"err" is set to zero if bpf_map_area_alloc() fails so it means we return
ERR_PTR(0) which is NULL.  The caller, find_and_alloc_map(), is not
expecting NULL returns and will oops.

Fixes: 174a79ff ("bpf: sockmap with sk redirect support")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Acked-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: John Fastabend <john.fastabend@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

Twice patches trying to constify inet{6}_protocol have been reverted:
39294c3d ("Revert "ipv6: constify inet6_protocol structures"") to
revert 3a3a4e30 and then 03157937 ("Revert "ipv4: make
net_protocol const"") to revert aa8db499.

Add a comment that the structures can not be const because the
early_demux field can change based on a sysctl.
Signed-off-by: David Ahern <dsahern@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

The xen driver initializes struct ubuf_info fields using designated
initializers. I recently moved these fields inside a nested anonymous
struct inside an anonymous union. I had missed this use case.

This breaks compilation of xen-netback with older compilers.
>From kbuild bot with gcc-4.4.7:

   drivers/net//xen-netback/interface.c: In function
   'xenvif_init_queue':
   >> drivers/net//xen-netback/interface.c:554: error: unknown field 'ctx' specified in initializer
   >> drivers/net//xen-netback/interface.c:554: warning: missing braces around initializer
      drivers/net//xen-netback/interface.c:554: warning: (near initialization for '(anonymous).<anonymous>')
   >> drivers/net//xen-netback/interface.c:554: warning: initialization makes integer from pointer without a cast
   >> drivers/net//xen-netback/interface.c:555: error: unknown field 'desc' specified in initializer

Add double braces around the designated initializers to match their
nested position in the struct. After this, compilation succeeds again.

Fixes: 4ab6c99d ("sock: MSG_ZEROCOPY notification coalescing")
Reported-by: kbuild bot <lpk@intel.com>
Signed-off-by: Willem de Bruijn <willemb@google.com>
Acked-by: Wei Liu <wei.liu2@citrix.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

William Tu says:

====================
gre: add collect_md mode for ERSPAN tunnel

This patch series provide collect_md mode for ERSPAN tunnel.  The fist patch
refactors the existing gre_fb_xmit function by exacting the route cache
portion into a new function called prepare_fb_xmit.  The second patch
introduces the collect_md mode for ERSPAN tunnel, by calling the
prepare_fb_xmit function and adding ERSPAN specific logic.  The final patch
adds the test case using bpf_skb_{set,get}_tunnel_{key,opt}.
====================
Signed-off-by: David S. Miller <davem@davemloft.net>

Extend existing tests for vxlan, gre, geneve, ipip to
include ERSPAN tunnel.
Signed-off-by: William Tu <u9012063@gmail.com>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

Similar to gre, vxlan, geneve, ipip tunnels, allow ERSPAN tunnels to
operate in 'collect metadata' mode.  bpf_skb_[gs]et_tunnel_key() helpers
can make use of it right away.  OVS can use it as well in the future.
Signed-off-by: William Tu <u9012063@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

The patch refactors the gre_fb_xmit function, by creating
prepare_fb_xmit function for later ERSPAN collect_md mode patch.
Signed-off-by: William Tu <u9012063@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

This reverts commit aa8db499.

Early demux structs can not be made const. Doing so results in:
[   84.967355] BUG: unable to handle kernel paging request at ffffffff81684b10
[   84.969272] IP: proc_configure_early_demux+0x1e/0x3d
[   84.970544] PGD 1a0a067
[   84.970546] P4D 1a0a067
[   84.971212] PUD 1a0b063
[   84.971733] PMD 80000000016001e1

