diff mbox series

[bpf-next,2/7] bpf: add bpf_skc_to_mptcp_sock_proto

Message ID 20220420222459.307649-3-mathew.j.martineau@linux.intel.com (mailing list archive)
State Superseded
Delegated to: BPF
Headers show
Series bpf: mptcp: Support for mptcp_sock and is_mptcp | expand

Checks

Context Check Description
netdev/tree_selection success Clearly marked for bpf-next, async
netdev/fixes_present success Fixes tag not required for -next series
netdev/subject_prefix success Link
netdev/cover_letter success Series has a cover letter
netdev/patch_count success Link
netdev/header_inline success No static functions without inline keyword in header files
netdev/build_32bit success Errors and warnings before: 1812 this patch: 1812
netdev/cc_maintainers warning 8 maintainers not CCed: songliubraving@fb.com davem@davemloft.net pabeni@redhat.com kpsingh@kernel.org kafai@fb.com yhs@fb.com john.fastabend@gmail.com kuba@kernel.org
netdev/build_clang fail Errors and warnings before: 200 this patch: 200
netdev/module_param success Was 0 now: 0
netdev/verify_signedoff success Signed-off-by tag matches author and committer
netdev/verify_fixes success No Fixes tag
netdev/build_allmodconfig_warn success Errors and warnings before: 1822 this patch: 1822
netdev/checkpatch warning WARNING: added, moved or deleted file(s), does MAINTAINERS need updating? WARNING: line length of 83 exceeds 80 columns WARNING: line length of 87 exceeds 80 columns WARNING: line length of 94 exceeds 80 columns
netdev/kdoc success Errors and warnings before: 0 this patch: 0
netdev/source_inline success Was 0 now: 0
bpf/vmtest-bpf-next-VM_Test-1 fail Logs for Kernel LATEST on ubuntu-latest + selftests
bpf/vmtest-bpf-next-VM_Test-2 fail Logs for Kernel LATEST on z15 + selftests
bpf/vmtest-bpf-next-PR fail merge-conflict

Commit Message

Mat Martineau April 20, 2022, 10:24 p.m. UTC 
From: Geliang Tang <geliang.tang@suse.com>

This patch implements a new struct bpf_func_proto, named
bpf_skc_to_mptcp_sock_proto. Define a new bpf_id BTF_SOCK_TYPE_MPTCP,
and a new helper bpf_skc_to_mptcp_sock(), which invokes another new
helper bpf_mptcp_sock_from_subflow() in net/mptcp/bpf.c to get struct
mptcp_sock from a given subflow socket.

Co-developed-by: Nicolas Rybowski <nicolas.rybowski@tessares.net>
Signed-off-by: Nicolas Rybowski <nicolas.rybowski@tessares.net>
Co-developed-by: Matthieu Baerts <matthieu.baerts@tessares.net>
Signed-off-by: Matthieu Baerts <matthieu.baerts@tessares.net>
Signed-off-by: Geliang Tang <geliang.tang@suse.com>
Signed-off-by: Mat Martineau <mathew.j.martineau@linux.intel.com>
---
 include/linux/btf_ids.h        |  3 ++-
 include/net/mptcp.h            |  6 ++++++
 include/uapi/linux/bpf.h       |  7 +++++++
 net/core/filter.c              | 17 +++++++++++++++++
 net/mptcp/Makefile             |  4 ++++
 net/mptcp/bpf.c                | 22 ++++++++++++++++++++++
 scripts/bpf_doc.py             |  2 ++
 tools/include/uapi/linux/bpf.h |  7 +++++++
 8 files changed, 67 insertions(+), 1 deletion(-)
 create mode 100644 net/mptcp/bpf.c

Comments

Daniel Borkmann April 25, 2022, 2:26 p.m. UTC | #1 
On 4/21/22 12:24 AM, Mat Martineau wrote:
[...]
>   static const struct bpf_func_proto *
>   bpf_sk_base_func_proto(enum bpf_func_id func_id);
> @@ -11279,6 +11280,19 @@ const struct bpf_func_proto bpf_skc_to_unix_sock_proto = {
>   	.ret_btf_id		= &btf_sock_ids[BTF_SOCK_TYPE_UNIX],
>   };
>   
> +BPF_CALL_1(bpf_skc_to_mptcp_sock, struct sock *, sk)
> +{
> +	return (unsigned long)bpf_mptcp_sock_from_subflow(sk);
> +}
> +
> +static const struct bpf_func_proto bpf_skc_to_mptcp_sock_proto = {
> +	.func		= bpf_skc_to_mptcp_sock,
> +	.gpl_only	= false,
> +	.ret_type	= RET_PTR_TO_BTF_ID_OR_NULL,
> +	.arg1_type	= ARG_PTR_TO_SOCK_COMMON,
> +	.ret_btf_id	= &btf_sock_ids[BTF_SOCK_TYPE_MPTCP],
> +};

