Re: [PATCH RFC net-next v2 1/3] vsock: support sockmap

[Stefano Garzarella]

On Mon, Jan 30, 2023 at 08:35:12PM -0800, Bobby Eshleman wrote:
> This patch adds sockmap support for vsock sockets. It is intended to be
> usable by all transports, but only the virtio transport is implemented.
>
> Signed-off-by: Bobby Eshleman <bobby.eshleman@xxxxxxxxxxxxx>
> ---
> drivers/vhost/vsock.c                   |   1 +
> include/linux/virtio_vsock.h            |   1 +
> include/net/af_vsock.h                  |  17 ++++
> net/vmw_vsock/Makefile                  |   1 +
> net/vmw_vsock/af_vsock.c                |  55 ++++++++--
> net/vmw_vsock/virtio_transport.c        |   2 +
> net/vmw_vsock/virtio_transport_common.c |  24 +++++
> net/vmw_vsock/vsock_bpf.c               | 175 ++++++++++++++++++++++++++++++++
> net/vmw_vsock/vsock_loopback.c          |   2 +
> 9 files changed, 272 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/vhost/vsock.c b/drivers/vhost/vsock.c
> index 1f3b89c885cc..3c6dc036b904 100644
> --- a/drivers/vhost/vsock.c
> +++ b/drivers/vhost/vsock.c
> @@ -439,6 +439,7 @@ static struct virtio_transport vhost_transport = {
> 		.notify_send_post_enqueue = virtio_transport_notify_send_post_enqueue,
> 		.notify_buffer_size       = virtio_transport_notify_buffer_size,
>
> +		.read_skb = virtio_transport_read_skb,
> 	},
>
> 	.send_pkt = vhost_transport_send_pkt,
> diff --git a/include/linux/virtio_vsock.h b/include/linux/virtio_vsock.h
> index 3f9c16611306..c58453699ee9 100644
> --- a/include/linux/virtio_vsock.h
> +++ b/include/linux/virtio_vsock.h
> @@ -245,4 +245,5 @@ u32 virtio_transport_get_credit(struct virtio_vsock_sock *vvs, u32 wanted);
> void virtio_transport_put_credit(struct virtio_vsock_sock *vvs, u32 credit);
> void virtio_transport_deliver_tap_pkt(struct sk_buff *skb);
> int virtio_transport_purge_skbs(void *vsk, struct sk_buff_head *list);
> +int virtio_transport_read_skb(struct vsock_sock *vsk, skb_read_actor_t read_actor);
> #endif /* _LINUX_VIRTIO_VSOCK_H */
> diff --git a/include/net/af_vsock.h b/include/net/af_vsock.h
> index 568a87c5e0d0..a73f5fbd296a 100644
> --- a/include/net/af_vsock.h
> +++ b/include/net/af_vsock.h
> @@ -75,6 +75,7 @@ struct vsock_sock {
> 	void *trans;
> };
>
> +s64 vsock_connectible_has_data(struct vsock_sock *vsk);
> s64 vsock_stream_has_data(struct vsock_sock *vsk);
> s64 vsock_stream_has_space(struct vsock_sock *vsk);
> struct sock *vsock_create_connected(struct sock *parent);
> @@ -173,6 +174,9 @@ struct vsock_transport {
>
> 	/* Addressing. */
> 	u32 (*get_local_cid)(void);
> +
> +	/* Read a single skb */
> +	int (*read_skb)(struct vsock_sock *, skb_read_actor_t);
> };
>
> /**** CORE ****/
> @@ -225,5 +229,18 @@ int vsock_init_tap(void);
> int vsock_add_tap(struct vsock_tap *vt);
> int vsock_remove_tap(struct vsock_tap *vt);
> void vsock_deliver_tap(struct sk_buff *build_skb(void *opaque), void *opaque);
> +int vsock_connectible_recvmsg(struct socket *sock, struct msghdr *msg, size_t len,
> +			      int flags);
> +int vsock_dgram_recvmsg(struct socket *sock, struct msghdr *msg,
> +			       size_t len, int flags);

checkpatch complains: "CHECK: Alignment should match open parenthesis"

