well as __neigh_notify(), only read the updated neighbor
fields, and never modify them. (Apart from locking.)
Signed-off-by: Petr Machata <petrm@nvidia.com>
Reviewed-by: Ido Schimmel <idosch@nvidia.com>
Reviewed-by: Simon Horman <horms@kernel.org>
Link: https://patch.msgid.link/f3ef74d5460f14c4d102b8a5857d4a6624da9a5a.1769012464.git.petrm@nvidia.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
The obvious idea behind the helper is to keep together the two bits that
should be done either both or neither: the internal notifier chain message,
and the netlink notification.
To make sure that the notification sent reflects the change being made, the
netlink message needs to be send inside the critical section where the
neighbor is changed. But for the notifier chain, there is no such need: the
listeners do not assume lock, and often in fact just schedule a delayed
work to act on the neighbor later. At least one in fact also takes the
neighbor lock. Therefore these two items have each different locking needs.
Now we could unlock inside the helper, but I find that error prone, and the
fact that the notification is conditional in the first place does not help
to make the call site obvious.
So in this patch, the helper is instead removed and the body, which is just
these two calls, inlined. That way we can use each notifier independently.
Signed-off-by: Petr Machata <petrm@nvidia.com>
Reviewed-by: Ido Schimmel <idosch@nvidia.com>
Reviewed-by: Simon Horman <horms@kernel.org>
Link: https://patch.msgid.link/e65dce5882bc6f4aa2530b8a4877d0e003071a1a.1769012464.git.petrm@nvidia.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
ARP queue processing unlocks the neighbor lock, which can allow another
thread to asynchronously perform a neighbor update and send an out of order
notification. Therefore this needs to be done after the notification is
sent.
Move it just before the end of the critical section. Since
neigh_update_process_arp_queue() unlocks, it does not form a part of the
critical section anymore but it can benefit from the lock being taken. The
intention is to eventually do the RTNL notification before this call.
This motion crosses a call to neigh_update_is_router(), which should not
influence processing of the ARP queue.
Signed-off-by: Petr Machata <petrm@nvidia.com>
Reviewed-by: Ido Schimmel <idosch@nvidia.com>
Reviewed-by: Simon Horman <horms@kernel.org>
Link: https://patch.msgid.link/9ea7159e71430ebdc837ebcc880a76b7e82e52a4.1769012464.git.petrm@nvidia.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
In order to make manipulation with this bit of code clearer, extract it
to a helper function, neigh_update_process_arp_queue().
Signed-off-by: Petr Machata <petrm@nvidia.com>
Reviewed-by: Ido Schimmel <idosch@nvidia.com>
Reviewed-by: Simon Horman <horms@kernel.org>
Link: https://patch.msgid.link/8b0fa0abe2cf0e24484903f5436fe0ac64163057.1769012464.git.petrm@nvidia.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Andy Roulin has described an issue with the current neighbor notification
scheme as follows. This was also presented publicly at the link below.
neigh_update sends a rtnl notification if an update, e.g.,
nud_state change, was done but there is no guarantee of
ordering of the rtnl notifications. Consider the following
scenario:
userspace thread kernel thread
================ =============
neigh_update
write_lock_bh(n->lock)
n->nud_state = STALE
write_unlock_bh(n->lock)
neigh_notify
neigh_fill_info
read_lock_bh(n->lock)
ndm->nud_state = STALE
read_unlock_bh(n->lock)
-------------------------->
neigh:update
write_lock_bh(n->lock)
n->nud_state = REACHABLE
write_unlock_bh(n->lock)
neigh_notify
neigh_fill_info
read_lock_bh(n->lock)
ndm->nud_state = REACHABLE
read_unlock_bh(n->lock)
rtnl_nofify
RTNL REACHABLE sent
<--------
rtnl_notify
RTNL STALE sent
In this scenario, the kernel neigh is updated first to STALE and
then REACHABLE but the netlink notifications are sent out of order,
first REACHABLE and then STALE.
The solution is to send the netlink message inside the same critical
section that formats the message. That way both the contents and ordering
of the message reflect the same state, and we cannot see the abovementioned
out-of-order delivery.
