Dan Carpenter reports:

The patch 6acc9b43: "bpf: Add helper to retrieve socket in BPF"
from Oct 2, 2018, leads to the following Smatch complaint:

    net/core/filter.c:4893 bpf_sk_lookup()
    error: we previously assumed 'skb->dev' could be null (see line 4885)

Fix this issue by checking skb->dev before using it.
Signed-off-by: Joe Stringer <joe@wand.net.nz>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

The map-in-map frequently serves as a mechanism for atomic
snapshotting of state that a BPF program might record.  The current
implementation is dangerous to use in this way, however, since
userspace has no way of knowing when all programs that might have
retrieved the "old" value of the map may have completed.

This change ensures that map update operations on map-in-map map types
always wait for all references to the old map to drop before returning
to userspace.
Signed-off-by: Daniel Colascione <dancol@google.com>
Reviewed-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

When test_flow_dissector.sh runs it complains that it can't find script
with_addr.sh:

./test_flow_dissector.sh: line 81: ./with_addr.sh: No such file or
directory

Rework so that with_addr.sh gets installed, add it to
TEST_PROGS_EXTENDED variable.

Fixes: 50b3ed57 ("selftests/bpf: test bpf flow dissection")
Signed-off-by: Anders Roxell <anders.roxell@linaro.org>
Acked-by: Song Liu <songliubraving@fb.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>

When test_lwt_seg6local.sh was added commit c99a84ea
("selftests/bpf: test for seg6local End.BPF action") config fragment
wasn't added, and without CONFIG_LWTUNNEL enabled we see this:
Error: CONFIG_LWTUNNEL is not enabled in this kernel.
selftests: test_lwt_seg6local [FAILED]
Signed-off-by: Anders Roxell <anders.roxell@linaro.org>
Acked-by: Song Liu <songliubraving@fb.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>

Adding EXTRA_LDFLAGS allowing user to specify extra flags
for LD_FLAGS variable. Also adding LDFLAGS to build command
line.
Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Acked-by: Song Liu <songliubraving@fb.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>

Adding EXTRA_CFLAGS allowing user to specify extra flags
for CFLAGS variable.
Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Acked-by: Song Liu <songliubraving@fb.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>

Use __u32 instead u32 in libbpf.c and also use
uapi perf_event.h instead of tools/perf/perf-sys.h.
Signed-off-by: Yonghong Song <yhs@fb.com>
Acked-by: Song Liu <songliubraving@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

Jesper Dangaard Brouer says:

====================
While implementing PoC building blocks for eBPF code XDP+TC that can
manipulate VLANs headers, I discovered a bug in generic-XDP.

The fix should be backported to stable kernels.  Even-though
generic-XDP was introduced in v4.12, I think the bug is not exposed
until v4.14 in the mentined fixes commit.
====================
Acked-by: Song Liu <songliubraving@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

This XDP selftest also contain a small TC-bpf component. It provoke
the generic-XDP bug fixed in previous commit.

The selftest itself shows how to do VLAN manipulation from XDP and TC.
The test demonstrate how XDP ingress can remove a VLAN tag, and how TC
egress can add back a VLAN tag.

This use-case originates from a production need by ISP (kviknet.dk),
who gets DSL-lines terminated as VLAN Q-in-Q tagged packets, and want
to avoid having an net_device for every end-customer on the box doing
the L2 to L3 termination.
  The test-setup is done via a veth-pair and creating two network
namespaces (ns1 and ns2).  The 'ns1' simulate the ISP network that are
loading the BPF-progs stripping and adding VLAN IDs.  The 'ns2'
simulate the DSL-customer that are using VLAN tagged packets.

Running the script with --interactive, will simply not call the
cleanup function.  This gives the effect of creating a testlab, that
the users can inspect and play with.  The --verbose option will simply
request that the shell will print input lines as they are read, this
include comments, which in effect make the comments visible docs.
Reported-by: Yoel Caspersen <yoel@kviknet.dk>
Signed-off-by: Jesper Dangaard Brouer <brouer@redhat.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

The helper bpf_skb_vlan_push is needed by next patch, and the helper
bpf_skb_vlan_pop is added for completeness, regarding VLAN helpers.
Signed-off-by: Jesper Dangaard Brouer <brouer@redhat.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

XDP can modify (and resize) the Ethernet header in the packet.

