Cross-merge networking fixes after downstream PR (net-6.15-rc5).

No conflicts or adjacent changes.

Signed-off-by: Jakub Kicinski <kuba@kernel.org>

When building the latest samples/bpf on LoongArch Fedora

     make M=samples/bpf

There are compilation errors as follows:

In file included from ./linux/samples/bpf/sockex2_kern.c:2:
In file included from ./include/uapi/linux/in.h:25:
In file included from ./include/linux/socket.h:8:
In file included from ./include/linux/uio.h:9:
In file included from ./include/linux/thread_info.h:60:
In file included from ./arch/loongarch/include/asm/thread_info.h:15:
In file included from ./arch/loongarch/include/asm/processor.h:13:
In file included from ./arch/loongarch/include/asm/cpu-info.h:11:
./arch/loongarch/include/asm/loongarch.h:13:10: fatal error: 'larchintrin.h' file not found
         ^~~~~~~~~~~~~~~
1 error generated.

larchintrin.h is included in /usr/lib64/clang/14.0.6/include,
and the header file location is specified at compile time.

Test on LoongArch Fedora:
https://github.com/fedora-remix-loongarch/releases-info

Signed-off-by: Haoran Jiang <jianghaoran@kylinos.cn>
Signed-off-by: zhangxi <zhangxi@kylinos.cn>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20250425095042.838824-1-jianghaoran@kylinos.cn

DCCP was orphaned in 2021 by commit 054c4610bd05 ("MAINTAINERS: dccp:
move Gerrit Renker to CREDITS"), which noted that the last maintainer
had been inactive for five years.

In recent years, it has become a playground for syzbot, and most changes
to DCCP have been odd bug fixes triggered by syzbot.  Apart from that,
the only changes have been driven by treewide or networking API updates
or adjustments related to TCP.

Thus, in 2023, we announced we would remove DCCP in 2025 via commit
b144fcaf46d4 ("dccp: Print deprecation notice.").

Since then, only one individual has contacted the netdev mailing list. [0]

There is ongoing research for Multipath DCCP.  The repository is hosted
on GitHub [1], and development is not taking place through the upstream
community.  While the repository is published under the GPLv2 license,
the scheduling part remains proprietary, with a LICENSE file [2] stating:

  "This is not Open Source software."

The researcher mentioned a plan to address the licensing issue, upstream
the patches, and step up as a maintainer, but there has been no further
communication since then.

Maintaining DCCP for a decade without any real users has become a burden.

Therefore, it's time to remove it.

Removing DCCP will also provide significant benefits to TCP.  It allows
us to freely reorganize the layout of struct inet_connection_sock, which
is currently shared with DCCP, and optimize it to reduce the number of
cachelines accessed in the TCP fast path.

Note that we keep DCCP netfilter modules as requested.  [3]

Link: https://lore.kernel.org/netdev/20230710182253.81446-1-kuniyu@amazon.com/T/#u #[0]
Link: https://github.com/telekom/mp-dccp #[1]
Link: https://github.com/telekom/mp-dccp/blob/mpdccp_v03_k5.10/net/dccp/non_gpl_scheduler/LICENSE #[2]
Link: https://lore.kernel.org/netdev/Z_VQ0KlCRkqYWXa-@calendula/ #[3]
Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Acked-by: Paul Moore <paul@paul-moore.com> (LSM and SELinux)
Acked-by: Casey Schaufler <casey@schaufler-ca.com>
Link: https://patch.msgid.link/20250410023921.11307-3-kuniyu@amazon.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

Commit 13b25489b6f8 ("kbuild: change working directory to external
module directory with M=") changed kbuild working directory of bpf
sample programs to samples/bpf, which broke the vmlinux path for
VMLINUX_BTF, as the Makefiles assume the current work directory to be
the kernel output directory and use a relative path (i.e., ./vmlinux):

  Makefile:316: *** Cannot find a vmlinux for VMLINUX_BTF at any of "  /path/to/linux/samples/bpf/vmlinux", build the kernel or set VMLINUX_BTF like "VMLINUX_BTF=/sys/kernel/btf/vmlinux" or VMLINUX_H variable.  Stop.

Correctly refer to the kernel output directory using $(objtree).

Fixes: 13b25489b6f8 ("kbuild: change working directory to external module directory with M=")
Signed-off-by: Jinghao Jia <jinghao7@illinois.edu>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Tested-by: Ruowen Qin <ruqin@redhat.com>
Link: https://lore.kernel.org/bpf/20250203085506.220297-3-jinghao7@illinois.edu

Cross-merge bpf fixes after downstream PR.