Even with this patch, a remaining issue that the contents of the message
may not reflect the changes made to the neighbor. A kernel thread might
still interrupt a userspace thread after the change is done, but before
formatting and sending the message. Then what we would see is two messages
with the same contents. The following patches will attempt to address that
issue.
To support those future patches, convert __neigh_notify() to a helper that
assumes that the neighbor lock is already taken by having it call
__neigh_fill_info() instead of neigh_fill_info(). Add a new helper,
neigh_notify(), which takes the lock before calling __neigh_notify().
Migrate all callers to use the latter.
Link: https://lore.kernel.org/netdev/ed6768c1-80b8-aee2-e545-b51661d49336@nvidia.com/
Signed-off-by: Petr Machata <petrm@nvidia.com>
Reviewed-by: Ido Schimmel <idosch@nvidia.com>
Reviewed-by: Simon Horman <horms@kernel.org>
Link: https://patch.msgid.link/4b4368dcc5f5a7e407009cb6c36b69cfb5282864.1769012464.git.petrm@nvidia.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
The netlink message needs to be formatted and sent inside the critical
section where the neighbor is changed, so that it reflects the
notified-upon neighbor state. Because it will happen inside an already
existing critical section, it has to assume that the neighbor lock is held.
Add a helper __neigh_fill_info(), which is like neigh_fill_info(), but
makes this assumption. Convert neigh_fill_info() to a wrapper around this
new helper.
Signed-off-by: Petr Machata <petrm@nvidia.com>
Reviewed-by: Ido Schimmel <idosch@nvidia.com>
Reviewed-by: Simon Horman <horms@kernel.org>
Link: https://patch.msgid.link/7ec20113d5d809200e3534d3ed8f0004514914b8.1769012464.git.petrm@nvidia.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Only neigh_for_each() and neigh_seq_start/stop() are on the
reader side of neigh_table.lock.
Let's convert rwlock to the plain spinlock.
Signed-off-by: Kuniyuki Iwashima <kuniyu@google.com>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Link: https://patch.msgid.link/20251022054004.2514876-6-kuniyu@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
neightbl_set() fetches neigh_tables[] and updates attributes under
write_lock_bh(&tbl->lock), so RTNL is not needed.
neigh_table_clear() synchronises RCU only, and rcu_dereference_rtnl()
protects nothing here.
If we released RCU after fetching neigh_tables[], there would be no
synchronisation to block neigh_table_clear() further, so RCU is held
until the end of the function.
Another option would be to protect neigh_tables[] user with SRCU
and add synchronize_srcu() in neigh_table_clear().
But, holding RCU should be fine as we hold write_lock_bh() for the
rest of neightbl_set() anyway.
Let's perform RTM_SETNEIGHTBL under RCU and drop RTNL.
Signed-off-by: Kuniyuki Iwashima <kuniyu@google.com>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Link: https://patch.msgid.link/20251022054004.2514876-5-kuniyu@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
neightbl_dump_info() calls these functions for each neigh_tables[]
entry:
1. neightbl_fill_info() for tbl->parms
2. neightbl_fill_param_info() for tbl->parms_list (except tbl->parms)
Both functions rely on the table lock (read_lock_bh(&tbl->lock))
and RTNL is not needed.
Let's fetch the table under RCU and convert RTM_GETNEIGHTBL to RCU.
Note that the first entry of tbl->parms_list is tbl->parms.list and
embedded in neigh_table, so list_next_entry() is safe.
Signed-off-by: Kuniyuki Iwashima <kuniyu@google.com>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Link: https://patch.msgid.link/20251022054004.2514876-4-kuniyu@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
NEIGH_VAR() is read locklessly in the fast path, and IPv6 ndisc uses
NEIGH_VAR_SET() locklessly.
The next patch will convert neightbl_dump_info() to RCU.
Let's annotate accesses to neigh_param with READ_ONCE() and WRITE_ONCE().