BPF CI (https://github.com/kernel-patches/bpf/runs/6136052684?check_suite_focus=true) fails with:

   #7   base:FAIL
   libbpf: prog '_sockops': BPF program load failed: Invalid argument
   libbpf: prog '_sockops': -- BEGIN PROG LOAD LOG --
   0: R1=ctx(off=0,imm=0) R10=fp0
   ; int op = (int)ctx->op;
   0: (61) r2 = *(u32 *)(r1 +0)          ; R1=ctx(off=0,imm=0) R2_w=scalar(umax=4294967295,var_off=(0x0; 0xffffffff))
   ; if (op != BPF_SOCK_OPS_TCP_CONNECT_CB)
   1: (56) if w2 != 0x3 goto pc+50       ; R2_w=3
   ; sk = ctx->sk;
   2: (79) r6 = *(u64 *)(r1 +184)        ; R1=ctx(off=0,imm=0) R6_w=sock_or_null(id=1,off=0,imm=0)
   ; if (!sk)
   3: (15) if r6 == 0x0 goto pc+48       ; R6_w=sock(off=0,imm=0)
   ; tcp_sk = bpf_tcp_sock(sk);
   4: (bf) r1 = r6                       ; R1_w=sock(off=0,imm=0) R6_w=sock(off=0,imm=0)
   5: (85) call bpf_tcp_sock#96          ; R0_w=tcp_sock_or_null(id=2,off=0,imm=0)
   6: (bf) r7 = r0                       ; R0=tcp_sock_or_null(id=2,off=0,imm=0) R7=tcp_sock_or_null(id=2,off=0,imm=0)
   ; if (!tcp_sk)
   7: (15) if r7 == 0x0 goto pc+44       ; R7=tcp_sock(off=0,imm=0)
   ; if (!tcp_sk->is_mptcp) {
   8: (61) r1 = *(u32 *)(r7 +112)        ; R1_w=scalar(umax=4294967295,var_off=(0x0; 0xffffffff)) R7=tcp_sock(off=0,imm=0)
   ; if (!tcp_sk->is_mptcp) {
   9: (56) if w1 != 0x0 goto pc+14 24: R0=tcp_sock(off=0,imm=0) R1_w=scalar(umax=4294967295,var_off=(0x0; 0xffffffff)) R6=sock(off=0,imm=0) R7=tcp_sock(off=0,imm=0) R10=fp0
   ; msk = bpf_skc_to_mptcp_sock(sk);
   24: (bf) r1 = r6                      ; R1_w=sock(off=0,imm=0) R6=sock(off=0,imm=0)
   25: (85) call bpf_skc_to_mptcp_sock#194
   invalid return type 8 of func bpf_skc_to_mptcp_sock#194
   processed 34 insns (limit 1000000) max_states_per_insn 0 total_states 3 peak_states 3 mark_read 1
   -- END PROG LOAD LOG --
   libbpf: failed to load program '_sockops'
   libbpf: failed to load object './mptcp_sock.o'
   run_test:FAIL:165
   test_base:FAIL:227
   (network_helpers.c:88: errno: Protocol not supported) Failed to create server socket
   test_base:FAIL:241
   RTNETLINK answers: No such file or directory
   Error talking to the kernel
[...]

Looking at bpf_skc_to_tcp6_sock(), do we similarly need a BTF_TYPE_EMIT() here?

Thanks,
Daniel
Daniel Borkmann April 25, 2022, 2:29 p.m. UTC | #2 
On 4/25/22 4:26 PM, Daniel Borkmann wrote:
[...]
> 
> Looking at bpf_skc_to_tcp6_sock(), do we similarly need a BTF_TYPE_EMIT() here?

(Plus, CONFIG_MPTCP should be enabled in CI config (Andrii).)

