sock_map: Introduce BPF_SK_SKB_VERDICT

Reusing BPF_SK_SKB_STREAM_VERDICT is possible but its name is
confusing and more importantly we still want to distinguish them
from user-space. So we can just reuse the stream verdict code but
introduce a new type of eBPF program, skb_verdict. Users are not
allowed to attach stream_verdict and skb_verdict programs to the
same map.

Signed-off-by: Cong Wang <cong.wang@bytedance.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: John Fastabend <john.fastabend@gmail.com>
Link: https://lore.kernel.org/bpf/20210331023237.41094-10-xiyou.wangcong@gmail.com

include/linux/skmsg.h

@@ -58,6 +58,7 @@ struct sk_psock_progs {
 	struct bpf_prog			*msg_parser;
 	struct bpf_prog			*stream_parser;
 	struct bpf_prog			*stream_verdict;
+	struct bpf_prog			*skb_verdict;
 };
 
 enum sk_psock_state_bits {
@@ -487,6 +488,7 @@ static inline void psock_progs_drop(struct sk_psock_progs *progs)
 	psock_set_prog(&progs->msg_parser, NULL);
 	psock_set_prog(&progs->stream_parser, NULL);
 	psock_set_prog(&progs->stream_verdict, NULL);
+	psock_set_prog(&progs->skb_verdict, NULL);
 }
 
 int sk_psock_tls_strp_read(struct sk_psock *psock, struct sk_buff *skb);

include/uapi/linux/bpf.h

@@ -957,6 +957,7 @@ enum bpf_attach_type {
 	BPF_XDP_CPUMAP,
 	BPF_SK_LOOKUP,
 	BPF_XDP,
+	BPF_SK_SKB_VERDICT,
 	__MAX_BPF_ATTACH_TYPE
 };
 

kernel/bpf/syscall.c

@@ -2948,6 +2948,7 @@ attach_type_to_prog_type(enum bpf_attach_type attach_type)
 		return BPF_PROG_TYPE_SK_MSG;
 	case BPF_SK_SKB_STREAM_PARSER:
 	case BPF_SK_SKB_STREAM_VERDICT:
+	case BPF_SK_SKB_VERDICT:
 		return BPF_PROG_TYPE_SK_SKB;
 	case BPF_LIRC_MODE2:
 		return BPF_PROG_TYPE_LIRC_MODE2;

net/core/skmsg.c

@@ -697,7 +697,7 @@ void sk_psock_drop(struct sock *sk, struct sk_psock *psock)
 	rcu_assign_sk_user_data(sk, NULL);
 	if (psock->progs.stream_parser)
 		sk_psock_stop_strp(sk, psock);
-	else if (psock->progs.stream_verdict)
+	else if (psock->progs.stream_verdict || psock->progs.skb_verdict)
 		sk_psock_stop_verdict(sk, psock);
 	write_unlock_bh(&sk->sk_callback_lock);
 
@@ -1024,6 +1024,8 @@ static int sk_psock_verdict_recv(read_descriptor_t *desc, struct sk_buff *skb,
 	}
 	skb_set_owner_r(skb, sk);
 	prog = READ_ONCE(psock->progs.stream_verdict);
+	if (!prog)
+		prog = READ_ONCE(psock->progs.skb_verdict);
 	if (likely(prog)) {
 		skb_dst_drop(skb);
 		skb_bpf_redirect_clear(skb);

net/core/sock_map.c

@@ -156,6 +156,8 @@ static void sock_map_del_link(struct sock *sk,
 				strp_stop = true;
 			if (psock->saved_data_ready && stab->progs.stream_verdict)
 				verdict_stop = true;
+			if (psock->saved_data_ready && stab->progs.skb_verdict)
+				verdict_stop = true;
 			list_del(&link->list);
 			sk_psock_free_link(link);
 		}
@@ -232,6 +234,7 @@ static int sock_map_link(struct bpf_map *map, struct sock *sk)
 	struct sk_psock_progs *progs = sock_map_progs(map);
 	struct bpf_prog *stream_verdict = NULL;
 	struct bpf_prog *stream_parser = NULL;
+	struct bpf_prog *skb_verdict = NULL;
 	struct bpf_prog *msg_parser = NULL;
 	struct sk_psock *psock;
 	int ret;
@@ -268,6 +271,15 @@ static int sock_map_link(struct bpf_map *map, struct sock *sk)
 		}
 	}
 
