With legacy nexthops, when net.ipv4.fib_multipath_use_neigh is set,
fib_select_multipath() will never set res->nhc to a nexthop that is not
good (as per fib_good_nh()). OTOH, with nexthop objects,
nexthop_select_path_hthr() may return a nexthop that failed the
nexthop_is_good_nh() test even if there was one that passed. Refactor
nexthop_select_path_hthr() to follow a selection logic more similar to
fib_select_multipath().
The issue can be demonstrated with the following sequence of commands. The
first block shows that things work as expected with legacy nexthops. The
last sequence of `ip rou get` in the second block shows the problem case -
some routes still use the .2 nexthop.
sysctl net.ipv4.fib_multipath_use_neigh=1
ip link add dummy1 up type dummy
ip rou add 198.51.100.0/24 nexthop via 192.0.2.1 dev dummy1 onlink nexthop via 192.0.2.2 dev dummy1 onlink
for i in {10..19}; do ip -o rou get 198.51.100.$i; done
ip neigh add 192.0.2.1 dev dummy1 nud failed
echo ".1 failed:" # results should not use .1
for i in {10..19}; do ip -o rou get 198.51.100.$i; done
ip neigh del 192.0.2.1 dev dummy1
ip neigh add 192.0.2.2 dev dummy1 nud failed
echo ".2 failed:" # results should not use .2
for i in {10..19}; do ip -o rou get 198.51.100.$i; done
ip link del dummy1
ip link add dummy1 up type dummy
ip nexthop add id 1 via 192.0.2.1 dev dummy1 onlink
ip nexthop add id 2 via 192.0.2.2 dev dummy1 onlink
ip nexthop add id 1001 group 1/2
ip rou add 198.51.100.0/24 nhid 1001
for i in {10..19}; do ip -o rou get 198.51.100.$i; done
ip neigh add 192.0.2.1 dev dummy1 nud failed
echo ".1 failed:" # results should not use .1
for i in {10..19}; do ip -o rou get 198.51.100.$i; done
ip neigh del 192.0.2.1 dev dummy1
ip neigh add 192.0.2.2 dev dummy1 nud failed
echo ".2 failed:" # results should not use .2
for i in {10..19}; do ip -o rou get 198.51.100.$i; done
ip link del dummy1
Signed-off-by: Ido Schimmel <idosch@nvidia.com>
Signed-off-by: Benjamin Poirier <bpoirier@nvidia.com>
Reviewed-by: David Ahern <dsahern@kernel.org>
Link: https://lore.kernel.org/r/20230719-nh_select-v2-3-04383e89f868@nvidia.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
For legacy nexthops, there is fib_good_nh() to check the neighbor validity.
In order to make the nexthop object code more similar to the legacy nexthop
code, factor out the nexthop object neighbor validity check into its own
function.
Signed-off-by: Ido Schimmel <idosch@nvidia.com>
Signed-off-by: Benjamin Poirier <bpoirier@nvidia.com>
Reviewed-by: David Ahern <dsahern@kernel.org>
Link: https://lore.kernel.org/r/20230719-nh_select-v2-2-04383e89f868@nvidia.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
The loop in nexthop_select_path_hthr() includes code to check for neighbor
validity. Since this does not apply to fdb nexthops, simplify the loop by
moving the fdb nexthop selection to its own function.
Signed-off-by: Ido Schimmel <idosch@nvidia.com>
Signed-off-by: Benjamin Poirier <bpoirier@nvidia.com>
Reviewed-by: David Ahern <dsahern@kernel.org>
Link: https://lore.kernel.org/r/20230719-nh_select-v2-1-04383e89f868@nvidia.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
rcu_bh is no longer a win, especially for objects freed
with standard call_rcu().
Switch neighbour code to no longer disable BH when not necessary.
Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
We have many lockless accesses to n->nud_state.
Before adding another one in the following patch,
add annotations to readers and writers.
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: David Ahern <dsahern@kernel.org>
Reviewed-by: Martin KaFai Lau <martin.lau@kernel.org>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
As explained by Julian, fib_nh_scope is related to fib_nh_gw4, but
fib_info_update_nhc_saddr() needs the scope of the route, which is
the scope "before" fib_nh_scope, ie fib_nh_scope - 1.
This patch fixes the problem described in commit 747c143072 ("ip: fix
dflt addr selection for connected nexthop").
Fixes: 597cfe4fc3 ("nexthop: Add support for IPv4 nexthops")
Link: https://lore.kernel.org/netdev/6c8a44ba-c2d5-cdf-c5c7-5baf97cba38@ssi.bg/
Signed-off-by: Nicolas Dichtel <nicolas.dichtel@6wind.com>
Reviewed-by: Julian Anastasov <ja@ssi.bg>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
While reading nexthop_compat_mode, it can be changed concurrently.
Thus, we need to add READ_ONCE() to its readers.
Fixes: 4f80116d3d ("net: ipv4: add sysctl for nexthop api compatibility mode")
Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
cleanup_net() is competing with other rtnl users.
nexthop_net_exit() seems a good candidate for exit_batch(),
as this gives chance for cleanup_net() to progress much faster,
holding rtnl a bit longer.