Note that ndisc_ifinfo_sysctl_change() uses &NEIGH_VAR() and we cannot
use '&' with READ_ONCE(), so NEIGH_VAR_PTR() is introduced.
Note also that NEIGH_VAR_INIT() does not need WRITE_ONCE() as it is before
parms is published. Also, the only user hippi_neigh_setup_dev() is no
longer called since commit e3804cbebb ("net: remove COMPAT_NET_DEV_OPS"),
which looks wrong, but probably no one uses HIPPI and RoadRunner.
Signed-off-by: Kuniyuki Iwashima <kuniyu@google.com>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Link: https://patch.msgid.link/20251022054004.2514876-3-kuniyu@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
We will convert RTM_GETNEIGHTBL to RCU soon, where we traverse
tbl->parms_list under RCU in neightbl_dump_info().
Let's use RCU list helper for neigh_parms in neigh_parms_alloc()
and neigh_parms_release().
neigh_table_init() uses the plain list_add() for the default
neigh_parm that is embedded in the table and not yet published.
Note that neigh_parms_release() already uses call_rcu() to free
neigh_parms.
Signed-off-by: Kuniyuki Iwashima <kuniyu@google.com>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Link: https://patch.msgid.link/20251022054004.2514876-2-kuniyu@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Merge in late fixes to prepare for the 6.17 net-next PR.
Conflicts:
net/core/neighbour.c
1bbb76a899 ("neighbour: Fix null-ptr-deref in neigh_flush_dev().")
13a936bb99 ("neighbour: Protect tbl->phash_buckets[] with a dedicated mutex.")
03dc03fa04 ("neighbor: Add NTF_EXT_VALIDATED flag for externally validated entries")
Adjacent changes:
drivers/net/usb/usbnet.c
0d9cfc9b8c ("net: usbnet: Avoid potential RCU stall on LINK_CHANGE event")
2c04d279e8 ("net: usb: Convert tasklet API to new bottom half workqueue mechanism")
net/ipv6/route.c
31d7d67ba1 ("ipv6: annotate data-races around rt->fib6_nsiblings")
1caf272972 ("ipv6: adopt dst_dev() helper")
3b3ccf9ed0 ("net: Remove unnecessary NULL check for lwtunnel_fill_encap()")
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
neigh_add() updates pneigh_entry() found or created by pneigh_create().
This update is serialised by RTNL, but we will remove it.
Let's move the update part to pneigh_create() and make it return errno
instead of a pointer of pneigh_entry.
Now, the pneigh code is RTNL free.
Signed-off-by: Kuniyuki Iwashima <kuniyu@google.com>
Link: https://patch.msgid.link/20250716221221.442239-16-kuniyu@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
tbl->phash_buckets[] is only modified in the slow path by pneigh_create()
and pneigh_delete() under the table lock.
Both of them are called under RTNL, so no extra lock is needed, but we
will remove RTNL from the paths.
pneigh_create() looks up a pneigh_entry, and this part can be lockless,
but it would complicate the logic like
1. lookup
2. allocate pengih_entry for GFP_KERNEL
3. lookup again but under lock
4. if found, return it after freeing the allocated memory
5. else, return the new one
Instead, let's add a per-table mutex and run lookup and allocation
under it.
Note that updating pneigh_entry part in neigh_add() is still protected
by RTNL and will be moved to pneigh_create() in the next patch.
Signed-off-by: Kuniyuki Iwashima <kuniyu@google.com>
Link: https://patch.msgid.link/20250716221221.442239-15-kuniyu@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Now, all callers of pneigh_lookup() are under RCU, and the read
lock there is no longer needed.
Let's drop the lock, inline __pneigh_lookup_1() to pneigh_lookup(),
and call it from pneigh_create().
The next patch will remove tbl->lock from pneigh_create().
Signed-off-by: Kuniyuki Iwashima <kuniyu@google.com>
Link: https://patch.msgid.link/20250716221221.442239-14-kuniyu@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
__pneigh_lookup() is the lockless version of pneigh_lookup(),
but its only caller pndisc_is_router() holds the table lock and
reads pneigh_netry.flags.
