linux-stable.git/include/net, branch v5.10.95

net_sched: restore "mpu xxx" handling

2022-01-27T09:54:35+00:00

commit fb80445c438c78b40b547d12b8d56596ce4ccfeb upstream.

commit 56b765b79e9a ("htb: improved accuracy at high rates") broke
"overhead X", "linklayer atm" and "mpu X" attributes.

"overhead X" and "linklayer atm" have already been fixed. This restores
the "mpu X" handling, as might be used by DOCSIS or Ethernet shaping:

    tc class add ... htb rate X overhead 4 mpu 64

The code being fixed is used by htb, tbf and act_police. Cake has its
own mpu handling. qdisc_calculate_pkt_len still uses the size table
containing values adjusted for mpu by user space.

iproute2 tc has always passed mpu into the kernel via a tc_ratespec
structure, but the kernel never directly acted on it, merely stored it
so that it could be read back by `tc class show`.

Rather, tc would generate length-to-time tables that included the mpu
(and linklayer) in their construction, and the kernel used those tables.

Since v3.7, the tables were no longer used. Along with "mpu", this also
broke "overhead" and "linklayer" which were fixed in 01cb71d2d47b
("net_sched: restore "overhead xxx" handling", v3.10) and 8a8e3d84b171
("net_sched: restore "linklayer atm" handling", v3.11).

"overhead" was fixed by simply restoring use of tc_ratespec::overhead -
this had originally been used by the kernel but was initially omitted
from the new non-table-based calculations.

"linklayer" had been handled in the table like "mpu", but the mode was
not originally passed in tc_ratespec. The new implementation was made to
handle it by getting new versions of tc to pass the mode in an extended
tc_ratespec, and for older versions of tc the table contents were analysed
at load time to deduce linklayer.

As "mpu" has always been given to the kernel in tc_ratespec,
accompanying the mpu-based table, we can restore system functionality
with no userspace change by making the kernel act on the tc_ratespec
value.

Fixes: 56b765b79e9a ("htb: improved accuracy at high rates")
Signed-off-by: Kevin Bracey 
Cc: Eric Dumazet 
Cc: Jiri Pirko 
Cc: Vimalkumar 
Link: https://lore.kernel.org/r/20220112170210.1014351-1-kevin@bracey.fi
Signed-off-by: Jakub Kicinski 
Signed-off-by: Greg Kroah-Hartman

inet: frags: annotate races around fqdir->dead and fqdir->high_thresh

2022-01-27T09:54:33+00:00

commit 91341fa0003befd097e190ec2a4bf63ad957c49a upstream.

Both fields can be read/written without synchronization,
add proper accessors and documentation.

Fixes: d5dd88794a13 ("inet: fix various use-after-free in defrags units")
Signed-off-by: Eric Dumazet 
Signed-off-by: David S. Miller 
Signed-off-by: Greg Kroah-Hartman

xfrm: rate limit SA mapping change message to user space

2022-01-27T09:54:18+00:00

[ Upstream commit 4e484b3e969b52effd95c17f7a86f39208b2ccf4 ]

Kernel generates mapping change message, XFRM_MSG_MAPPING,
when a source port chage is detected on a input state with UDP
encapsulation set.  Kernel generates a message for each IPsec packet
with new source port.  For a high speed flow per packet mapping change
message can be excessive, and can overload the user space listener.

Introduce rate limiting for XFRM_MSG_MAPPING message to the user space.

The rate limiting is configurable via netlink, when adding a new SA or
updating it. Use the new attribute XFRMA_MTIMER_THRESH in seconds.

v1->v2 change:
	update xfrm_sa_len()

v2->v3 changes:
	use u32 insted unsigned long to reduce size of struct xfrm_state
	fix xfrm_ompat size Reported-by: kernel test robot 
	accept XFRM_MSG_MAPPING only when XFRMA_ENCAP is present

Co-developed-by: Thomas Egerer 
Signed-off-by: Thomas Egerer 
Signed-off-by: Antony Antony 
Signed-off-by: Steffen Klassert 
Signed-off-by: Sasha Levin

sctp: use call_rcu to free endpoint

2022-01-05T11:40:30+00:00

[ Upstream commit 5ec7d18d1813a5bead0b495045606c93873aecbb ]

This patch is to delay the endpoint free by calling call_rcu() to fix
another use-after-free issue in sctp_sock_dump():