There is a bug in generic-XDP, because skb->protocol and skb->pkt_type
are setup before reaching (netif_receive_)generic_xdp.

This bug was hit when XDP were popping VLAN headers (changing
eth->h_proto), as skb->protocol still contains VLAN-indication
(ETH_P_8021Q) causing invocation of skb_vlan_untag(skb), which corrupt
the packet (basically popping the VLAN again).

This patch catch if XDP changed eth header in such a way, that SKB
fields needs to be updated.

V2: on request from Song Liu, use ETH_HLEN instead of mac_len,
in __skb_push() as eth_type_trans() use ETH_HLEN in paired skb_pull_inline().

Fixes: d4455169 ("net: xdp: support xdp generic on virtual devices")
Signed-off-by: Jesper Dangaard Brouer <brouer@redhat.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

Prashant Bhole says:

====================
Currently when map a lookup fails, user space API can not make any
distinction whether given key was not found or lookup is not supported
by particular map.

In this series we modify return value of maps which do not support
lookup. Lookup on such map implementation will return -EOPNOTSUPP.
bpf() syscall with BPF_MAP_LOOKUP_ELEM command will set EOPNOTSUPP
errno. We also handle this error in bpftool to print appropriate
message.

Patch 1: adds handling of BPF_MAP_LOOKUP ELEM command of bpf syscall
such that errno will set to EOPNOTSUPP when map doesn't support lookup

Patch 2: Modifies the return value of map_lookup_elem() to EOPNOTSUPP
for maps which do not support lookup

Patch 3: Splits do_dump() in bpftool/map.c. Element printing code is
moved out into new function dump_map_elem(). This was done in order to
reduce deep indentation and accomodate further changes.

Patch 4: Changes in bpftool to print strerror() message when lookup
error is occured. This will result in appropriate message like
"Operation not supported" when map doesn't support lookup.

Patch 5: test_verifier: change fixup map naming convention as
suggested by Alexei

Patch 6: Added verifier tests to check whether verifier rejects call
to bpf_map_lookup_elem from bpf program. For all map types those
do not support map lookup.
====================
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

map_lookup_elem isn't supported by certain map types like:
- BPF_MAP_TYPE_PROG_ARRAY
- BPF_MAP_TYPE_STACK_TRACE
- BPF_MAP_TYPE_XSKMAP
- BPF_MAP_TYPE_SOCKMAP/BPF_MAP_TYPE_SOCKHASH
Let's add verfier tests to check whether verifier prevents
bpf_map_lookup_elem call on above programs from bpf program.
Signed-off-by: Prashant Bhole <bhole_prashant_q7@lab.ntt.co.jp>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Song Liu <songliubraving@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

Currently fixup map are named like fixup_map1, fixup_map2, and so on.
As suggested by Alexei let's change change map names such that we can
identify map type by looking at the name.

This patch is basically a find and replace change:
fixup_map1  ->  fixup_map_hash_8b
fixup_map2  ->  fixup_map_hash_48b
fixup_map3  ->  fixup_map_hash_16b
fixup_map4  ->  fixup_map_array_48b
Suggested-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Prashant Bhole <bhole_prashant_q7@lab.ntt.co.jp>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Song Liu <songliubraving@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

Since map lookup error can be ENOENT or EOPNOTSUPP, let's print
strerror() as error message in normal and JSON output.

This patch adds helper function print_entry_error() to print
entry from lookup error occurs

Example: Following example dumps a map which does not support lookup.