This is because accessing pneigh_entry after pneigh_lookup() was
illegal unless the caller holds RTNL or the table lock.
Now, pneigh_entry is guaranteed to be alive during the RCU critical
section.
Let's call pneigh_lookup() and use READ_ONCE() for n->flags in
pndisc_is_router() and remove __pneigh_lookup().
Signed-off-by: Kuniyuki Iwashima <kuniyu@google.com>
Link: https://patch.msgid.link/20250716221221.442239-13-kuniyu@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Now pneigh_entry is guaranteed to be alive during the
RCU critical section even without holding tbl->lock.
Let's use rcu_dereference() in pneigh_get_{first,next}().
Note that neigh_seq_start() still holds tbl->lock for the
normal neighbour entry.
Signed-off-by: Kuniyuki Iwashima <kuniyu@google.com>
Link: https://patch.msgid.link/20250716221221.442239-12-kuniyu@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Now pneigh_entry is guaranteed to be alive during the
RCU critical section even without holding tbl->lock.
Let's drop read_lock_bh(&tbl->lock) and use rcu_dereference()
to iterate tbl->phash_buckets[] in pneigh_dump_table()
Signed-off-by: Kuniyuki Iwashima <kuniyu@google.com>
Link: https://patch.msgid.link/20250716221221.442239-11-kuniyu@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Only __dev_get_by_index() is the RTNL dependant in neigh_get().
Let's replace it with dev_get_by_index_rcu() and convert RTM_GETNEIGH
to RCU.
Signed-off-by: Kuniyuki Iwashima <kuniyu@google.com>
Link: https://patch.msgid.link/20250716221221.442239-10-kuniyu@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
We will convert pneigh readers to RCU, and its flags and protocol
will be read locklessly.
Let's annotate the access to the two fields.
Note that all access to pn->permanent is under RTNL (neigh_add()
and pneigh_ifdown_and_unlock()), so WRITE_ONCE() and READ_ONCE()
are not needed.
Signed-off-by: Kuniyuki Iwashima <kuniyu@google.com>
Link: https://patch.msgid.link/20250716221221.442239-9-kuniyu@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
We will convert RTM_GETNEIGH to RCU.
neigh_get() looks up pneigh_entry by pneigh_lookup() and passes
it to pneigh_fill_info().
Then, we must ensure that the entry is alive till pneigh_fill_info()
completes, but read_lock_bh(&tbl->lock) in pneigh_lookup() does not
guarantee that.
Also, we will convert all readers of tbl->phash_buckets[] to RCU.
Let's use call_rcu() to free pneigh_entry and update phash_buckets[]
and ->next by rcu_assign_pointer().
pneigh_ifdown_and_unlock() uses list_head to avoid overwriting
->next and moving RCU iterators to another list.
pndisc_destructor() (only IPv6 ndisc uses this) uses a mutex, so it
is not delayed to call_rcu(), where we cannot sleep. This is fine
because the mcast code works with RCU and ipv6_dev_mc_dec() frees
mcast objects after RCU grace period.
While at it, we change the return type of pneigh_ifdown_and_unlock()
to void.
Signed-off-by: Kuniyuki Iwashima <kuniyu@google.com>
Link: https://patch.msgid.link/20250716221221.442239-8-kuniyu@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
The next patch will free pneigh_entry with call_rcu().
Then, we need to annotate neigh_table.phash_buckets[] and
pneigh_entry.next with __rcu.
To make the next patch cleaner, let's annotate the fields in advance.
Currently, all accesses to the fields are under the neigh table lock,
so rcu_dereference_protected() is used with 1 for now, but most of them
(except in pneigh_delete() and pneigh_ifdown_and_unlock()) will be
replaced with rcu_dereference() and rcu_dereference_check().
Note that pneigh_ifdown_and_unlock() changes pneigh_entry.next to a
local list, which is illegal because the RCU iterator could be moved
to another list. This part will be fixed in the next patch.
Signed-off-by: Kuniyuki Iwashima <kuniyu@google.com>
Link: https://patch.msgid.link/20250716221221.442239-7-kuniyu@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
pneigh_lookup() has ASSERT_RTNL() in the middle of the function, which
is confusing.