> +
> +#ifdef CONFIG_BPF_SYSCALL
> +extern struct proto vsock_proto;
> +int vsock_bpf_update_proto(struct sock *sk, struct sk_psock *psock, bool restore);
> +void __init vsock_bpf_build_proto(void);
> +#else
> +static inline void __init vsock_bpf_build_proto(void)
> +{}
> +#endif
>
> #endif /* __AF_VSOCK_H__ */
> diff --git a/net/vmw_vsock/Makefile b/net/vmw_vsock/Makefile
> index 6a943ec95c4a..5da74c4a9f1d 100644
> --- a/net/vmw_vsock/Makefile
> +++ b/net/vmw_vsock/Makefile
> @@ -8,6 +8,7 @@ obj-$(CONFIG_HYPERV_VSOCKETS) += hv_sock.o
> obj-$(CONFIG_VSOCKETS_LOOPBACK) += vsock_loopback.o
>
> vsock-y += af_vsock.o af_vsock_tap.o vsock_addr.o
> +vsock-$(CONFIG_BPF_SYSCALL) += vsock_bpf.o
>
> vsock_diag-y += diag.o
>
> diff --git a/net/vmw_vsock/af_vsock.c b/net/vmw_vsock/af_vsock.c
> index 19aea7cba26e..f2cc04fb8b13 100644
> --- a/net/vmw_vsock/af_vsock.c
> +++ b/net/vmw_vsock/af_vsock.c
> @@ -116,10 +116,13 @@ static void vsock_sk_destruct(struct sock *sk);
> static int vsock_queue_rcv_skb(struct sock *sk, struct sk_buff *skb);
>
> /* Protocol family. */
> -static struct proto vsock_proto = {
> +struct proto vsock_proto = {
> 	.name = "AF_VSOCK",
> 	.owner = THIS_MODULE,
> 	.obj_size = sizeof(struct vsock_sock),
> +#ifdef CONFIG_BPF_SYSCALL
> +	.psock_update_sk_prot = vsock_bpf_update_proto,
> +#endif
> };
>
> /* The default peer timeout indicates how long we will wait for a peer response
> @@ -865,7 +868,7 @@ s64 vsock_stream_has_data(struct vsock_sock *vsk)
> }
> EXPORT_SYMBOL_GPL(vsock_stream_has_data);
>
> -static s64 vsock_connectible_has_data(struct vsock_sock *vsk)
> +s64 vsock_connectible_has_data(struct vsock_sock *vsk)
> {
> 	struct sock *sk = sk_vsock(vsk);
>
> @@ -874,6 +877,7 @@ static s64 vsock_connectible_has_data(struct vsock_sock *vsk)
> 	else
> 		return vsock_stream_has_data(vsk);
> }
> +EXPORT_SYMBOL_GPL(vsock_connectible_has_data);
>
> s64 vsock_stream_has_space(struct vsock_sock *vsk)
> {
> @@ -1131,6 +1135,13 @@ static __poll_t vsock_poll(struct file *file, struct socket *sock,
> 	return mask;
> }
>
> +static int vsock_read_skb(struct sock *sk, skb_read_actor_t read_actor)
> +{
> +	struct vsock_sock *vsk = vsock_sk(sk);
> +
> +	return vsk->transport->read_skb(vsk, read_actor);
> +}
> +
> static int vsock_dgram_sendmsg(struct socket *sock, struct msghdr *msg,
> 			       size_t len)
> {
> @@ -1241,19 +1252,34 @@ static int vsock_dgram_connect(struct socket *sock,
>
> 	memcpy(&vsk->remote_addr, remote_addr, sizeof(vsk->remote_addr));
> 	sock->state = SS_CONNECTED;
> +	sk->sk_state = TCP_ESTABLISHED;
>
> out:
> 	release_sock(sk);
> 	return err;
> }
>
> -static int vsock_dgram_recvmsg(struct socket *sock, struct msghdr *msg,
> -			       size_t len, int flags)
> +int vsock_dgram_recvmsg(struct socket *sock, struct msghdr *msg,
> +			size_t len, int flags)
> {
> -	struct vsock_sock *vsk = vsock_sk(sock->sk);
> +#ifdef CONFIG_BPF_SYSCALL
> +	const struct proto *prot;
> +#endif
> +	struct vsock_sock *vsk;
> +	struct sock *sk;
> +
> +	sk = sock->sk;
> +	vsk = vsock_sk(sk);
> +
> +#ifdef CONFIG_BPF_SYSCALL
> +	prot = READ_ONCE(sk->sk_prot);
> +	if (prot != &vsock_proto)
> +		return prot->recvmsg(sk, msg, len, flags, NULL);
> +#endif
>
> 	return vsk->transport->dgram_dequeue(vsk, msg, len, flags);
> }
> +EXPORT_SYMBOL_GPL(vsock_dgram_recvmsg);
>
> static const struct proto_ops vsock_dgram_ops = {
> 	.family = PF_VSOCK,
> @@ -1272,6 +1298,7 @@ static const struct proto_ops vsock_dgram_ops = {