Output before:
root# bpftool map -jp dump id 40
[
    "key": ["0x0a","0x00","0x00","0x00"
    ],
    "value": {
        "error": "can\'t lookup element"
    },
    "key": ["0x0b","0x00","0x00","0x00"
    ],
    "value": {
        "error": "can\'t lookup element"
    }
]

root# bpftool map dump id 40
can't lookup element with key:
0a 00 00 00
can't lookup element with key:
0b 00 00 00
Found 0 elements

Output after changes:
root# bpftool map dump -jp  id 45
[
    "key": ["0x0a","0x00","0x00","0x00"
    ],
    "value": {
        "error": "Operation not supported"
    },
    "key": ["0x0b","0x00","0x00","0x00"
    ],
    "value": {
        "error": "Operation not supported"
    }
]

root# bpftool map dump id 45
key:
0a 00 00 00
value:
Operation not supported
key:
0b 00 00 00
value:
Operation not supported
Found 0 elements
Signed-off-by: Prashant Bhole <bhole_prashant_q7@lab.ntt.co.jp>
Acked-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Song Liu <songliubraving@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

do_dump() function in bpftool/map.c has deep indentations. In order
to reduce deep indent, let's move element printing code out of
do_dump() into dump_map_elem() function.
Signed-off-by: Prashant Bhole <bhole_prashant_q7@lab.ntt.co.jp>
Acked-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Song Liu <songliubraving@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

Return ERR_PTR(-EOPNOTSUPP) from map_lookup_elem() methods of below
map types:
- BPF_MAP_TYPE_PROG_ARRAY
- BPF_MAP_TYPE_STACK_TRACE
- BPF_MAP_TYPE_XSKMAP
- BPF_MAP_TYPE_SOCKMAP/BPF_MAP_TYPE_SOCKHASH
Signed-off-by: Prashant Bhole <bhole_prashant_q7@lab.ntt.co.jp>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Song Liu <songliubraving@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

The error value returned by map_lookup_elem doesn't differentiate
whether lookup was failed because of invalid key or lookup is not
supported.

Lets add handling for -EOPNOTSUPP return value of map_lookup_elem()
method of map, with expectation from map's implementation that it
should return -EOPNOTSUPP if lookup is not supported.

The errno for bpf syscall for BPF_MAP_LOOKUP_ELEM command will be set
to EOPNOTSUPP if map lookup is not supported.
Signed-off-by: Prashant Bhole <bhole_prashant_q7@lab.ntt.co.jp>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Song Liu <songliubraving@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

In btf_parse_hdr(), the length of the btf data header is firstly copied
from the user space to 'hdr_len' and checked to see whether it is larger
than 'btf_data_size'. If yes, an error code EINVAL is returned. Otherwise,
the whole header is copied again from the user space to 'btf->hdr'.
However, after the second copy, there is no check between
'btf->hdr->hdr_len' and 'hdr_len' to confirm that the two copies get the
same value. Given that the btf data is in the user space, a malicious user
can race to change the data between the two copies. By doing so, the user
can provide malicious data to the kernel and cause undefined behavior.

This patch adds a necessary check after the second copy, to make sure
'btf->hdr->hdr_len' has the same value as 'hdr_len'. Otherwise, an error
code EINVAL will be returned.
Signed-off-by: Wenwen Wang <wang6495@umn.edu>
Acked-by: Song Liu <songliubraving@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

Alexei Starovoitov says:

====================
pull-request: bpf-next 2018-10-08

The following pull-request contains BPF updates for your *net-next* tree.

The main changes are:

1) sk_lookup_[tcp|udp] and sk_release helpers from Joe Stringer which allow
BPF programs to perform lookups for sockets in a network namespace. This would
allow programs to determine early on in processing whether the stack is
expecting to receive the packet, and perform some action (eg drop,
forward somewhere) based on this information.

2) per-cpu cgroup local storage from Roman Gushchin.
Per-cpu cgroup local storage is very similar to simple cgroup storage
except all the data is per-cpu. The main goal of per-cpu variant is to
implement super fast counters (e.g. packet counters), which don't require
neither lookups, neither atomic operations in a fast path.
The example of these hybrid counters is in selftests/bpf/netcnt_prog.c

3) allow HW offload of programs with BPF-to-BPF function calls from Quentin Monnet

4) support more than 64-byte key/value in HW offloaded BPF maps from Jakub Kicinski

5) rename of libbpf interfaces from Andrey Ignatov.
libbpf is maturing as a library and should follow good practices in
library design and implementation to play well with other libraries.
This patch set brings consistent naming convention to global symbols.

