Jesper Dangaard Brouer says:

====================
V3: Hopefully fixed all issues point out by Yonghong Song

V2: Addressed issues point out by Yonghong Song
 - Please ACK patch 2/3 again
 - Added ACKs and reviewed-by to other patches

This patchset is focused on improvements for XDP forwarding sample
named xdp_fwd, which leverage the existing FIB routing tables as
described in LPC2018[1] talk by David Ahern.

The primary motivation is to illustrate how Toke's recent work
improves usability of XDP_REDIRECT via lookups in devmap. The other
patches are to help users understand the sample.

I have more improvements to xdp_fwd, but those might requires changes
to libbpf.  Thus, sending these patches first as they are isolated.

[1] http://vger.kernel.org/lpc-networking2018.html#session-1
====================
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>

Make it clear that this XDP program depend on the network
stack to do the ARP resolution.  This is connected with the
BPF_FIB_LKUP_RET_NO_NEIGH return code from bpf_fib_lookup().

Another common mistake (seen via XDP-tutorial) is that users
don't realize that sysctl net.ipv{4,6}.conf.all.forwarding
setting is honored by bpf_fib_lookup.
Reported-by: Anton Protopopov <a.s.protopopov@gmail.com>
Signed-off-by: Jesper Dangaard Brouer <brouer@redhat.com>
Reviewed-by: David Ahern <dsahern@gmail.com>
Acked-by: Yonghong Song <yhs@fb.com>
Reviewed-by: Toke Høiland-Jørgensen <toke@redhat.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>

This address the TODO in samples/bpf/xdp_fwd_kern.c, which points out
that the chosen egress index should be checked for existence in the
devmap. This can now be done via taking advantage of Toke's work in
commit 0cdbb4b0 ("devmap: Allow map lookups from eBPF").

This change makes xdp_fwd more practically usable, as this allows for
a mixed environment, where IP-forwarding fallback to network stack, if
the egress device isn't configured to use XDP.
Signed-off-by: Jesper Dangaard Brouer <brouer@redhat.com>
Reviewed-by: David Ahern <dsahern@gmail.com>
Reviewed-by: Toke Høiland-Jørgensen <toke@redhat.com>
Acked-by: Yonghong Song <yhs@fb.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>

The devmap name 'tx_port' came from a copy-paste from xdp_redirect_map
which only have a single TX port. Change name to xdp_tx_ports
to make it more descriptive.
Signed-off-by: Jesper Dangaard Brouer <brouer@redhat.com>
Reviewed-by: David Ahern <dsahern@gmail.com>
Acked-by: Yonghong Song <yhs@fb.com>
Reviewed-by: Toke Høiland-Jørgensen <toke@redhat.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>

Use kmap instead of page_address as it's not always in low memory.
Acked-by: Björn Töpel <bjorn.topel@intel.com>
Signed-off-by: Ivan Khoronzhuk <ivan.khoronzhuk@linaro.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>

On my local machine, I have the following compilation errors:
=====
  In file included from prog_tests/core_reloc.c:3:0:
  ./progs/core_reloc_types.h:517:46: error: expected ‘=’, ‘,’, ‘;’, ‘asm’ or ‘__attribute__’ before ‘fancy_char_ptr_t’
 typedef const char * const volatile restrict fancy_char_ptr_t;
                                              ^
  ./progs/core_reloc_types.h:527:2: error: unknown type name ‘fancy_char_ptr_t’
    fancy_char_ptr_t d;
    ^
=====

I am using gcc 4.8.5. Later compilers may change their behavior not emitting the
error. Nevertheless, let us fix the issue. "restrict" can be tested
without typedef.

Fixes: 9654e2ae ("selftests/bpf: add CO-RE relocs modifiers/typedef tests")
Cc: Andrii Nakryiko <andriin@fb.com>
Signed-off-by: Yonghong Song <yhs@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

Andrii Nakryiko says:

====================
This patch set implements central part of CO-RE (Compile Once - Run
Everywhere, see [0] and [1] for slides and video): relocating fields offsets.
Most of the details are written down as comments to corresponding parts of the
code.

