From dbafd7ddd62369b2f3926ab847cbf8fc40e800b7 Mon Sep 17 00:00:00 2001 From: Martin KaFai Lau Date: Tue, 12 Mar 2019 10:23:04 -0700 Subject: [PATCH] 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: Martin KaFai Lau Signed-off-by: Alexei Starovoitov --- include/uapi/linux/bpf.h | 11 ++++++++++- net/core/filter.c | 21 +++++++++++++++++++++ 2 files changed, 31 insertions(+), 1 deletion(-) diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h index 3c38ac9a92a7c4..983b25cb608d40 100644 --- a/include/uapi/linux/bpf.h +++ b/include/uapi/linux/bpf.h @@ -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 diff --git a/net/core/filter.c b/net/core/filter.c index 36b6afacf83c1d..647c63a7b25b67 100644 --- a/net/core/filter.c +++ b/net/core/filter.c @@ -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);