Cheers,
Daniel
Daniel Borkmann April 25, 2022, 2:33 p.m. UTC | #3 
On 4/21/22 12:24 AM, Mat Martineau wrote:
[...]
> diff --git a/include/net/mptcp.h b/include/net/mptcp.h
> index 0a3b0fb04a3b..5b3a6f783182 100644
> --- a/include/net/mptcp.h
> +++ b/include/net/mptcp.h
> @@ -283,4 +283,10 @@ static inline int mptcpv6_init(void) { return 0; }
>   static inline void mptcpv6_handle_mapped(struct sock *sk, bool mapped) { }
>   #endif
>   
> +#if defined(CONFIG_MPTCP) && defined(CONFIG_BPF_JIT) && defined(CONFIG_BPF_SYSCALL)
> +struct mptcp_sock *bpf_mptcp_sock_from_subflow(struct sock *sk);
> +#else
> +static inline struct mptcp_sock *bpf_mptcp_sock_from_subflow(struct sock *sk) { return NULL; }
> +#endif
> +

Where is this relevant to JIT specifically?

Thanks,
Daniel
Mat Martineau April 25, 2022, 6:11 p.m. UTC | #4 
On Mon, 25 Apr 2022, Daniel Borkmann wrote:

> On 4/21/22 12:24 AM, Mat Martineau wrote:
> [...]
>> diff --git a/include/net/mptcp.h b/include/net/mptcp.h
>> index 0a3b0fb04a3b..5b3a6f783182 100644
>> --- a/include/net/mptcp.h
>> +++ b/include/net/mptcp.h
>> @@ -283,4 +283,10 @@ static inline int mptcpv6_init(void) { return 0; }
>>   static inline void mptcpv6_handle_mapped(struct sock *sk, bool mapped) { 
>> }
>>   #endif
>>   +#if defined(CONFIG_MPTCP) && defined(CONFIG_BPF_JIT) && 
>> defined(CONFIG_BPF_SYSCALL)
>> +struct mptcp_sock *bpf_mptcp_sock_from_subflow(struct sock *sk);
>> +#else
>> +static inline struct mptcp_sock *bpf_mptcp_sock_from_subflow(struct sock 
>> *sk) { return NULL; }
>> +#endif
>> +
>
> Where is this relevant to JIT specifically?
>

That's carried over from the build conditions for bpf_tcp_ca.c in 
net/ipv4/Makefile:

ifeq ($(CONFIG_BPF_JIT),y)
obj-$(CONFIG_BPF_SYSCALL) += bpf_tcp_ca.o
endif

Looks like the reasoning for that (in the CA code) is the use of 
bpf_struct_ops in bpf_tcp_ca.c

While this patch series for MPTCP does not use bpf_struct_ops, and JIT is 
not necessary for bpf_mptcp_sock_from_subflow(), the upcoming MPTCP 
scheduler-in-BPF patches do use bpf_struct_ops. So that dependency found 
its way in to this series - but now that you point it out, 
bpf_mptcp_sock_from_subflow() shouldn't be limited by CONFIG_BPF_JIT and 
we can separately check for the JIT dependency for the scheduler code. 
Will fix that in v2.


--
Mat Martineau
Intel
Mat Martineau April 25, 2022, 6:35 p.m. UTC | #5 
On Mon, 25 Apr 2022, Daniel Borkmann wrote:

> On 4/21/22 12:24 AM, Mat Martineau wrote:
> [...]
>>   static const struct bpf_func_proto *
>>   bpf_sk_base_func_proto(enum bpf_func_id func_id);
>> @@ -11279,6 +11280,19 @@ const struct bpf_func_proto 
>> bpf_skc_to_unix_sock_proto = {
>>   	.ret_btf_id		= &btf_sock_ids[BTF_SOCK_TYPE_UNIX],
>>   };
>>   +BPF_CALL_1(bpf_skc_to_mptcp_sock, struct sock *, sk)
>> +{
>> +	return (unsigned long)bpf_mptcp_sock_from_subflow(sk);
>> +}
>> +
>> +static const struct bpf_func_proto bpf_skc_to_mptcp_sock_proto = {
>> +	.func		= bpf_skc_to_mptcp_sock,
>> +	.gpl_only	= false,
>> +	.ret_type	= RET_PTR_TO_BTF_ID_OR_NULL,
>> +	.arg1_type	= ARG_PTR_TO_SOCK_COMMON,
>> +	.ret_btf_id	= &btf_sock_ids[BTF_SOCK_TYPE_MPTCP],
>> +};
>
> BPF CI 
> (https://github.com/kernel-patches/bpf/runs/6136052684?check_suite_focus=true) 
> fails with:
>
>  #7   base:FAIL
>  libbpf: prog '_sockops': BPF program load failed: Invalid argument
>  libbpf: prog '_sockops': -- BEGIN PROG LOAD LOG --
>  0: R1=ctx(off=0,imm=0) R10=fp0
>  ; int op = (int)ctx->op;
>  0: (61) r2 = *(u32 *)(r1 +0)          ; R1=ctx(off=0,imm=0) 
> R2_w=scalar(umax=4294967295,var_off=(0x0; 0xffffffff))
>  ; if (op != BPF_SOCK_OPS_TCP_CONNECT_CB)
>  1: (56) if w2 != 0x3 goto pc+50       ; R2_w=3
>  ; sk = ctx->sk;
>  2: (79) r6 = *(u64 *)(r1 +184)        ; R1=ctx(off=0,imm=0) 
> R6_w=sock_or_null(id=1,off=0,imm=0)
>  ; if (!sk)
>  3: (15) if r6 == 0x0 goto pc+48       ; R6_w=sock(off=0,imm=0)
>  ; tcp_sk = bpf_tcp_sock(sk);
>  4: (bf) r1 = r6                       ; R1_w=sock(off=0,imm=0) 
> R6_w=sock(off=0,imm=0)
>  5: (85) call bpf_tcp_sock#96          ; 
> R0_w=tcp_sock_or_null(id=2,off=0,imm=0)
>  6: (bf) r7 = r0                       ; 
> R0=tcp_sock_or_null(id=2,off=0,imm=0) R7=tcp_sock_or_null(id=2,off=0,imm=0)
>  ; if (!tcp_sk)
>  7: (15) if r7 == 0x0 goto pc+44       ; R7=tcp_sock(off=0,imm=0)
>  ; if (!tcp_sk->is_mptcp) {
>  8: (61) r1 = *(u32 *)(r7 +112)        ; 
> R1_w=scalar(umax=4294967295,var_off=(0x0; 0xffffffff)) 
> R7=tcp_sock(off=0,imm=0)
>  ; if (!tcp_sk->is_mptcp) {
>  9: (56) if w1 != 0x0 goto pc+14 24: R0=tcp_sock(off=0,imm=0) 
> R1_w=scalar(umax=4294967295,var_off=(0x0; 0xffffffff)) R6=sock(off=0,imm=0) 
> R7=tcp_sock(off=0,imm=0) R10=fp0
>  ; msk = bpf_skc_to_mptcp_sock(sk);
>  24: (bf) r1 = r6                      ; R1_w=sock(off=0,imm=0) 
> R6=sock(off=0,imm=0)
>  25: (85) call bpf_skc_to_mptcp_sock#194
>  invalid return type 8 of func bpf_skc_to_mptcp_sock#194
>  processed 34 insns (limit 1000000) max_states_per_insn 0 total_states 3 
> peak_states 3 mark_read 1
>  -- END PROG LOAD LOG --
>  libbpf: failed to load program '_sockops'
>  libbpf: failed to load object './mptcp_sock.o'
>  run_test:FAIL:165
>  test_base:FAIL:227
>  (network_helpers.c:88: errno: Protocol not supported) Failed to create 
> server socket
>  test_base:FAIL:241
>  RTNETLINK answers: No such file or directory
>  Error talking to the kernel
> [...]
>
> Looking at bpf_skc_to_tcp6_sock(), do we similarly need a BTF_TYPE_EMIT() 
> here?
>

Geliang, in addition to the BTF_TYPE_EMIT() can you also take a look at 
the places in kernel/trace/bpf_trace.c and kernel/bpf/verifier.c where 
bpf_skc_to_tcp6_sock and bpf_skc_to_tcp6_sock_proto are referenced?

--
Mat Martineau
Intel
Andrii Nakryiko April 26, 2022, 6:36 a.m. UTC | #6 
On Mon, Apr 25, 2022 at 7:29 AM Daniel Borkmann <daniel@iogearbox.net> wrote:
>
> On 4/25/22 4:26 PM, Daniel Borkmann wrote:
> [...]
> >
> > Looking at bpf_skc_to_tcp6_sock(), do we similarly need a BTF_TYPE_EMIT() here?
>
> (Plus, CONFIG_MPTCP should be enabled in CI config (Andrii).)

