linux.git/include/uapi/linux/netfilter, branch v5.7

netfilter: nf_tables: reintroduce the NFT_SET_CONCAT flag

2020-04-07T16:23:04+00:00

Stefano originally proposed to introduce this flag, users hit EOPNOTSUPP
in new binaries with old kernels when defining a set with ranges in
a concatenation.

Fixes: f3a2181e16f1 ("netfilter: nf_tables: Support for sets with multiple ranged fields")
Reviewed-by: Stefano Brivio 
Signed-off-by: Pablo Neira Ayuso

netfilter: xt_IDLETIMER: target v1 - match Android layout

2020-04-05T21:26:37+00:00

Android has long had an extension to IDLETIMER to send netlink
messages to userspace, see:
  https://android.googlesource.com/kernel/common/+/refs/heads/android-mainline/include/uapi/linux/netfilter/xt_IDLETIMER.h#42
Note: this is idletimer target rev 1, there is no rev 0 in
the Android common kernel sources, see registration at:
  https://android.googlesource.com/kernel/common/+/refs/heads/android-mainline/net/netfilter/xt_IDLETIMER.c#483

When we compare that to upstream's new idletimer target rev 1:
  https://git.kernel.org/pub/scm/linux/kernel/git/pablo/nf-next.git/tree/include/uapi/linux/netfilter/xt_IDLETIMER.h#n46

We immediately notice that these two rev 1 structs are the
same size and layout, and that while timer_type and send_nl_msg
are differently named and serve a different purpose, they're
at the same offset.

This makes them impossible to tell apart - and thus one cannot
know in a mixed Android/vanilla environment whether one means
timer_type or send_nl_msg.

Since this is iptables/netfilter uapi it introduces a problem
between iptables (vanilla vs Android) userspace and kernel
(vanilla vs Android) if the two don't match each other.

Additionally when at some point in the future Android picks up
5.7+ it's not at all clear how to resolve the resulting merge
conflict.

Furthermore, since upgrading the kernel on old Android phones
is pretty much impossible there does not seem to be an easy way
out of this predicament.

The only thing I've been able to come up with is some super
disgusting kernel version >= 5.7 check in the iptables binary
to flip between different struct layouts.

By adding a dummy field to the vanilla Linux kernel header file
we can force the two structs to be compatible with each other.

Long term I think I would like to deprecate send_nl_msg out of
Android entirely, but I haven't quite been able to figure out
exactly how we depend on it.  It seems to be very similar to
sysfs notifications but with some extra info.

Currently it's actually always enabled whenever Android uses
the IDLETIMER target, so we could also probably entirely
remove it from the uapi in favour of just always enabling it,
but again we can't upgrade old kernels already in the field.

(Also note that this doesn't change the structure's size,
as it is simply fitting into the pre-existing padding, and
that since 5.7 hasn't been released yet, there's still time
to make this uapi visible change)

Cc: Manoj Basapathi 
Cc: Subash Abhinov Kasiviswanathan 
Signed-off-by: Maciej Żenczykowski 
Signed-off-by: Pablo Neira Ayuso

netfilter: flowtable: add counter support

2020-03-27T17:32:37+00:00

Add a new flag to turn on flowtable counters which are stored in the
conntrack entry.

Signed-off-by: Pablo Neira Ayuso

netfilter: nf_tables: add enum nft_flowtable_flags to uapi

2020-03-27T17:32:36+00:00

Expose the NFT_FLOWTABLE_HW_OFFLOAD flag through uapi.

Signed-off-by: Pablo Neira Ayuso

netfilter: nf_tables: allow to specify stateful expression in set definition

2020-03-19T10:37:31+00:00

This patch allows users to specify the stateful expression for the
elements in this set via NFTA_SET_EXPR. This new feature allows you to
turn on counters for all of the elements in this set.

