Commit Graph

3918 Commits

Author SHA1 Message Date
Pablo Neira Ayuso
2335ba704f netlink: add NLM_F_NONREC flag for deletion requests
In the last NFWS in Faro, Portugal, we discussed that netlink is lacking
the semantics to request non recursive deletions, ie. do not delete an
object iff it has child objects that hang from this parent object that
the user requests to be deleted.

We need this new flag to solve a problem for the iptables-compat
backward compatibility utility, that runs iptables commands using the
existing nf_tables netlink interface. Specifically, custom chains in
iptables cannot be deleted if there are rules in it, however, nf_tables
allows to remove any chain that is populated with content. To sort out
this asymmetry, iptables-compat userspace sets this new NLM_F_NONREC
flag to obtain the same semantics that iptables provides.

This new flag should only be used for deletion requests. Note this new
flag value overlaps with the existing:

* NLM_F_ROOT for get requests.
* NLM_F_REPLACE for new requests.

However, those flags should not ever be used in deletion requests.

Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
2017-09-04 17:34:54 +02:00
Pablo M. Bermudo Garay
a691205571 netfilter: nft_limit: add stateful object type
Register a new limit stateful object type into the stateful object
infrastructure.

Signed-off-by: Pablo M. Bermudo Garay <pablombg@gmail.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
2017-09-04 13:25:16 +02:00
Vishwanath Pai
bea74641e3 netfilter: xt_hashlimit: add rate match mode
This patch adds a new feature to hashlimit that allows matching on the
current packet/byte rate without rate limiting. This can be enabled
with a new flag --hashlimit-rate-match. The match returns true if the
current rate of packets is above/below the user specified value.

The main difference between the existing algorithm and the new one is
that the existing algorithm rate-limits the flow whereas the new
algorithm does not. Instead it *classifies* the flow based on whether
it is above or below a certain rate. I will demonstrate this with an
example below. Let us assume this rule:

iptables -A INPUT -m hashlimit --hashlimit-above 10/s -j new_chain

If the packet rate is 15/s, the existing algorithm would ACCEPT 10
packets every second and send 5 packets to "new_chain".

But with the new algorithm, as long as the rate of 15/s is sustained,
all packets will continue to match and every packet is sent to new_chain.

This new functionality will let us classify different flows based on
their current rate, so that further decisions can be made on them based on
what the current rate is.

This is how the new algorithm works:
We divide time into intervals of 1 (sec/min/hour) as specified by
the user. We keep track of the number of packets/bytes processed in the
current interval. After each interval we reset the counter to 0.

When we receive a packet for match, we look at the packet rate
during the current interval and the previous interval to make a
decision:

if [ prev_rate < user and cur_rate < user ]
        return Below
else
        return Above

Where cur_rate is the number of packets/bytes seen in the current
interval, prev is the number of packets/bytes seen in the previous
interval and 'user' is the rate specified by the user.

We also provide flexibility to the user for choosing the time
interval using the option --hashilmit-interval. For example the user can
keep a low rate like x/hour but still keep the interval as small as 1
second.

To preserve backwards compatibility we have to add this feature in a new
revision, so I've created revision 3 for hashlimit. The two new options
we add are:

--hashlimit-rate-match
--hashlimit-rate-interval

I have updated the help text to add these new options. Also added a few
tests for the new options.

Suggested-by: Igor Lubashev <ilubashe@akamai.com>
Reviewed-by: Josh Hunt <johunt@akamai.com>
Signed-off-by: Vishwanath Pai <vpai@akamai.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
2017-09-04 12:54:42 +02:00
David S. Miller
b63f6044d8 Merge git://git.kernel.org/pub/scm/linux/kernel/git/pablo/nf-next
Pablo Neira Ayuso says:

====================
Netfilter updates for net-next

The following patchset contains Netfilter updates for your net-next
tree. Basically, updates to the conntrack core, enhancements for
nf_tables, conversion of netfilter hooks from linked list to array to
improve memory locality and asorted improvements for the Netfilter
codebase. More specifically, they are:

1) Add expection to hashes after timer initialization to prevent
   access from another CPU that walks on the hashes and calls
   del_timer(), from Florian Westphal.