[   84.972669] Oops: 0003 [#1] SMP
[   84.973065] Modules linked in: ip6table_filter ip6_tables veth vrf
[   84.973833] CPU: 0 PID: 955 Comm: sysctl Not tainted 4.13.0-rc6+ #22
[   84.974612] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.7.5-20140531_083030-gandalf 04/01/2014
[   84.975855] task: ffff88003854ce00 task.stack: ffffc900005a4000
[   84.976580] RIP: 0010:proc_configure_early_demux+0x1e/0x3d
[   84.977253] RSP: 0018:ffffc900005a7dd0 EFLAGS: 00010246
[   84.977891] RAX: ffffffff81684b10 RBX: 0000000000000001 RCX: 0000000000000000
[   84.978759] RDX: 0000000000000000 RSI: 0000000000000006 RDI: 0000000000000000
[   84.979628] RBP: ffffc900005a7dd0 R08: 0000000000000000 R09: 0000000000000000
[   84.980501] R10: 0000000000000001 R11: 0000000000000008 R12: 0000000000000001
[   84.981373] R13: ffffffffffffffea R14: ffffffff81a9b4c0 R15: 0000000000000002
[   84.982249] FS:  00007feb237b7700(0000) GS:ffff88003fc00000(0000) knlGS:0000000000000000
[   84.983231] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[   84.983941] CR2: ffffffff81684b10 CR3: 0000000038492000 CR4: 00000000000406f0
[   84.984817] Call Trace:
[   84.985133]  proc_tcp_early_demux+0x29/0x30

I think this is the second time such a patch has been reverted.

Cc: Bhumika Goyal <bhumirks@gmail.com>
Signed-off-by: David Ahern <dsahern@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

Make this const as it is either used during a copy operation or passed
to a const argument of the function rhltable_init
Signed-off-by: Bhumika Goyal <bhumirks@gmail.com>
Acked-by: Santosh Shilimkar <santosh.shilimkar@oracle.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

Make these const as they are only passed to a const argument of the
function inet_add_protocol.
Signed-off-by: Bhumika Goyal <bhumirks@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

Make this const as it is only passed to a const argument of the function
ebt_register_table.
Signed-off-by: Bhumika Goyal <bhumirks@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

John Fastabend says:

====================
sockmap UAPI updates and fixes

This series updates sockmap UAPI, adds additional test cases and
provides a couple fixes.

First the UAPI changes. The original API added two sockmap specific
API artifacts (a) a new map_flags field with a sockmap specific update
command and (b) a new sockmap specific attach field in the attach data
structure. After this series instead of attaching programs with a
single command now two commands are used to attach programs to maps
individually. This allows us to add new programs easily in the future
and avoids any specific sockmap data structure additions. The
map_flags field is also removed and instead we allow socks to be
added to multiple maps that may or may not have programs attached.
This allows users to decide if a sock should run a SK_SKB program type
on receive based on the map it is attached to. This is a nice
improvement. See patches for specific details.

More test cases were added to test above changes and also stress test
the interface.

Finally two fixes/improvements were made. First a missing rcu
section was added. Second now sockmap can build without KCM being
used to trigger 'y' on CONFIG_STREAM_PARSER by selecting a new
BPF config option.
====================
Signed-off-by: David S. Miller <davem@davemloft.net>

Sockmap is a bit different than normal stress tests that can run
in parallel as is. We need to reuse the same socket pool and map
pool to get good stress test cases.
Signed-off-by: John Fastabend <john.fastabend@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

SOCKMAP uses strparser code (compiled with Kconfig option
CONFIG_STREAM_PARSER) to run the parser BPF program. Without this
config option set sockmap wont be compiled. However, at the moment
the only way to pull in the strparser code is to enable KCM.

To resolve this create a BPF specific config option to pull
only the strparser piece in that sockmap needs. This also
allows folks who want to use BPF/syscall/maps but don't need
sockmap to easily opt out.
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>

After userspace pushes sockets into a sockmap it may not be receiving
data (assuming stream_{parser|verdict} programs are attached). But, it
may still want to manage the socks. A common pattern is to poll/select
for a POLLRDHUP event so we can close the sock.

This patch adds the logic to wake up these listeners.

Also add TCP_SYN_SENT to the list of events to handle. We don't want
to break the connection just because we happen to be in this state.
Signed-off-by: John Fastabend <john.fastabend@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

When attaching a program to sockmap we need to check map type
is correct.

Fixes: 174a79ff ("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>

Tests packet read/writes and additional skb fields.
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>

Add some more sockmap tests to cover,

 - forwarding to NULL entries
 - more than two maps to test list ops
 - forwarding to different map
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>

References to psock must be done inside RCU critical section.