Patch #1 adds a bunch of commonly useful btf_xxx helpers to simplify working
with BTF types.
Patch #2 converts existing libbpf code to these new helpers and removes some
of pre-existing ones.
Patch #3 adds loading of .BTF.ext offset relocations section and macros to
work with its contents.
Patch #4 implements CO-RE relocations algorithm in libbpf.
Patch #5 introduced BPF_CORE_READ macro, hiding usage of Clang's
__builtin_preserve_access_index intrinsic that records offset relocation.
Patches #6-#14 adds selftests validating various parts of relocation handling,
type compatibility, etc.

For all tests to work, you'll need latest Clang/LLVM supporting
__builtin_preserve_access_index intrinsic, used for recording offset
relocations. Kernel on which selftests run should have BTF information built
in (CONFIG_DEBUG_INFO_BTF=y).

  [0] http://vger.kernel.org/bpfconf2019.html#session-2
  [1] http://vger.kernel.org/lpc-bpf2018.html#session-2

v5->v6:
- fix bad comment formatting for real (Alexei);

v4->v5:
- drop constness for btf_xxx() helpers, allowing to avoid type casts (Alexei);
- rebase on latest bpf-next, change test__printf back to printf;

v3->v4:
- added btf_xxx helpers (Alexei);
- switched libbpf code to new helpers;
- reduced amount of logging and simplified format in few places (Alexei);
- made flavor name parsing logic more strict (exactly three underscores);
- no uname() error checking (Alexei);
- updated misc tests to reflect latest Clang fixes (Yonghong);

v2->v3:
- enclose BPF_CORE_READ args in parens (Song);

v1->v2:
- add offsetofend(), fix btf_ext optional fields checks (Song);
- add bpf_core_dump_spec() for logging spec representation;
- move special first element processing out of the loop (Song);
- typo fixes (Song);
- drop BPF_ST | BPF_MEM insn relocation (Alexei);
- extracted BPF_CORE_READ into bpf_helpers (Alexei);
- added extra tests validating Clang capturing relocs correctly (Yonghong);
- switch core_relocs.c to use sub-tests;
- updated mods tests after Clang bug was fixed (Yonghong);
- fix bug enumerating candidate types;
====================
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

Add tests validating few edge-cases of capturing offset relocations.
Signed-off-by: Andrii Nakryiko <andriin@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

Add various tests validating handling compatible/incompatible integer
types.
Signed-off-by: Andrii Nakryiko <andriin@fb.com>
Acked-by: Song Liu <songliubraving@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

Add test validating correct relocation handling for cases where pointer
to something is used as an array. E.g.:

  int *ptr = ...;
  int x = ptr[42];
Signed-off-by: Andrii Nakryiko <andriin@fb.com>
Acked-by: Song Liu <songliubraving@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

Add tests validating correct handling of various combinations of
typedefs and const/volatile/restrict modifiers.
Signed-off-by: Andrii Nakryiko <andriin@fb.com>
Acked-by: Song Liu <songliubraving@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

Test CO-RE relocation handling of ints, enums, pointers, func protos, etc.
Signed-off-by: Andrii Nakryiko <andriin@fb.com>
Acked-by: Song Liu <songliubraving@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

Add tests for various array handling/relocation scenarios.
Signed-off-by: Andrii Nakryiko <andriin@fb.com>
Acked-by: Song Liu <songliubraving@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

Add a bunch of test validating correct handling of nested
structs/unions.
Signed-off-by: Andrii Nakryiko <andriin@fb.com>
Acked-by: Song Liu <songliubraving@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

Add tests verifying that BPF program can use various struct/union
"flavors" to extract data from the same target struct/union.
Signed-off-by: Andrii Nakryiko <andriin@fb.com>
Acked-by: Song Liu <songliubraving@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

Add CO-RE relocation test runner. Add one simple test validating that
libbpf's logic for searching for kernel image and loading BTF out of it
works.
Signed-off-by: Andrii Nakryiko <andriin@fb.com>
Acked-by: Song Liu <songliubraving@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

Add BPF_CORE_READ macro used in tests to do bpf_core_read(), which
automatically captures offset relocation.
Signed-off-by: Andrii Nakryiko <andriin@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

This patch implements the core logic for BPF CO-RE offsets relocations.
Every instruction that needs to be relocated has corresponding
bpf_offset_reloc as part of BTF.ext. Relocations are performed by trying
to match recorded "local" relocation spec against potentially many
compatible "target" types, creating corresponding spec. Details of the
algorithm are noted in corresponding comments in the code.
Signed-off-by: Andrii Nakryiko <andriin@fb.com>
Acked-by: Song Liu <songliubraving@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

Add support for BPF CO-RE offset relocations. Add section/record
iteration macros for .BTF.ext. These macro are useful for iterating over
each .BTF.ext record, either for dumping out contents or later for BPF
CO-RE relocation handling.