2) Don't update nf_tables chain counters from hot path, this is only
   used by the x_tables compatibility layer.

3) Get rid of nested rcu_read_lock() calls from netfilter hook path.
   Hooks are always guaranteed to run from rcu read side, so remove
   nested rcu_read_lock() where possible. Patch from Taehee Yoo.

4) nf_tables new ruleset generation notifications include PID and name
   of the process that has updated the ruleset, from Phil Sutter.

5) Use skb_header_pointer() from nft_fib, so we can reuse this code from
   the nf_family netdev family. Patch from Pablo M. Bermudo.

6) Add support for nft_fib in nf_tables netdev family, also from Pablo.

7) Use deferrable workqueue for conntrack garbage collection, to reduce
   power consumption, from Patch from Subash Abhinov Kasiviswanathan.

8) Add nf_ct_expect_iterate_net() helper and use it. From Florian
   Westphal.

9) Call nf_ct_unconfirmed_destroy only from cttimeout, from Florian.

10) Drop references on conntrack removal path when skbuffs has escaped via
    nfqueue, from Florian.

11) Don't queue packets to nfqueue with dying conntrack, from Florian.

12) Constify nf_hook_ops structure, from Florian.

13) Remove neededlessly branch in nf_tables trace code, from Phil Sutter.

14) Add nla_strdup(), from Phil Sutter.

15) Rise nf_tables objects name size up to 255 chars, people want to use
    DNS names, so increase this according to what RFC 1035 specifies.
    Patch series from Phil Sutter.

16) Kill nf_conntrack_default_on, it's broken. Default on conntrack hook
    registration on demand, suggested by Eric Dumazet, patch from Florian.

17) Remove unused variables in compat_copy_entry_from_user both in
    ip_tables and arp_tables code. Patch from Taehee Yoo.

18) Constify struct nf_conntrack_l4proto, from Julia Lawall.

19) Constify nf_loginfo structure, also from Julia.

20) Use a single rb root in connlimit, from Taehee Yoo.

21) Remove unused netfilter_queue_init() prototype, from Taehee Yoo.

22) Use audit_log() instead of open-coding it, from Geliang Tang.

23) Allow to mangle tcp options via nft_exthdr, from Florian.

24) Allow to fetch TCP MSS from nft_rt, from Florian. This includes
    a fix for a miscalculation of the minimal length.

25) Simplify branch logic in h323 helper, from Nick Desaulniers.

26) Calculate netlink attribute size for conntrack tuple at compile
    time, from Florian.

27) Remove protocol name field from nf_conntrack_{l3,l4}proto structure.
    From Florian.

28) Remove holes in nf_conntrack_l4proto structure, so it becomes
    smaller. From Florian.

29) Get rid of print_tuple() indirection for /proc conntrack listing.
    Place all the code in net/netfilter/nf_conntrack_standalone.c.
    Patch from Florian.

30) Do not built in print_conntrack() if CONFIG_NF_CONNTRACK_PROCFS is
    off. From Florian.

31) Constify most nf_conntrack_{l3,l4}proto helper functions, from
    Florian.

32) Fix broken indentation in ebtables extensions, from Colin Ian King.

33) Fix several harmless sparse warning, from Florian.

34) Convert netfilter hook infrastructure to use array for better memory
    locality, joint work done by Florian and Aaron Conole. Moreover, add
    some instrumentation to debug this.

35) Batch nf_unregister_net_hooks() calls, to call synchronize_net once
    per batch, from Florian.

36) Get rid of noisy logging in ICMPv6 conntrack helper, from Florian.

37) Get rid of obsolete NFDEBUG() instrumentation, from Varsha Rao.

38) Remove unused code in the generic protocol tracker, from Davide
    Caratti.