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: David Ahern <dsahern@kernel.org>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
sock.h is pretty heavily used (5k objects rebuilt on x86 after
it's touched). We can drop the include of filter.h from it and
add a forward declaration of struct sk_filter instead.
This decreases the number of rebuilt objects when bpf.h
is touched from ~5k to ~1k.
There's a lot of missing includes this was masking. Primarily
in networking tho, this time.
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Marc Kleine-Budde <mkl@pengutronix.de>
Acked-by: Florian Fainelli <f.fainelli@gmail.com>
Acked-by: Nikolay Aleksandrov <nikolay@nvidia.com>
Acked-by: Stefano Garzarella <sgarzare@redhat.com>
Link: https://lore.kernel.org/bpf/20211229004913.513372-1-kuba@kernel.org
We can optimize resilient nexthop group replaces by reducing the number of
synchronize_net calls. After commit 1005f19b93 ("net: nexthop: release
IPv6 per-cpu dsts when replacing a nexthop group") we always do a
synchronize_net because we must ensure no new dsts can be created for the
replaced group's removed nexthops, but we already did that when replacing
resilient groups, so if we always call synchronize_net after any group
type replacement we'll take care of both cases and reduce synchronize_net
calls for resilient groups.
Suggested-by: Ido Schimmel <idosch@idosch.org>
Signed-off-by: Nikolay Aleksandrov <nikolay@nvidia.com>
Reviewed-by: Ido Schimmel <idosch@nvidia.com>
Tested-by: Ido Schimmel <idosch@nvidia.com>
Reviewed-by: David Ahern <dsahern@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
When replacing a nexthop group, we must release the IPv6 per-cpu dsts of
the removed nexthop entries after an RCU grace period because they
contain references to the nexthop's net device and to the fib6 info.
With specific series of events[1] we can reach net device refcount
imbalance which is unrecoverable. IPv4 is not affected because dsts
don't take a refcount on the route.
[1]
$ ip nexthop list
id 200 via 2002:db8::2 dev bridge.10 scope link onlink
id 201 via 2002:db8::3 dev bridge scope link onlink
id 203 group 201/200
$ ip -6 route
2001:db8::10 nhid 203 metric 1024 pref medium
nexthop via 2002:db8::3 dev bridge weight 1 onlink
nexthop via 2002:db8::2 dev bridge.10 weight 1 onlink
Create rt6_info through one of the multipath legs, e.g.:
$ taskset -a -c 1 ./pkt_inj 24 bridge.10 2001:db8::10
(pkt_inj is just a custom packet generator, nothing special)
Then remove that leg from the group by replace (let's assume it is id
200 in this case):
$ ip nexthop replace id 203 group 201
Now remove the IPv6 route:
$ ip -6 route del 2001:db8::10/128
The route won't be really deleted due to the stale rt6_info holding 1
refcnt in nexthop id 200.
At this point we have the following reference count dependency:
(deleted) IPv6 route holds 1 reference over nhid 203
nh 203 holds 1 ref over id 201
nh 200 holds 1 ref over the net device and the route due to the stale
rt6_info
Now to create circular dependency between nh 200 and the IPv6 route, and
also to get a reference over nh 200, restore nhid 200 in the group:
$ ip nexthop replace id 203 group 201/200
And now we have a permanent circular dependncy because nhid 203 holds a
reference over nh 200 and 201, but the route holds a ref over nh 203 and
is deleted.
To trigger the bug just delete the group (nhid 203):
$ ip nexthop del id 203
It won't really be deleted due to the IPv6 route dependency, and now we
have 2 unlinked and deleted objects that reference each other: the group
and the IPv6 route. Since the group drops the reference it holds over its
entries at free time (i.e. its own refcount needs to drop to 0) that will
never happen and we get a permanent ref on them, since one of the entries
holds a reference over the IPv6 route it will also never be released.
At this point the dependencies are:
(deleted, only unlinked) IPv6 route holds reference over group nh 203
(deleted, only unlinked) group nh 203 holds reference over nh 201 and 200
nh 200 holds 1 ref over the net device and the route due to the stale
rt6_info
This is the last point where it can be fixed by running traffic through
nh 200, and specifically through the same CPU so the rt6_info (dst) will
get released due to the IPv6 genid, that in turn will free the IPv6
route, which in turn will free the ref count over the group nh 203.
If nh 200 is deleted at this point, it will never be released due to the
ref from the unlinked group 203, it will only be unlinked:
$ ip nexthop del id 200
$ ip nexthop
$
Now we can never release that stale rt6_info, we have IPv6 route with ref
over group nh 203, group nh 203 with ref over nh 200 and 201, nh 200 with
rt6_info (dst) with ref over the net device and the IPv6 route. All of
these objects are only unlinked, and cannot be released, thus they can't
release their ref counts.