When called with the last argument, creat, 0, pneigh_lookup() literally
looks up a proxy neighbour entry. This is the case of the reader path
as the fast path and RTM_GETNEIGH.
pneigh_lookup(), however, creates a pneigh_entry when called with creat 1
from RTM_NEWNEIGH and SIOCSARP, which require RTNL.
Let's split pneigh_lookup() into two functions.
We will convert all the reader paths to RCU, and read_lock_bh(&tbl->lock)
in the new pneigh_lookup() will be dropped.
Signed-off-by: Kuniyuki Iwashima <kuniyu@google.com>
Link: https://patch.msgid.link/20250716221221.442239-6-kuniyu@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
neigh_valid_get_req() calls neigh_find_table() to fetch neigh_tables[].
neigh_find_table() uses rcu_dereference_rtnl(), but RTNL actually does
not protect it at all; neigh_table_clear() can be called without RTNL
and only waits for RCU readers by synchronize_rcu().
Fortunately, there is no bug because IPv4 is built-in, IPv6 cannot be
unloaded, and DECNET was removed.
To fetch neigh_tables[] by rcu_dereference() later, let's move
neigh_find_table() from neigh_valid_get_req() to neigh_get().
Signed-off-by: Kuniyuki Iwashima <kuniyu@google.com>
Link: https://patch.msgid.link/20250716221221.442239-5-kuniyu@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
We will remove RTNL for neigh_get() and run it under RCU instead.
neigh_get_reply() and pneigh_get_reply() allocate skb with GFP_KERNEL.
Let's move the allocation before __dev_get_by_index() in neigh_get().
Now, neigh_get_reply() and pneigh_get_reply() are inlined and
rtnl_unicast() is factorised.
We will convert pneigh_lookup() to __pneigh_lookup() later.
Signed-off-by: Kuniyuki Iwashima <kuniyu@google.com>
Link: https://patch.msgid.link/20250716221221.442239-4-kuniyu@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
We will remove RTNL for neigh_get() and run it under RCU instead.
neigh_get() returns -EINVAL in the following cases:
* NDA_DST is not specified
* Both ndm->ndm_ifindex and NTF_PROXY are not specified
These validations do not require RCU.
Let's move them to neigh_valid_get_req().
While at it, the extack string for the first case is replaced with
NL_SET_ERR_ATTR_MISS().
Signed-off-by: Kuniyuki Iwashima <kuniyu@google.com>
Link: https://patch.msgid.link/20250716221221.442239-3-kuniyu@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
neigh_get() passes 4 local variable pointers to neigh_valid_get_req().
If it returns a pointer of struct ndmsg, we do not need to pass two
of them.
Signed-off-by: Kuniyuki Iwashima <kuniyu@google.com>
Link: https://patch.msgid.link/20250716221221.442239-2-kuniyu@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
tl;dr
=====
Add a new neighbor flag ("extern_valid") that can be used to indicate to
the kernel that a neighbor entry was learned and determined to be valid
externally. The kernel will not try to remove or invalidate such an
entry, leaving these decisions to the user space control plane. This is
needed for EVPN multi-homing where a neighbor entry for a multi-homed
host needs to be synced across all the VTEPs among which the host is
multi-homed.
Background
==========
In a typical EVPN multi-homing setup each host is multi-homed using a
set of links called ES (Ethernet Segment, i.e., LAG) to multiple leaf
switches (VTEPs). VTEPs that are connected to the same ES are called ES
peers.
When a neighbor entry is learned on a VTEP, it is distributed to both ES
peers and remote VTEPs using EVPN MAC/IP advertisement routes. ES peers
use the neighbor entry when routing traffic towards the multi-homed host
and remote VTEPs use it for ARP/NS suppression.
Motivation
==========
If the ES link between a host and the VTEP on which the neighbor entry
was locally learned goes down, the EVPN MAC/IP advertisement route will
be withdrawn and the neighbor entries will be removed from both ES peers
and remote VTEPs. Routing towards the multi-homed host and ARP/NS
suppression can fail until another ES peer locally learns the neighbor
entry and distributes it via an EVPN MAC/IP advertisement route.
