Add documentation for eBPF helper functions to bpf.h user header file.
This documentation can be parsed with the Python script provided in
another commit of the patch series, in order to provide a RST document
that can later be converted into a man page.

The objective is to make the documentation easily understandable and
accessible to all eBPF developers, including beginners.

This patch contains descriptions for the following helper functions, all
written by Alexei:

- bpf_get_current_pid_tgid()
- bpf_get_current_uid_gid()
- bpf_get_current_comm()
- bpf_skb_vlan_push()
- bpf_skb_vlan_pop()
- bpf_skb_get_tunnel_key()
- bpf_skb_set_tunnel_key()
- bpf_redirect()
- bpf_perf_event_output()
- bpf_get_stackid()
- bpf_get_current_task()

v4:
- bpf_redirect(): Fix typo: "XDP_ABORT" changed to "XDP_ABORTED". Add
  note on bpf_redirect_map() providing better performance. Replace "Save
  for" with "Except for".
- bpf_skb_vlan_push(): Clarify comment about invalidated verifier
  checks.
- bpf_skb_vlan_pop(): Clarify comment about invalidated verifier
  checks.
- bpf_skb_get_tunnel_key(): Add notes on tunnel_id, "collect metadata"
  mode, and example tunneling protocols with which it can be used.
- bpf_skb_set_tunnel_key(): Add a reference to the description of
  bpf_skb_get_tunnel_key().
- bpf_perf_event_output(): Specify that, and for what purpose, the
  helper can be used with programs attached to TC and XDP.

v3:
- bpf_skb_get_tunnel_key(): Change and improve description and example.
- bpf_redirect(): Improve description of BPF_F_INGRESS flag.
- bpf_perf_event_output(): Fix first sentence of description. Delete
  wrong statement on context being evaluated as a struct pt_reg. Remove
  the long yet incomplete example.
- bpf_get_stackid(): Add a note about PERF_MAX_STACK_DEPTH being
  configurable.

Cc: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Quentin Monnet <quentin.monnet@netronome.com>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>

Add documentation for eBPF helper functions to bpf.h user header file.
This documentation can be parsed with the Python script provided in
another commit of the patch series, in order to provide a RST document
that can later be converted into a man page.

The objective is to make the documentation easily understandable and
accessible to all eBPF developers, including beginners.

This patch contains descriptions for the following helper functions, all
written by Alexei:

- bpf_map_lookup_elem()
- bpf_map_update_elem()
- bpf_map_delete_elem()
- bpf_probe_read()
- bpf_ktime_get_ns()
- bpf_trace_printk()
- bpf_skb_store_bytes()
- bpf_l3_csum_replace()
- bpf_l4_csum_replace()
- bpf_tail_call()
- bpf_clone_redirect()

v4:
- bpf_map_lookup_elem(): Add "const" qualifier for key.
- bpf_map_update_elem(): Add "const" qualifier for key and value.
- bpf_map_lookup_elem(): Add "const" qualifier for key.
- bpf_skb_store_bytes(): Clarify comment about invalidated verifier
  checks.
- bpf_l3_csum_replace(): Mention L3 instead of just IP, and add a note
  about bpf_csum_diff().
- bpf_l4_csum_replace(): Mention L4 instead of just TCP/UDP, and add a
  note about bpf_csum_diff().
- bpf_tail_call(): Bring minor edits to description.
- bpf_clone_redirect(): Add a note about the relation with
  bpf_redirect(). Also clarify comment about invalidated verifier
  checks.

v3:
- bpf_map_lookup_elem(): Fix description of restrictions for flags
  related to the existence of the entry.
- bpf_trace_printk(): State that trace_pipe can be configured. Fix
  return value in case an unknown format specifier is met. Add a note on
  kernel log notice when the helper is used. Edit example.
- bpf_tail_call(): Improve comment on stack inheritance.
- bpf_clone_redirect(): Improve description of BPF_F_INGRESS flag.

