Re: [PATCH RFC net-next v5 01/14] af_vsock: generalize vsock_dgram_recvmsg() to all transports

Arseniy Krasnov
2023-07-24T18:11:51Z

On 19.07.2023 03:50, Bobby Eshleman wrote:
> This commit drops the transport->dgram_dequeue callback and makes
> vsock_dgram_recvmsg() generic to all transports.
>
> To make this possible, two transport-level changes are introduced:
> - implementation of the ->dgram_addr_init() callback to initialize
> the sockaddr_vm structure with data from incoming socket buffers.
> - transport implementations set the skb->data pointer to the beginning
> of the payload prior to adding the skb to the socket's receive queue.
> That is, they must use skb_pull() before enqueuing. This is an
> agreement between the transport and the socket layer that skb->data
> always points to the beginning of the payload (and not, for example,
> the packet header).
>
> Signed-off-by: Bobby Eshleman <bobby.eshleman@bytedance.com>
> ---
> drivers/vhost/vsock.c | 1 -
> include/linux/virtio_vsock.h | 5 ---
> include/net/af_vsock.h | 3 +-
> net/vmw_vsock/af_vsock.c | 40 ++++++++++++++++++++++-
> net/vmw_vsock/hyperv_transport.c | 7 ----
> net/vmw_vsock/virtio_transport.c | 1 -
> net/vmw_vsock/virtio_transport_common.c | 9 -----
> net/vmw_vsock/vmci_transport.c | 58 ++++++---------------------------
> net/vmw_vsock/vsock_loopback.c | 1 -
> 9 files changed, 50 insertions(+), 75 deletions(-)
>
> diff --git a/drivers/vhost/vsock.c b/drivers/vhost/vsock.c
> index 6578db78f0ae..ae8891598a48 100644
> --- a/drivers/vhost/vsock.c
> +++ b/drivers/vhost/vsock.c
> @@ -410,7 +410,6 @@ static struct virtio_transport vhost_transport = {
> .cancel_pkt = vhost_transport_cancel_pkt,
>
> .dgram_enqueue = virtio_transport_dgram_enqueue,
> - .dgram_dequeue = virtio_transport_dgram_dequeue,
> .dgram_bind = virtio_transport_dgram_bind,
> .dgram_allow = virtio_transport_dgram_allow,
>
> diff --git a/include/linux/virtio_vsock.h b/include/linux/virtio_vsock.h
> index c58453699ee9..18cbe8d37fca 100644
> --- a/include/linux/virtio_vsock.h
> +++ b/include/linux/virtio_vsock.h
> @@ -167,11 +167,6 @@ virtio_transport_stream_dequeue(struct vsock_sock *vsk,
> size_t len,
> int type);
> int
> -virtio_transport_dgram_dequeue(struct vsock_sock *vsk,
> - struct msghdr *msg,
> - size_t len, int flags);
> -
> -int
> virtio_transport_seqpacket_enqueue(struct vsock_sock *vsk,
> struct msghdr *msg,
> size_t len);
> diff --git a/include/net/af_vsock.h b/include/net/af_vsock.h
> index 0e7504a42925..305d57502e89 100644
> --- a/include/net/af_vsock.h
> +++ b/include/net/af_vsock.h
> @@ -120,11 +120,10 @@ struct vsock_transport {
>
> /* DGRAM. */
> int (*dgram_bind)(struct vsock_sock *, struct sockaddr_vm *);
> - int (*dgram_dequeue)(struct vsock_sock *vsk, struct msghdr *msg,
> - size_t len, int flags);
> int (*dgram_enqueue)(struct vsock_sock *, struct sockaddr_vm *,
> struct msghdr *, size_t len);
> bool (*dgram_allow)(u32 cid, u32 port);
> + void (*dgram_addr_init)(struct sk_buff *skb, struct sockaddr_vm *addr);
>
> /* STREAM. */
> /* TODO: stream_bind() */
> diff --git a/net/vmw_vsock/af_vsock.c b/net/vmw_vsock/af_vsock.c
> index deb72a8c44a7..ad71e084bf2f 100644
> --- a/net/vmw_vsock/af_vsock.c
> +++ b/net/vmw_vsock/af_vsock.c
> @@ -1272,11 +1272,15 @@ static int vsock_dgram_connect(struct socket *sock,
> int vsock_dgram_recvmsg(struct socket *sock, struct msghdr *msg,
> size_t len, int flags)
> {
> + const struct vsock_transport *transport;
> #ifdef CONFIG_BPF_SYSCALL
> const struct proto *prot;
> #endif
> struct vsock_sock *vsk;
> + struct sk_buff *skb;
> + size_t payload_len;
> struct sock *sk;
> + int err;
>
> sk = sock->sk;
> vsk = vsock_sk(sk);
> @@ -1287,7 +1291,41 @@ int vsock_dgram_recvmsg(struct socket *sock, struct msghdr *msg,
> return prot->recvmsg(sk, msg, len, flags, NULL);
> #endif
>
> - return vsk->transport->dgram_dequeue(vsk, msg, len, flags);
> + if (flags & MSG_OOB || flags & MSG_ERRQUEUE)
> + return -EOPNOTSUPP;
> +
> + transport = vsk->transport;
> +
> + /* Retrieve the head sk_buff from the socket's receive queue. */
> + err = 0;
> + skb = skb_recv_datagram(sk_vsock(vsk), flags, &err);
> + if (!skb)
> + return err;
> +
> + payload_len = skb->len;
> +
> + if (payload_len > len) {
> + payload_len = len;
> + msg->msg_flags |= MSG_TRUNC;
> + }
> +
> + /* Place the datagram payload in the user's iovec. */
> + err = skb_copy_datagram_msg(skb, 0, msg, payload_len);
> + if (err)
> + goto out;
> +
> + if (msg->msg_name) {
> + /* Provide the address of the sender. */
> + DECLARE_SOCKADDR(struct sockaddr_vm *, vm_addr, msg->msg_name);
> +
> + transport->dgram_addr_init(skb, vm_addr);