Fixes: 174a79ff ("bpf: sockmap with sk redirect support")
Signed-off-by: John Fastabend <john.fastabend@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

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: 174a79ff ("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>

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: 174a79ff ("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>

This patch solves the following error:
arch/arm/boot/dts/rk3228-evb.dtb: ERROR (phandle_references): Reference to non-existent node or label "phy0"

Fixess db40f15b ("ARM: dts: rk3228-evb: Enable the integrated PHY for gmac")
Signed-off-by: David Wu <david.wu@rock-chips.com>
Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: David S. Miller <davem@davemloft.net>

The MVPP22_XLG_CTRL1_FRAMESIZELIMIT define is used as an offset, but is
defined as BIT(0). Updated its name to contains "OFFS" as in offset and
fix its value using the offset value, 0.
Reported-by: Stefan Chulski <stefanc@marvell.com>
Signed-off-by: Antoine Tenart <antoine.tenart@free-electrons.com>
Fixes: 76eb1b1d ("net: mvpp2: set maximum packet size for 10G ports")
Signed-off-by: David S. Miller <davem@davemloft.net>

Jeff Kirsher says:

====================
40GbE Intel Wired LAN Driver Updates 2017-08-25

This series contains updates to i40e and i40evf only.

Mitch adjusts the max packet size to account for two VLAN tags.

Sudheer provides a fix to ensure that the watchdog timer is scheduled
immediately after admin queue operations are scheduled in i40evf_down().
Fixes an issue by adding locking around the admin queue command and
update of state variables so that adminq_subtask will have the accurate
information whenever it gets scheduled.

Anjali fixes a bug where the PF flag setup should happen before the VMDq
RSS queue count is initialized for VMDq VSI to get the right number of
queues for RSS in the case of x722 devices.  Fixed a problem with the
hardware ATR eviction feature where the NVM setting was incorrect.

Jake separates the flags into two types, hw_features and flags.  The
hw_features flags contain a set of features which are enabled at init
time and will not contain feature flags that can be toggled.  Everything
else will remain in the flags variable, and can be modified anytime
during run time.  We should not be directly copying a cpumask_t, since
it is bitmap and might not be copied correctly, so use cpumask_copy()
instead.

Stefan Assmann makes vf _offload_flags more "generic" by renaming it to
vf_cap_flags, which allows other capabilities besides offloading to be
added.

Alan makes it such that if adaptive-rx/tx is enabled, the user cannot
make any manual adjustments to interrupt moderation.  Also makes it so
that if ITR is disabled by adaptive-rx/tx is then enabled, ITR will be
re-enabled.

v2: Dropped patches #1 & #8 from the original patch series submission,
    while Jesse and Jake re-work their patches based on feedback from
    David Miller.  Also removed the duplicate patch 3 that was
    accidentally sent out twice in the previous submission.
====================
Signed-off-by: David S. Miller <davem@davemloft.net>

Jakub Kicinski says:

====================
nfp: SR-IOV ndos support

This set adds basic SR-IOV including setting/getting VF MAC addresses,
VLANs, link state and spoofcheck settings.  It is wired up for both
vNICs and representors (note: ip link will not report VF settings on
VF/PF representors because they are not linked to the PF PCI device).

Pablo and team add the basic implementation, Simon and Dirk follow
up with the representor plumbing.
====================
Signed-off-by: David S. Miller <davem@davemloft.net>

Add basic ndo_set/get_vf to support SR-IOV on all types
of port representors.
Signed-off-by: Simon Horman <simon.horman@netronome.com>
Signed-off-by: Dirk van der Merwe <dirk.vandermerwe@netronome.com>
Reviewed-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

Add basic ndo_set/get_vf to support SR-IOV.

VF to egress phy static mapping by now.