> 	.recvmsg = vsock_dgram_recvmsg,
> 	.mmap = sock_no_mmap,
> 	.sendpage = sock_no_sendpage,
> +	.read_skb = vsock_read_skb,
> };
>
> static int vsock_transport_cancel_pkt(struct vsock_sock *vsk)
> @@ -2086,13 +2113,16 @@ static int __vsock_seqpacket_recvmsg(struct sock *sk, struct msghdr *msg,
> 	return err;
> }
>
> -static int
> +int
> vsock_connectible_recvmsg(struct socket *sock, struct msghdr *msg, size_t len,
> 			  int flags)
> {
> 	struct sock *sk;
> 	struct vsock_sock *vsk;
> 	const struct vsock_transport *transport;
> +#ifdef CONFIG_BPF_SYSCALL
> +	const struct proto *prot;
> +#endif
> 	int err;
>
> 	sk = sock->sk;
> @@ -2139,6 +2169,14 @@ vsock_connectible_recvmsg(struct socket *sock, struct msghdr *msg, size_t len,
> 		goto out;
> 	}
>
> +#ifdef CONFIG_BPF_SYSCALL
> +	prot = READ_ONCE(sk->sk_prot);
> +	if (prot != &vsock_proto) {
> +		release_sock(sk);
> +		return prot->recvmsg(sk, msg, len, flags, NULL);
> +	}
> +#endif
> +
> 	if (sk->sk_type == SOCK_STREAM)
> 		err = __vsock_stream_recvmsg(sk, msg, len, flags);
> 	else
> @@ -2148,6 +2186,7 @@ vsock_connectible_recvmsg(struct socket *sock, struct msghdr *msg, size_t len,
> 	release_sock(sk);
> 	return err;
> }
> +EXPORT_SYMBOL_GPL(vsock_connectible_recvmsg);
>
> static int vsock_set_rcvlowat(struct sock *sk, int val)
> {
> @@ -2188,6 +2227,7 @@ static const struct proto_ops vsock_stream_ops = {
> 	.mmap = sock_no_mmap,
> 	.sendpage = sock_no_sendpage,
> 	.set_rcvlowat = vsock_set_rcvlowat,
> +	.read_skb = vsock_read_skb,
> };
>
> static const struct proto_ops vsock_seqpacket_ops = {
> @@ -2209,6 +2249,7 @@ static const struct proto_ops vsock_seqpacket_ops = {
> 	.recvmsg = vsock_connectible_recvmsg,
> 	.mmap = sock_no_mmap,
> 	.sendpage = sock_no_sendpage,
> +	.read_skb = vsock_read_skb,
> };
>
> static int vsock_create(struct net *net, struct socket *sock,
> @@ -2348,6 +2389,8 @@ static int __init vsock_init(void)
> 		goto err_unregister_proto;
> 	}
>
> +	vsock_bpf_build_proto();
> +
> 	return 0;
>
> err_unregister_proto:
> diff --git a/net/vmw_vsock/virtio_transport.c b/net/vmw_vsock/virtio_transport.c
> index 28b5a8e8e094..e95df847176b 100644
> --- a/net/vmw_vsock/virtio_transport.c
> +++ b/net/vmw_vsock/virtio_transport.c
> @@ -457,6 +457,8 @@ static struct virtio_transport virtio_transport = {
> 		.notify_send_pre_enqueue  = virtio_transport_notify_send_pre_enqueue,
> 		.notify_send_post_enqueue = virtio_transport_notify_send_post_enqueue,
> 		.notify_buffer_size       = virtio_transport_notify_buffer_size,
> +
> +		.read_skb = virtio_transport_read_skb,
> 	},
>
> 	.send_pkt = virtio_transport_send_pkt,
> diff --git a/net/vmw_vsock/virtio_transport_common.c b/net/vmw_vsock/virtio_transport_common.c
> index a1581c77cf84..82bdaf61ee02 100644
> --- a/net/vmw_vsock/virtio_transport_common.c
> +++ b/net/vmw_vsock/virtio_transport_common.c
> @@ -1388,6 +1388,30 @@ int virtio_transport_purge_skbs(void *vsk, struct sk_buff_head *queue)
> }
> EXPORT_SYMBOL_GPL(virtio_transport_purge_skbs);
>
> +int virtio_transport_read_skb(struct vsock_sock *vsk, skb_read_actor_t recv_actor)
> +{
> +	struct virtio_vsock_sock *vvs = vsk->trans;
> +	struct sock *sk = sk_vsock(vsk);
> +	struct sk_buff *skb;
> +	int off = 0;
> +	int copied;
> +	int err;
> +
> +	spin_lock_bh(&vvs->rx_lock);
> +	/* Use __skb_recv_datagram() for race-free handling of the receive. It
> +	 * works for types other than dgrams. */