+	skb_verdict = READ_ONCE(progs->skb_verdict);
+	if (skb_verdict) {
+		skb_verdict = bpf_prog_inc_not_zero(skb_verdict);
+		if (IS_ERR(skb_verdict)) {
+			ret = PTR_ERR(skb_verdict);
+			goto out_put_msg_parser;
+		}
+	}
+
 no_progs:
 	psock = sock_map_psock_get_checked(sk);
 	if (IS_ERR(psock)) {
@@ -278,6 +290,9 @@ no_progs:
 	if (psock) {
 		if ((msg_parser && READ_ONCE(psock->progs.msg_parser)) ||
 		    (stream_parser  && READ_ONCE(psock->progs.stream_parser)) ||
+		    (skb_verdict && READ_ONCE(psock->progs.skb_verdict)) ||
+		    (skb_verdict && READ_ONCE(psock->progs.stream_verdict)) ||
+		    (stream_verdict && READ_ONCE(psock->progs.skb_verdict)) ||
 		    (stream_verdict && READ_ONCE(psock->progs.stream_verdict))) {
 			sk_psock_put(sk, psock);
 			ret = -EBUSY;
@@ -309,6 +324,9 @@ no_progs:
 	} else if (!stream_parser && stream_verdict && !psock->saved_data_ready) {
 		psock_set_prog(&psock->progs.stream_verdict, stream_verdict);
 		sk_psock_start_verdict(sk,psock);
+	} else if (!stream_verdict && skb_verdict && !psock->saved_data_ready) {
+		psock_set_prog(&psock->progs.skb_verdict, skb_verdict);
+		sk_psock_start_verdict(sk, psock);
 	}
 	write_unlock_bh(&sk->sk_callback_lock);
 	return 0;
@@ -317,6 +335,9 @@ out_unlock_drop:
 out_drop:
 	sk_psock_put(sk, psock);
 out_progs:
+	if (skb_verdict)
+		bpf_prog_put(skb_verdict);
+out_put_msg_parser:
 	if (msg_parser)
 		bpf_prog_put(msg_parser);
 out_put_stream_parser:
@@ -1442,8 +1463,15 @@ static int sock_map_prog_update(struct bpf_map *map, struct bpf_prog *prog,
 		break;
 #endif
 	case BPF_SK_SKB_STREAM_VERDICT:
+		if (progs->skb_verdict)
+			return -EBUSY;
 		pprog = &progs->stream_verdict;
 		break;
+	case BPF_SK_SKB_VERDICT:
+		if (progs->stream_verdict)
+			return -EBUSY;
+		pprog = &progs->skb_verdict;
+		break;
 	default:
 		return -EOPNOTSUPP;
 	}

tools/bpf/bpftool/common.c

@@ -57,6 +57,7 @@ const char * const attach_type_name[__MAX_BPF_ATTACH_TYPE] = {
 
 	[BPF_SK_SKB_STREAM_PARSER]	= "sk_skb_stream_parser",
 	[BPF_SK_SKB_STREAM_VERDICT]	= "sk_skb_stream_verdict",
+	[BPF_SK_SKB_VERDICT]		= "sk_skb_verdict",
 	[BPF_SK_MSG_VERDICT]		= "sk_msg_verdict",
 	[BPF_LIRC_MODE2]		= "lirc_mode2",
 	[BPF_FLOW_DISSECTOR]		= "flow_dissector",

tools/bpf/bpftool/prog.c

@@ -76,6 +76,7 @@ enum dump_mode {
 static const char * const attach_type_strings[] = {
 	[BPF_SK_SKB_STREAM_PARSER] = "stream_parser",
 	[BPF_SK_SKB_STREAM_VERDICT] = "stream_verdict",
+	[BPF_SK_SKB_VERDICT] = "skb_verdict",
 	[BPF_SK_MSG_VERDICT] = "msg_verdict",
 	[BPF_FLOW_DISSECTOR] = "flow_dissector",
 	[__MAX_BPF_ATTACH_TYPE] = NULL,

tools/include/uapi/linux/bpf.h

@@ -957,6 +957,7 @@ enum bpf_attach_type {
 	BPF_XDP_CPUMAP,
 	BPF_SK_LOOKUP,
 	BPF_XDP,
+	BPF_SK_SKB_VERDICT,
 	__MAX_BPF_ATTACH_TYPE
 };