Do we need check that dgram_addr_init != NULL? because I see that not all transports have this
callback set in this patch

> + msg->msg_namelen = sizeof(*vm_addr);
> + }
> + err = payload_len;
> +
> +out:
> + skb_free_datagram(&vsk->sk, skb);
> + return err;
> }
> EXPORT_SYMBOL_GPL(vsock_dgram_recvmsg);
>
> diff --git a/net/vmw_vsock/hyperv_transport.c b/net/vmw_vsock/hyperv_transport.c
> index 7cb1a9d2cdb4..7f1ea434656d 100644
> --- a/net/vmw_vsock/hyperv_transport.c
> +++ b/net/vmw_vsock/hyperv_transport.c
> @@ -556,12 +556,6 @@ static int hvs_dgram_bind(struct vsock_sock *vsk, struct sockaddr_vm *addr)
> return -EOPNOTSUPP;
> }
>
> -static int hvs_dgram_dequeue(struct vsock_sock *vsk, struct msghdr *msg,
> - size_t len, int flags)
> -{
> - return -EOPNOTSUPP;
> -}
> -
> static int hvs_dgram_enqueue(struct vsock_sock *vsk,
> struct sockaddr_vm *remote, struct msghdr *msg,
> size_t dgram_len)
> @@ -833,7 +827,6 @@ static struct vsock_transport hvs_transport = {
> .shutdown = hvs_shutdown,
>
> .dgram_bind = hvs_dgram_bind,
> - .dgram_dequeue = hvs_dgram_dequeue,
> .dgram_enqueue = hvs_dgram_enqueue,
> .dgram_allow = hvs_dgram_allow,
>
> diff --git a/net/vmw_vsock/virtio_transport.c b/net/vmw_vsock/virtio_transport.c
> index e95df847176b..66edffdbf303 100644
> --- a/net/vmw_vsock/virtio_transport.c
> +++ b/net/vmw_vsock/virtio_transport.c
> @@ -429,7 +429,6 @@ static struct virtio_transport virtio_transport = {
> .cancel_pkt = virtio_transport_cancel_pkt,
>
> .dgram_bind = virtio_transport_dgram_bind,
> - .dgram_dequeue = virtio_transport_dgram_dequeue,
> .dgram_enqueue = virtio_transport_dgram_enqueue,
> .dgram_allow = virtio_transport_dgram_allow,
>
> diff --git a/net/vmw_vsock/virtio_transport_common.c b/net/vmw_vsock/virtio_transport_common.c
> index b769fc258931..01ea1402ad40 100644
> --- a/net/vmw_vsock/virtio_transport_common.c
> +++ b/net/vmw_vsock/virtio_transport_common.c
> @@ -583,15 +583,6 @@ virtio_transport_seqpacket_enqueue(struct vsock_sock *vsk,
> }
> EXPORT_SYMBOL_GPL(virtio_transport_seqpacket_enqueue);
>
> -int
> -virtio_transport_dgram_dequeue(struct vsock_sock *vsk,
> - struct msghdr *msg,
> - size_t len, int flags)
> -{
> - return -EOPNOTSUPP;
> -}
> -EXPORT_SYMBOL_GPL(virtio_transport_dgram_dequeue);
> -
> s64 virtio_transport_stream_has_data(struct vsock_sock *vsk)
> {
> struct virtio_vsock_sock *vvs = vsk->trans;
> diff --git a/net/vmw_vsock/vmci_transport.c b/net/vmw_vsock/vmci_transport.c
> index b370070194fa..0bbbdb222245 100644
> --- a/net/vmw_vsock/vmci_transport.c
> +++ b/net/vmw_vsock/vmci_transport.c
