Commit dbafd7dd authored by Martin KaFai Lau's avatar Martin KaFai Lau Committed by Alexei Starovoitov
Browse files

bpf: Add bpf_get_listener_sock(struct bpf_sock *sk) helper 



Add a new helper "struct bpf_sock *bpf_get_listener_sock(struct bpf_sock *sk)"
which returns a bpf_sock in TCP_LISTEN state.  It will trace back to
the listener sk from a request_sock if possible.  It returns NULL
for all other cases.

No reference is taken because the helper ensures the sk is
in SOCK_RCU_FREE (where the TCP_LISTEN sock should be in).
Hence, bpf_sk_release() is unnecessary and the verifier does not
allow bpf_sk_release(listen_sk) to be called either.

The following is also allowed because the bpf_prog is run under
rcu_read_lock():

	sk = bpf_sk_lookup_tcp();
	/* if (!sk) { ... } */
	listen_sk = bpf_get_listener_sock(sk);
	/* if (!listen_sk) { ... } */
	bpf_sk_release(sk);
	src_port = listen_sk->src_port; /* Allowed */

Signed-off-by: default avatarMartin KaFai Lau <kafai@fb.com>
Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
parent 1b986589

include/uapi/linux/bpf.h

+10 −1
Original line number Diff line number Diff line
@@ -2366,6 +2366,14 @@ union bpf_attr { 
 *             current value is ect (ECN capable). Works with IPv6 and IPv4.

 *     Return

 *             1 if set, 0 if not set.

 *

 * struct bpf_sock *bpf_get_listener_sock(struct bpf_sock *sk)

 *	Description

 *		Return a **struct bpf_sock** pointer in TCP_LISTEN state.

 *		bpf_sk_release() is unnecessary and not allowed.

 *	Return

 *		A **struct bpf_sock** pointer on success, or NULL in

 *		case of failure.

 */

#define __BPF_FUNC_MAPPER(FN)		\

	FN(unspec),			\
@@ -2465,7 +2473,8 @@ union bpf_attr { 
	FN(spin_unlock),		\

	FN(sk_fullsock),		\

	FN(tcp_sock),			\

	FN(skb_ecn_set_ce),

	FN(skb_ecn_set_ce),		\

	FN(get_listener_sock),



/* integer value in 'imm' field of BPF_CALL instruction selects which helper

 * function eBPF program intends to call

net/core/filter.c

+21 −0
Original line number Diff line number Diff line
@@ -5418,6 +5418,23 @@ static const struct bpf_func_proto bpf_tcp_sock_proto = { 
	.arg1_type	= ARG_PTR_TO_SOCK_COMMON,

};



BPF_CALL_1(bpf_get_listener_sock, struct sock *, sk)

{

	sk = sk_to_full_sk(sk);



	if (sk->sk_state == TCP_LISTEN && sock_flag(sk, SOCK_RCU_FREE))

		return (unsigned long)sk;



	return (unsigned long)NULL;

}



static const struct bpf_func_proto bpf_get_listener_sock_proto = {

	.func		= bpf_get_listener_sock,

	.gpl_only	= false,

	.ret_type	= RET_PTR_TO_SOCKET_OR_NULL,

	.arg1_type	= ARG_PTR_TO_SOCK_COMMON,

};



BPF_CALL_1(bpf_skb_ecn_set_ce, struct sk_buff *, skb)

{

	unsigned int iphdr_len;
@@ -5603,6 +5620,8 @@ cg_skb_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog) 
#ifdef CONFIG_INET

	case BPF_FUNC_tcp_sock:

		return &bpf_tcp_sock_proto;

	case BPF_FUNC_get_listener_sock:

		return &bpf_get_listener_sock_proto;

	case BPF_FUNC_skb_ecn_set_ce:

		return &bpf_skb_ecn_set_ce_proto;

#endif
@@ -5698,6 +5717,8 @@ tc_cls_act_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog) 
		return &bpf_sk_release_proto;

	case BPF_FUNC_tcp_sock:

		return &bpf_tcp_sock_proto;

	case BPF_FUNC_get_listener_sock:

		return &bpf_get_listener_sock_proto;

#endif

	default:

		return bpf_base_func_proto(func_id);

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