  BUG: KASAN: use-after-free in __lock_acquire+0x36d9/0x4c20
  Call Trace:
    __lock_acquire+0x36d9/0x4c20 kernel/locking/lockdep.c:3218
    lock_acquire+0x1ed/0x520 kernel/locking/lockdep.c:3844
    __raw_spin_lock_bh include/linux/spinlock_api_smp.h:135 [inline]
    _raw_spin_lock_bh+0x31/0x40 kernel/locking/spinlock.c:168
    spin_lock_bh include/linux/spinlock.h:334 [inline]
    __lock_sock+0x203/0x350 net/core/sock.c:2253
    lock_sock_nested+0xfe/0x120 net/core/sock.c:2774
    lock_sock include/net/sock.h:1492 [inline]
    sctp_sock_dump+0x122/0xb20 net/sctp/diag.c:324
    sctp_for_each_transport+0x2b5/0x370 net/sctp/socket.c:5091
    sctp_diag_dump+0x3ac/0x660 net/sctp/diag.c:527
    __inet_diag_dump+0xa8/0x140 net/ipv4/inet_diag.c:1049
    inet_diag_dump+0x9b/0x110 net/ipv4/inet_diag.c:1065
    netlink_dump+0x606/0x1080 net/netlink/af_netlink.c:2244
    __netlink_dump_start+0x59a/0x7c0 net/netlink/af_netlink.c:2352
    netlink_dump_start include/linux/netlink.h:216 [inline]
    inet_diag_handler_cmd+0x2ce/0x3f0 net/ipv4/inet_diag.c:1170
    __sock_diag_cmd net/core/sock_diag.c:232 [inline]
    sock_diag_rcv_msg+0x31d/0x410 net/core/sock_diag.c:263
    netlink_rcv_skb+0x172/0x440 net/netlink/af_netlink.c:2477
    sock_diag_rcv+0x2a/0x40 net/core/sock_diag.c:274

This issue occurs when asoc is peeled off and the old sk is freed after
getting it by asoc->base.sk and before calling lock_sock(sk).

To prevent the sk free, as a holder of the sk, ep should be alive when
calling lock_sock(). This patch uses call_rcu() and moves sock_put and
ep free into sctp_endpoint_destroy_rcu(), so that it's safe to try to
hold the ep under rcu_read_lock in sctp_transport_traverse_process().

If sctp_endpoint_hold() returns true, it means this ep is still alive
and we have held it and can continue to dump it; If it returns false,
it means this ep is dead and can be freed after rcu_read_unlock, and
we should skip it.

In sctp_sock_dump(), after locking the sk, if this ep is different from
tsp->asoc->ep, it means during this dumping, this asoc was peeled off
before calling lock_sock(), and the sk should be skipped; If this ep is
the same with tsp->asoc->ep, it means no peeloff happens on this asoc,
and due to lock_sock, no peeloff will happen either until release_sock.

Note that delaying endpoint free won't delay the port release, as the
port release happens in sctp_endpoint_destroy() before calling call_rcu().
Also, freeing endpoint by call_rcu() makes it safe to access the sk by
asoc->base.sk in sctp_assocs_seq_show() and sctp_rcv().

Thanks Jones to bring this issue up.

v1->v2:
  - improve the changelog.
  - add kfree(ep) into sctp_endpoint_destroy_rcu(), as Jakub noticed.

Reported-by: syzbot+9276d76e83e3bcde6c99@syzkaller.appspotmail.com
Reported-by: Lee Jones 
Fixes: d25adbeb0cdb ("sctp: fix an use-after-free issue in sctp_sock_dump")
Signed-off-by: Xin Long 
Signed-off-by: David S. Miller 
Signed-off-by: Sasha Levin

netfilter: conntrack: annotate data-races around ct->timeout

2021-12-14T10:32:37+00:00

commit 802a7dc5cf1bef06f7b290ce76d478138408d6b1 upstream.

(struct nf_conn)->timeout can be read/written locklessly,
add READ_ONCE()/WRITE_ONCE() to prevent load/store tearing.

