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net/smc: Introduce smc_ops #8312

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Pull request for series with
subject: net/smc: Introduce smc_ops
version: 4
url: https://patchwork.kernel.org/project/netdevbpf/list/?series=922409

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Upstream branch: 96ea081
series: https://patchwork.kernel.org/project/netdevbpf/list/?series=922409
version: 4

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Upstream branch: 73b9075
series: https://patchwork.kernel.org/project/netdevbpf/list/?series=922409
version: 4

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Upstream branch: 8c21f88
series: https://patchwork.kernel.org/project/netdevbpf/list/?series=922409
version: 4

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Upstream branch: 2532608
series: https://patchwork.kernel.org/project/netdevbpf/list/?series=922409
version: 4

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At least one diff in series https://patchwork.kernel.org/project/netdevbpf/list/?series=922409 expired. Closing PR.

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Upstream branch: f44275e
series: https://patchwork.kernel.org/project/netdevbpf/list/?series=922749
version: 5

D. Wythe added 4 commits January 6, 2025 20:26
Exports three necessary symbols for implementing struct_ops with
tristate subsystem.

To hold or release refcnt of struct_ops refcnt by inline funcs
bpf_try_module_get and bpf_module_put which use bpf_struct_ops_get(put)
conditionally.

And to copy obj name from one to the other with effective checks by
bpf_obj_name_cpy.

Signed-off-by: D. Wythe <[email protected]>
The introduction of IPPROTO_SMC enables eBPF programs to determine
whether to use SMC based on the context of socket creation, such as
network namespaces, PID and comm name, etc.

As a subsequent enhancement, to introduce a new generic hook that
allows decisions on whether to use SMC or not at runtime, including
but not limited to local/remote IP address or ports.

Moreover, in the future, we can achieve more complex extensions to the
protocol stack by extending this ops.

Signed-off-by: D. Wythe <[email protected]>
To implement injection capability for smc via struct_ops, so that
user can make their own smc_ops to modify the behavior of smc stack.

Currently, user can write their own implememtion to choose whether to
use SMC or not before TCP 3rd handshake to be comleted. In the future,
users can implement more complex functions on smc by expanding it.

Signed-off-by: D. Wythe <[email protected]>
When a struct_ops named xxx_ops was registered by a module, and
it will be used in both built-in modules and the module itself,
so that the btf_type of xxx_ops will be present in btf_vmlinux
instead of in btf_mod, which means that the btf_type of
bpf_struct_ops_xxx_ops and xxx_ops will not be in the same btf.

Here are four possible case:

+--------+-------------+-------------+---------------------------------+
|        | st_opx_xxx  | xxx         |                                 |
+--------+-------------+-------------+---------------------------------+
| case 0 | btf_vmlinux | bft_vmlinux | be used and reg only in vmlinux |
+--------+-------------+-------------+---------------------------------+
| case 1 | btf_vmlinux | bpf_mod     | INVALID                         |
+--------+-------------+-------------+---------------------------------+
| case 2 | btf_mod     | btf_vmlinux | reg in mod but be used both in  |
|        |             |             | vmlinux and mod.                |
+--------+-------------+-------------+---------------------------------+
| case 3 | btf_mod     | btf_mod     | be used and reg only in mod     |
+--------+-------------+-------------+---------------------------------+

At present, cases 0, 1, and 3 can be correctly identified, because
st_ops_xxx is searched from the same btf with xxx. In order to
handle case 2 correctly without affecting other cases, we cannot simply
change the search method for st_ops_xxx from find_btf_by_prefix_kind()
to find_ksym_btf_id(), because in this way, case 1 will not be
recognized anymore.

To address this issue, if st_ops_xxx cannot be found in the btf with xxx
and mod_btf does not exist, do find_ksym_btf_id() again to
avoid such issue.

Fixes: 590a008 ("bpf: libbpf: Add STRUCT_OPS support")
Signed-off-by: D. Wythe <[email protected]>
This tests introduces a tiny smc_ops for filtering SMC connections based on
IP pairs, and also adds a realistic topology model to verify this ops.

Also, we can only use SMC loopback under CI test, so an
additional configuration needs to be enabled.

Follow the steps below to run this test.

make -C tools/testing/selftests/bpf
cd tools/testing/selftests/bpf
sudo ./test_progs -t smc

Results shows:
Summary: 1/1 PASSED, 0 SKIPPED, 0 FAILED

Signed-off-by: D. Wythe <[email protected]>
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Upstream branch: f44275e
series: https://patchwork.kernel.org/project/netdevbpf/list/?series=922749
version: 5

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At least one diff in series https://patchwork.kernel.org/project/netdevbpf/list/?series=922749 expired. Closing PR.

@kernel-patches-daemon-bpf kernel-patches-daemon-bpf bot deleted the series/916210=>bpf-next branch January 10, 2025 08:58
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