Should be done once [0] is merged in.

  [0] https://github.com/kernel-patches/vmtest/pull/77

>
> Cheers,
> Daniel
diff mbox series

Patch

diff --git a/include/linux/btf_ids.h b/include/linux/btf_ids.h
index bc5d9cc34e4c..335a19092368 100644
--- a/include/linux/btf_ids.h
+++ b/include/linux/btf_ids.h
@@ -178,7 +178,8 @@  extern struct btf_id_set name;
 	BTF_SOCK_TYPE(BTF_SOCK_TYPE_TCP6, tcp6_sock)			\
 	BTF_SOCK_TYPE(BTF_SOCK_TYPE_UDP, udp_sock)			\
 	BTF_SOCK_TYPE(BTF_SOCK_TYPE_UDP6, udp6_sock)			\
-	BTF_SOCK_TYPE(BTF_SOCK_TYPE_UNIX, unix_sock)
+	BTF_SOCK_TYPE(BTF_SOCK_TYPE_UNIX, unix_sock)			\
+	BTF_SOCK_TYPE(BTF_SOCK_TYPE_MPTCP, mptcp_sock)
 
 enum {
 #define BTF_SOCK_TYPE(name, str) name,
diff --git a/include/net/mptcp.h b/include/net/mptcp.h
index 0a3b0fb04a3b..5b3a6f783182 100644
--- a/include/net/mptcp.h
+++ b/include/net/mptcp.h
@@ -283,4 +283,10 @@  static inline int mptcpv6_init(void) { return 0; }
 static inline void mptcpv6_handle_mapped(struct sock *sk, bool mapped) { }
 #endif
 
+#if defined(CONFIG_MPTCP) && defined(CONFIG_BPF_JIT) && defined(CONFIG_BPF_SYSCALL)
+struct mptcp_sock *bpf_mptcp_sock_from_subflow(struct sock *sk);
+#else
+static inline struct mptcp_sock *bpf_mptcp_sock_from_subflow(struct sock *sk) { return NULL; }
+#endif
+
 #endif /* __NET_MPTCP_H */
diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index 9ef1f3e1c22f..785f2cb15495 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -5143,6 +5143,12 @@  union bpf_attr {
  *		The **hash_algo** is returned on success,
  *		**-EOPNOTSUP** if the hash calculation failed or **-EINVAL** if
  *		invalid arguments are passed.
+ *
+ * struct mptcp_sock *bpf_skc_to_mptcp_sock(void *sk)
+ *	Description
+ *		Dynamically cast a *sk* pointer to a *mptcp_sock* pointer.
+ *	Return
+ *		*sk* if casting is valid, or **NULL** otherwise.
  */
 #define __BPF_FUNC_MAPPER(FN)		\
 	FN(unspec),			\
@@ -5339,6 +5345,7 @@  union bpf_attr {
 	FN(copy_from_user_task),	\
 	FN(skb_set_tstamp),		\
 	FN(ima_file_hash),		\
+	FN(skc_to_mptcp_sock),		\
 	/* */
 
 /* integer value in 'imm' field of BPF_CALL instruction selects which helper
diff --git a/net/core/filter.c b/net/core/filter.c
index 7b1867f1f422..4081c55f6f78 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -78,6 +78,7 @@ 
 #include <linux/btf_ids.h>
 #include <net/tls.h>
 #include <net/xdp.h>
+#include <net/mptcp.h>
 
 static const struct bpf_func_proto *
 bpf_sk_base_func_proto(enum bpf_func_id func_id);
@@ -11279,6 +11280,19 @@  const struct bpf_func_proto bpf_skc_to_unix_sock_proto = {
 	.ret_btf_id		= &btf_sock_ids[BTF_SOCK_TYPE_UNIX],
 };
 