BUG: KCSAN: data-race in __nf_conntrack_alloc / __nf_conntrack_find_get

write to 0xffff888132e78c08 of 4 bytes by task 6029 on cpu 0:
 __nf_conntrack_alloc+0x158/0x280 net/netfilter/nf_conntrack_core.c:1563
 init_conntrack+0x1da/0xb30 net/netfilter/nf_conntrack_core.c:1635
 resolve_normal_ct+0x502/0x610 net/netfilter/nf_conntrack_core.c:1746
 nf_conntrack_in+0x1c5/0x88f net/netfilter/nf_conntrack_core.c:1901
 ipv6_conntrack_local+0x19/0x20 net/netfilter/nf_conntrack_proto.c:414
 nf_hook_entry_hookfn include/linux/netfilter.h:142 [inline]
 nf_hook_slow+0x72/0x170 net/netfilter/core.c:619
 nf_hook include/linux/netfilter.h:262 [inline]
 NF_HOOK include/linux/netfilter.h:305 [inline]
 ip6_xmit+0xa3a/0xa60 net/ipv6/ip6_output.c:324
 inet6_csk_xmit+0x1a2/0x1e0 net/ipv6/inet6_connection_sock.c:135
 __tcp_transmit_skb+0x132a/0x1840 net/ipv4/tcp_output.c:1402
 tcp_transmit_skb net/ipv4/tcp_output.c:1420 [inline]
 tcp_write_xmit+0x1450/0x4460 net/ipv4/tcp_output.c:2680
 __tcp_push_pending_frames+0x68/0x1c0 net/ipv4/tcp_output.c:2864
 tcp_push_pending_frames include/net/tcp.h:1897 [inline]
 tcp_data_snd_check+0x62/0x2e0 net/ipv4/tcp_input.c:5452
 tcp_rcv_established+0x880/0x10e0 net/ipv4/tcp_input.c:5947
 tcp_v6_do_rcv+0x36e/0xa50 net/ipv6/tcp_ipv6.c:1521
 sk_backlog_rcv include/net/sock.h:1030 [inline]
 __release_sock+0xf2/0x270 net/core/sock.c:2768
 release_sock+0x40/0x110 net/core/sock.c:3300
 sk_stream_wait_memory+0x435/0x700 net/core/stream.c:145
 tcp_sendmsg_locked+0xb85/0x25a0 net/ipv4/tcp.c:1402
 tcp_sendmsg+0x2c/0x40 net/ipv4/tcp.c:1440
 inet6_sendmsg+0x5f/0x80 net/ipv6/af_inet6.c:644
 sock_sendmsg_nosec net/socket.c:704 [inline]
 sock_sendmsg net/socket.c:724 [inline]
 __sys_sendto+0x21e/0x2c0 net/socket.c:2036
 __do_sys_sendto net/socket.c:2048 [inline]
 __se_sys_sendto net/socket.c:2044 [inline]
 __x64_sys_sendto+0x74/0x90 net/socket.c:2044
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x44/0xd0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x44/0xae

read to 0xffff888132e78c08 of 4 bytes by task 17446 on cpu 1:
 nf_ct_is_expired include/net/netfilter/nf_conntrack.h:286 [inline]
 ____nf_conntrack_find net/netfilter/nf_conntrack_core.c:776 [inline]
 __nf_conntrack_find_get+0x1c7/0xac0 net/netfilter/nf_conntrack_core.c:807
 resolve_normal_ct+0x273/0x610 net/netfilter/nf_conntrack_core.c:1734
 nf_conntrack_in+0x1c5/0x88f net/netfilter/nf_conntrack_core.c:1901
 ipv6_conntrack_local+0x19/0x20 net/netfilter/nf_conntrack_proto.c:414
 nf_hook_entry_hookfn include/linux/netfilter.h:142 [inline]
 nf_hook_slow+0x72/0x170 net/netfilter/core.c:619
 nf_hook include/linux/netfilter.h:262 [inline]
 NF_HOOK include/linux/netfilter.h:305 [inline]
 ip6_xmit+0xa3a/0xa60 net/ipv6/ip6_output.c:324
 inet6_csk_xmit+0x1a2/0x1e0 net/ipv6/inet6_connection_sock.c:135
 __tcp_transmit_skb+0x132a/0x1840 net/ipv4/tcp_output.c:1402
 __tcp_send_ack+0x1fd/0x300 net/ipv4/tcp_output.c:3956
 tcp_send_ack+0x23/0x30 net/ipv4/tcp_output.c:3962
 __tcp_ack_snd_check+0x2d8/0x510 net/ipv4/tcp_input.c:5478
 tcp_ack_snd_check net/ipv4/tcp_input.c:5523 [inline]
 tcp_rcv_established+0x8c2/0x10e0 net/ipv4/tcp_input.c:5948
 tcp_v6_do_rcv+0x36e/0xa50 net/ipv6/tcp_ipv6.c:1521
 sk_backlog_rcv include/net/sock.h:1030 [inline]
 __release_sock+0xf2/0x270 net/core/sock.c:2768
 release_sock+0x40/0x110 net/core/sock.c:3300
 tcp_sendpage+0x94/0xb0 net/ipv4/tcp.c:1114
 inet_sendpage+0x7f/0xc0 net/ipv4/af_inet.c:833
 rds_tcp_xmit+0x376/0x5f0 net/rds/tcp_send.c:118
 rds_send_xmit+0xbed/0x1500 net/rds/send.c:367
 rds_send_worker+0x43/0x200 net/rds/threads.c:200
 process_one_work+0x3fc/0x980 kernel/workqueue.c:2298
 worker_thread+0x616/0xa70 kernel/workqueue.c:2445
 kthread+0x2c7/0x2e0 kernel/kthread.c:327
 ret_from_fork+0x1f/0x30