I think I will have material for a second Netfilter batch in my queue if
time allow to make it fit in this merge window.
====================

Signed-off-by: David S. Miller <davem@davemloft.net>
2017-09-03 17:08:42 -07:00
Ivan Delalande
c03fa9bcac tcp_diag: report TCP MD5 signing keys and addresses
Report TCP MD5 (RFC2385) signing keys, addresses and address prefixes to
processes with CAP_NET_ADMIN requesting INET_DIAG_INFO. Currently it is
not possible to retrieve these from the kernel once they have been
configured on sockets.

Signed-off-by: Ivan Delalande <colona@arista.com>
Acked-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2017-09-01 18:38:09 -07:00
David S. Miller
6026e043d0 Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net
Three cases of simple overlapping changes.

Signed-off-by: David S. Miller <davem@davemloft.net>
2017-09-01 17:42:05 -07:00
David Ahern
482dca939f bpf: Add mark and priority to sock options that can be set
Add socket mark and priority to fields that can be set by
ebpf program when a socket is created.

Signed-off-by: David Ahern <dsahern@gmail.com>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: David S. Miller <davem@davemloft.net>
2017-09-01 06:05:15 +01:00
Arkadi Sharshevsky
1797f5b3cf devlink: Add IPv6 header for dpipe
This will be used by the IPv6 host table which will be introduced in the
following patches. The fields in the header are added per-use. This header
is global and can be reused by many drivers.

Signed-off-by: Arkadi Sharshevsky <arkadis@mellanox.com>
Signed-off-by: Jiri Pirko <jiri@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2017-08-31 14:42:19 -07:00
Subash Abhinov Kasiviswanathan
cdf4969c42 net: arp: Add support for raw IP device
Define the raw IP type. This is needed for raw IP net devices
like rmnet.

Signed-off-by: Subash Abhinov Kasiviswanathan <subashab@codeaurora.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
2017-08-30 11:41:13 -07:00
Subash Abhinov Kasiviswanathan
7373ae7e8f net: ether: Add support for multiplexing and aggregation type
Define the Qualcomm multiplexing and aggregation (MAP) ether type 0x00F9.
This is needed for receiving data in the MAP protocol like RMNET. This is
not an officially registered ID.

Signed-off-by: Subash Abhinov Kasiviswanathan <subashab@codeaurora.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
2017-08-30 11:41:13 -07:00
Florian Westphal
31770e34e4 tcp: Revert "tcp: remove header prediction"
This reverts commit 45f119bf93.

Eric Dumazet says:
  We found at Google a significant regression caused by
  45f119bf93 tcp: remove header prediction

  In typical RPC  (TCP_RR), when a TCP socket receives data, we now call
  tcp_ack() while we used to not call it.

  This touches enough cache lines to cause a slowdown.

so problem does not seem to be HP removal itself but the tcp_ack()
call.  Therefore, it might be possible to remove HP after all, provided
one finds a way to elide tcp_ack for most cases.

Reported-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: David S. Miller <davem@davemloft.net>
2017-08-30 11:20:09 -07:00
Jiri Benc
155e6f6497 ether: add NSH ethertype
The NSH draft says:

   An IEEE EtherType, 0x894F, has been allocated for NSH.

Signed-off-by: Jiri Benc <jbenc@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2017-08-29 15:16:52 -07:00
Alexander Aring
2804fd3af6 if_ether: add forces ife lfb type
This patch adds the forces IFE lfb type according to IEEE registered
ethertypes. See http://standards-oui.ieee.org/ethertype/eth.txt for more
information. Since there exists the IFE subsystem it can be used there.

This patch also use the correct word "ForCES" instead of "FoRCES" which
is a spelling error inside the IEEE ethertype specification.

Signed-off-by: Alexander Aring <aring@mojatatu.com>
Acked-by: Jamal Hadi Salim <jhs@mojatatu.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2017-08-29 15:14:18 -07:00
John Fastabend
2f857d0460 bpf: sockmap, remove STRPARSER map_flags and add multi-map support
The addition of map_flags BPF_SOCKMAP_STRPARSER flags was to handle a
specific use case where we want to have BPF parse program disabled on
an entry in a sockmap.