Checkpatch:
  WARNING: Block comments use a trailing */ on a separate line

Since we also use this convention in the other comments in this file,
I would follow it.

> +	skb = __skb_recv_datagram(sk, &vvs->rx_queue, MSG_DONTWAIT, &off, &err);
> +	spin_unlock_bh(&vvs->rx_lock);
> +
> +	if (!skb)
> +		return err;
> +
> +	copied = recv_actor(sk, skb);
> +	kfree_skb(skb);
> +	return copied;
> +}
> +EXPORT_SYMBOL_GPL(virtio_transport_read_skb);
> +
> MODULE_LICENSE("GPL v2");
> MODULE_AUTHOR("Asias He");
> MODULE_DESCRIPTION("common code for virtio vsock");
> diff --git a/net/vmw_vsock/vsock_bpf.c b/net/vmw_vsock/vsock_bpf.c
> new file mode 100644
> index 000000000000..ee92a1f42031
> --- /dev/null
> +++ b/net/vmw_vsock/vsock_bpf.c
> @@ -0,0 +1,175 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/* Copyright (c) 2022 Bobby Eshleman <bobby.eshleman@xxxxxxxxxxxxx>
> + *
> + * 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);		\
> +		})

Some suggestions from checkpatch that I would fix:

CHECK: Macro argument '__sk' may be better as '(__sk)' to avoid precedence issues
CHECK: Macro argument '__psock' may be better as '(__psock)' to avoid precedence issues

> +
> +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 int vsock_msg_wait_data(struct sock *sk, struct sk_psock *psock, long timeo)

IIUC now this function returns 0 when there isn't data and 1 when there
is data, maybe better to change the return type to bool.

> +{
> +	int ret = 0;
> +
> +	DEFINE_WAIT_FUNC(wait, woken_wake_function);
> +
> +	if (sk->sk_shutdown & RCV_SHUTDOWN)
> +		return 1;
> +
> +	if (!timeo)
> +		return ret;
> +
> +	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);
> +	lock_sock(sk);
> +	if (unlikely(!psock)) {
> +		release_sock(sk);

I'm not sure we need the lock to check psock, so can we move this
block before the lock_sock?

> +		return __vsock_recvmsg(sk, msg, len, flags);
> +	}
> +
> +	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);
> +	}
> +
> +msg_bytes_ready:

I saw that this code is also in unix_bpf.c and tcp_bpf.c, so I guess
it's acceptable, but I would have avoided using a label to go back.
I prefer a to use goto only for centralized exiting of functions.

One possible refactoring (not tested):

        copied = sk_msg_recvmsg(sk, psock, msg, len, flags);
        while (!copied) {
                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);
        }
        ...

I'm not sure why we need to call release_sock() and sk_psock_put()
before __vsock_recvmsg(). If it is not needed we can simplify more the
previous code.

The rest LGTM.

Thanks,
Stefano

> +	copied = sk_msg_recvmsg(sk, psock, msg, len, flags);
> +	if (!copied) {
> +		long timeo;
> +		int data;
> +
> +		timeo = sock_rcvtimeo(sk, flags & MSG_DONTWAIT);
> +		data = vsock_msg_wait_data(sk, psock, timeo);
> +		if (data) {
> +			if (!sk_psock_queue_empty(psock))
> +				goto msg_bytes_ready;
> +			release_sock(sk);
> +			sk_psock_put(sk, psock);
> +			return __vsock_recvmsg(sk, msg, len, flags);
> +		}
> +		copied = -EAGAIN;
> +	}
> +	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);
> +}
> diff --git a/net/vmw_vsock/vsock_loopback.c b/net/vmw_vsock/vsock_loopback.c
> index 671e03240fc5..40753b661c13 100644
> --- a/net/vmw_vsock/vsock_loopback.c
> +++ b/net/vmw_vsock/vsock_loopback.c
> @@ -94,6 +94,8 @@ static struct virtio_transport loopback_transport = {
> 		.notify_send_pre_enqueue  = virtio_transport_notify_send_pre_enqueue,
> 		.notify_send_post_enqueue = virtio_transport_notify_send_post_enqueue,
> 		.notify_buffer_size       = virtio_transport_notify_buffer_size,
> +
> +		.read_skb = virtio_transport_read_skb,
> 	},
>
> 	.send_pkt = vsock_loopback_send_pkt,
>
> --
> 2.35.1