Message from syslogd@dev at Nov 19 14:04:10 ...
kernel:[73501.828730] unregister_netdevice: waiting for bridge.10 to become free. Usage count = 3
Message from syslogd@dev at Nov 19 14:04:20 ...
kernel:[73512.068811] unregister_netdevice: waiting for bridge.10 to become free. Usage count = 3
Fixes: 7bf4796dd0 ("nexthops: add support for replace")
Signed-off-by: Nikolay Aleksandrov <nikolay@nvidia.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
syzkaller discovered memory leaks [1] that can be reduced to the
following commands:
# ip nexthop add id 1 blackhole
# devlink dev reload pci/0000:06:00.0
As part of the reload flow, mlxsw will unregister its netdevs and then
unregister from the nexthop notification chain. Before unregistering
from the notification chain, mlxsw will receive delete notifications for
nexthop objects using netdevs registered by mlxsw or their uppers. mlxsw
will not receive notifications for nexthops using netdevs that are not
dismantled as part of the reload flow. For example, the blackhole
nexthop above that internally uses the loopback netdev as its nexthop
device.
One way to fix this problem is to have listeners flush their nexthop
tables after unregistering from the notification chain. This is
error-prone as evident by this patch and also not symmetric with the
registration path where a listener receives a dump of all the existing
nexthops.
Therefore, fix this problem by replaying delete notifications for the
listener being unregistered. This is symmetric to the registration path
and also consistent with the netdev notification chain.
The above means that unregister_nexthop_notifier(), like
register_nexthop_notifier(), will have to take RTNL in order to iterate
over the existing nexthops and that any callers of the function cannot
hold RTNL. This is true for mlxsw and netdevsim, but not for the VXLAN
driver. To avoid a deadlock, change the latter to unregister its nexthop
listener without holding RTNL, making it symmetric to the registration
path.
[1]
unreferenced object 0xffff88806173d600 (size 512):
comm "syz-executor.0", pid 1290, jiffies 4295583142 (age 143.507s)
hex dump (first 32 bytes):
41 9d 1e 60 80 88 ff ff 08 d6 73 61 80 88 ff ff A..`......sa....
08 d6 73 61 80 88 ff ff 01 00 00 00 00 00 00 00 ..sa............
backtrace:
[<ffffffff81a6b576>] kmemleak_alloc_recursive include/linux/kmemleak.h:43 [inline]
[<ffffffff81a6b576>] slab_post_alloc_hook+0x96/0x490 mm/slab.h:522
[<ffffffff81a716d3>] slab_alloc_node mm/slub.c:3206 [inline]
[<ffffffff81a716d3>] slab_alloc mm/slub.c:3214 [inline]
[<ffffffff81a716d3>] kmem_cache_alloc_trace+0x163/0x370 mm/slub.c:3231
[<ffffffff82e8681a>] kmalloc include/linux/slab.h:591 [inline]
[<ffffffff82e8681a>] kzalloc include/linux/slab.h:721 [inline]
[<ffffffff82e8681a>] mlxsw_sp_nexthop_obj_group_create drivers/net/ethernet/mellanox/mlxsw/spectrum_router.c:4918 [inline]
[<ffffffff82e8681a>] mlxsw_sp_nexthop_obj_new drivers/net/ethernet/mellanox/mlxsw/spectrum_router.c:5054 [inline]
[<ffffffff82e8681a>] mlxsw_sp_nexthop_obj_event+0x59a/0x2910 drivers/net/ethernet/mellanox/mlxsw/spectrum_router.c:5239
[<ffffffff813ef67d>] notifier_call_chain+0xbd/0x210 kernel/notifier.c:83
[<ffffffff813f0662>] blocking_notifier_call_chain kernel/notifier.c:318 [inline]
[<ffffffff813f0662>] blocking_notifier_call_chain+0x72/0xa0 kernel/notifier.c:306
[<ffffffff8384b9c6>] call_nexthop_notifiers+0x156/0x310 net/ipv4/nexthop.c:244
[<ffffffff83852bd8>] insert_nexthop net/ipv4/nexthop.c:2336 [inline]
[<ffffffff83852bd8>] nexthop_add net/ipv4/nexthop.c:2644 [inline]
[<ffffffff83852bd8>] rtm_new_nexthop+0x14e8/0x4d10 net/ipv4/nexthop.c:2913
[<ffffffff833e9a78>] rtnetlink_rcv_msg+0x448/0xbf0 net/core/rtnetlink.c:5572
[<ffffffff83608703>] netlink_rcv_skb+0x173/0x480 net/netlink/af_netlink.c:2504
[<ffffffff833de032>] rtnetlink_rcv+0x22/0x30 net/core/rtnetlink.c:5590
[<ffffffff836069de>] netlink_unicast_kernel net/netlink/af_netlink.c:1314 [inline]
[<ffffffff836069de>] netlink_unicast+0x5ae/0x7f0 net/netlink/af_netlink.c:1340
[<ffffffff83607501>] netlink_sendmsg+0x8e1/0xe30 net/netlink/af_netlink.c:1929
[<ffffffff832fde84>] sock_sendmsg_nosec net/socket.c:704 [inline]
[<ffffffff832fde84>] sock_sendmsg net/socket.c:724 [inline]
[<ffffffff832fde84>] ____sys_sendmsg+0x874/0x9f0 net/socket.c:2409
[<ffffffff83304a44>] ___sys_sendmsg+0x104/0x170 net/socket.c:2463
[<ffffffff83304c01>] __sys_sendmsg+0x111/0x1f0 net/socket.c:2492
[<ffffffff83304d5d>] __do_sys_sendmsg net/socket.c:2501 [inline]
[<ffffffff83304d5d>] __se_sys_sendmsg net/socket.c:2499 [inline]
[<ffffffff83304d5d>] __x64_sys_sendmsg+0x7d/0xc0 net/socket.c:2499
Fixes: 2a014b200b ("mlxsw: spectrum_router: Add support for nexthop objects")
Signed-off-by: Ido Schimmel <idosch@nvidia.com>
Reviewed-by: Petr Machata <petrm@nvidia.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
The resilient nexthop group torture tests in fib_nexthop.sh exposed a
possible division by zero while replacing a resilient group [1]. The
division by zero occurs when the data path sees a resilient nexthop
group with zero buckets.