6) relicense libbpf as LGPL-2.1 OR BSD-2-Clause from Alexei Starovoitov
to let Apache2 projects use libbpf

7) various AF_XDP fixes from Björn and Magnus
====================
Signed-off-by: David S. Miller <davem@davemloft.net>

Pablo Neira Ayuso says:

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

The following patchset contains Netfilter updates for your net-next tree:

1) Support for matching on ipsec policy already set in the route, from
   Florian Westphal.

2) Split set destruction into deactivate and destroy phase to make it
   fit better into the transaction infrastructure, also from Florian.
   This includes a patch to warn on imbalance when setting the new
   activate and deactivate interfaces.

3) Release transaction list from the workqueue to remove expensive
   synchronize_rcu() from configuration plane path. This speeds up
   configuration plane quite a bit. From Florian Westphal.

4) Add new xfrm/ipsec extension, this new extension allows you to match
   for ipsec tunnel keys such as source and destination address, spi and
   reqid. From Máté Eckl and Florian Westphal.

5) Add secmark support, this includes connsecmark too, patches
   from Christian Gottsche.

6) Allow to specify remaining bytes in xt_quota, from Chenbo Feng.
   One follow up patch to calm a clang warning for this one, from
   Nathan Chancellor.

7) Flush conntrack entries based on layer 3 family, from Kristian Evensen.

8) New revision for cgroups2 to shrink the path field.

9) Get rid of obsolete need_conntrack(), as a result from recent
   demodularization works.

10) Use WARN_ON instead of BUG_ON, from Florian Westphal.

11) Unused exported symbol in nf_nat_ipv4_fn(), from Florian.

12) Remove superfluous check for timeout netlink parser and dump
    functions in layer 4 conntrack helpers.

13) Unnecessary redundant rcu read side locks in NAT redirect,
    from Taehee Yoo.

14) Pass nf_hook_state structure to error handlers, patch from
    Florian Westphal.

15) Remove ->new() interface from layer 4 protocol trackers. Place
    them in the ->packet() interface. From Florian.

16) Place conntrack ->error() handling in the ->packet() interface.
    Patches from Florian Westphal.

17) Remove unused parameter in the pernet initialization path,
    also from Florian.

18) Remove additional parameter to specify layer 3 protocol when
    looking up for protocol tracker. From Florian.

19) Shrink array of layer 4 protocol trackers, from Florian.

20) Check for linear skb only once from the ALG NAT mangling
    codebase, from Taehee Yoo.

21) Use rhashtable_walk_enter() instead of deprecated
    rhashtable_walk_init(), also from Taehee.

22) No need to flush all conntracks when only one single address
    is gone, from Tan Hu.

23) Remove redundant check for NAT flags in flowtable code, from
    Taehee Yoo.

24) Use rhashtable_lookup() instead of rhashtable_lookup_fast()
    from netfilter codebase, since rcu read lock side is already
    assumed in this path.
====================
Signed-off-by: David S. Miller <davem@davemloft.net>

The newly added TCP and UDP handling fails to link when CONFIG_INET
is disabled:

net/core/filter.o: In function `sk_lookup':
filter.c:(.text+0x7ff8): undefined reference to `tcp_hashinfo'
filter.c:(.text+0x7ffc): undefined reference to `tcp_hashinfo'
filter.c:(.text+0x8020): undefined reference to `__inet_lookup_established'
filter.c:(.text+0x8058): undefined reference to `__inet_lookup_listener'
filter.c:(.text+0x8068): undefined reference to `udp_table'
filter.c:(.text+0x8070): undefined reference to `udp_table'
filter.c:(.text+0x808c): undefined reference to `__udp4_lib_lookup'
net/core/filter.o: In function `bpf_sk_release':
filter.c:(.text+0x82e8): undefined reference to `sock_gen_put'

Wrap the related sections of code in #ifdefs for the config option.

Furthermore, sk_lookup() should always have been marked 'static', this
also avoids a warning about a missing prototype when building with
'make W=1'.