Cc: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Quentin Monnet <quentin.monnet@netronome.com>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>

Remove previous "overview" of eBPF helpers from user bpf.h header.
Replace it by a comment explaining how to process the new documentation
(to come in following patches) with a Python script to produce RST, then
man page documentation.

Also add the aforementioned Python script under scripts/. It is used to
process include/uapi/linux/bpf.h and to extract helper descriptions, to
turn it into a RST document that can further be processed with rst2man
to produce a man page. The script takes one "--filename <path/to/file>"
option. If the script is launched from scripts/ in the kernel root
directory, it should be able to find the location of the header to
parse, and "--filename <path/to/file>" is then optional. If it cannot
find the file, then the option becomes mandatory. RST-formatted
documentation is printed to standard output.

Typical workflow for producing the final man page would be:

    $ ./scripts/bpf_helpers_doc.py \
            --filename include/uapi/linux/bpf.h > /tmp/bpf-helpers.rst
    $ rst2man /tmp/bpf-helpers.rst > /tmp/bpf-helpers.7
    $ man /tmp/bpf-helpers.7

Note that the tool kernel-doc cannot be used to document eBPF helpers,
whose signatures are not available directly in the header files
(pre-processor directives are used to produce them at the beginning of
the compilation process).

v4:
- Also remove overviews for newly added bpf_xdp_adjust_tail() and
  bpf_skb_get_xfrm_state().
- Remove vague statement about what helpers are restricted to GPL
  programs in "LICENSE" section for man page footer.
- Replace license boilerplate with SPDX tag for Python script.

v3:
- Change license for man page.
- Remove "for safety reasons" from man page header text.
- Change "packets metadata" to "packets" in man page header text.
- Move and fix comment on helpers introducing no overhead.
- Remove "NOTES" section from man page footer.
- Add "LICENSE" section to man page footer.
- Edit description of file include/uapi/linux/bpf.h in man page footer.
Signed-off-by: Quentin Monnet <quentin.monnet@netronome.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>

William Tu says:

====================
The patch series provide end-to-end eBPF tunnel testsute.  A common topology
is created below for all types of tunnels:

Topology:
---------
     root namespace   |     at_ns0 namespace
                      |
      -----------     |     -----------
      | tnl dev |     |     | tnl dev |  (overlay network)
      -----------     |     -----------
      metadata-mode   |     native-mode
       with bpf       |
                      |
      ----------      |     ----------
      |  veth1  | --------- |  veth0  |  (underlay network)
      ----------    peer    ----------

Device Configuration
--------------------
 Root namespace with metadata-mode tunnel + BPF
 Device names and addresses:
       veth1 IP: 172.16.1.200, IPv6: 00::22 (underlay)
       tunnel dev <type>11, ex: gre11, IPv4: 10.1.1.200 (overlay)

 Namespace at_ns0 with native tunnel
 Device names and addresses:
       veth0 IPv4: 172.16.1.100, IPv6: 00::11 (underlay)
       tunnel dev <type>00, ex: gre00, IPv4: 10.1.1.100 (overlay)

End-to-end ping packet flow
---------------------------
 Most of the tests start by namespace creation, device configuration,
 then ping the underlay and overlay network.  When doing 'ping 10.1.1.100'
 from root namespace, the following operations happen:
 1) Route lookup shows 10.1.1.100/24 belongs to tnl dev, fwd to tnl dev.
 2) Tnl device's egress BPF program is triggered and set the tunnel metadata,
    with remote_ip=172.16.1.200 and others.
 3) Outer tunnel header is prepended and route the packet to veth1's egress
 4) veth0's ingress queue receive the tunneled packet at namespace at_ns0
 5) Tunnel protocol handler, ex: vxlan_rcv, decap the packet
 6) Forward the packet to the overlay tnl dev

