bpf, sk_msg: Add get socket storage helpers

Add helpers to use local socket storage.
Signed-off-by: John Fastabend <john.fastabend@gmail.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Yonghong Song <yhs@fb.com>
Link: https://lore.kernel.org/bpf/159033907577.12355.14740125020572756560.stgit@john-Precision-5820-TowerSigned-off-by: Alexei Starovoitov <ast@kernel.org>

include/uapi/linux/bpf.h

@@ -3645,6 +3645,8 @@ struct sk_msg_md {
 	__u32 remote_port;	/* Stored in network byte order */
 	__u32 local_port;	/* stored in host byte order */
 	__u32 size;		/* Total size of sk_msg */
+
+	__bpf_md_ptr(struct bpf_sock *, sk); /* current socket */
 };
 
 struct sk_reuseport_md {

net/core/filter.c

@@ -6449,6 +6449,10 @@ sk_msg_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
 		return &bpf_get_current_uid_gid_proto;
 	case BPF_FUNC_get_current_pid_tgid:
 		return &bpf_get_current_pid_tgid_proto;
+	case BPF_FUNC_sk_storage_get:
+		return &bpf_sk_storage_get_proto;
+	case BPF_FUNC_sk_storage_delete:
+		return &bpf_sk_storage_delete_proto;
 #ifdef CONFIG_CGROUPS
 	case BPF_FUNC_get_current_cgroup_id:
 		return &bpf_get_current_cgroup_id_proto;
@@ -7273,6 +7277,11 @@ static bool sk_msg_is_valid_access(int off, int size,
 		if (size != sizeof(__u64))
 			return false;
 		break;
+	case offsetof(struct sk_msg_md, sk):
+		if (size != sizeof(__u64))
+			return false;
+		info->reg_type = PTR_TO_SOCKET;
+		break;
 	case bpf_ctx_range(struct sk_msg_md, family):
 	case bpf_ctx_range(struct sk_msg_md, remote_ip4):
 	case bpf_ctx_range(struct sk_msg_md, local_ip4):
@@ -8609,6 +8618,12 @@ static u32 sk_msg_convert_ctx_access(enum bpf_access_type type,
 				      si->dst_reg, si->src_reg,
 				      offsetof(struct sk_msg_sg, size));
 		break;
+
+	case offsetof(struct sk_msg_md, sk):
+		*insn++ = BPF_LDX_MEM(BPF_FIELD_SIZEOF(struct sk_msg, sk),
+				      si->dst_reg, si->src_reg,
+				      offsetof(struct sk_msg, sk));
+		break;
 	}
 
 	return insn - insn_buf;

tools/include/uapi/linux/bpf.h

@@ -3645,6 +3645,8 @@ struct sk_msg_md {
 	__u32 remote_port;	/* Stored in network byte order */
 	__u32 local_port;	/* stored in host byte order */
 	__u32 size;		/* Total size of sk_msg */
+
+	__bpf_md_ptr(struct bpf_sock *, sk); /* current socket */
 };
 
 struct sk_reuseport_md {