The tests replace a resilient nexthop group in a loop while traffic is
forwarded through it. The tests do not specify the number of buckets
while performing the replacement, resulting in the kernel allocating a
stub resilient table (i.e, 'struct nh_res_table') with zero buckets.
This table should never be visible to the data path, but the old nexthop
group (i.e., 'oldg') might still be used by the data path when the stub
table is assigned to it.
Fix this by only assigning the stub table to the old nexthop group after
making sure the group is no longer used by the data path.
Tested with fib_nexthops.sh:
Tests passed: 222
Tests failed: 0
[1]
divide error: 0000 [#1] PREEMPT SMP KASAN
CPU: 0 PID: 1850 Comm: ping Not tainted 5.14.0-custom-10271-ga86eb53057fe #1107
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.14.0-4.fc34 04/01/2014
RIP: 0010:nexthop_select_path+0x2d2/0x1a80
[...]
Call Trace:
fib_select_multipath+0x79b/0x1530
fib_select_path+0x8fb/0x1c10
ip_route_output_key_hash_rcu+0x1198/0x2da0
ip_route_output_key_hash+0x190/0x340
ip_route_output_flow+0x21/0x120
raw_sendmsg+0x91d/0x2e10
inet_sendmsg+0x9e/0xe0
__sys_sendto+0x23d/0x360
__x64_sys_sendto+0xe1/0x1b0
do_syscall_64+0x35/0x80
entry_SYSCALL_64_after_hwframe+0x44/0xae
Cc: stable@vger.kernel.org
Fixes: 283a72a559 ("nexthop: Add implementation of resilient next-hop groups")
Signed-off-by: Ido Schimmel <idosch@nvidia.com>
Reviewed-by: Petr Machata <petrm@nvidia.com>
Reviewed-by: David Ahern <dsahern@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
Currently, a multi-part nexthop dump is restarted based on the number of
nexthops that have been dumped so far. This can result in a lot of
nexthops not being dumped when nexthops are simultaneously deleted:
# ip nexthop | wc -l
65536
# ip nexthop flush
Dump was interrupted and may be inconsistent.
Flushed 36040 nexthops
# ip nexthop | wc -l
29496
Instead, restart the dump based on the nexthop identifier (fixed number)
of the last successfully dumped nexthop:
# ip nexthop | wc -l
65536
# ip nexthop flush
Dump was interrupted and may be inconsistent.
Flushed 65536 nexthops
# ip nexthop | wc -l
0
Reported-by: Maksym Yaremchuk <maksymy@nvidia.com>
Tested-by: Maksym Yaremchuk <maksymy@nvidia.com>
Signed-off-by: Ido Schimmel <idosch@nvidia.com>
Reviewed-by: Petr Machata <petrm@nvidia.com>
Reviewed-by: David Ahern <dsahern@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
After resilient next-hop groups have been added recently, there are two
types of multipath next-hop groups: the legacy "mpath", and the new
"resilient". Calling the legacy next-hop group type "mpath" is unfortunate,
because that describes the fact that a packet could be forwarded in one of
several paths, which is also true for the resilient next-hop groups.
Therefore, to make the naming clearer, rename various artifacts to reflect
the assumptions made. Therefore as of this patch:
- The flag for multipath groups is nh_grp_entry::is_multipath. This
includes the legacy and resilient groups, as well as any future group
types that behave as multipath groups.
Functions that assume this have "mpath" in the name.
- The flag for legacy multipath groups is nh_grp_entry::hash_threshold.
Functions that assume this have "hthr" in the name.
- The flag for resilient groups is nh_grp_entry::resilient.
Functions that assume this have "res" in the name.
Besides the above, struct nh_grp_entry::mpath was renamed to ::hthr as
well.
UAPI artifacts were obviously left intact.
Suggested-by: David Ahern <dsahern@gmail.com>
Signed-off-by: Petr Machata <petrm@nvidia.com>
Reviewed-by: David Ahern <dsahern@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
Now that all the code is in place, stop rejecting requests to create
resilient next-hop groups.
Signed-off-by: Petr Machata <petrm@nvidia.com>
Reviewed-by: Ido Schimmel <idosch@nvidia.com>
Reviewed-by: David Ahern <dsahern@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
Nexthop replacements et.al. are notified through netlink, but if a delayed
work migrates buckets on the background, userspace will stay oblivious.
Notify these as RTM_NEWNEXTHOPBUCKET events.
Signed-off-by: Petr Machata <petrm@nvidia.com>
Reviewed-by: Ido Schimmel <idosch@nvidia.com>
Reviewed-by: David Ahern <dsahern@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
Allow getting (but not setting) individual buckets to inspect the next hop
mapped therein, idle time, and flags.