Trivial conflict:
tools/testing/selftests/bpf/prog_tests/verifier.c

Adjacent changes in:
Auto-merging kernel/bpf/verifier.c
Auto-merging samples/bpf/Makefile
Auto-merging tools/testing/selftests/bpf/.gitignore
Auto-merging tools/testing/selftests/bpf/Makefile
Auto-merging tools/testing/selftests/bpf/prog_tests/verifier.c

Signed-off-by: Alexei Starovoitov <ast@kernel.org>

Before commit [1], the value of a variable TPROGS_USER_CFLAGS was
passed to libbpf make command as a part of EXTRA_CFLAGS.
This commit makes sure that the value of TPROGS_USER_CFLAGS is still
passed to libbpf make command, in order to maintain backwards build
scripts compatibility.

[1] commit 5a6ea7022ff4 ("samples/bpf: Remove unnecessary -I flags from libbpf EXTRA_CFLAGS")

Fixes: 5a6ea7022ff4 ("samples/bpf: Remove unnecessary -I flags from libbpf EXTRA_CFLAGS")
Suggested-by: Viktor Malik <vmalik@redhat.com>
Signed-off-by: Eduard Zingerman <eddyz87@gmail.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Acked-by: Viktor Malik <vmalik@redhat.com>
Link: https://lore.kernel.org/bpf/20241204173416.142240-1-eddyz87@gmail.com

Commit [0] breaks samples/bpf build:

    $ make M=samples/bpf
    ...
    make -C /path/to/kernel/samples/bpf/../../tools/lib/bpf \
     ...
     EXTRA_CFLAGS=" \
     ...
     -fsanitize=bounds \
     -I/path/to/kernel/usr/include \
     ...
    	/path/to/kernel/samples/bpf/libbpf/libbpf.a install_headers
      CC      /path/to/kernel/samples/bpf/libbpf/staticobjs/libbpf.o
    In file included from libbpf.c:29:
    /path/to/kernel/tools/include/linux/err.h:35:8: error: 'inline' can only appear on functions
       35 | static inline void * __must_check ERR_PTR(long error_)
          |        ^

The error is caused by `objtree` variable changing definition from `.`
(dot) to an absolute path:
- The variable TPROGS_CFLAGS is constructed as follows:
  ...
  TPROGS_CFLAGS += -I$(objtree)/usr/include
- It is passed as EXTRA_CFLAGS for libbpf compilation:
  $(LIBBPF): ...
    ...
	$(MAKE) -C $(LIBBPF_SRC) RM='rm -rf' EXTRA_CFLAGS="$(TPROGS_CFLAGS)"
- Before commit [0], the line passed to libbpf makefile was
  '-I./usr/include', where '.' referred to LIBBPF_SRC due to -C flag.
  The directory $(LIBBPF_SRC)/usr/include does not exist and thus
  was never resolved by C compiler.
- After commit [0], the line passed to libbpf makefile became:
  '<output-dir>/usr/include', this directory exists and is resolved by
  C compiler.
- Both 'tools/include' and 'usr/include' define files err.h and types.h.
- libbpf expects headers like 'linux/err.h' and 'linux/types.h'
  defined in 'tools/include', not 'usr/include', hence the compilation
  error.

This commit removes unnecessary -I flags from libbpf compilation.
(libbpf sets up the necessary includes at lib/bpf/Makefile:63).

Changes v1 [1] -> v2:
- dropped unnecessary replacement of KBUILD_OUTPUT with $(objtree)
  (Andrii)
Changes v2 [2] -> v3:
- make sure --sysroot option is set for libbpf's EXTRA_CFLAGS,
  if $(SYSROOT) is set (Stanislav)

[0] commit 13b25489b6f8 ("kbuild: change working directory to external module directory with M=")
[1] https://lore.kernel.org/bpf/20241202212154.3174402-1-eddyz87@gmail.com/
[2] https://lore.kernel.org/bpf/20241202234741.3492084-1-eddyz87@gmail.com/

Fixes: 13b25489b6f8 ("kbuild: change working directory to external module directory with M=")
Signed-off-by: Eduard Zingerman <eddyz87@gmail.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Acked-by: Stanislav Fomichev <sdf@fomichev.me>
Link: https://lore.kernel.org/bpf/20241203182222.3915763-1-eddyz87@gmail.com

The variable is never referenced in the code, just remove it
that this problem was discovered by reading code

Signed-off-by: Zhu Jun <zhujun2@cmss.chinamobile.com>
Link: https://lore.kernel.org/r/20241120032241.5657-1-zhujun2@cmss.chinamobile.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

The variable is never referenced in the code, just remove it.

Signed-off-by: Zhu Jun <zhujun2@cmss.chinamobile.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20241111061514.3257-1-zhujun2@cmss.chinamobile.com

These variables are never referenced in the code, just remove them.

Signed-off-by: Zhu Jun <zhujun2@cmss.chinamobile.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20241111062312.3541-1-zhujun2@cmss.chinamobile.com