Test Cases
-----------------------------
 Tunnel Type |  BPF Programs
-----------------------------
 GRE:          gre_set_tunnel, gre_get_tunnel
 IP6GRE:       ip6gretap_set_tunnel, ip6gretap_get_tunnel
 ERSPAN:       erspan_set_tunnel, erspan_get_tunnel
 IP6ERSPAN:    ip4ip6erspan_set_tunnel, ip4ip6erspan_get_tunnel
 VXLAN:        vxlan_set_tunnel, vxlan_get_tunnel
 IP6VXLAN:     ip6vxlan_set_tunnel, ip6vxlan_get_tunnel
 GENEVE:       geneve_set_tunnel, geneve_get_tunnel
 IP6GENEVE:    ip6geneve_set_tunnel, ip6geneve_get_tunnel
 IPIP:         ipip_set_tunnel, ipip_get_tunnel
 IP6IP:        ipip6_set_tunnel, ipip6_get_tunnel,
               ip6ip6_set_tunnel, ip6ip6_get_tunnel
 XFRM:         xfrm_get_state
====================
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>

Move the testsuite to
selftests/bpf/{test_tunnel_kern.c, test_tunnel.sh}
Signed-off-by: William Tu <u9012063@gmail.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>

The patch migrates the original tests at samples/bpf/tcbpf2_kern.c
and samples/bpf/test_tunnel_bpf.sh to selftests.  There are a couple
changes from the original:
    1) add ipv6 vxlan, ipv6 geneve, ipv6 ipip tests
    2) simplify the original ipip tests (remove iperf tests)
    3) improve documentation
    4) use bpf_ntoh* and bpf_hton* api

In summary, 'test_tunnel_kern.o' contains the following bpf program:
  GRE: gre_set_tunnel, gre_get_tunnel
  IP6GRE: ip6gretap_set_tunnel, ip6gretap_get_tunnel
  ERSPAN: erspan_set_tunnel, erspan_get_tunnel
  IP6ERSPAN: ip4ip6erspan_set_tunnel, ip4ip6erspan_get_tunnel
  VXLAN: vxlan_set_tunnel, vxlan_get_tunnel
  IP6VXLAN: ip6vxlan_set_tunnel, ip6vxlan_get_tunnel
  GENEVE: geneve_set_tunnel, geneve_get_tunnel
  IP6GENEVE: ip6geneve_set_tunnel, ip6geneve_get_tunnel
  IPIP: ipip_set_tunnel, ipip_get_tunnel
  IP6IP: ipip6_set_tunnel, ipip6_get_tunnel,
         ip6ip6_set_tunnel, ip6ip6_get_tunnel
  XFRM: xfrm_get_state
Signed-off-by: William Tu <u9012063@gmail.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>

When bpf_adjust_tail was introduced for generic xdp, it changed skb's tail
pointer, so it was pointing to the new "end of the packet". However skb's
len field wasn't properly modified, so on the wire ethernet frame had
original (or even bigger, if adjust_head was used) size. This diff is
fixing this.

Fixes: 198d83bb (" bpf: make generic xdp compatible w/ bpf_xdp_adjust_tail")
Signed-off-by: Nikita V. Shirokov <tehnerd@tehnerd.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>

Display the license "gpl" string in bpftool prog command, like:

  # bpftool prog list
  5: tracepoint  name func  tag 57cd311f2e27366b  gpl
          loaded_at Apr 26/09:37  uid 0
          xlated 16B  not jited  memlock 4096B

  # bpftool --json --pretty prog show
  [{
          "id": 5,
          "type": "tracepoint",
          "name": "func",
          "tag": "57cd311f2e27366b",
          "gpl_compatible": true,
          "loaded_at": "Apr 26/09:37",
          "uid": 0,
          "bytes_xlated": 16,
          "jited": false,
          "bytes_memlock": 4096
      }
  ]
Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>

Syncing the bpf.h uapi header with tools.
Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>

Adding gpl_compatible flag to struct bpf_prog_info
so it can be dumped via bpf_prog_get_info_by_fd and
displayed via bpftool progs dump.

