Commit 0dd061a6 authored by Geliang Tang's avatar Geliang Tang Committed by Martin KaFai Lau
Browse files

bpf: Add update_socket_protocol hook 

Add a hook named update_socket_protocol in __sys_socket(), for bpf
progs to attach to and update socket protocol. One user case is to
force legacy TCP apps to create and use MPTCP sockets instead of
TCP ones.

Define a fmod_ret set named bpf_mptcp_fmodret_ids, add the hook
update_socket_protocol into this set, and register it in
bpf_mptcp_kfunc_init().

Closes: https://github.com/multipath-tcp/mptcp_net-next/issues/79


Acked-by: default avatarMatthieu Baerts <matthieu.baerts@tessares.net>
Acked-by: default avatarYonghong Song <yonghong.song@linux.dev>
Signed-off-by: default avatarGeliang Tang <geliang.tang@suse.com>
Link: https://lore.kernel.org/r/ac84be00f97072a46f8a72b4e2be46cbb7fa5053.1692147782.git.geliang.tang@suse.com


Signed-off-by: default avatarMartin KaFai Lau <martin.lau@kernel.org>
parent 053bbf9b

net/mptcp/bpf.c

+15 −0
Original line number Diff line number Diff line
@@ -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);

net/socket.c

+25 −1
Original line number Diff line number Diff line
@@ -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);