To enable other parts of libbpf to work with .BTF.ext contents, moved
a bunch of type definitions into libbpf_internal.h.
Signed-off-by: Andrii Nakryiko <andriin@fb.com>
Acked-by: Song Liu <songliubraving@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

Simplify code by relying on newly added BTF helper functions.
Signed-off-by: Andrii Nakryiko <andriin@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

Add lots of frequently used helpers that simplify working with BTF
types.
Signed-off-by: Andrii Nakryiko <andriin@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

Stanislav Fomichev says:

====================
I was looking into converting test_sockops* to test_progs framework
and that requires using cgroup_helpers.c which rely on stdio/stderr.
Let's use open_memstream to override stdout into buffer during
subtests instead of custom test_{v,}printf wrappers. That lets
us continue to use stdio in the subtests and dump it on failure
if required.

That would also fix bpf_find_map which currently uses printf to
signal failure (missed during test_printf conversion).
====================
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

Small (un)related cleanup.

Cc: Andrii Nakryiko <andriin@fb.com>
Acked-by: Andrii Nakryiko <andriin@fb.com>
Signed-off-by: Stanislav Fomichev <sdf@google.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

Now that test__printf is a simple wraper around printf, let's drop it
(and test__vprintf as well).

Cc: Andrii Nakryiko <andriin@fb.com>
Acked-by: Andrii Nakryiko <andriin@fb.com>
Signed-off-by: Stanislav Fomichev <sdf@google.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

Use open_memstream to override stdout during test execution.
The copy of the original stdout is held in env.stdout and used
to print subtest info and dump failed log.

test_{v,}printf are now simple wrappers around stdout and will be
removed in the next patch.

v5:
* fix -v crash by always setting env.std{in,err} (Alexei Starovoitov)
* drop force_log check from stdio_hijack (Andrii Nakryiko)

v4:
* one field per line for stdout/stderr (Andrii Nakryiko)

v3:
* don't do strlen over log_buf, log_cnt has it already (Andrii Nakryiko)

v2:
* add ifdef __GLIBC__ around open_memstream (maybe pointless since
  we already depend on glibc for argp_parse)
* hijack stderr as well (Andrii Nakryiko)
* don't hijack for every test, do it once (Andrii Nakryiko)
* log_cap -> log_size (Andrii Nakryiko)
* do fseeko in a proper place (Andrii Nakryiko)
* check open_memstream returned value (Andrii Nakryiko)

Cc: Andrii Nakryiko <andriin@fb.com>
Acked-by: Andrii Nakryiko <andriin@fb.com>
Signed-off-by: Stanislav Fomichev <sdf@google.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

Add a test with multiple exit conditions.
It's not an infinite loop only when the verifier can properly track
all math on variable 'i' through all possible ways of executing this loop.

barrier()s are needed to disable llvm optimization that combines multiple
branches into fewer branches.
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Yonghong Song <yhs@fb.com>

Add a test that returns a 'random' number between [0, 2^20)
If state pruning is not working correctly for loop body the number of
processed insns will be 2^20 * num_of_insns_in_loop_body and the program
will be rejected.
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Andrii Nakryiko <andriin@fb.com>
Acked-by: Yonghong Song <yhs@fb.com>

Stanislav Fomichev says:

====================
Current setsockopt hook is limited to the size of the buffer that
user had supplied. Since we always allocate memory and copy the value
into kernel space, allocate just a little bit more in case BPF
program needs to override input data with a larger value.

The canonical example is TCP_CONGESTION socket option where
input buffer is a string and if user calls it with a short string,
BPF program has no way of extending it.

The tests are extended with TCP_CONGESTION use case.
====================
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

Ignore SOL_TCP:TCP_CONGESTION in getsockopt and always override
SOL_TCP:TCP_CONGESTION with "cubic" in setsockopt hook.