Signed-off-by: Petr Machata <petrm@nvidia.com>
Reviewed-by: Ido Schimmel <idosch@nvidia.com>
Reviewed-by: David Ahern <dsahern@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
Add a dump handler for resilient next hop buckets. When next-hop group ID
is given, it walks buckets of that group, otherwise it walks buckets of all
groups. It then dumps the buckets whose next hops match the given filtering
criteria.
Signed-off-by: Petr Machata <petrm@nvidia.com>
Reviewed-by: Ido Schimmel <idosch@nvidia.com>
Reviewed-by: David Ahern <dsahern@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
Implement the netlink messages that allow creation and dumping of resilient
nexthop groups.
Signed-off-by: Petr Machata <petrm@nvidia.com>
Reviewed-by: Ido Schimmel <idosch@nvidia.com>
Reviewed-by: David Ahern <dsahern@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
The kernel periodically checks the idle time of nexthop buckets to
determine if they are idle and can be re-populated with a new nexthop.
When the resilient nexthop group is offloaded to hardware, the kernel
will not see activity on nexthop buckets unless it is reported from
hardware.
Add a function that can be periodically called by device drivers to
report activity on nexthop buckets after querying it from the underlying
device.
Signed-off-by: Ido Schimmel <idosch@nvidia.com>
Reviewed-by: Petr Machata <petrm@nvidia.com>
Reviewed-by: David Ahern <dsahern@kernel.org>
Signed-off-by: Petr Machata <petrm@nvidia.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Add a function that can be called by device drivers to set "offload" or
"trap" indication on nexthop buckets following nexthop notifications and
other changes such as a neighbour becoming invalid.
Signed-off-by: Ido Schimmel <idosch@nvidia.com>
Reviewed-by: Petr Machata <petrm@nvidia.com>
Reviewed-by: David Ahern <dsahern@kernel.org>
Signed-off-by: Petr Machata <petrm@nvidia.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Implement the following notifications towards drivers:
- NEXTHOP_EVENT_REPLACE, when a resilient nexthop group is created.
- NEXTHOP_EVENT_BUCKET_REPLACE any time there is a change in assignment of
next hops to hash table buckets. That includes replacements, deletions,
and delayed upkeep cycles. Some bucket notifications can be vetoed by the
driver, to make it possible to propagate bucket busy-ness flags from the
HW back to the algorithm. Some are however forced, e.g. if a next hop is
deleted, all buckets that use this next hop simply must be migrated,
whether the HW wishes so or not.
- NEXTHOP_EVENT_RES_TABLE_PRE_REPLACE, before a resilient nexthop group is
replaced. Usually the driver will get the bucket notifications as well,
and could veto those. But in some cases, a bucket may not be migrated
immediately, but during delayed upkeep, and that is too late to roll the
transaction back. This notification allows the driver to take a look and
veto the new proposed group up front, before anything is committed.
Signed-off-by: Petr Machata <petrm@nvidia.com>
Reviewed-by: Ido Schimmel <idosch@nvidia.com>
Reviewed-by: David Ahern <dsahern@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
At this moment, there is only one type of next-hop group: an mpath group,
which implements the hash-threshold algorithm.
To select a next hop, hash-threshold algorithm first assigns a range of
hashes to each next hop in the group, and then selects the next hop by
comparing the SKB hash with the individual ranges. When a next hop is
removed from the group, the ranges are recomputed, which leads to
reassignment of parts of hash space from one next hop to another. While
there will usually be some overlap between the previous and the new
distribution, some traffic flows change the next hop that they resolve to.
That causes problems e.g. as established TCP connections are reset, because
the traffic is forwarded to a server that is not familiar with the
connection.
Resilient hashing is a technique to address the above problem. Resilient
next-hop group has another layer of indirection between the group itself
and its constituent next hops: a hash table. The selection algorithm uses a
straightforward modulo operation to choose a hash bucket, and then reads
the next hop that this bucket contains, and forwards traffic there.
This indirection brings an important feature. In the hash-threshold
algorithm, the range of hashes associated with a next hop must be
continuous. With a hash table, mapping between the hash table buckets and
the individual next hops is arbitrary. Therefore when a next hop is deleted
the buckets that held it are simply reassigned to other next hops. When
weights of next hops in a group are altered, it may be possible to choose a
subset of buckets that are currently not used for forwarding traffic, and
use those to satisfy the new next-hop distribution demands, keeping the
"busy" buckets intact. This way, established flows are ideally kept being
forwarded to the same endpoints through the same paths as before the
next-hop group change.
In a nutshell, the algorithm works as follows. Each next hop has a number
of buckets that it wants to have, according to its weight and the number of
buckets in the hash table. In case of an event that might cause bucket
allocation change, the numbers for individual next hops are updated,
similarly to how ranges are updated for mpath group next hops. Following
that, a new "upkeep" algorithm runs, and for idle buckets that belong to a
next hop that is currently occupying more buckets than it wants (it is
"overweight"), it migrates the buckets to one of the next hops that has
fewer buckets than it wants (it is "underweight"). If, after this, there
are still underweight next hops, another upkeep run is scheduled to a
future time.
