vsock: support sockmap

This patch adds sockmap support for vsock sockets. It is intended to be
usable by all transports, but only the virtio and loopback transports
are implemented.

SOCK_STREAM, SOCK_DGRAM, and SOCK_SEQPACKET are all supported.

Signed-off-by: Bobby Eshleman <bobby.eshleman@bytedance.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Reviewed-by: Stefano Garzarella <sgarzare@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 174 insertions, 0 deletions

diff --git a/net/vmw_vsock/vsock_bpf.c b/net/vmw_vsock/vsock_bpf.c
new file mode 100644
index 000000000000..a3c97546ab84
--- /dev/null
+++ b/net/vmw_vsock/vsock_bpf.c
@@ -0,0 +1,174 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2022 Bobby Eshleman <bobby.eshleman@bytedance.com>
+ *
+ * Based off of net/unix/unix_bpf.c
+ */
+
+#include <linux/bpf.h>
+#include <linux/module.h>
+#include <linux/skmsg.h>
+#include <linux/socket.h>
+#include <linux/wait.h>
+#include <net/af_vsock.h>
+#include <net/sock.h>
+
+#define vsock_sk_has_data(__sk, __psock)				\
+		({	!skb_queue_empty(&(__sk)->sk_receive_queue) ||	\
+			!skb_queue_empty(&(__psock)->ingress_skb) ||	\
+			!list_empty(&(__psock)->ingress_msg);		\
+		})
+
+static struct proto *vsock_prot_saved __read_mostly;
+static DEFINE_SPINLOCK(vsock_prot_lock);
+static struct proto vsock_bpf_prot;
+
+static bool vsock_has_data(struct sock *sk, struct sk_psock *psock)
+{
+	struct vsock_sock *vsk = vsock_sk(sk);
+	s64 ret;
+
+	ret = vsock_connectible_has_data(vsk);
+	if (ret > 0)
+		return true;
+
+	return vsock_sk_has_data(sk, psock);
+}
+
+static bool vsock_msg_wait_data(struct sock *sk, struct sk_psock *psock, long timeo)
+{
+	bool ret;
+
+	DEFINE_WAIT_FUNC(wait, woken_wake_function);
+
+	if (sk->sk_shutdown & RCV_SHUTDOWN)
+		return true;
+
+	if (!timeo)
+		return false;
+
+	add_wait_queue(sk_sleep(sk), &wait);
+	sk_set_bit(SOCKWQ_ASYNC_WAITDATA, sk);
+	ret = vsock_has_data(sk, psock);
+	if (!ret) {
+		wait_woken(&wait, TASK_INTERRUPTIBLE, timeo);
+		ret = vsock_has_data(sk, psock);
+	}
+	sk_clear_bit(SOCKWQ_ASYNC_WAITDATA, sk);
+	remove_wait_queue(sk_sleep(sk), &wait);
+	return ret;
+}
+
+static int __vsock_recvmsg(struct sock *sk, struct msghdr *msg, size_t len, int flags)
+{
+	struct socket *sock = sk->sk_socket;
+	int err;
+
+	if (sk->sk_type == SOCK_STREAM || sk->sk_type == SOCK_SEQPACKET)
+		err = vsock_connectible_recvmsg(sock, msg, len, flags);
+	else if (sk->sk_type == SOCK_DGRAM)
+		err = vsock_dgram_recvmsg(sock, msg, len, flags);
+	else
+		err = -EPROTOTYPE;
+
+	return err;
+}
+
+static int vsock_bpf_recvmsg(struct sock *sk, struct msghdr *msg,
+			     size_t len, int flags, int *addr_len)
+{
+	struct sk_psock *psock;
+	int copied;
+
+	psock = sk_psock_get(sk);
+	if (unlikely(!psock))
+		return __vsock_recvmsg(sk, msg, len, flags);
+
+	lock_sock(sk);
+	if (vsock_has_data(sk, psock) && sk_psock_queue_empty(psock)) {
+		release_sock(sk);
+		sk_psock_put(sk, psock);
+		return __vsock_recvmsg(sk, msg, len, flags);
+	}
+
+	copied = sk_msg_recvmsg(sk, psock, msg, len, flags);
+	while (copied == 0) {
+		long timeo = sock_rcvtimeo(sk, flags & MSG_DONTWAIT);
+
+		if (!vsock_msg_wait_data(sk, psock, timeo)) {
+			copied = -EAGAIN;
+			break;
+		}
+
+		if (sk_psock_queue_empty(psock)) {
+			release_sock(sk);
+			sk_psock_put(sk, psock);
+			return __vsock_recvmsg(sk, msg, len, flags);
+		}
+
+		copied = sk_msg_recvmsg(sk, psock, msg, len, flags);
+	}
+
+	release_sock(sk);
+	sk_psock_put(sk, psock);
+
+	return copied;
+}
+
+/* Copy of original proto with updated sock_map methods */
+static struct proto vsock_bpf_prot = {
+	.close = sock_map_close,
+	.recvmsg = vsock_bpf_recvmsg,
+	.sock_is_readable = sk_msg_is_readable,
+	.unhash = sock_map_unhash,
+};
+
+static void vsock_bpf_rebuild_protos(struct proto *prot, const struct proto *base)
+{
+	*prot        = *base;
+	prot->close  = sock_map_close;
+	prot->recvmsg = vsock_bpf_recvmsg;
+	prot->sock_is_readable = sk_msg_is_readable;
+}
+
+static void vsock_bpf_check_needs_rebuild(struct proto *ops)
+{
+	/* Paired with the smp_store_release() below. */
+	if (unlikely(ops != smp_load_acquire(&vsock_prot_saved))) {
+		spin_lock_bh(&vsock_prot_lock);
+		if (likely(ops != vsock_prot_saved)) {
+			vsock_bpf_rebuild_protos(&vsock_bpf_prot, ops);
+			/* Make sure proto function pointers are updated before publishing the
+			 * pointer to the struct.
+			 */
+			smp_store_release(&vsock_prot_saved, ops);
+		}
+		spin_unlock_bh(&vsock_prot_lock);
+	}
+}
+
+int vsock_bpf_update_proto(struct sock *sk, struct sk_psock *psock, bool restore)
+{
+	struct vsock_sock *vsk;
+
+	if (restore) {
+		sk->sk_write_space = psock->saved_write_space;
+		sock_replace_proto(sk, psock->sk_proto);
+		return 0;
+	}
+
+	vsk = vsock_sk(sk);
+	if (!vsk->transport)
+		return -ENODEV;
+
+	if (!vsk->transport->read_skb)
+		return -EOPNOTSUPP;
+
+	vsock_bpf_check_needs_rebuild(psock->sk_proto);
+	sock_replace_proto(sk, &vsock_bpf_prot);
+	return 0;
+}
+
+void __init vsock_bpf_build_proto(void)
+{
+	vsock_bpf_rebuild_protos(&vsock_bpf_prot, &vsock_proto);
+}