Fixes: 6acc9b43 ("bpf: Add helper to retrieve socket in BPF")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Joe Stringer <joe@wand.net.nz>
Acked-by: Song Liu <songliubraving@fb.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>

Clang warns:

net/netfilter/xt_quota.c:47:44: warning: 'aligned' attribute ignored
when parsing type [-Wignored-attributes]
        BUILD_BUG_ON(sizeof(atomic64_t) != sizeof(__aligned_u64));
                                                  ^~~~~~~~~~~~~

Use 'sizeof(__u64)' instead, as the alignment doesn't affect the size
of the type.

Fixes: e9837e55 ("netfilter: xt_quota: fix the behavior of xt_quota module")
Signed-off-by: Nathan Chancellor <natechancellor@gmail.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

Until now, both Rx and Tx confirmation frames handled during
NAPI poll were counted toward the NAPI budget. However, Tx
confirmations are lighter to process than Rx frames, which can
skew the amount of work actually done inside one NAPI cycle.

Update the code to only count Rx frames toward the NAPI budget
and set a separate threshold on how many Tx conf frames can be
processed in one poll cycle.

The NAPI poll routine stops when either the budget is consumed
by Rx frames or when Tx confirmation frames reach this threshold.
Signed-off-by: Ioana Radulescu <ruxandra.radulescu@nxp.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

Fixes gcc '-Wunused-but-set-variable' warning:

drivers/net/ethernet/mscc/ocelot_board.c: In function 'mscc_ocelot_probe':
drivers/net/ethernet/mscc/ocelot_board.c:262:17: warning:
 variable 'phy_mode' set but not used [-Wunused-but-set-variable]
   enum phy_mode phy_mode;

It never used since introduction in
commit 71e32a20 ("net: mscc: ocelot: make use of SerDes PHYs for handling their configuration")
Signed-off-by: YueHaibing <yuehaibing@huawei.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

Sabrina Dubroca says:

====================
selftests: add more PMTU tests

The current selftests for PMTU cover VTI tunnels, but there's nothing
about the generation and handling of PMTU exceptions by intermediate
routers. This series adds and improves existing helpers, then adds
IPv4 and IPv6 selftests with a setup involving an intermediate router.

Joint work with Stefano Brivio.
====================
Signed-off-by: David S. Miller <davem@davemloft.net>

Commit d1f1b9cb ("selftests: net: Introduce first PMTU test") and
follow-ups introduced some PMTU tests, but they all rely on tunneling,
and, particularly, on VTI.

These new tests use simple routing to exercise the generation and
update of PMTU exceptions in IPv4 and IPv6.
Signed-off-by: Sabrina Dubroca <sd@queasysnail.net>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
Reviewed-by: David Ahern <dsahern@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

The mtu_parse helper introduced in commit f2c929fe ("selftests:
pmtu: Factor out MTU parsing helper") can only handle "mtu 1234", but
not "mtu lock 1234". Extend it, so that we can do IPv4 tests with PMTU
smaller than net.ipv4.route.min_pmtu
Signed-off-by: Sabrina Dubroca <sd@queasysnail.net>
Reviewed-by: David Ahern <dsahern@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

Introduce and use a function that checks PMTU values against
expected values and logs error messages, to remove some clutter.
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
Signed-off-by: Sabrina Dubroca <sd@queasysnail.net>
Reviewed-by: David Ahern <dsahern@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

Notice that in this particular case, I replaced the
"--v-- fall through --v--" comment with a proper
"fall through", which is what GCC is expecting to
find.

This fix is part of the ongoing efforts to enabling
-Wimplicit-fallthrough
Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

David Ahern says:

====================
rtnetlink: Add support for rigid checking of data in dump request

There are many use cases where a user wants to influence what is
returned in a dump for some rtnetlink command: one is wanting data
for a different namespace than the one the request is received and
another is limiting the amount of data returned in the dump to a
specific set of interest to userspace, reducing the cpu overhead of
both kernel and userspace. Unfortunately, the kernel has historically
not been strict with checking for the proper header or checking the
values passed in the header. This lenient implementation has allowed
iproute2 and other packages to pass any struct or data in the dump
request as long as the family is the first byte. For example, ifinfomsg
struct is used by iproute2 for all generic dump requests - links,
addresses, routes and rules when it is really only valid for link
requests.