However, Alexei found the API a bit cumbersome and I agreed. Lets
remove the STRPARSER flag and support the use case by allowing socks
to be in multiple maps. This allows users to create two maps one with
programs attached and one without. When socks are added to maps they
now inherit any programs attached to the map. This is a nice
generalization and IMO improves the API.

The API rules are less ambiguous and do not need a flag:

  - When a sock is added to a sockmap we have two cases,

     i. The sock map does not have any attached programs so
        we can add sock to map without inheriting bpf programs.
        The sock may exist in 0 or more other maps.

    ii. The sock map has an attached BPF program. To avoid duplicate
        bpf programs we only add the sock entry if it does not have
        an existing strparser/verdict attached, returning -EBUSY if
        a program is already attached. Otherwise attach the program
        and inherit strparser/verdict programs from the sock map.

This allows for socks to be in a multiple maps for redirects and
inherit a BPF program from a single map.

Also this patch simplifies the logic around BPF_{EXIST|NOEXIST|ANY}
flags. In the original patch I tried to be extra clever and only
update map entries when necessary. Now I've decided the complexity
is not worth it. If users constantly update an entry with the same
sock for no reason (i.e. update an entry without actually changing
any parameters on map or sock) we still do an alloc/release. Using
this and allowing multiple entries of a sock to exist in a map the
logic becomes much simpler.

Note: Now that multiple maps are supported the "maps" pointer called
when a socket is closed becomes a list of maps to remove the sock from.
To keep the map up to date when a sock is added to the sockmap we must
add the map/elem in the list. Likewise when it is removed we must
remove it from the list. This results in searching the per psock list
on delete operation. On TCP_CLOSE events we walk the list and remove
the psock from all map/entry locations. I don't see any perf
implications in this because at most I have a psock in two maps. If
a psock were to be in many maps its possibly this might be noticeable
on delete but I can't think of a reason to dup a psock in many maps.
The sk_callback_lock is used to protect read/writes to the list. This
was convenient because in all locations we were taking the lock
anyways just after working on the list. Also the lock is per sock so
in normal cases we shouldn't see any contention.

Suggested-by: Alexei Starovoitov <ast@kernel.org>
Fixes: 174a79ff95 ("bpf: sockmap with sk redirect support")
Signed-off-by: John Fastabend <john.fastabend@gmail.com>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
2017-08-28 11:13:21 -07:00
John Fastabend
464bc0fd62 bpf: convert sockmap field attach_bpf_fd2 to type
In the initial sockmap API we provided strparser and verdict programs
using a single attach command by extending the attach API with a the
attach_bpf_fd2 field.

However, if we add other programs in the future we will be adding a
field for every new possible type, attach_bpf_fd(3,4,..). This
seems a bit clumsy for an API. So lets push the programs using two
new type fields.

   BPF_SK_SKB_STREAM_PARSER
   BPF_SK_SKB_STREAM_VERDICT

This has the advantage of having a readable name and can easily be
extended in the future.

Updates to samples and sockmap included here also generalize tests
slightly to support upcoming patch for multiple map support.

Signed-off-by: John Fastabend <john.fastabend@gmail.com>
Fixes: 174a79ff95 ("bpf: sockmap with sk redirect support")
Suggested-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
2017-08-28 11:13:21 -07:00
Dan Williams
7a14724f54 libnvdimm: clean up command definitions
Remove the command payloads that do not have an associated libnvdimm
ioctl. I.e. remove the payloads that would only ever be carried in the
ND_CMD_CALL envelope. This prevents userspace from growing unnecessary
dependencies on this kernel header when userspace already has everything
it needs to craft and send these commands.

Cc: Jerry Hoemann <jerry.hoemann@hpe.com>
Reported-by: Yasunori Goto <y-goto@jp.fujitsu.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
2017-08-28 08:33:20 -07:00
David Lebrun
38ee7f2d47 ipv6: sr: add support for encapsulation of L2 frames
This patch implements the L2 frame encapsulation mechanism, referred to
as T.Encaps.L2 in the SRv6 specifications [1].