"draft-rbickhart-evpn-ip-mac-proxy-adv-03" [1] suggests avoiding these
intermittent failures by having the ES peers install the neighbor
entries as before, but also injecting EVPN MAC/IP advertisement routes
with a proxy indication. When the previously mentioned ES link goes down
and the original EVPN MAC/IP advertisement route is withdrawn, the ES
peers will not withdraw their neighbor entries, but instead start aging
timers for the proxy indication.
If an ES peer locally learns the neighbor entry (i.e., it becomes
"reachable"), it will restart its aging timer for the entry and emit an
EVPN MAC/IP advertisement route without a proxy indication. An ES peer
will stop its aging timer for the proxy indication if it observes the
removal of the proxy indication from at least one of the ES peers
advertising the entry.
In the event that the aging timer for the proxy indication expired, an
ES peer will withdraw its EVPN MAC/IP advertisement route. If the timer
expired on all ES peers and they all withdrew their proxy
advertisements, the neighbor entry will be completely removed from the
EVPN fabric.
Implementation
==============
In the above scheme, when the control plane (e.g., FRR) advertises a
neighbor entry with a proxy indication, it expects the corresponding
entry in the data plane (i.e., the kernel) to remain valid and not be
removed due to garbage collection or loss of carrier. The control plane
also expects the kernel to notify it if the entry was learned locally
(i.e., became "reachable") so that it will remove the proxy indication
from the EVPN MAC/IP advertisement route. That is why these entries
cannot be programmed with dummy states such as "permanent" or "noarp".
Instead, add a new neighbor flag ("extern_valid") which indicates that
the entry was learned and determined to be valid externally and should
not be removed or invalidated by the kernel. The kernel can probe the
entry and notify user space when it becomes "reachable" (it is initially
installed as "stale"). However, if the kernel does not receive a
confirmation, have it return the entry to the "stale" state instead of
the "failed" state.
In other words, an entry marked with the "extern_valid" flag behaves
like any other dynamically learned entry other than the fact that the
kernel cannot remove or invalidate it.
One can argue that the "extern_valid" flag should not prevent garbage
collection and that instead a neighbor entry should be programmed with
both the "extern_valid" and "extern_learn" flags. There are two reasons
for not doing that:
1. Unclear why a control plane would like to program an entry that the
kernel cannot invalidate but can completely remove.
2. The "extern_learn" flag is used by FRR for neighbor entries learned
on remote VTEPs (for ARP/NS suppression) whereas here we are
concerned with local entries. This distinction is currently irrelevant
for the kernel, but might be relevant in the future.
Given that the flag only makes sense when the neighbor has a valid
state, reject attempts to add a neighbor with an invalid state and with
this flag set. For example:
# ip neigh add 192.0.2.1 nud none dev br0.10 extern_valid
Error: Cannot create externally validated neighbor with an invalid state.
# ip neigh add 192.0.2.1 lladdr 00:11:22:33:44:55 nud stale dev br0.10 extern_valid
# ip neigh replace 192.0.2.1 nud failed dev br0.10 extern_valid
Error: Cannot mark neighbor as externally validated with an invalid state.
The above means that a neighbor cannot be created with the
"extern_valid" flag and flags such as "use" or "managed" as they result
in a neighbor being created with an invalid state ("none") and
immediately getting probed:
# ip neigh add 192.0.2.1 lladdr 00:11:22:33:44:55 nud stale dev br0.10 extern_valid use
Error: Cannot create externally validated neighbor with an invalid state.