Alexei noticed 4-byte hole in struct bpf_prog_info,
so we put the u32 flags field in there, and we can
keep adding bit fields in there without breaking
user space.
Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>

Jakub Kicinski says:

====================
This set adds an optimization run to the NFP jit to turn ADD and SUB
instructions with negative immediate into the opposite operation with
a positive immediate. NFP can fit small immediates into the instructions
but it can't ever fit negative immediates. Addition of small negative
immediates is quite common in BPF programs for stack address calculations,
therefore this optimization gives us non-negligible savings in instruction
count (up to 4%).
====================
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>

Comparison instruction requires a subtraction.  If the constant
is negative we are more likely to fit it into a NFP instruction
directly if we change the sign and use addition.
Signed-off-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>

There are quite a few compare instructions now, use a table
to translate BPF instruction code to NFP instruction parameters
instead of parameterizing helpers.  This saves LOC and makes
future extensions easier.
Signed-off-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>

NFP instruction set can fit small immediates into the instruction.
Negative integers, however, will never fit because they will have
highest bit set.  If we swap the ALU op between ADD and SUB and
negate the constant we have a better chance of fitting small negative
integers into the instruction itself and saving one or two cycles.

immed[gprB_21, 0xfffffffc]
alu[gprA_4, gprA_4, +, gprB_21], gpr_wrboth
immed[gprB_21, 0xffffffff]
alu[gprA_5, gprA_5, +carry, gprB_21], gpr_wrboth

now becomes:

alu[gprA_4, gprA_4, -, 4], gpr_wrboth
alu[gprA_5, gprA_5, -carry, 0], gpr_wrboth
Signed-off-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>

Whitespace cleanup - remove double space.
Signed-off-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>

When test_sockmap was running outside of selftests and was not being
run by build bots it was reasonable to spend significant amount of
time running various tests. The number of tests is high because many
different I/O iterators are run.

However, now that test_sockmap is part of selftests rather than
iterate through all I/O sides only test a minimal set of min/max
values along with a few "normal" I/O ops. Also remove the long
running tests. They can be run from other test frameworks on a regular
cadence.

This significanly reduces runtime of test_sockmap.

Before:

$ time sudo ./test_sockmap  > /dev/null

real    4m47.521s
user    0m0.370s
sys     0m3.131s

After:

$ time sudo ./test_sockmap  > /dev/null

real    0m0.514s
user    0m0.104s
sys     0m0.430s

The CLI is still available for users that want to test the long
running tests that do the larger send/recv tests.
Signed-off-by: John Fastabend <john.fastabend@gmail.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>

John Fastabend says:

====================
This series moves ./samples/sockmap into BPF selftests. There are a
few good reasons to do this. First, by pushing this into selftests
the tests will be run automatically. Second, sockmap was not really
a sample of anything anymore, but rather a large set of tests.

Note: There are three recent fixes outstanding against bpf branch
that can be detected occasionally by the automated tests here.

https://patchwork.ozlabs.org/patch/903138/
https://patchwork.ozlabs.org/patch/903139/
https://patchwork.ozlabs.org/patch/903140/
====================
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>

The BPF sample sockmap is redundant now that equivelant tests exist
in the BPF selftests. Lets remove this sample and only keep the
selftest version that will be run as part of the selftest suite.
Signed-off-by: John Fastabend <john.fastabend@gmail.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>

This adds a new test program test_sockmap which is the old sample
sockmap program. By moving the sample program here we can now run it
as part of the self tests suite. To support this a populate_progs()
routine is added to load programs and maps which was previously done
with load_bpf_file(). This is needed because self test libs do not
provide a similar routine. Also we now use the cgroup_helpers
routines to manage cgroup use instead of manually creating one and
supplying it to the CLI.

Notice we keep the CLI around though because it is useful for dbg
and specialized testing.

To run use ./test_sockmap and the result should be,

Summary 660 PASSED, 0 SKIPPED, 0 FAILED
Signed-off-by: John Fastabend <john.fastabend@gmail.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>

If no options are passed to sockmap after this patch we run a set of
tests using various options and sendmsg/sendpage sizes. This replaces
the sockmap_test.sh script.
Signed-off-by: John Fastabend <john.fastabend@gmail.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>

By moving sockmap_test from shell script into C we can run it directly
from selftests, but we can also push the input/output around in proper
structures.