A new type of SRv6 tunnel mode is added (SEG6_IPTUN_MODE_L2ENCAP). It only
accepts packets with an existing MAC header (i.e., it will not work for
locally generated packets). The resulting packet looks like IPv6 -> SRH ->
Ethernet -> original L3 payload. The next header field of the SRH is set to
NEXTHDR_NONE.

[1] https://tools.ietf.org/html/draft-filsfils-spring-srv6-network-programming-01

Signed-off-by: David Lebrun <david.lebrun@uclouvain.be>
Signed-off-by: David S. Miller <davem@davemloft.net>
2017-08-25 17:10:23 -07:00
Arkadi Sharshevsky
3fb886ecea devlink: Add IPv4 header for dpipe
This will be used by the IPv4 host table which will be introduced in the
following patches. This header is global and can be reused by many
drivers.

Signed-off-by: Arkadi Sharshevsky <arkadis@mellanox.com>
Signed-off-by: Jiri Pirko <jiri@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2017-08-24 09:33:16 -07:00
Arkadi Sharshevsky
1177009131 devlink: Add Ethernet header for dpipe
This will be used by the IPv4 host table which will be introduced in the
following patches. This header is global and can be reused by many
drivers.

Signed-off-by: Arkadi Sharshevsky <arkadis@mellanox.com>
Signed-off-by: Jiri Pirko <jiri@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2017-08-24 09:33:15 -07:00
Omar Sandoval
1e6ec9ea89 Revert "loop: support 4k physical blocksize"
There's some stuff still up in the air, let's not get stuck with a
subpar ABI. I'll follow up with something better for 4.14.

Signed-off-by: Omar Sandoval <osandov@fb.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
2017-08-23 15:57:55 -06:00
William Tu
84e54fe0a5 gre: introduce native tunnel support for ERSPAN
The patch adds ERSPAN type II tunnel support.  The implementation
is based on the draft at [1].  One of the purposes is for Linux
box to be able to receive ERSPAN monitoring traffic sent from
the Cisco switch, by creating a ERSPAN tunnel device.
In addition, the patch also adds ERSPAN TX, so Linux virtual
switch can redirect monitored traffic to the ERSPAN tunnel device.
The traffic will be encapsulated into ERSPAN and sent out.

The implementation reuses tunnel key as ERSPAN session ID, and
field 'erspan' as ERSPAN Index fields:
./ip link add dev ers11 type erspan seq key 100 erspan 123 \
			local 172.16.1.200 remote 172.16.1.100

To use the above device as ERSPAN receiver, configure
Nexus 5000 switch as below:

monitor session 100 type erspan-source
  erspan-id 123
  vrf default
  destination ip 172.16.1.200
  source interface Ethernet1/11 both
  source interface Ethernet1/12 both
  no shut
monitor erspan origin ip-address 172.16.1.100 global

[1] https://tools.ietf.org/html/draft-foschiano-erspan-01
[2] iproute2 patch: http://marc.info/?l=linux-netdev&m=150306086924951&w=2
[3] test script: http://marc.info/?l=linux-netdev&m=150231021807304&w=2

Signed-off-by: William Tu <u9012063@gmail.com>
Signed-off-by: Meenakshi Vohra <mvohra@vmware.com>
Cc: Alexey Kuznetsov <kuznet@ms2.inr.ac.ru>
Cc: Hideaki YOSHIFUJI <yoshfuji@linux-ipv6.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
2017-08-22 14:29:30 -07:00
David S. Miller
a43dce9358 Merge branch 'master' of git://git.kernel.org/pub/scm/linux/kernel/git/klassert/ipsec-next
Steffen Klassert says:

====================
pull request (net-next): ipsec-next 2017-08-21

1) Support RX checksum with IPsec crypto offload for esp4/esp6.
   From Ilan Tayari.

2) Fixup IPv6 checksums when doing IPsec crypto offload.
   From Yossi Kuperman.