Chances are there are not enough "idle" buckets to satisfy the new demands.
The algorithm has knobs to select both what it means for a bucket to be
idle, and for whether and when to forcefully migrate buckets if there keeps
being an insufficient number of idle buckets.
There are three users of the resilient data structures.
- The forwarding code accesses them under RCU, and does not modify them
except for updating the time a selected bucket was last used.
- Netlink code, running under RTNL, which may modify the data.
- The delayed upkeep code, which may modify the data. This runs unlocked,
and mutual exclusion between the RTNL code and the delayed upkeep is
maintained by canceling the delayed work synchronously before the RTNL
code touches anything. Later it restarts the delayed work if necessary.
The RTNL code has to implement next-hop group replacement, next hop
removal, etc. For removal, the mpath code uses a neat trick of having a
backup next hop group structure, doing the necessary changes offline, and
then RCU-swapping them in. However, the hash tables for resilient hashing
are about an order of magnitude larger than the groups themselves (the size
might be e.g. 4K entries), and it was felt that keeping two of them is an
overkill. Both the primary next-hop group and the spare therefore use the
same resilient table, and writers are careful to keep all references valid
for the forwarding code. The hash table references next-hop group entries
from the next-hop group that is currently in the primary role (i.e. not
spare). During the transition from primary to spare, the table references a
mix of both the primary group and the spare. When a next hop is deleted,
the corresponding buckets are not set to NULL, but instead marked as empty,
so that the pointer is valid and can be used by the forwarding code. The
buckets are then migrated to a new next-hop group entry during upkeep. The
only times that the hash table is invalid is the very beginning and very
end of its lifetime. Between those points, it is always kept valid.
This patch introduces the core support code itself. It does not handle
notifications towards drivers, which are kept as if the group were an mpath
one. It does not handle netlink either. The only bit currently exposed to
user space is the new next-hop group type, and that is currently bounced.
There is therefore no way to actually access this code.
Signed-off-by: Petr Machata <petrm@nvidia.com>
Reviewed-by: Ido Schimmel <idosch@nvidia.com>
Reviewed-by: David Ahern <dsahern@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
- RTM_NEWNEXTHOP et.al. that handle resilient groups will have a new nested
attribute, NHA_RES_GROUP, whose elements are attributes NHA_RES_GROUP_*.
- RTM_NEWNEXTHOPBUCKET et.al. is a suite of new messages that will
currently serve only for dumping of individual buckets of resilient next
hop groups. For nexthop group buckets, these messages will carry a nested
attribute NHA_RES_BUCKET, whose elements are attributes NHA_RES_BUCKET_*.
There are several reasons why a new suite of messages is created for
nexthop buckets instead of overloading the information on the existing
RTM_{NEW,DEL,GET}NEXTHOP messages.
First, a nexthop group can contain a large number of nexthop buckets (4k
is not unheard of). This imposes limits on the amount of information that
can be encoded for each nexthop bucket given a netlink message is limited
to 64k bytes.
Second, while RTM_NEWNEXTHOPBUCKET is only used for notifications at
this point, in the future it can be extended to provide user space with
control over nexthop buckets configuration.
- The new group type is NEXTHOP_GRP_TYPE_RES. Note that nexthop code is
adjusted to bounce groups with that type for now.
Signed-off-by: Ido Schimmel <idosch@nvidia.com>
Reviewed-by: Petr Machata <petrm@nvidia.com>
Reviewed-by: David Ahern <dsahern@kernel.org>
Signed-off-by: Petr Machata <petrm@nvidia.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
With the introduction of resilient nexthop groups, there will be two types
of multipath groups: the current hash-threshold "mpath" ones, and resilient
groups. Both are multipath, but to determine the fact, the system needs to
consider two flags. This might prove costly in the datapath. Therefore,
introduce a new flag, that should be set for next-hop groups that have more
than one nexthop, and should be considered multipath.
Signed-off-by: Petr Machata <petrm@nvidia.com>
Reviewed-by: Ido Schimmel <idosch@nvidia.com>
Reviewed-by: David Ahern <dsahern@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
The cited function currently uses rtnl_dereference() to get nh_info from a
handed-in nexthop. However, under the resilient hashing scheme, this
function will not always be called under RTNL, sometimes the mutual
exclusion will be achieved differently. Therefore move the nh_info
extraction from the function to its callers to make it possible to use a
different synchronization guarantee.
Signed-off-by: Petr Machata <petrm@nvidia.com>
Reviewed-by: Ido Schimmel <idosch@nvidia.com>
Reviewed-by: David Ahern <dsahern@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
Currently, replace assumes that the new group that is given is a
fully-formed object. But mpath groups really only have one attribute, and
that is the constituent next hop configuration. This may not be universally
true. From the usability perspective, it is desirable to allow the replace
operation to adjust just the constituent next hop configuration and leave
the group attributes as such intact.
But the object that keeps track of whether an attribute was or was not
given is the nh_config object, not the next hop or next-hop group. To allow
(selective) attribute updates during NH group replacement, propagate `cfg'
to replace_nexthop() and further to replace_nexthop_grp().