Signed-off-by: Pablo Neira Ayuso

netfilter: nft_tunnel: add support for geneve opts

2020-03-15T14:20:16+00:00

Like vxlan and erspan opts, geneve opts should also be supported in
nft_tunnel. The difference is geneve RFC (draft-ietf-nvo3-geneve-14)
allows a geneve packet to carry multiple geneve opts. So with this
patch, nftables/libnftnl would do:

  # nft add table ip filter
  # nft add chain ip filter input { type filter hook input priority 0 \; }
  # nft add tunnel filter geneve_02 { type geneve\; id 2\; \
    ip saddr 192.168.1.1\; ip daddr 192.168.1.2\; \
    sport 9000\; dport 9001\; dscp 1234\; ttl 64\; flags 1\; \
    opts \"1:1:34567890,2:2:12121212,3:3:1212121234567890\"\; }
  # nft list tunnels table filter
    table ip filter {
    	tunnel geneve_02 {
    		id 2
    		ip saddr 192.168.1.1
    		ip daddr 192.168.1.2
    		sport 9000
    		dport 9001
    		tos 18
    		ttl 64
    		flags 1
    		geneve opts 1:1:34567890,2:2:12121212,3:3:1212121234567890
    	}
    }

v1->v2:
  - no changes, just post it separately.

Signed-off-by: Xin Long 
Signed-off-by: Pablo Neira Ayuso

netfilter: xtables: Add snapshot of hardidletimer target

2020-03-15T14:20:16+00:00

This is a snapshot of hardidletimer netfilter target.

This patch implements a hardidletimer Xtables target that can be
used to identify when interfaces have been idle for a certain period
of time.

Timers are identified by labels and are created when a rule is set
with a new label. The rules also take a timeout value (in seconds) as
an option. If more than one rule uses the same timer label, the timer
will be restarted whenever any of the rules get a hit.

One entry for each timer is created in sysfs. This attribute contains
the timer remaining for the timer to expire. The attributes are
located under the xt_idletimer class:

/sys/class/xt_idletimer/timers/

When the timer expires, the target module sends a sysfs notification
to the userspace, which can then decide what to do (eg. disconnect to
save power)

Compared to IDLETIMER, HARDIDLETIMER can send notifications when
CPU is in suspend too, to notify the timer expiry.

v1->v2: Moved all functionality into IDLETIMER module to avoid
code duplication per comment from Florian.

Signed-off-by: Manoj Basapathi 
Signed-off-by: Subash Abhinov Kasiviswanathan 
Signed-off-by: Pablo Neira Ayuso

netfilter: conntrack: allow insertion of clashing entries

2020-02-17T09:55:14+00:00

This patch further relaxes the need to drop an skb due to a clash with
an existing conntrack entry.

Current clash resolution handles the case where the clash occurs between
two identical entries (distinct nf_conn objects with same tuples), i.e.:

                    Original                        Reply
existing: 10.2.3.4:42 -> 10.8.8.8:53      10.2.3.4:42 <- 10.0.0.6:5353
clashing: 10.2.3.4:42 -> 10.8.8.8:53      10.2.3.4:42 <- 10.0.0.6:5353

... existing handling will discard the unconfirmed clashing entry and
makes skb->_nfct point to the existing one.  The skb can then be
processed normally just as if the clash would not have existed in the
first place.

For other clashes, the skb needs to be dropped.
This frequently happens with DNS resolvers that send A and AAAA queries
back-to-back when NAT rules are present that cause packets to get
different DNAT transformations applied, for example:

-m statistics --mode random ... -j DNAT --dnat-to 10.0.0.6:5353
-m statistics --mode random ... -j DNAT --dnat-to 10.0.0.7:5353

In this case the A or AAAA query is dropped which incurs a costly
delay during name resolution.

This patch also allows this collision type:
                       Original                   Reply
existing: 10.2.3.4:42 -> 10.8.8.8:53      10.2.3.4:42 <- 10.0.0.6:5353
clashing: 10.2.3.4:42 -> 10.8.8.8:53      10.2.3.4:42 <- 10.0.0.7:5353

In this case, clash is in original direction -- the reply direction
is still unique.

The change makes it so that when the 2nd colliding packet is received,
the clashing conntrack is tagged with new IPS_NAT_CLASH_BIT, gets a fixed
1 second timeout and is inserted in the reply direction only.

The entry is hidden from 'conntrack -L', it will time out quickly
and it can be early dropped because it will never progress to the
ASSURED state.

To avoid special-casing the delete code path to special case
the ORIGINAL hlist_nulls node, a new helper, "hlist_nulls_add_fake", is
added so hlist_nulls_del() will work.