There is 1 is example where the kernel deals with the wrong struct: link
dumps after VF support was added. Older iproute2 was sending rtgenmsg as
the header instead of ifinfomsg so a patch was added to try and detect
old userspace vs new:
e5eca6d4 ("rtnetlink: fix userspace API breakage for iproute2 < v3.9.0")

The latest example is Christian's patch set wanting to return addresses for
a target namespace. It guesses the header struct is an ifaddrmsg and if it
guesses wrong a netlink warning is generated in the kernel log on every
address dump which is unacceptable.

Another example where the kernel is a bit lenient is route dumps: iproute2
can send either a request with either ifinfomsg or a rtmsg as the header
struct, yet the kernel always treats the header as an rtmsg (see
inet_dump_fib and rtm_flags check). The header inconsistency impacts the
ability to add kernel side filters for route dumps - a necessary feature
for scale setups with 100k+ routes.

How to resolve the problem of not breaking old userspace yet be able to
move forward with new features such as kernel side filtering which are
crucial for efficient operation at high scale?

This patch set addresses the problem by adding a new socket flag,
NETLINK_DUMP_STRICT_CHK, that userspace can use with setsockopt to
request strict checking of headers and attributes on dump requests and
hence unlock the ability to use kernel side filters as they are added.

Kernel side, the dump handlers are updated to verify the message contains
at least the expected header struct:
    RTM_GETLINK:       ifinfomsg
    RTM_GETADDR:       ifaddrmsg
    RTM_GETMULTICAST:  ifaddrmsg
    RTM_GETANYCAST:    ifaddrmsg
    RTM_GETADDRLABEL:  ifaddrlblmsg
    RTM_GETROUTE:      rtmsg
    RTM_GETSTATS:      if_stats_msg
    RTM_GETNEIGH:      ndmsg
    RTM_GETNEIGHTBL:   ndtmsg
    RTM_GETNSID:       rtgenmsg
    RTM_GETRULE:       fib_rule_hdr
    RTM_GETNETCONF:    netconfmsg
    RTM_GETMDB:        br_port_msg

And then every field in the header struct should be 0 with the exception
of the family. There are a few exceptions to this rule where the kernel
already influences the data returned by values in the struct. Next the
message should not contain attributes unless the kernel implements
filtering for it. Any unexpected data causes the dump to fail with EINVAL.
If the new flag is honored by the kernel and the dump contents adjusted
by any data passed in the request, the dump handler can set the
NLM_F_DUMP_FILTERED flag in the netlink message header.

For old userspace on new kernel there is no impact as all checks are
wrapped in a check on the new strict flag. For new userspace on old
kernel, the data in the headers and any appended attributes are
silently ignored though the setsockopt failing is the clue to userspace
the feature is not supported. New userspace on new kernel gets the
requested data dump.

iproute2 patches can be found here:
    https://github.com/dsahern/iproute2 dump-enhancements

Major changes since v1
- inner header is supposed to be 4-bytes aligned. So for dumps that
  should not have attributes appended changed the check to use:
        if (nlmsg_attrlen(nlh, sizeof(hdr)))
  Only impacts patches with headers that are not multiples of 4-bytes
  (rtgenmsg, netconfmsg), but applied the change to all patches not
  calling nlmsg_parse for consistency.

- Added nlmsg_parse_strict and nla_parse_strict for tighter control on
  attribute parsing. There should be no unknown attribute types or extra
  bytes.

