Re: [PATCH RFC net-next v5 11/14] vhost/vsock: implement datagram support

Michael S. Tsirkin
2023-07-26T18:40:37Z

On Wed, Jul 19, 2023 at 12:50:15AM +0000, Bobby Eshleman wrote:
> This commit implements datagram support for vhost/vsock by teaching
> vhost to use the common virtio transport datagram functions.
>
> If the virtio RX buffer is too small, then the transmission is
> abandoned, the packet dropped, and EHOSTUNREACH is added to the socket's
> error queue.
>
> Signed-off-by: Bobby Eshleman <bobby.eshleman@bytedance.com>

EHOSTUNREACH?

> ---
> drivers/vhost/vsock.c | 62 +++++++++++++++++++++++++++++++++++++++++++++---
> net/vmw_vsock/af_vsock.c | 5 +++-
> 2 files changed, 63 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/vhost/vsock.c b/drivers/vhost/vsock.c
> index d5d6a3c3f273..da14260c6654 100644
> --- a/drivers/vhost/vsock.c
> +++ b/drivers/vhost/vsock.c
> @@ -8,6 +8,7 @@
> */
> #include <linux/miscdevice.h>
> #include <linux/atomic.h>
> +#include <linux/errqueue.h>
> #include <linux/module.h>
> #include <linux/mutex.h>
> #include <linux/vmalloc.h>
> @@ -32,7 +33,8 @@
> enum {
> VHOST_VSOCK_FEATURES = VHOST_FEATURES |
> (1ULL << VIRTIO_F_ACCESS_PLATFORM) |
> - (1ULL << VIRTIO_VSOCK_F_SEQPACKET)
> + (1ULL << VIRTIO_VSOCK_F_SEQPACKET) |
> + (1ULL << VIRTIO_VSOCK_F_DGRAM)
> };
>
> enum {
> @@ -56,6 +58,7 @@ struct vhost_vsock {
> atomic_t queued_replies;
>
> u32 guest_cid;
> + bool dgram_allow;
> bool seqpacket_allow;
> };
>
> @@ -86,6 +89,32 @@ static struct vhost_vsock *vhost_vsock_get(u32 guest_cid)
> return NULL;
> }
>
> +/* Claims ownership of the skb, do not free the skb after calling! */
> +static void
> +vhost_transport_error(struct sk_buff *skb, int err)
> +{
> + struct sock_exterr_skb *serr;
> + struct sock *sk = skb->sk;
> + struct sk_buff *clone;
> +
> + serr = SKB_EXT_ERR(skb);
> + memset(serr, 0, sizeof(*serr));
> + serr->ee.ee_errno = err;
> + serr->ee.ee_origin = SO_EE_ORIGIN_NONE;
> +
> + clone = skb_clone(skb, GFP_KERNEL);
> + if (!clone)
> + return;
> +
> + if (sock_queue_err_skb(sk, clone))
> + kfree_skb(clone);
> +
> + sk->sk_err = err;
> + sk_error_report(sk);
> +
> + kfree_skb(skb);
> +}
> +
> static void
> vhost_transport_do_send_pkt(struct vhost_vsock *vsock,
> struct vhost_virtqueue *vq)
> @@ -160,9 +189,15 @@ vhost_transport_do_send_pkt(struct vhost_vsock *vsock,
> hdr = virtio_vsock_hdr(skb);
>
> /* If the packet is greater than the space available in the
> - * buffer, we split it using multiple buffers.
> + * buffer, we split it using multiple buffers for connectible
> + * sockets and drop the packet for datagram sockets.
> */

won't this break things like recently proposed zerocopy?
I think splitup has to be supported for all types.

> if (payload_len > iov_len - sizeof(*hdr)) {
> + if (le16_to_cpu(hdr->type) == VIRTIO_VSOCK_TYPE_DGRAM) {
> + vhost_transport_error(skb, EHOSTUNREACH);
> + continue;
> + }
> +
> payload_len = iov_len - sizeof(*hdr);
>
> /* As we are copying pieces of large packet's buffer to
> @@ -394,6 +429,7 @@ static bool vhost_vsock_more_replies(struct vhost_vsock *vsock)
> return val < vq->num;
> }
>
> +static bool vhost_transport_dgram_allow(u32 cid, u32 port);
> static bool vhost_transport_seqpacket_allow(u32 remote_cid);
>
> static struct virtio_transport vhost_transport = {
> @@ -410,7 +446,8 @@ static struct virtio_transport vhost_transport = {
> .cancel_pkt = vhost_transport_cancel_pkt,
>
> .dgram_enqueue = virtio_transport_dgram_enqueue,
> - .dgram_allow = virtio_transport_dgram_allow,
> + .dgram_allow = vhost_transport_dgram_allow,
> + .dgram_addr_init = virtio_transport_dgram_addr_init,
>
> .stream_enqueue = virtio_transport_stream_enqueue,
> .stream_dequeue = virtio_transport_stream_dequeue,
> @@ -443,6 +480,22 @@ static struct virtio_transport vhost_transport = {
> .send_pkt = vhost_transport_send_pkt,
> };
>
> +static bool vhost_transport_dgram_allow(u32 cid, u32 port)
> +{
> + struct vhost_vsock *vsock;
> + bool dgram_allow = false;
> +
> + rcu_read_lock();
> + vsock = vhost_vsock_get(cid);
> +
> + if (vsock)
> + dgram_allow = vsock->dgram_allow;
> +
> + rcu_read_unlock();
> +
> + return dgram_allow;
> +}
> +
> static bool vhost_transport_seqpacket_allow(u32 remote_cid)
> {
> struct vhost_vsock *vsock;
> @@ -799,6 +852,9 @@ static int vhost_vsock_set_features(struct vhost_vsock *vsock, u64 features)
> if (features & (1ULL << VIRTIO_VSOCK_F_SEQPACKET))
> vsock->seqpacket_allow = true;
>
> + if (features & (1ULL << VIRTIO_VSOCK_F_DGRAM))
> + vsock->dgram_allow = true;
> +
> for (i = 0; i < ARRAY_SIZE(vsock->vqs); i++) {
> vq = &vsock->vqs[i];
> mutex_lock(&vq->mutex);
> diff --git a/net/vmw_vsock/af_vsock.c b/net/vmw_vsock/af_vsock.c
> index e73f3b2c52f1..449ed63ac2b0 100644
> --- a/net/vmw_vsock/af_vsock.c
> +++ b/net/vmw_vsock/af_vsock.c
> @@ -1427,9 +1427,12 @@ int vsock_dgram_recvmsg(struct socket *sock, struct msghdr *msg,
> return prot->recvmsg(sk, msg, len, flags, NULL);
> #endif
>
> - if (flags & MSG_OOB || flags & MSG_ERRQUEUE)
> + if (unlikely(flags & MSG_OOB))
> return -EOPNOTSUPP;
>
> + if (unlikely(flags & MSG_ERRQUEUE))
> + return sock_recv_errqueue(sk, msg, len, SOL_VSOCK, 0);
> +
> transport = vsk->transport;
>
> /* Retrieve the head sk_buff from the socket's receive queue. */
>
> --
> 2.30.2