3) Auto load the xfrom offload modules if a user installs
   a SA that requests IPsec offload. From Ilan Tayari.

4) Clear RX offload informations in xfrm_input to not
   confuse the TX path with stale offload informations.
   From Ilan Tayari.

5) Allow IPsec GSO for local sockets if the crypto operation
   will be offloaded.

6) Support setting of an output mark to the xfrm_state.
   This mark can be used to to do the tunnel route lookup.
   From Lorenzo Colitti.
====================

Signed-off-by: David S. Miller <davem@davemloft.net>
2017-08-21 09:29:47 -07:00
Martin KaFai Lau
96eabe7a40 bpf: Allow selecting numa node during map creation
The current map creation API does not allow to provide the numa-node
preference.  The memory usually comes from where the map-creation-process
is running.  The performance is not ideal if the bpf_prog is known to
always run in a numa node different from the map-creation-process.

One of the use case is sharding on CPU to different LRU maps (i.e.
an array of LRU maps).  Here is the test result of map_perf_test on
the INNER_LRU_HASH_PREALLOC test if we force the lru map used by
CPU0 to be allocated from a remote numa node:

[ The machine has 20 cores. CPU0-9 at node 0. CPU10-19 at node 1 ]

># taskset -c 10 ./map_perf_test 512 8 1260000 8000000
5:inner_lru_hash_map_perf pre-alloc 1628380 events per sec
4:inner_lru_hash_map_perf pre-alloc 1626396 events per sec
3:inner_lru_hash_map_perf pre-alloc 1626144 events per sec
6:inner_lru_hash_map_perf pre-alloc 1621657 events per sec
2:inner_lru_hash_map_perf pre-alloc 1621534 events per sec
1:inner_lru_hash_map_perf pre-alloc 1620292 events per sec
7:inner_lru_hash_map_perf pre-alloc 1613305 events per sec
0:inner_lru_hash_map_perf pre-alloc 1239150 events per sec  #<<<

After specifying numa node:
># taskset -c 10 ./map_perf_test 512 8 1260000 8000000
5:inner_lru_hash_map_perf pre-alloc 1629627 events per sec
3:inner_lru_hash_map_perf pre-alloc 1628057 events per sec
1:inner_lru_hash_map_perf pre-alloc 1623054 events per sec
6:inner_lru_hash_map_perf pre-alloc 1616033 events per sec
2:inner_lru_hash_map_perf pre-alloc 1614630 events per sec
4:inner_lru_hash_map_perf pre-alloc 1612651 events per sec
7:inner_lru_hash_map_perf pre-alloc 1609337 events per sec
0:inner_lru_hash_map_perf pre-alloc 1619340 events per sec #<<<

This patch adds one field, numa_node, to the bpf_attr.  Since numa node 0
is a valid node, a new flag BPF_F_NUMA_NODE is also added.  The numa_node
field is honored if and only if the BPF_F_NUMA_NODE flag is set.

Numa node selection is not supported for percpu map.

This patch does not change all the kmalloc.  F.e.
'htab = kzalloc()' is not changed since the object
is small enough to stay in the cache.

Signed-off-by: Martin KaFai Lau <kafai@fb.com>
Acked-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Alexei Starovoitov <ast@fb.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2017-08-19 21:35:43 -07:00
Florian Westphal
6b5dc98e8f netfilter: rt: add support to fetch path mss
to be used in combination with tcp option set support to mimic
iptables TCPMSS --clamp-mss-to-pmtu.

v2: Eric Dumazet points out dst must be initialized.

Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
2017-08-19 13:15:10 +02:00
Florian Westphal
99d1712bc4 netfilter: exthdr: tcp option set support
This allows setting 2 and 4 byte quantities in the tcp option space.
Main purpose is to allow native replacement for xt_TCPMSS to
work around pmtu blackholes.

Writes to kind and len are now allowed at the moment, it does not seem
useful to do this as it causes corruption of the tcp option space.

We can always lift this restriction later if a use-case appears.

Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
2017-08-19 13:15:10 +02:00