Example:

      CPU A:                               CPU B:
1.  10.2.3.4:42 -> 10.8.8.8:53 (A)
2.                                         10.2.3.4:42 -> 10.8.8.8:53 (AAAA)
3.  Apply DNAT, reply changed to 10.0.0.6
4.                                         10.2.3.4:42 -> 10.8.8.8:53 (AAAA)
5.                                         Apply DNAT, reply changed to 10.0.0.7
6. confirm/commit to conntrack table, no collisions
7.                                         commit clashing entry

Reply comes in:

10.2.3.4:42 <- 10.0.0.6:5353 (A)
 -> Finds a conntrack, DNAT is reversed & packet forwarded to 10.2.3.4:42
10.2.3.4:42 <- 10.0.0.7:5353 (AAAA)
 -> Finds a conntrack, DNAT is reversed & packet forwarded to 10.2.3.4:42
    The conntrack entry is deleted from table, as it has the NAT_CLASH
    bit set.

In case of a retransmit from ORIGINAL dir, all further packets will get
the DNAT transformation to 10.0.0.6.

I tried to come up with other solutions but they all have worse
problems.

Alternatives considered were:
1.  Confirm ct entries at allocation time, not in postrouting.
 a. will cause uneccesarry work when the skb that creates the
    conntrack is dropped by ruleset.
 b. in case nat is applied, ct entry would need to be moved in
    the table, which requires another spinlock pair to be taken.
 c. breaks the 'unconfirmed entry is private to cpu' assumption:
    we would need to guard all nfct->ext allocation requests with
    ct->lock spinlock.

2. Make the unconfirmed list a hash table instead of a pcpu list.
   Shares drawback c) of the first alternative.

3. Document this is expected and force users to rearrange their
   ruleset (e.g. by using "-m cluster" instead of "-m statistics").
   nft has the 'jhash' expression which can be used instead of 'numgen'.

   Major drawback: doesn't fix what I consider a bug, not very realistic
   and I believe its reasonable to have the existing rulesets to 'just
   work'.

4. Document this is expected and force users to steer problematic
   packets to the same CPU -- this would serialize the "allocate new
   conntrack entry/nat table evaluation/perform nat/confirm entry", so
   no race can occur.  Similar drawback to 3.

Another advantage of this patch compared to 1) and 2) is that there are
no changes to the hot path; things are handled in the udp tracker and
the clash resolution path.

Cc: rcu@vger.kernel.org
Cc: "Paul E. McKenney" 
Cc: Josh Triplett 
Cc: Jozsef Kadlecsik 
Signed-off-by: Florian Westphal 
Signed-off-by: Pablo Neira Ayuso

netfilter: nf_tables: Support for sets with multiple ranged fields

2020-01-27T07:54:30+00:00

Introduce a new nested netlink attribute, NFTA_SET_DESC_CONCAT, used
to specify the length of each field in a set concatenation.

This allows set implementations to support concatenation of multiple
ranged items, as they can divide the input key into matching data for
every single field. Such set implementations would be selected as
they specify support for NFT_SET_INTERVAL and allow desc->field_count
to be greater than one. Explicitly disallow this for nft_set_rbtree.

In order to specify the interval for a set entry, userspace would
include in NFTA_SET_DESC_CONCAT attributes field lengths, and pass
range endpoints as two separate keys, represented by attributes
NFTA_SET_ELEM_KEY and NFTA_SET_ELEM_KEY_END.

While at it, export the number of 32-bit registers available for
packet matching, as nftables will need this to know the maximum
number of field lengths that can be specified.

For example, "packets with an IPv4 address between 192.0.2.0 and
192.0.2.42, with destination port between 22 and 25", can be
expressed as two concatenated elements:

  NFTA_SET_ELEM_KEY:            192.0.2.0 . 22
  NFTA_SET_ELEM_KEY_END:        192.0.2.42 . 25

and NFTA_SET_DESC_CONCAT attribute would contain:

  NFTA_LIST_ELEM
    NFTA_SET_FIELD_LEN:		4
  NFTA_LIST_ELEM
    NFTA_SET_FIELD_LEN:		2

v4: No changes
v3: Complete rework, NFTA_SET_DESC_CONCAT instead of NFTA_SET_SUBKEY
v2: No changes

Signed-off-by: Stefano Brivio 
Signed-off-by: Pablo Neira Ayuso

netfilter: nf_tables: add NFTA_SET_ELEM_KEY_END attribute

2020-01-27T07:54:30+00:00

Add NFTA_SET_ELEM_KEY_END attribute to convey the closing element of the
interval between kernel and userspace.

This patch also adds the NFT_SET_EXT_KEY_END extension to store the
closing element value in this interval.

v4: No changes
v3: New patch

[sbrivio: refactor error paths and labels; add corresponding
  nft_set_ext_type for new key; rebase]
Signed-off-by: Pablo Neira Ayuso