However, keep the CLI options around because they are useful for
debugging when a paticular pattern of msghdr or sockmap options
trips up the sockmap code path.
Signed-off-by: John Fastabend <john.fastabend@gmail.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>

Since test_sock_addr is not supposed to run by itself,
remove it from TEST_GEN_PROGS and add it to
TEST_GEN_PROGS_EXTENDED. This way, run_tests will
not run test_sock_addr. The corresponding test to run
is test_sock_addr.sh.
Signed-off-by: Yonghong Song <yhs@fb.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>

Fixes: c0fa1b6c ("bpf: btf: Add BTF tests")
Signed-off-by: Anders Roxell <anders.roxell@linaro.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>

Paul Chaignon says:

====================
Currently, helpers that expect ARG_PTR_TO_MAP_KEY and ARG_PTR_TO_MAP_VALUE
can only access stack and packet memory.  This patchset allows these
helpers to directly access map values by passing registers of type
PTR_TO_MAP_VALUE.

The first patch changes the verifier; the second adds new test cases.

The first three versions of this patchset were sent on the iovisor-dev
mailing list only.

Changelogs:
  Changes in v5:
    - Refactor using check_helper_mem_access.
  Changes in v4:
    - Rebase.
  Changes in v3:
    - Bug fixes.
    - Negative test cases.
  Changes in v2:
    - Additional test cases for adjusted maps.
====================
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>

This patch adds new test cases for accesses to map values from map
helpers.
Signed-off-by: Paul Chaignon <paul.chaignon@orange.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>

Helpers that expect ARG_PTR_TO_MAP_KEY and ARG_PTR_TO_MAP_VALUE can only
access stack and packet memory.  Allow these helpers to directly access
map values by passing registers of type PTR_TO_MAP_VALUE.

This change removes the need for an extra copy to the stack when using a
map value to perform a second map lookup, as in the following:

struct bpf_map_def SEC("maps") infobyreq = {
    .type = BPF_MAP_TYPE_HASHMAP,
    .key_size = sizeof(struct request *),
    .value_size = sizeof(struct info_t),
    .max_entries = 1024,
};
struct bpf_map_def SEC("maps") counts = {
    .type = BPF_MAP_TYPE_HASHMAP,
    .key_size = sizeof(struct info_t),
    .value_size = sizeof(u64),
    .max_entries = 1024,
};
SEC("kprobe/blk_account_io_start")
int bpf_blk_account_io_start(struct pt_regs *ctx)
{
    struct info_t *info = bpf_map_lookup_elem(&infobyreq, &ctx->di);
    u64 *count = bpf_map_lookup_elem(&counts, info);
    (*count)++;
}
Signed-off-by: Paul Chaignon <paul.chaignon@orange.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>

Eyal Birger says:

====================
This patchset adds support for fetching XFRM state information from
an eBPF program called from TC.

The first patch introduces a helper for fetching an XFRM state from the
skb's secpath. The XFRM state is modeled using a new virtual struct which
contains the SPI, peer address, and reqid values of the state; This struct
can be extended in the future to provide additional state information.

The second patch adds a test example in test_tunnel_bpf.sh. The sample
validates the correct extraction of state information by the eBPF program.

v3:
  - Kept SPI and peer IPv4 address in state in network byte order
    following suggestion from Alexei Starovoitov
v2:
  - Fixed two comments by Daniel Borkmann:
    - disallow reserved flags in helper call
    - avoid compiling in helper code when CONFIG_XFRM is off
====================
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>

Add a test for fetching xfrm state parameters from a tc program running
on ingress.
Signed-off-by: Eyal Birger <eyal.birger@gmail.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>

This commit introduces a helper which allows fetching xfrm state
parameters by eBPF programs attached to TC.