Use vfcfg ABI version 2 to write the info to the FW and collect
the return value from the mailbox.
Signed-off-by: Pablo Cascón <pablo.cascon@netronome.com>
Signed-off-by: Jimmy Kizito <jimmy.kizito@netronome.com>
Signed-off-by: Rami Tomer <rami.tomer@netronome.com>
Signed-off-by: Simon Horman <simon.horman@netronome.com>
Signed-off-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

syszkaller got a hang in tcp stack, related to a bug in
tcp_sendpage_locked()

root@syzkaller:~# cat /proc/3059/stack
[<ffffffff83de926c>] __lock_sock+0x1dc/0x2f0
[<ffffffff83de9473>] lock_sock_nested+0xf3/0x110
[<ffffffff8408ce01>] tcp_sendmsg+0x21/0x50
[<ffffffff84163b6f>] inet_sendmsg+0x11f/0x5e0
[<ffffffff83dd8eea>] sock_sendmsg+0xca/0x110
[<ffffffff83dd9547>] kernel_sendmsg+0x47/0x60
[<ffffffff83de35dc>] sock_no_sendpage+0x1cc/0x280
[<ffffffff8408916b>] tcp_sendpage_locked+0x10b/0x160
[<ffffffff84089203>] tcp_sendpage+0x43/0x60
[<ffffffff841641da>] inet_sendpage+0x1aa/0x660
[<ffffffff83dd4fcd>] kernel_sendpage+0x8d/0xe0
[<ffffffff83dd50ac>] sock_sendpage+0x8c/0xc0
[<ffffffff81b63300>] pipe_to_sendpage+0x290/0x3b0
[<ffffffff81b67243>] __splice_from_pipe+0x343/0x750
[<ffffffff81b6a459>] splice_from_pipe+0x1e9/0x330
[<ffffffff81b6a5e0>] generic_splice_sendpage+0x40/0x50
[<ffffffff81b6b1d7>] SyS_splice+0x7b7/0x1610
[<ffffffff84d77a01>] entry_SYSCALL_64_fastpath+0x1f/0xbe

Fixes: 306b13eb ("proto_ops: Add locked held versions of sendmsg and sendpage")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reported-by: Dmitry Vyukov <dvyukov@google.com>
Cc: Tom Herbert <tom@quantonium.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

Cong Wang says:

====================
net_sched: clean up tc classes and u32 filter

Patch 1 and patch 2 prepare for patch 3. Major changes
are in patch 3 and patch 4, details are there too.

v2: Add patch 1 and 2, group all into a patchset
    Fix a coding style issue in patch 4
====================
Signed-off-by: David S. Miller <davem@davemloft.net>

It is ugly to hide a u32-filter-specific pointer inside Qdisc,
this breaks the TC layers:

1. Qdisc is a generic representation, should not have any specific
   data of any type

2. Qdisc layer is above filter layer, should only save filters in
   the list of struct tcf_proto.

This pointer is used as the head of the chain of u32 hash tables,
that is struct tc_u_hnode, because u32 filter is very special,
it allows to create multiple hash tables within one qdisc and
across multiple u32 filters.

Instead of using this ugly pointer, we can just save it in a global
hash table key'ed by (dev ifindex, qdisc handle), therefore we can
still treat it as a per qdisc basis data structure conceptually.

Of course, because of network namespaces, this key is not unique
at all, but it is fine as we already have a pointer to Qdisc in
struct tc_u_common, we can just compare the pointers when collision.

And this only affects slow paths, has no impact to fast path,
thanks to the pointer ->tp_c.

Cc: Jamal Hadi Salim <jhs@mojatatu.com>
Cc: Jiri Pirko <jiri@resnulli.us>
Signed-off-by: Cong Wang <xiyou.wangcong@gmail.com>
Acked-by: Jiri Pirko <jiri@mellanox.com>
Acked-by: Jamal Hadi Salim <jhs@mojatatu.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

For TC classes, their ->get() and ->put() are always paired, and the
reference counting is completely useless, because:

1) For class modification and dumping paths, we already hold RTNL lock,
   so all of these ->get(),->change(),->put() are atomic.

2) For filter bindiing/unbinding, we use other reference counter than
   this one, and they should have RTNL lock too.

3) For ->qlen_notify(), it is special because it is called on ->enqueue()
   path, but we already hold qdisc tree lock there, and we hold this
   tree lock when graft or delete the class too, so it should not be gone
   or changed until we release the tree lock.

Therefore, this patch removes ->get() and ->put(), but:

1) Adds a new ->find() to find the pointer to a class by classid, no
   refcnt.

2) Move the original class destroy upon the last refcnt into ->delete(),
   right after releasing tree lock. This is fine because the class is
   already removed from hash when holding the lock.