value changed: 0x00027cc2 -> 0x00000000

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 17446 Comm: kworker/u4:5 Tainted: G        W         5.16.0-rc4-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Workqueue: krdsd rds_send_worker

Note: I chose an arbitrary commit for the Fixes: tag,
because I do not think we need to backport this fix to very old kernels.

Fixes: e37542ba111f ("netfilter: conntrack: avoid possible false sharing")
Signed-off-by: Eric Dumazet 
Reported-by: syzbot 
Signed-off-by: Pablo Neira Ayuso 
Signed-off-by: Greg Kroah-Hartman

bonding: make tx_rebalance_counter an atomic

2021-12-14T10:32:36+00:00

commit dac8e00fb640e9569cdeefd3ce8a75639e5d0711 upstream.

KCSAN reported a data-race [1] around tx_rebalance_counter
which can be accessed from different contexts, without
the protection of a lock/mutex.

[1]
BUG: KCSAN: data-race in bond_alb_init_slave / bond_alb_monitor

write to 0xffff888157e8ca24 of 4 bytes by task 7075 on cpu 0:
 bond_alb_init_slave+0x713/0x860 drivers/net/bonding/bond_alb.c:1613
 bond_enslave+0xd94/0x3010 drivers/net/bonding/bond_main.c:1949
 do_set_master net/core/rtnetlink.c:2521 [inline]
 __rtnl_newlink net/core/rtnetlink.c:3475 [inline]
 rtnl_newlink+0x1298/0x13b0 net/core/rtnetlink.c:3506
 rtnetlink_rcv_msg+0x745/0x7e0 net/core/rtnetlink.c:5571
 netlink_rcv_skb+0x14e/0x250 net/netlink/af_netlink.c:2491
 rtnetlink_rcv+0x18/0x20 net/core/rtnetlink.c:5589
 netlink_unicast_kernel net/netlink/af_netlink.c:1319 [inline]
 netlink_unicast+0x5fc/0x6c0 net/netlink/af_netlink.c:1345
 netlink_sendmsg+0x6e1/0x7d0 net/netlink/af_netlink.c:1916
 sock_sendmsg_nosec net/socket.c:704 [inline]
 sock_sendmsg net/socket.c:724 [inline]
 ____sys_sendmsg+0x39a/0x510 net/socket.c:2409
 ___sys_sendmsg net/socket.c:2463 [inline]
 __sys_sendmsg+0x195/0x230 net/socket.c:2492
 __do_sys_sendmsg net/socket.c:2501 [inline]
 __se_sys_sendmsg net/socket.c:2499 [inline]
 __x64_sys_sendmsg+0x42/0x50 net/socket.c:2499
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x44/0xd0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x44/0xae

read to 0xffff888157e8ca24 of 4 bytes by task 1082 on cpu 1:
 bond_alb_monitor+0x8f/0xc00 drivers/net/bonding/bond_alb.c:1511
 process_one_work+0x3fc/0x980 kernel/workqueue.c:2298
 worker_thread+0x616/0xa70 kernel/workqueue.c:2445
 kthread+0x2c7/0x2e0 kernel/kthread.c:327
 ret_from_fork+0x1f/0x30

value changed: 0x00000001 -> 0x00000064

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 1082 Comm: kworker/u4:3 Not tainted 5.16.0-rc3-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Workqueue: bond1 bond_alb_monitor

Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Signed-off-by: Eric Dumazet 
Reported-by: syzbot 
Signed-off-by: David S. Miller 
Signed-off-by: Greg Kroah-Hartman

ipv4: convert fib_num_tclassid_users to atomic_t

2021-12-08T08:03:26+00:00

commit 213f5f8f31f10aa1e83187ae20fb7fa4e626b724 upstream.