Signed-off-by: Petr Machata <petrm@nvidia.com>
Reviewed-by: Ido Schimmel <idosch@nvidia.com>
Reviewed-by: David Ahern <dsahern@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
As far as user space is concerned, blackhole nexthops do not have a
nexthop device and therefore should not be affected by the
administrative or carrier state of any netdev.
However, when the loopback netdev goes down all the blackhole nexthops
are flushed. This happens because internally the kernel associates
blackhole nexthops with the loopback netdev.
This behavior is both confusing to those not familiar with kernel
internals and also diverges from the legacy API where blackhole IPv4
routes are not flushed when the loopback netdev goes down:
# ip route add blackhole 198.51.100.0/24
# ip link set dev lo down
# ip route show 198.51.100.0/24
blackhole 198.51.100.0/24
Blackhole IPv6 routes are flushed, but at least user space knows that
they are associated with the loopback netdev:
# ip -6 route show 2001:db8:1::/64
blackhole 2001:db8:1::/64 dev lo metric 1024 pref medium
Fix this by only flushing blackhole nexthops when the loopback netdev is
unregistered.
Fixes: ab84be7e54 ("net: Initial nexthop code")
Signed-off-by: Ido Schimmel <idosch@nvidia.com>
Reported-by: Donald Sharp <sharpd@nvidia.com>
Reviewed-by: David Ahern <dsahern@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Validation of messages for get / del of a next hop is the same as will be
validation of messages for get of a resilient next hop group bucket. The
difference is that policy for resilient next hop group buckets is a
superset of that used for next-hop get.
It is therefore possible to reuse the code that validates the nhmsg fields,
extracts the next-hop ID, and validates that. To that end, extract from
nh_valid_get_del_req() a helper __nh_valid_get_del_req() that does just
that.
Make the nlh argument const so that the function can be called from the
dump context, which only has a const nlh. Propagate the constness to
nh_valid_get_del_req().
Signed-off-by: Petr Machata <petrm@nvidia.com>
Reviewed-by: Ido Schimmel <idosch@nvidia.com>
Reviewed-by: David Ahern <dsahern@kernel.org>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
In order to allow different handling for next-hop tree dumper and for
bucket dumper, parameterize the next-hop tree walker with a callback. Add
rtm_dump_nexthop_cb() with just the bits relevant for next-hop tree
dumping.
Signed-off-by: Petr Machata <petrm@nvidia.com>
Reviewed-by: Ido Schimmel <idosch@nvidia.com>
Reviewed-by: David Ahern <dsahern@kernel.org>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Extract from rtm_dump_nexthop() a helper to walk the next hop tree. A
separate function for this will be reusable from the bucket dumper.
Signed-off-by: Petr Machata <petrm@nvidia.com>
Reviewed-by: Ido Schimmel <idosch@nvidia.com>
Reviewed-by: David Ahern <dsahern@kernel.org>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
The dump operations need to keep state from one invocation to another. A
scratch area is dedicated for this purpose in the passed-in argument, cb,
namely via two aliased arrays, struct netlink_callback.args and .ctx.
Dumping of buckets will end up having to iterate over next hops as well,
and it would be nice to be able to reuse the iteration logic with the NH
dumper. The fact that the logic currently relies on fixed index to the
.args array, and the indices would have to be coordinated between the two
dumpers, makes this somewhat awkward.
To make the access patters clearer, introduce a helper struct with a NH
index, and instead of using the .args array directly, use it through this
structure.
Signed-off-by: Petr Machata <petrm@nvidia.com>
Reviewed-by: Ido Schimmel <idosch@nvidia.com>
Reviewed-by: David Ahern <dsahern@kernel.org>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Requests to dump nexthops have many attributes in common with those that
requests to dump buckets of resilient NH groups will have. However, they
have different policies. To allow reuse of this code, extract a
policy-agnostic wrapper out of nh_valid_dump_req(), and convert this
function into a thin wrapper around it.
Signed-off-by: Petr Machata <petrm@nvidia.com>
Reviewed-by: Ido Schimmel <idosch@nvidia.com>
Reviewed-by: David Ahern <dsahern@kernel.org>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Requests to dump nexthops have many attributes in common with those that
requests to dump buckets of resilient NH groups will have. In order to make
reuse of this code simpler, convert the code to use a single structure with
filtering configuration instead of passing around the parameters one by
one.
Signed-off-by: Petr Machata <petrm@nvidia.com>
Reviewed-by: Ido Schimmel <idosch@nvidia.com>
Reviewed-by: David Ahern <dsahern@kernel.org>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
After there are several next-hop group types, initialization and
finalization of notifier type needs to reflect the actual type. Transform
nh_notifier_grp_info_init() and _fini() to make extending them easier.
Signed-off-by: Petr Machata <petrm@nvidia.com>
Reviewed-by: Ido Schimmel <idosch@nvidia.com>
Reviewed-by: David Ahern <dsahern@kernel.org>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Currently there are only two types of in-kernel nexthop notification.
The two are distinguished by the 'is_grp' boolean field in 'struct
nh_notifier_info'.
As more notification types are introduced for more next-hop group types, a
boolean is not an easily extensible interface. Instead, convert it to an
enum.