Call setsockopt(SOL_TCP, TCP_CONGESTION) with short optval ("nv")
to make sure BPF program has enough buffer space to replace it
with "cubic".
Signed-off-by: Stanislav Fomichev <sdf@google.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

Since we always allocate memory, allocate just a little bit more
for the BPF program in case it need to override user input with
bigger value. The canonical example is TCP_CONGESTION where
input string might be too small to override (nv -> bbr or cubic).

16 bytes are chosen to match the size of TCP_CA_NAME_MAX and can
be extended in the future if needed.
Signed-off-by: Stanislav Fomichev <sdf@google.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

Takshak said in the original submission:

With different bpf attach_flags available to attach bpf programs specially
with BPF_F_ALLOW_OVERRIDE and BPF_F_ALLOW_MULTI, the list of effective
bpf-programs available to any sub-cgroups really needs to be available for
easy debugging.

Using BPF_F_QUERY_EFFECTIVE flag, one can get the list of not only attached
bpf-programs to a cgroup but also the inherited ones from parent cgroup.

So a new option is introduced to use BPF_F_QUERY_EFFECTIVE query flag here
to list all the effective bpf-programs available for execution at a specified
cgroup.

Reused modified test program test_cgroup_attach from tools/testing/selftests/bpf:
  # ./test_cgroup_attach

With old bpftool:

 # bpftool cgroup show /sys/fs/cgroup/cgroup-test-work-dir/cg1/
  ID       AttachType      AttachFlags     Name
  271      egress          multi           pkt_cntr_1
  272      egress          multi           pkt_cntr_2

Attached new program pkt_cntr_4 in cg2 gives following:

 # bpftool cgroup show /sys/fs/cgroup/cgroup-test-work-dir/cg1/cg2
  ID       AttachType      AttachFlags     Name
  273      egress          override        pkt_cntr_4

And with new "effective" option it shows all effective programs for cg2:

 # bpftool cgroup show /sys/fs/cgroup/cgroup-test-work-dir/cg1/cg2 effective
  ID       AttachType      AttachFlags     Name
  273      egress          override        pkt_cntr_4
  271      egress          override        pkt_cntr_1
  272      egress          override        pkt_cntr_2

Compared to original submission use a local flag instead of global
option.

We need to clear query_flags on every command, in case batch mode
wants to use varying settings.

v2: (Takshak)
 - forbid duplicated flags;
 - fix cgroup path freeing.
Signed-off-by: Takshak Chahande <ctakshak@fb.com>
Signed-off-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Reviewed-by: Quentin Monnet <quentin.monnet@netronome.com>
Reviewed-by: Takshak Chahande <ctakshak@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

Clear buffered output once test or subtests finishes even if test was
successful. Not doing this leads to accumulation of output from previous
tests and on first failed tests lots of irrelevant output will be
dumped, greatly confusing things.

v1->v2: fix Fixes tag, add more context to patch

Fixes: 3a516a0a ("selftests/bpf: add sub-tests support for test_progs")
Signed-off-by: Andrii Nakryiko <andriin@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

Petar Penkov says:

====================
This patch series introduces a BPF helper function that allows generating SYN
cookies from BPF. Currently, this helper is enabled at both the TC hook and the
XDP hook.

The first two patches in the series add/modify several TCP helper functions to
allow for SKB-less operation, as is the case at the XDP hook.

The third patch introduces the bpf_tcp_gen_syncookie helper function which
generates a SYN cookie for either XDP or TC programs. The return value of
this function contains both the MSS value, encoded in the cookie, and the
cookie itself.

The last three patches sync tools/ and add a test.

Performance evaluation:
I sent 10Mpps to a fixed port on a host with 2 10G bonded Mellanox 4 NICs from
random IPv6 source addresses. Without XDP I observed 7.2Mpps (syn-acks) being
sent out if the IPv6 packets carry 20 bytes of TCP options or 7.6Mpps if they
carry no options. If I attached a simple program that checks if a packet is
IPv6/TCP/SYN, looks up the socket, issues a cookie, and sends it back out after
swapping src/dest, recomputing the checksum, and setting the ACK flag, I
observed 10Mpps being sent back out.