Before commit faa041a40b9f ("ipv4: Create cleanup helper for fib_nh")
changes to net->ipv4.fib_num_tclassid_users were protected by RTNL.

After the change, this is no longer the case, as free_fib_info_rcu()
runs after rcu grace period, without rtnl being held.

Fixes: faa041a40b9f ("ipv4: Create cleanup helper for fib_nh")
Signed-off-by: Eric Dumazet 
Cc: David Ahern 
Reviewed-by: David Ahern 
Signed-off-by: David S. Miller 
Signed-off-by: Greg Kroah-Hartman

tcp: fix page frag corruption on page fault

2021-12-08T08:03:23+00:00

commit dacb5d8875cc6cd3a553363b4d6f06760fcbe70c upstream.

Steffen reported a TCP stream corruption for HTTP requests
served by the apache web-server using a cifs mount-point
and memory mapping the relevant file.

The root cause is quite similar to the one addressed by
commit 20eb4f29b602 ("net: fix sk_page_frag() recursion from
memory reclaim"). Here the nested access to the task page frag
is caused by a page fault on the (mmapped) user-space memory
buffer coming from the cifs file.

The page fault handler performs an smb transaction on a different
socket, inside the same process context. Since sk->sk_allaction
for such socket does not prevent the usage for the task_frag,
the nested allocation modify "under the hood" the page frag
in use by the outer sendmsg call, corrupting the stream.

The overall relevant stack trace looks like the following:

httpd 78268 [001] 3461630.850950:      probe:tcp_sendmsg_locked:
        ffffffff91461d91 tcp_sendmsg_locked+0x1
        ffffffff91462b57 tcp_sendmsg+0x27
        ffffffff9139814e sock_sendmsg+0x3e
        ffffffffc06dfe1d smb_send_kvec+0x28
        [...]
        ffffffffc06cfaf8 cifs_readpages+0x213
        ffffffff90e83c4b read_pages+0x6b
        ffffffff90e83f31 __do_page_cache_readahead+0x1c1
        ffffffff90e79e98 filemap_fault+0x788
        ffffffff90eb0458 __do_fault+0x38
        ffffffff90eb5280 do_fault+0x1a0
        ffffffff90eb7c84 __handle_mm_fault+0x4d4
        ffffffff90eb8093 handle_mm_fault+0xc3
        ffffffff90c74f6d __do_page_fault+0x1ed
        ffffffff90c75277 do_page_fault+0x37
        ffffffff9160111e page_fault+0x1e
        ffffffff9109e7b5 copyin+0x25
        ffffffff9109eb40 _copy_from_iter_full+0xe0
        ffffffff91462370 tcp_sendmsg_locked+0x5e0
        ffffffff91462370 tcp_sendmsg_locked+0x5e0
        ffffffff91462b57 tcp_sendmsg+0x27
        ffffffff9139815c sock_sendmsg+0x4c
        ffffffff913981f7 sock_write_iter+0x97
        ffffffff90f2cc56 do_iter_readv_writev+0x156
        ffffffff90f2dff0 do_iter_write+0x80
        ffffffff90f2e1c3 vfs_writev+0xa3
        ffffffff90f2e27c do_writev+0x5c
        ffffffff90c042bb do_syscall_64+0x5b
        ffffffff916000ad entry_SYSCALL_64_after_hwframe+0x65

The cifs filesystem rightfully sets sk_allocations to GFP_NOFS,
we can avoid the nesting using the sk page frag for allocation
lacking the __GFP_FS flag. Do not define an additional mm-helper
for that, as this is strictly tied to the sk page frag usage.

v1 -> v2:
 - use a stricted sk_page_frag() check instead of reordering the
   code (Eric)

Reported-by: Steffen Froemer 
Fixes: 5640f7685831 ("net: use a per task frag allocator")
Signed-off-by: Paolo Abeni 
Reviewed-by: Eric Dumazet 
Signed-off-by: David S. Miller 
Signed-off-by: Greg Kroah-Hartman

wireguard: device: reset peer src endpoint when netns exits

2021-12-08T08:03:22+00:00

commit 20ae1d6aa159eb91a9bf09ff92ccaa94dbea92c2 upstream.