Signed-off-by: Ido Schimmel <idosch@nvidia.com>
Reviewed-by: Petr Machata <petrm@nvidia.com>
Signed-off-by: Petr Machata <petrm@nvidia.com>
Reviewed-by: David Ahern <dsahern@kernel.org>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Most of the code that deals with nexthop groups relies on the fact that the
group is of exactly one well-known type. Currently there is only one type,
"mpath", but as more next-hop group types come, it becomes desirable to
have a central place where the setting is validated. Introduce such place
into nexthop_create_group(), such that the check is done before the code
that relies on that invariant is invoked.
Signed-off-by: Petr Machata <petrm@nvidia.com>
Reviewed-by: Ido Schimmel <idosch@nvidia.com>
Reviewed-by: David Ahern <dsahern@kernel.org>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
The values that a next-hop group needs to keep track of depend on the group
type. Introduce a union to separate fields specific to the mpath groups
from fields specific to other group types.
Signed-off-by: Petr Machata <petrm@nvidia.com>
Reviewed-by: Ido Schimmel <idosch@nvidia.com>
Reviewed-by: David Ahern <dsahern@kernel.org>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
The logic for selecting path depends on the next-hop group type. Adapt the
nexthop_select_path() to dispatch according to the group type.
Signed-off-by: Petr Machata <petrm@nvidia.com>
Reviewed-by: Ido Schimmel <idosch@nvidia.com>
Reviewed-by: David Ahern <dsahern@kernel.org>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
nexthop_free_mpath really should be nexthop_free_group. Rename it.
Signed-off-by: David Ahern <dsahern@kernel.org>
Reviewed-by: Ido Schimmel <idosch@nvidia.com>
Signed-off-by: Petr Machata <petrm@nvidia.com>
Reviewed-by: David Ahern <dsahern@kernel.org>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
This policy is currently only used for creation of new next hops and new
next hop groups. Rename it accordingly and remove the two attributes that
are not valid in that context: NHA_GROUPS and NHA_MASTER.
For consistency with other policies, do not mention policy array size in
the declarator, and replace NHA_MAX for ARRAY_SIZE as appropriate.
Note that with this commit, NHA_MAX and __NHA_MAX are not used anymore.
Leave them in purely as a user API.
Signed-off-by: Petr Machata <petrm@nvidia.com>
Reviewed-by: David Ahern <dsahern@kernel.org>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
This function uses the global nexthop policy, but only accepts four
particular attributes. Create a new policy that only includes the four
supported attributes, and use it. Convert the loop to a series of ifs.
Signed-off-by: Petr Machata <petrm@nvidia.com>
Reviewed-by: David Ahern <dsahern@kernel.org>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
This function uses the global nexthop policy only to then bounce all
arguments except for NHA_ID. Instead, just create a new policy that
only includes the one allowed attribute.
Signed-off-by: Petr Machata <petrm@nvidia.com>
Reviewed-by: David Ahern <dsahern@kernel.org>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
The function nh_check_attr_group() is called to validate nexthop groups.
The intention of that code seems to have been to bounce all attributes
above NHA_GROUP_TYPE except for NHA_FDB. However instead it bounces all
these attributes except when NHA_FDB attribute is present--then it accepts
them.
NHA_FDB validation that takes place before, in rtm_to_nh_config(), already
bounces NHA_OIF, NHA_BLACKHOLE, NHA_ENCAP and NHA_ENCAP_TYPE. Yet further
back, NHA_GROUPS and NHA_MASTER are bounced unconditionally.
But that still leaves NHA_GATEWAY as an attribute that would be accepted in
FDB nexthop groups (with no meaning), so long as it keeps the address
family as unspecified:
# ip nexthop add id 1 fdb via 127.0.0.1
# ip nexthop add id 10 fdb via default group 1
The nexthop code is still relatively new and likely not used very broadly,
and the FDB bits are newer still. Even though there is a reproducer out
there, it relies on an improbable gateway arguments "via default", "via
all" or "via any". Given all this, I believe it is OK to reformulate the
condition to do the right thing and bounce NHA_GATEWAY.
Fixes: 38428d6871 ("nexthop: support for fdb ecmp nexthops")
Signed-off-by: Petr Machata <petrm@nvidia.com>
Signed-off-by: Ido Schimmel <idosch@nvidia.com>
Reviewed-by: David Ahern <dsahern@kernel.org>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
In case of error, remove the nexthop group entry from the list to which
it was previously added.
Fixes: 430a049190 ("nexthop: Add support for nexthop groups")
Signed-off-by: Ido Schimmel <idosch@nvidia.com>
Reviewed-by: Petr Machata <petrm@nvidia.com>
Reviewed-by: David Ahern <dsahern@kernel.org>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
A reference was not taken for the current nexthop entry, so do not try
to put it in the error path.
Fixes: 430a049190 ("nexthop: Add support for nexthop groups")
Signed-off-by: Ido Schimmel <idosch@nvidia.com>
Reviewed-by: Petr Machata <petrm@nvidia.com>
Reviewed-by: David Ahern <dsahern@kernel.org>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
When registering a new notifier to the nexthop notification chain,
replay all the existing nexthops to the new notifier so that it will
have a complete picture of the available nexthops.
Signed-off-by: Ido Schimmel <idosch@nvidia.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Benjamin Poirier