+BPF_CALL_1(bpf_skc_to_mptcp_sock, struct sock *, sk)
+{
+	return (unsigned long)bpf_mptcp_sock_from_subflow(sk);
+}
+
+static const struct bpf_func_proto bpf_skc_to_mptcp_sock_proto = {
+	.func		= bpf_skc_to_mptcp_sock,
+	.gpl_only	= false,
+	.ret_type	= RET_PTR_TO_BTF_ID_OR_NULL,
+	.arg1_type	= ARG_PTR_TO_SOCK_COMMON,
+	.ret_btf_id	= &btf_sock_ids[BTF_SOCK_TYPE_MPTCP],
+};
+
 BPF_CALL_1(bpf_sock_from_file, struct file *, file)
 {
 	return (unsigned long)sock_from_file(file);
@@ -11321,6 +11335,9 @@  bpf_sk_base_func_proto(enum bpf_func_id func_id)
 	case BPF_FUNC_skc_to_unix_sock:
 		func = &bpf_skc_to_unix_sock_proto;
 		break;
+	case BPF_FUNC_skc_to_mptcp_sock:
+		func = &bpf_skc_to_mptcp_sock_proto;
+		break;
 	case BPF_FUNC_ktime_get_coarse_ns:
 		return &bpf_ktime_get_coarse_ns_proto;
 	default:
diff --git a/net/mptcp/Makefile b/net/mptcp/Makefile
index e54daceac58b..168c55d1c917 100644
--- a/net/mptcp/Makefile
+++ b/net/mptcp/Makefile
@@ -10,3 +10,7 @@  obj-$(CONFIG_INET_MPTCP_DIAG) += mptcp_diag.o
 mptcp_crypto_test-objs := crypto_test.o
 mptcp_token_test-objs := token_test.o
 obj-$(CONFIG_MPTCP_KUNIT_TEST) += mptcp_crypto_test.o mptcp_token_test.o
+
+ifeq ($(CONFIG_BPF_JIT),y)
+obj-$(CONFIG_BPF_SYSCALL) += bpf.o
+endif
diff --git a/net/mptcp/bpf.c b/net/mptcp/bpf.c
new file mode 100644
index 000000000000..535602ba2582
--- /dev/null
+++ b/net/mptcp/bpf.c
@@ -0,0 +1,22 @@ 
+// SPDX-License-Identifier: GPL-2.0
+/* Multipath TCP
+ *
+ * Copyright (c) 2020, Tessares SA.
+ * Copyright (c) 2022, SUSE.
+ *
+ * Author: Nicolas Rybowski <nicolas.rybowski@tessares.net>
+ */
+
+#define pr_fmt(fmt) "MPTCP: " fmt
+
+#include <linux/bpf.h>
+#include "protocol.h"
+
+struct mptcp_sock *bpf_mptcp_sock_from_subflow(struct sock *sk)
+{
+	if (sk && sk_fullsock(sk) && sk->sk_protocol == IPPROTO_TCP && sk_is_mptcp(sk))
+		return mptcp_sk(mptcp_subflow_ctx(sk)->conn);
+
+	return NULL;
+}
+EXPORT_SYMBOL(bpf_mptcp_sock_from_subflow);
diff --git a/scripts/bpf_doc.py b/scripts/bpf_doc.py
index 096625242475..d5452f7eb996 100755
--- a/scripts/bpf_doc.py
+++ b/scripts/bpf_doc.py
@@ -633,6 +633,7 @@  class PrinterHelpers(Printer):
             'struct socket',
             'struct file',
             'struct bpf_timer',
+            'struct mptcp_sock',
     ]
     known_types = {
             '...',
@@ -682,6 +683,7 @@  class PrinterHelpers(Printer):
             'struct socket',
             'struct file',
             'struct bpf_timer',
+            'struct mptcp_sock',
     }
     mapped_types = {
             'u8': '__u8',
diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h
index 9ef1f3e1c22f..785f2cb15495 100644
--- a/tools/include/uapi/linux/bpf.h
+++ b/tools/include/uapi/linux/bpf.h
@@ -5143,6 +5143,12 @@  union bpf_attr {
  *		The **hash_algo** is returned on success,
  *		**-EOPNOTSUP** if the hash calculation failed or **-EINVAL** if
  *		invalid arguments are passed.
+ *
+ * struct mptcp_sock *bpf_skc_to_mptcp_sock(void *sk)
+ *	Description
+ *		Dynamically cast a *sk* pointer to a *mptcp_sock* pointer.
+ *	Return
+ *		*sk* if casting is valid, or **NULL** otherwise.
  */
 #define __BPF_FUNC_MAPPER(FN)		\
 	FN(unspec),			\
@@ -5339,6 +5345,7 @@  union bpf_attr {
 	FN(copy_from_user_task),	\
 	FN(skb_set_tstamp),		\
 	FN(ima_file_hash),		\
+	FN(skc_to_mptcp_sock),		\
 	/* */
 
 /* integer value in 'imm' field of BPF_CALL instruction selects which helper