Each peer's endpoint contains a dst_cache entry that takes a reference
to another netdev. When the containing namespace exits, we take down the
socket and prevent future sockets from being created (by setting
creating_net to NULL), which removes that potential reference on the
netns. However, it doesn't release references to the netns that a netdev
cached in dst_cache might be taking, so the netns still might fail to
exit. Since the socket is gimped anyway, we can simply clear all the
dst_caches (by way of clearing the endpoint src), which will release all
references.

However, the current dst_cache_reset function only releases those
references lazily. But it turns out that all of our usages of
wg_socket_clear_peer_endpoint_src are called from contexts that are not
exactly high-speed or bottle-necked. For example, when there's
connection difficulty, or when userspace is reconfiguring the interface.
And in particular for this patch, when the netns is exiting. So for
those cases, it makes more sense to call dst_release immediately. For
that, we add a small helper function to dst_cache.

This patch also adds a test to netns.sh from Hangbin Liu to ensure this
doesn't regress.

Tested-by: Hangbin Liu 
Reported-by: Xiumei Mu 
Cc: Toke Høiland-Jørgensen 
Cc: Paolo Abeni 
Fixes: 900575aa33a3 ("wireguard: device: avoid circular netns references")
Signed-off-by: Jason A. Donenfeld 
Signed-off-by: Jakub Kicinski 
Signed-off-by: Greg Kroah-Hartman

ipv6: fix memory leak in fib6_rule_suppress

2021-12-08T08:03:21+00:00

commit cdef485217d30382f3bf6448c54b4401648fe3f1 upstream.

The kernel leaks memory when a `fib` rule is present in IPv6 nftables
firewall rules and a suppress_prefix rule is present in the IPv6 routing
rules (used by certain tools such as wg-quick). In such scenarios, every
incoming packet will leak an allocation in `ip6_dst_cache` slab cache.

After some hours of `bpftrace`-ing and source code reading, I tracked
down the issue to ca7a03c41753 ("ipv6: do not free rt if
FIB_LOOKUP_NOREF is set on suppress rule").

The problem with that change is that the generic `args->flags` always have
`FIB_LOOKUP_NOREF` set[1][2] but the IPv6-specific flag
`RT6_LOOKUP_F_DST_NOREF` might not be, leading to `fib6_rule_suppress` not
decreasing the refcount when needed.

How to reproduce:
 - Add the following nftables rule to a prerouting chain:
     meta nfproto ipv6 fib saddr . mark . iif oif missing drop
   This can be done with:
     sudo nft create table inet test
     sudo nft create chain inet test test_chain '{ type filter hook prerouting priority filter + 10; policy accept; }'
     sudo nft add rule inet test test_chain meta nfproto ipv6 fib saddr . mark . iif oif missing drop
 - Run:
     sudo ip -6 rule add table main suppress_prefixlength 0
 - Watch `sudo slabtop -o | grep ip6_dst_cache` to see memory usage increase
   with every incoming ipv6 packet.

This patch exposes the protocol-specific flags to the protocol
specific `suppress` function, and check the protocol-specific `flags`
argument for RT6_LOOKUP_F_DST_NOREF instead of the generic
FIB_LOOKUP_NOREF when decreasing the refcount, like this.

[1]: https://github.com/torvalds/linux/blob/ca7a03c4175366a92cee0ccc4fec0038c3266e26/net/ipv6/fib6_rules.c#L71
[2]: https://github.com/torvalds/linux/blob/ca7a03c4175366a92cee0ccc4fec0038c3266e26/net/ipv6/fib6_rules.c#L99

Link: https://bugzilla.kernel.org/show_bug.cgi?id=215105
Fixes: ca7a03c41753 ("ipv6: do not free rt if FIB_LOOKUP_NOREF is set on suppress rule")
Cc: stable@vger.kernel.org
Signed-off-by: Jason A. Donenfeld 
Signed-off-by: David S. Miller 
Signed-off-by: Greg Kroah-Hartman