However, these flags can be used together with "extern_valid" after the
neighbor was created with a valid state:
# ip neigh add 192.0.2.1 lladdr 00:11:22:33:44:55 nud stale dev br0.10 extern_valid
# ip neigh replace 192.0.2.1 lladdr 00:11:22:33:44:55 nud stale dev br0.10 extern_valid use
One consequence of preventing the kernel from invalidating a neighbor
entry is that by default it will only try to determine reachability
using unicast probes. This can be changed using the "mcast_resolicit"
sysctl:
# sysctl net.ipv4.neigh.br0/10.mcast_resolicit
0
# tcpdump -nn -e -i br0.10 -Q out arp &
# ip neigh replace 192.0.2.1 lladdr 00:11:22:33:44:55 nud stale dev br0.10 extern_valid use
62:50:1d:11:93:6f > 00:11:22:33:44:55, ethertype ARP (0x0806), length 42: Request who-has 192.0.2.1 tell 192.0.2.2, length 28
62:50:1d:11:93:6f > 00:11:22:33:44:55, ethertype ARP (0x0806), length 42: Request who-has 192.0.2.1 tell 192.0.2.2, length 28
62:50:1d:11:93:6f > 00:11:22:33:44:55, ethertype ARP (0x0806), length 42: Request who-has 192.0.2.1 tell 192.0.2.2, length 28
# sysctl -wq net.ipv4.neigh.br0/10.mcast_resolicit=3
# ip neigh replace 192.0.2.1 lladdr 00:11:22:33:44:55 nud stale dev br0.10 extern_valid use
62:50:1d:11:93:6f > 00:11:22:33:44:55, ethertype ARP (0x0806), length 42: Request who-has 192.0.2.1 tell 192.0.2.2, length 28
62:50:1d:11:93:6f > 00:11:22:33:44:55, ethertype ARP (0x0806), length 42: Request who-has 192.0.2.1 tell 192.0.2.2, length 28
62:50:1d:11:93:6f > 00:11:22:33:44:55, ethertype ARP (0x0806), length 42: Request who-has 192.0.2.1 tell 192.0.2.2, length 28
62:50:1d:11:93:6f > ff:ff:ff:ff:ff:ff, ethertype ARP (0x0806), length 42: Request who-has 192.0.2.1 tell 192.0.2.2, length 28
62:50:1d:11:93:6f > ff:ff:ff:ff:ff:ff, ethertype ARP (0x0806), length 42: Request who-has 192.0.2.1 tell 192.0.2.2, length 28
62:50:1d:11:93:6f > ff:ff:ff:ff:ff:ff, ethertype ARP (0x0806), length 42: Request who-has 192.0.2.1 tell 192.0.2.2, length 28
iproute2 patches can be found here [2].
[1] https://datatracker.ietf.org/doc/html/draft-rbickhart-evpn-ip-mac-proxy-adv-03
[2] https://github.com/idosch/iproute2/tree/submit/extern_valid_v1
Signed-off-by: Ido Schimmel <idosch@nvidia.com>
Acked-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://patch.msgid.link/20250626073111.244534-2-idosch@nvidia.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
As discussesd before in [0] proxy entries (which are more configuration
than runtime data) should stay when the link (carrier) goes does down.
This is what happens for regular neighbour entries.
So lets fix this by:
- storing in proxy entries the fact that it was added as NUD_PERMANENT
- not removing NUD_PERMANENT proxy entries when the carrier goes down
(same as how it's done in neigh_flush_dev() for regular neigh entries)
[0]: https://lore.kernel.org/netdev/c584ef7e-6897-01f3-5b80-12b53f7b4bf4@kernel.org/
Signed-off-by: Nicolas Escande <nico.escande@gmail.com>
Reviewed-by: Kuniyuki Iwashima <kuniyu@google.com>
Link: https://patch.msgid.link/20250617141334.3724863-1-nico.escande@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Move this API to the canonical timer_*() namespace.
[ tglx: Redone against pre rc1 ]
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/all/aB2X0jCKQO56WdMt@gmail.com
Replace kfree_skb() used in neigh_resolve_output() and
neigh_connected_output() with kfree_skb_reason().
Following new skb drop reason is added:
/* failed to fill the device hard header */
SKB_DROP_REASON_NEIGH_HH_FILLFAIL
Signed-off-by: Qiu Yutan <qiu.yutan@zte.com.cn>
Signed-off-by: Jiang Kun <jiang.kun2@zte.com.cn>
Reviewed-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Reviewed-by: Xu Xin <xu.xin16@zte.com.cn>
Signed-off-by: David S. Miller <davem@davemloft.net>
Leverage the new nlmsg_payload() helper to avoid checking for message
size and then reading the nlmsg data.