For those who also use ->put() as ->unbind(), just rename them to reflect
this change.

Cc: Jamal Hadi Salim <jhs@mojatatu.com>
Signed-off-by: Cong Wang <xiyou.wangcong@gmail.com>
Acked-by: Jiri Pirko <jiri@mellanox.com>
Acked-by: Jamal Hadi Salim <jhs@mojatatu.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

Like for TC actions, ->delete() is a special case,
we have to prepare and fill the notification before delete
otherwise would get use-after-free after we remove the
reference count.
Signed-off-by: Cong Wang <xiyou.wangcong@gmail.com>
Acked-by: Jamal Hadi Salim <jhs@mojatatu.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

This is not needed if we move them up properly.
Signed-off-by: Cong Wang <xiyou.wangcong@gmail.com>
Acked-by: Jiri Pirko <jiri@mellanox.com>
Acked-by: Jamal Hadi Salim <jhs@mojatatu.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

The skb_pad() function frees the skb on error, so this code has a double
free.

Fixes: 00e57a6d ("net-next/hinic: Add Tx operation")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

David Lebrun says:

====================
net: updates for IPv6 Segment Routing

v2: seg6_lwt_headroom() is not relevant for lwtunnel_input_redirect()
    use cases, and L2ENCAP only uses this redirection. Fix incoherence
    between arbitrary MAC header size support and fixed headroom
    computation by setting only LWTUNNEL_STATE_INPUT_REDIRECT for L2ENCAP
    mode.

This patch series provides several updates for the SRv6 implementation. The
first patch leverages the existing infrastructure to support encapsulation
of IPv4 packets. The second patch implements the T.Encaps.L2 SR function,
enabling to encapsulate an L2 Ethernet frame within an IPv6+SRH packet.
The last three patches update the seg6local lightweight tunnel, and mainly
implement four new actions: End.T, End.DX2, End.DX4 and End.DT6.
====================
Signed-off-by: David S. Miller <davem@davemloft.net>

This patch implements the following seg6local actions.

- SEG6_LOCAL_ACTION_END_T: regular SRH processing and forward to the
  next-hop looked up in the specified routing table.

- SEG6_LOCAL_ACTION_END_DX2: decapsulate an L2 frame and forward it to
  the specified network interface.

- SEG6_LOCAL_ACTION_END_DX4: decapsulate an IPv4 packet and forward it,
  possibly to the specified next-hop.

- SEG6_LOCAL_ACTION_END_DT6: decapsulate an IPv6 packet and forward it
  to the next-hop looked up in the specified routing table.
Signed-off-by: David Lebrun <david.lebrun@uclouvain.be>
Signed-off-by: David S. Miller <davem@davemloft.net>

This patch adds three helper functions to be used with the seg6local packet
processing actions.

The decap_and_validate() function will be used by the End.D* actions, that
decapsulate an SR-enabled packet.

The advance_nextseg() function applies the fundamental operations to update
an SRH for the next segment.

The lookup_nexthop() function helps select the next-hop for the processed
SR packets. It supports an optional next-hop address to route the packet
specifically through it, and an optional routing table to use.
Signed-off-by: David Lebrun <david.lebrun@uclouvain.be>
Signed-off-by: David S. Miller <davem@davemloft.net>

This patch ensures that the seg6local lightweight tunnel is used solely
with IPv6 routes and processes only IPv6 packets.
Signed-off-by: David Lebrun <david.lebrun@uclouvain.be>
Signed-off-by: David S. Miller <davem@davemloft.net>

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-01Signed-off-by: David Lebrun <david.lebrun@uclouvain.be>
Signed-off-by: David S. Miller <davem@davemloft.net>

This patch enables the SRv6 encapsulation mode to carry an IPv4 payload.
All the infrastructure was already present, I just had to add a parameter
to seg6_do_srh_encap() to specify the inner packet protocol, and perform
some additional checks.

Usage example:
ip route add 1.2.3.4 encap seg6 mode encap segs fc00::1,fc00::2 dev eth0
Signed-off-by: David Lebrun <david.lebrun@uclouvain.be>
Signed-off-by: David S. Miller <davem@davemloft.net>