nf_tables: fix NULL pointer dereference in nft_inner_init()

We should check whether the NFTA_INNER_NUM netlink attribute is present
before accessing it, otherwise a null pointer deference error will occur.

Call Trace:
dump_stack_lvl+0x4f/0x90
print_report+0x3f0/0x620
kasan_report+0xcd/0x110
__asan_load4+0x84/0xa0
nft_inner_init+0x128/0x2e0
nf_tables_newrule+0x813/0x1230
nfnetlink_rcv_batch+0xec3/0x1170
nfnetlink_rcv+0x1e4/0x220
netlink_unicast+0x34e/0x4b0
netlink_sendmsg+0x45c/0x7e0
__sys_sendto+0x355/0x370
__x64_sys_sendto+0x84/0xa0
do_syscall_64+0x3f/0x90
entry_SYSCALL_64_after_hwframe+0x6e/0xd8

Fixes: 3a07327d10a0 ("netfilter: nft_inner: support for inner tunnel header matching")
Signed-off-by: Xingyuan Mo <hdthky0@gmail.com>
Signed-off-by: Florian Westphal <fw@strlen.de>

netfilter: nf_tables: Introduce NFT_MSG_GETRULE_RESET

Analogous to NFT_MSG_GETOBJ_RESET, but for rules: Reset stateful
expressions like counters or quotas. The latter two are the only
consumers, adjust their 'dump' callbacks to respect the parameter
introduced earlier.

Signed-off-by: Phil Sutter <phil@nwl.cc>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

netfilter: nf_tables: Extend nft_expr_ops::dump callback parameters

Add a 'reset' flag just like with nft_object_ops::dump. This will be
useful to reset "anonymous stateful objects", e.g. simple rule counters.

No functional change intended.

Signed-off-by: Phil Sutter <phil@nwl.cc>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

netfilter: nft_inner: fix return value check in nft_inner_parse_l2l3()

In nft_inner_parse_l2l3(), the return value of skb_header_pointer() is
'veth' instead of 'eth' when case 'htons(ETH_P_8021Q)' and fix it.

Fixes: 3a07327d10a0 ("netfilter: nft_inner: support for inner tunnel header matching")
Signed-off-by: Peng Wu <wupeng58@huawei.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

netfilter: nft_inner: set tunnel offset to GRE header offset

Set inner tunnel offset to the GRE header, this is redundant to existing
transport header offset, but this normalizes the handling of the tunnel
header regardless its location in the layering. GRE version 0 is overloaded
with RFCs, the type decorator in the inner expression might also be useful
to interpret matching fields from the netlink delinearize path in userspace.

Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

netfilter: nft_inner: add geneve support

Geneve tunnel header may contain options, parse geneve header and update
offset to point to the link layer header according to the opt_len field.

Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

netfilter: nft_meta: add inner match support

Add support for inner meta matching on:

- NFT_META_PROTOCOL: to match on the ethertype, this can be used
regardless tunnel protocol provides no link layer header, in that case
nft_inner sets on the ethertype based on the IP header version field.
- NFT_META_L4PROTO: to match on the layer 4 protocol.

These meta expression are usually autogenerated as dependencies by
userspace nftables.

Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

netfilter: nft_inner: add percpu inner context

Add NFT_PKTINFO_INNER_FULL flag to annotate that inner offsets are
available. Store nft_inner_tun_ctx object in percpu area to cache
existing inner offsets for this skbuff.

Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

netfilter: nft_inner: support for inner tunnel header matching

This new expression allows you to match on the inner headers that are
encapsulated by any of the existing tunneling protocols.

This expression parses the inner packet to set the link, network and
transport offsets, so the existing expressions (with a few updates) can
be reused to match on the inner headers.

The inner expression supports for different tunnel combinations such as:

- ethernet frame over IPv4/IPv6 packet, eg. VxLAN.
- IPv4/IPv6 packet over IPv4/IPv6 packet, eg. IPIP.
- IPv4/IPv6 packet over IPv4/IPv6 + transport header, eg. GRE.
- transport header (ESP or SCTP) over transport header (usually UDP)

The following fields are used to describe the tunnel protocol:

- flags, which describe how to parse the inner headers:

NFT_PAYLOAD_CTX_INNER_TUN, the tunnel provides its own header.
NFT_PAYLOAD_CTX_INNER_ETHER, the ethernet frame is available as inner header.
NFT_PAYLOAD_CTX_INNER_NH, the network header is available as inner header.
NFT_PAYLOAD_CTX_INNER_TH, the transport header is available as inner header.

For example, VxLAN sets on all of these flags. While GRE only sets on
NFT_PAYLOAD_CTX_INNER_NH and NFT_PAYLOAD_CTX_INNER_TH. Then, ESP over
UDP only sets on NFT_PAYLOAD_CTX_INNER_TH.

The tunnel description is composed of the following attributes:

- header size: in case the tunnel comes with its own header, eg. VxLAN.

- type: this provides a hint to userspace on how to delinearize the rule.
This is useful for VxLAN and Geneve since they run over UDP, since
transport does not provide a hint. This is also useful in case hardware
offload is ever supported. The type is not currently interpreted by the
kernel.

- expression: currently only payload supported. Follow up patch adds
also inner meta support which is required by autogenerated
dependencies. The exthdr expression should be supported too
at some point. There is a new inner_ops operation that needs to be
set on to allow to use an existing expression from the inner expression.

This patch adds a new NFT_PAYLOAD_TUN_HEADER base which allows to match
on the tunnel header fields, eg. vxlan vni.

The payload expression is embedded into nft_inner private area and this
private data area is passed to the payload inner eval function via
direct call.

Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>