[PATCH v2 bpf-next 11/13] bpf: Support BPF_FUNC_get_socket_cookie() for BPF_PROG_TYPE_SK_REUSEPORT.

[Kuniyuki Iwashima <kuniyu@amazon.co.jp>]

We will call sock_reuseport.prog for socket migration in the next commit,
so the eBPF program has to know which listener is closing in order to
select the new listener.

Currently, we can get a unique ID for each listener in the userspace by
calling bpf_map_lookup_elem() for BPF_MAP_TYPE_REUSEPORT_SOCKARRAY map.

This patch makes the sk pointer available in sk_reuseport_md so that we can
get the ID by BPF_FUNC_get_socket_cookie() in the eBPF program.

Link: https://lore.kernel.org/netdev/20201119001154.kapwihc2plp4f7zc@kafai-mbp.dhcp.thefacebook.com/
Suggested-by: Martin KaFai Lau <kafai@fb.com>
Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.co.jp>
---
 include/uapi/linux/bpf.h       |  8 ++++++++
 net/core/filter.c              | 22 ++++++++++++++++++++++
 tools/include/uapi/linux/bpf.h |  8 ++++++++
 3 files changed, 38 insertions(+)

diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index cf518e83df5c..a688a7a4fe85 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -1655,6 +1655,13 @@ union bpf_attr {
  * 		A 8-byte long non-decreasing number on success, or 0 if the
  * 		socket field is missing inside *skb*.
  *
+ * u64 bpf_get_socket_cookie(struct bpf_sock *sk)
+ * 	Description
+ * 		Equivalent to bpf_get_socket_cookie() helper that accepts
+ * 		*skb*, but gets socket from **struct bpf_sock** context.
+ * 	Return
+ * 		A 8-byte long non-decreasing number.
+ *
  * u64 bpf_get_socket_cookie(struct bpf_sock_addr *ctx)
  * 	Description
  * 		Equivalent to bpf_get_socket_cookie() helper that accepts
@@ -4463,6 +4470,7 @@ struct sk_reuseport_md {
 	__u32 bind_inany;	/* Is sock bound to an INANY address? */
 	__u32 hash;		/* A hash of the packet 4 tuples */
 	__u8 migration;		/* Migration type */
+	__bpf_md_ptr(struct bpf_sock *, sk); /* Current listening socket */
 };
 
 #define BPF_TAG_SIZE	8
diff --git a/net/core/filter.c b/net/core/filter.c
index 7bdf62f24044..9f7018e3f545 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -4631,6 +4631,18 @@ static const struct bpf_func_proto bpf_get_socket_cookie_sock_proto = {
 	.arg1_type	= ARG_PTR_TO_CTX,
 };
 
+BPF_CALL_1(bpf_get_socket_pointer_cookie, struct sock *, sk)
+{
+	return __sock_gen_cookie(sk);
+}
+
+static const struct bpf_func_proto bpf_get_socket_pointer_cookie_proto = {
+	.func		= bpf_get_socket_pointer_cookie,
+	.gpl_only	= false,
+	.ret_type	= RET_INTEGER,
+	.arg1_type	= ARG_PTR_TO_SOCKET,
+};
+
 BPF_CALL_1(bpf_get_socket_cookie_sock_ops, struct bpf_sock_ops_kern *, ctx)
 {
 	return __sock_gen_cookie(ctx->sk);
@@ -9989,6 +10001,8 @@ sk_reuseport_func_proto(enum bpf_func_id func_id,
 		return &sk_reuseport_load_bytes_proto;
 	case BPF_FUNC_skb_load_bytes_relative:
 		return &sk_reuseport_load_bytes_relative_proto;
+	case BPF_FUNC_get_socket_cookie:
+		return &bpf_get_socket_pointer_cookie_proto;
 	default:
 		return bpf_base_func_proto(func_id);
 	}
@@ -10022,6 +10036,10 @@ sk_reuseport_is_valid_access(int off, int size,
 		return prog->expected_attach_type == BPF_SK_REUSEPORT_SELECT_OR_MIGRATE &&
 			size == sizeof(__u8);
 
+	case offsetof(struct sk_reuseport_md, sk):
+		info->reg_type = PTR_TO_SOCKET;
+		return size == sizeof(__u64);
+
 	/* Fields that allow narrowing */
 	case bpf_ctx_range(struct sk_reuseport_md, eth_protocol):
 		if (size < sizeof_field(struct sk_buff, protocol))
@@ -10098,6 +10116,10 @@ static u32 sk_reuseport_convert_ctx_access(enum bpf_access_type type,
 	case offsetof(struct sk_reuseport_md, migration):
 		SK_REUSEPORT_LOAD_FIELD(migration);
 		break;
+
+	case offsetof(struct sk_reuseport_md, sk):
+		SK_REUSEPORT_LOAD_FIELD(sk);
+		break;
 	}
 
 	return insn - insn_buf;
diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h
index cf518e83df5c..a688a7a4fe85 100644
--- a/tools/include/uapi/linux/bpf.h
+++ b/tools/include/uapi/linux/bpf.h
@@ -1655,6 +1655,13 @@ union bpf_attr {
  * 		A 8-byte long non-decreasing number on success, or 0 if the
  * 		socket field is missing inside *skb*.
  *
+ * u64 bpf_get_socket_cookie(struct bpf_sock *sk)
+ * 	Description
+ * 		Equivalent to bpf_get_socket_cookie() helper that accepts
+ * 		*skb*, but gets socket from **struct bpf_sock** context.
+ * 	Return
+ * 		A 8-byte long non-decreasing number.
+ *
  * u64 bpf_get_socket_cookie(struct bpf_sock_addr *ctx)
  * 	Description
  * 		Equivalent to bpf_get_socket_cookie() helper that accepts
@@ -4463,6 +4470,7 @@ struct sk_reuseport_md {
 	__u32 bind_inany;	/* Is sock bound to an INANY address? */
 	__u32 hash;		/* A hash of the packet 4 tuples */
 	__u8 migration;		/* Migration type */
+	__bpf_md_ptr(struct bpf_sock *, sk); /* Current listening socket */
 };
 
 #define BPF_TAG_SIZE	8
-- 
2.17.2 (Apple Git-113)