- Moved validation to a helper in most cases

Changes since rfc-v2
- dropped the NLM_F_DUMP_FILTERED flag from target nsid dumps per
  Jiri's objections
- changed the opt-in uapi from a netlink message flag to a socket
  flag. setsockopt provides an api for userspace to definitively
  know if the kernel supports strict checking on dumps.
- re-ordered patches to peel off the extack on dumps if needed to
  keep this set size within limits
- misc cleanups in patches based on testing
====================
Acked-by: Christian Brauner <christian@brauner.io>
Signed-off-by: David S. Miller <davem@davemloft.net>

Update rtnl_fdb_dump for strict data checking. If the flag is set,
the dump request is expected to have an ndmsg struct as the header
potentially followed by one or more attributes. Any data passed in the
header or as an attribute is taken as a request to influence the data
returned. Only values supported by the dump handler are allowed to be
non-0 or set in the request. At the moment only the NDA_IFINDEX and
NDA_MASTER attributes are supported.
Signed-off-by: David Ahern <dsahern@gmail.com>
Acked-by: Christian Brauner <christian@brauner.io>
Signed-off-by: David S. Miller <davem@davemloft.net>

Move the existing input checking for rtnl_fdb_dump into a helper,
valid_fdb_dump_legacy. This function will retain the current
logic that works around the 2 headers that userspace has been
allowed to send up to this point.
Signed-off-by: David Ahern <dsahern@gmail.com>
Acked-by: Christian Brauner <christian@brauner.io>
Signed-off-by: David S. Miller <davem@davemloft.net>

Update br_mdb_dump for strict data checking. If the flag is set,
the dump request is expected to have a br_port_msg struct as the
header. All elements of the struct are expected to be 0 and no
attributes can be appended.
Signed-off-by: David Ahern <dsahern@gmail.com>
Acked-by: Christian Brauner <christian@brauner.io>
Signed-off-by: David S. Miller <davem@davemloft.net>

Update inet_netconf_dump_devconf, inet6_netconf_dump_devconf, and
mpls_netconf_dump_devconf for strict data checking. If the flag is set,
the dump request is expected to have an netconfmsg struct as the header.
The struct only has the family member and no attributes can be appended.
Signed-off-by: David Ahern <dsahern@gmail.com>
Acked-by: Christian Brauner <christian@brauner.io>
Signed-off-by: David S. Miller <davem@davemloft.net>

Update ip6addrlbl_dump for strict data checking. If the flag is set,
the dump request is expected to have an ifaddrlblmsg struct as the
header. All elements of the struct are expected to be 0 and no
attributes can be appended.
Signed-off-by: David Ahern <dsahern@gmail.com>
Acked-by: Christian Brauner <christian@brauner.io>
Signed-off-by: David S. Miller <davem@davemloft.net>

Update fib_nl_dumprule for strict data checking. If the flag is set,
the dump request is expected to have fib_rule_hdr struct as the header.
All elements of the struct are expected to be 0 and no attributes can
be appended.
Signed-off-by: David Ahern <dsahern@gmail.com>
Acked-by: Christian Brauner <christian@brauner.io>
Signed-off-by: David S. Miller <davem@davemloft.net>

Update rtnl_net_dumpid for strict data checking. If the flag is set,
the dump request is expected to have an rtgenmsg struct as the header
which has the family as the only element. No data may be appended.
Signed-off-by: David Ahern <dsahern@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

Update neightbl_dump_info for strict data checking. If the flag is set,
the dump request is expected to have an ndtmsg struct as the header.
All elements of the struct are expected to be 0 and no attributes can
be appended.
Signed-off-by: David Ahern <dsahern@gmail.com>
Acked-by: Christian Brauner <christian@brauner.io>
Signed-off-by: David S. Miller <davem@davemloft.net>

Update neigh_dump_info for strict data checking. If the flag is set,
the dump request is expected to have an ndmsg struct as the header
potentially followed by one or more attributes. Any data passed in the
header or as an attribute is taken as a request to influence the data
returned. Only values supported by the dump handler are allowed to be
non-0 or set in the request. At the moment only the NDA_IFINDEX and
NDA_MASTER attributes are supported.

Existing code does not fail the dump if nlmsg_parse fails. That behavior
is kept for non-strict checking.
Signed-off-by: David Ahern <dsahern@gmail.com>
Acked-by: Christian Brauner <christian@brauner.io>
Signed-off-by: David S. Miller <davem@davemloft.net>