Changes since v1:
1/ Added performance numbers to the cover letter
2/ Patch 2: Refactored a bit to fix compilation issues
3/ Patch 3: Changed ENOTSUPP to EOPNOTSUPP at Toke's suggestion

Changes since RFC:
1/ Cookie is returned in host order at Alexei's suggestion
2/ If cookies are not enabled via a sysctl, the helper function returns
   -ENOENT instead of -EINVAL at Lorenz's suggestion
3/ Fixed documentation to properly reflect that MSS is 16 bits at
   Lorenz's suggestion
4/ BPF helper requires TCP length to match ->doff field, rather than to simply
   be no more than 20 bytes at Eric and Alexei's suggestion
5/ Packet type is looked up from the packet version field, rather than from the
   socket. v4 packets are rejected on v6-only sockets but should work with
   dual stack listeners at Eric's suggestion
6/ Removed unnecessary `net` argument from helper function in patch 2 at
   Lorenz's suggestion
7/ Changed test to only pass MSS option so we can convince the verifier that the
   memory access is not out of bounds

Note that 7/ below illustrates the verifier might need to be extended to allow
passing a variable tcph->doff to the helper function like below:

__u32 thlen = tcph->doff * 4;
if (thlen < sizeof(*tcph))
	return;
__s64 cookie = bpf_tcp_gen_syncookie(sk, ipv4h, 20, tcph, thlen);
====================
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

Modify the existing bpf_tcp_check_syncookie test to also generate a
SYN cookie, pass the packet to the kernel, and verify that the two
cookies are the same (and both valid). Since cloned SKBs are skipped
during generic XDP, this test does not issue a SYN cookie when run in
XDP mode. We therefore only check that a valid SYN cookie was issued at
the TC hook.

Additionally, verify that the MSS for that SYN cookie is within
expected range.
Signed-off-by: Petar Penkov <ppenkov@google.com>
Reviewed-by: Lorenz Bauer <lmb@cloudflare.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

Expose bpf_tcp_gen_syncookie to selftests.
Signed-off-by: Petar Penkov <ppenkov@google.com>
Reviewed-by: Lorenz Bauer <lmb@cloudflare.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

Sync updated documentation for bpf_redirect_map.

Sync the bpf_tcp_gen_syncookie helper function definition with the one
in tools/uapi.
Signed-off-by: Petar Penkov <ppenkov@google.com>
Reviewed-by: Lorenz Bauer <lmb@cloudflare.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

This helper function allows BPF programs to try to generate SYN
cookies, given a reference to a listener socket. The function works
from XDP and with an skb context since bpf_skc_lookup_tcp can lookup a
socket in both cases.
Signed-off-by: Petar Penkov <ppenkov@google.com>
Suggested-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: Lorenz Bauer <lmb@cloudflare.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

This patch allows generation of a SYN cookie before an SKB has been
allocated, as is the case at XDP.
Signed-off-by: Petar Penkov <ppenkov@google.com>
Reviewed-by: Lorenz Bauer <lmb@cloudflare.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

This allows us to call this function before an SKB has been
allocated.
Signed-off-by: Petar Penkov <ppenkov@google.com>
Reviewed-by: Lorenz Bauer <lmb@cloudflare.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

Toke Høiland-Jørgensen says:

====================
This series adds a new map type, devmap_hash, that works like the existing
devmap type, but using a hash-based indexing scheme. This is useful for the use
case where a devmap is indexed by ifindex (for instance for use with the routing
table lookup helper). For this use case, the regular devmap needs to be sized
after the maximum ifindex number, not the number of devices in it. A hash-based
indexing scheme makes it possible to size the map after the number of devices it
should contain instead.

This was previously part of my patch series that also turned the regular
bpf_redirect() helper into a map-based one; for this series I just pulled out
the patches that introduced the new map type.

Changelog:

v5:

- Dynamically set the number of hash buckets by rounding up max_entries to the
  nearest power of two (mirroring the regular hashmap), as suggested by Jesper.

v4:

- Remove check_memlock parameter that was left over from an earlier patch
  series.
- Reorder struct members to avoid holes.

v3:

- Rework the split into different patches
- Use spin_lock_irqsave()
- Also add documentation and bash completion definitions for bpftool

v2:

- Split commit adding the new map type so uapi and tools changes are separate.

Changes to these patches since the previous series:

- Rebase on top of the other devmap changes (makes this one simpler!)
- Don't enforce key==val, but allow arbitrary indexes.
- Rename the type to devmap_hash to reflect the fact that it's just a hashmap now.
====================
Signed-off-by: Alexei Starovoitov <ast@kernel.org>