Signed-off-by: Breno Leitao <leitao@debian.org>
Reviewed-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Link: https://patch.msgid.link/20250417-nlmsg_v3-v1-1-9b09d9d7e61d@debian.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Update neigh_valid_get_req function to utilize the new nlmsg_payload()
helper function.
This change improves code clarity and safety by ensuring that the
Netlink message payload is properly validated before accessing its data.
Signed-off-by: Breno Leitao <leitao@debian.org>
Reviewed-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Link: https://patch.msgid.link/20250414-nlmsg-v2-3-3d90cb42c6af@debian.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Update neightbl_valid_dump_info function to utilize the new
nlmsg_payload() helper function.
This change improves code clarity and safety by ensuring that the
Netlink message payload is properly validated before accessing its data.
Signed-off-by: Breno Leitao <leitao@debian.org>
Reviewed-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Link: https://patch.msgid.link/20250414-nlmsg-v2-2-3d90cb42c6af@debian.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
timer_delete[_sync]() replaces del_timer[_sync](). Convert the whole tree
over and remove the historical wrapper inlines.
Conversion was done with coccinelle plus manual fixups where necessary.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Cross-merge networking fixes after downstream PR (net-6.14-rc8).
Conflict:
tools/testing/selftests/net/Makefile
03544faad7 ("selftest: net: add proc_net_pktgen")
3ed61b8938 ("selftests: net: test for lwtunnel dst ref loops")
tools/testing/selftests/net/config:
85cb3711ac ("selftests: net: Add test cases for link and peer netns")
3ed61b8938 ("selftests: net: test for lwtunnel dst ref loops")
Adjacent commits:
tools/testing/selftests/net/Makefile
c935af429e ("selftests: net: add support for testing SO_RCVMARK and SO_RCVPRIORITY")
355d940f4d ("Revert "selftests: Add IPv6 link-local address generation tests for GRE devices."")
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Previous commit 8b5c171bb3 ("neigh: new unresolved queue limits")
introduces new netlink attribute NDTPA_QUEUE_LENBYTES to represent
approximative value for deprecated QUEUE_LEN. However, it forgot to add
the associated nla_policy in nl_ntbl_parm_policy array. Fix it with one
simple NLA_U32 type policy.
Fixes: 8b5c171bb3 ("neigh: new unresolved queue limits")
Signed-off-by: Lin Ma <linma@zju.edu.cn>
Link: https://patch.msgid.link/20250315165113.37600-1-linma@zju.edu.cn
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
kzalloc() uses page allocator when size is larger than
KMALLOC_MAX_CACHE_SIZE, so the intention of commit ab101c553b
("neighbour: use kvzalloc()/kvfree()") can be achieved by using kzalloc().
When using GFP_ATOMIC, kvzalloc() only tries the kmalloc path,
since the vmalloc path does not support the flag.
In this case, kvzalloc() is equivalent to kzalloc() in that neither try
the vmalloc path, so this replacement brings no functional change.
This is primarily a cleanup change, as the original code functions
correctly.
This patch replaces kvzalloc() introduced by commit 41b3caa7c0
("neighbour: Add hlist_node to struct neighbour"), which is called in
the same context and with the same gfp flag as the aforementioned commit
ab101c553b ("neighbour: use kvzalloc()/kvfree()").
Signed-off-by: Kohei Enju <enjuk@amazon.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Link: https://patch.msgid.link/20250219102227.72488-1-enjuk@amazon.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
__neigh_notify() can be called without RTNL or RCU protection.
Use RCU protection to avoid potential UAF.
Fixes: 426b5303eb ("[NETNS]: Modify the neighbour table code so it handles multiple network namespaces")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: David Ahern <dsahern@kernel.org>
Reviewed-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Link: https://patch.msgid.link/20250207135841.1948589-4-edumazet@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