Prototype:
bpf_skb_get_xfrm_state(skb, index, xfrm_state, size, flags)

skb: pointer to skb
index: the index in the skb xfrm_state secpath array
xfrm_state: pointer to 'struct bpf_xfrm_state'
size: size of 'struct bpf_xfrm_state'
flags: reserved for future extensions

The helper returns 0 on success. Non zero if no xfrm state at the index
is found - or non exists at all.

struct bpf_xfrm_state currently includes the SPI, peer IPv4/IPv6
address and the reqid; it can be further extended by adding elements to
its end - indicating the populated fields by the 'size' argument -
keeping backwards compatibility.

Typical usage:

struct bpf_xfrm_state x = {};
bpf_skb_get_xfrm_state(skb, 0, &x, sizeof(x), 0);
...
Signed-off-by: Eyal Birger <eyal.birger@gmail.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>

This patch cleans up btf.h in uapi:
1) Rename "name" to "name_off" to better reflect it is an offset to the
   string section instead of a char array.
2) Remove unused value BTF_FLAGS_COMPR and BTF_MAGIC_SWAP
Suggested-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: Martin KaFai Lau <kafai@fb.com>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>

In commit 6870de43 ("bpf: make virtio compatible w/
bpf_xdp_adjust_tail") i didn't account for vi->hdr_len during new
packet's length calculation after bpf_prog_run in receive_mergeable.
because of this all packets, if they were passed to the kernel,
were truncated by 12 bytes.

Fixes:6870de43 ("bpf: make virtio compatible w/ bpf_xdp_adjust_tail")
Reported-by: David Ahern <dsahern@gmail.com>
Signed-off-by: Nikita V. Shirokov <tehnerd@tehnerd.com>
Acked-by: Jason Wang <jasowang@redhat.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>

The conversion of rndis friendly name to utf8 uses a standard
kernel routine which is optional in config. Therefore build
would fail for some configurations. Resolve by selecting needed
library.

Fixes: 0fe554a4 ("hv_netvsc: propogate Hyper-V friendly name into interface alias")
Signed-off-by: Stephen Hemminger <sthemmin@microsoft.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

Conflicts were simple overlapping changes in microchip
driver.
Signed-off-by: David S. Miller <davem@davemloft.net>

David Ahern says:

====================
net/ipv6: Another followup to the fib6_info change

Last one - for this week.

Patches 1, 2 and 7 are more cleanup patches - removing dead code,
moving code from a header to near its single caller, and updating
function name.

Patches 3-5 do some refactoring leading up to patch 6 which fixes
a NULL dereference. I have only managed to trigger a panic once, so
I can not definitively confirm it addresses the problem but it seems
pretty clear that it is a race on removing a 'from' reference on
an rt6_info and another path using that 'from' value to do
cookie checking.
====================
Signed-off-by: David S. Miller <davem@davemloft.net>

Dan reported an imbalance in fib6_check on use of f6i and checking
whether it is null. Since fib6_check is only called if f6i is non-null,
remove the unnecessary check.
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: David Ahern <dsahern@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

When a dst entry is created from a fib entry, the 'from' in rt6_info
is set to the fib entry. The 'from' reference is used most notably for
cookie checking - making sure stale dst entries are updated if the
fib entry is changed.

When a fib entry is deleted, the pcpu routes on it are walked releasing
the fib6_info reference. This is needed for the fib6_info cleanup to
happen and to make sure all device references are released in a timely
manner.

There is a race window when a FIB entry is deleted and the 'from' on the
pcpu route is dropped and the pcpu route hits a cookie check. Handle
this race using rcu on from.
Signed-off-by: David Ahern <dsahern@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

Code move only; no functional change intended.
Signed-off-by: David Ahern <dsahern@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

A later patch protects 'from' in rt6_info and this simplifies the
locking needed by it.
Signed-off-by: David Ahern <dsahern@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

A later patch protects 'from' in rt6_info and this simplifies the
locking needed by it.

With the move, the fib6_info_hold for the uncached_rt is no longer
needed since the rcu_lock is still held.
Signed-off-by: David Ahern <dsahern@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

rt6_get_cookie_safe takes a fib6_info and checks the sernum of
the node. Update the name to reflect its purpose.
Signed-off-by: David Ahern <dsahern@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>