Merge tag 'for-netdev' of https://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf-next

Daniel Borkmann says:

====================
pull-request: bpf-next 2023-08-16

We've added 17 non-merge commits during the last 6 day(s) which contain
a total of 20 files changed, 1179 insertions(+), 37 deletions(-).

The main changes are:

1) Add a BPF hook in sys_socket() to change the protocol ID
   from IPPROTO_TCP to IPPROTO_MPTCP to cover migration for legacy
   applications, from Geliang Tang.

2) Follow-up/fallout fix from the SO_REUSEPORT + bpf_sk_assign work
   to fix a splat on non-fullsock sks in inet[6]_steal_sock,
   from Lorenz Bauer.

3) Improvements to struct_ops links to avoid forcing presence of
   update/validate callbacks. Also add bpf_struct_ops fields documentation,
   from David Vernet.

4) Ensure libbpf sets close-on-exec flag on gzopen, from Marco Vedovati.

5) Several new tcx selftest additions and bpftool link show support for
   tcx and xdp links, from Daniel Borkmann.

6) Fix a smatch warning on uninitialized symbol in
   bpf_perf_link_fill_kprobe, from Yafang Shao.

7) BPF selftest fixes e.g. misplaced break in kfunc_call test,
   from Yipeng Zou.

8) Small cleanup to remove unused declaration bpf_link_new_file,
   from Yue Haibing.

9) Small typo fix to bpftool's perf help message, from Daniel T. Lee.

* tag 'for-netdev' of https://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf-next:
  selftests/bpf: Add mptcpify test
  selftests/bpf: Fix error checks of mptcp open_and_load
  selftests/bpf: Add two mptcp netns helpers
  bpf: Add update_socket_protocol hook
  bpftool: Implement link show support for xdp
  bpftool: Implement link show support for tcx
  selftests/bpf: Add selftest for fill_link_info
  bpf: Fix uninitialized symbol in bpf_perf_link_fill_kprobe()
  net: Fix slab-out-of-bounds in inet[6]_steal_sock
  bpf: Document struct bpf_struct_ops fields
  bpf: Support default .validate() and .update() behavior for struct_ops links
  selftests/bpf: Add various more tcx test cases
  selftests/bpf: Clean up fmod_ret in bench_rename test script
  selftests/bpf: Fix repeat option when kfunc_call verification fails
  libbpf: Set close-on-exec flag on gzopen
  bpftool: fix perf help message
  bpf: Remove unused declaration bpf_link_new_file()
====================

Link: https://lore.kernel.org/r/20230816212840.1539-1-daniel@iogearbox.net
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

2 files changed, 40 insertions, 1 deletions

diff --git a/net/mptcp/bpf.c b/net/mptcp/bpf.c
index 5a0a84ad94af..8a16672b94e2 100644
--- a/net/mptcp/bpf.c
+++ b/net/mptcp/bpf.c
@@ -19,3 +19,18 @@ struct mptcp_sock *bpf_mptcp_sock_from_subflow(struct sock *sk)
 
 	return NULL;
 }
+
+BTF_SET8_START(bpf_mptcp_fmodret_ids)
+BTF_ID_FLAGS(func, update_socket_protocol)
+BTF_SET8_END(bpf_mptcp_fmodret_ids)
+
+static const struct btf_kfunc_id_set bpf_mptcp_fmodret_set = {
+	.owner = THIS_MODULE,
+	.set   = &bpf_mptcp_fmodret_ids,
+};
+
+static int __init bpf_mptcp_kfunc_init(void)
+{
+	return register_btf_fmodret_id_set(&bpf_mptcp_fmodret_set);
+}
+late_initcall(bpf_mptcp_kfunc_init);
diff --git a/net/socket.c b/net/socket.c
index 5d4e37595e9a..fdb5233bf560 100644
--- a/net/socket.c
+++ b/net/socket.c
@@ -1657,12 +1657,36 @@ struct file *__sys_socket_file(int family, int type, int protocol)
 	return sock_alloc_file(sock, flags, NULL);
 }
 
+/*	A hook for bpf progs to attach to and update socket protocol.
+ *
+ *	A static noinline declaration here could cause the compiler to
+ *	optimize away the function. A global noinline declaration will
+ *	keep the definition, but may optimize away the callsite.
+ *	Therefore, __weak is needed to ensure that the call is still
+ *	emitted, by telling the compiler that we don't know what the
+ *	function might eventually be.
+ *
+ *	__diag_* below are needed to dismiss the missing prototype warning.
+ */
+
+__diag_push();
+__diag_ignore_all("-Wmissing-prototypes",
+		  "A fmod_ret entry point for BPF programs");
+
+__weak noinline int update_socket_protocol(int family, int type, int protocol)
+{
+	return protocol;
+}
+
+__diag_pop();
+
 int __sys_socket(int family, int type, int protocol)
 {
 	struct socket *sock;
 	int flags;
 
-	sock = __sys_socket_create(family, type, protocol);
+	sock = __sys_socket_create(family, type,
+				   update_socket_protocol(family, type, protocol));
 	if (IS_ERR(sock))
 		return PTR_ERR(sock);