> @@ -641,6 +641,7 @@ static int vmci_transport_recv_dgram_cb(void *data, struct vmci_datagram *dg)
> sock_hold(sk);
> skb_put(skb, size);
> memcpy(skb->data, dg, size);
> + skb_pull(skb, VMCI_DG_HEADERSIZE);
> sk_receive_skb(sk, skb, 0);
>
> return VMCI_SUCCESS;
> @@ -1731,57 +1732,18 @@ static int vmci_transport_dgram_enqueue(
> return err - sizeof(*dg);
> }
>
> -static int vmci_transport_dgram_dequeue(struct vsock_sock *vsk,
> - struct msghdr *msg, size_t len,
> - int flags)
> +static void vmci_transport_dgram_addr_init(struct sk_buff *skb,
> + struct sockaddr_vm *addr)
> {
> - int err;
> struct vmci_datagram *dg;
> - size_t payload_len;
> - struct sk_buff *skb;
> -
> - if (flags & MSG_OOB || flags & MSG_ERRQUEUE)
> - return -EOPNOTSUPP;
> -
> - /* Retrieve the head sk_buff from the socket's receive queue. */
> - err = 0;
> - skb = skb_recv_datagram(&vsk->sk, flags, &err);
> - if (!skb)
> - return err;
> -
> - dg = (struct vmci_datagram *)skb->data;
> - if (!dg)
> - /* err is 0, meaning we read zero bytes. */
> - goto out;
> -
> - payload_len = dg->payload_size;
> - /* Ensure the sk_buff matches the payload size claimed in the packet. */
> - if (payload_len != skb->len - sizeof(*dg)) {
> - err = -EINVAL;
> - goto out;
> - }
> -
> - if (payload_len > len) {
> - payload_len = len;
> - msg->msg_flags |= MSG_TRUNC;
> - }
> + unsigned int cid, port;
>
> - /* Place the datagram payload in the user's iovec. */
> - err = skb_copy_datagram_msg(skb, sizeof(*dg), msg, payload_len);
> - if (err)
> - goto out;
> -
> - if (msg->msg_name) {
> - /* Provide the address of the sender. */
> - DECLARE_SOCKADDR(struct sockaddr_vm *, vm_addr, msg->msg_name);
> - vsock_addr_init(vm_addr, dg->src.context, dg->src.resource);
> - msg->msg_namelen = sizeof(*vm_addr);
> - }
> - err = payload_len;
> + WARN_ONCE(skb->head == skb->data, "vmci vsock bug: bad dgram skb");
>
> -out:
> - skb_free_datagram(&vsk->sk, skb);
> - return err;
> + dg = (struct vmci_datagram *)skb->head;
> + cid = dg->src.context;
> + port = dg->src.resource;
> + vsock_addr_init(addr, cid, port);

I think we

1) can short this to:

vsock_addr_init(addr, dg->src.context, dg->src.resource);

2) w/o previous point, cid and port better be u32, as VMCI structure has u32 fields 'context' and
'resource' and 'vsock_addr_init()' also has u32 type for both arguments.

Thanks, Arseniy

> }
>
> static bool vmci_transport_dgram_allow(u32 cid, u32 port)
> @@ -2040,9 +2002,9 @@ static struct vsock_transport vmci_transport = {
> .release = vmci_transport_release,
> .connect = vmci_transport_connect,
> .dgram_bind = vmci_transport_dgram_bind,
> - .dgram_dequeue = vmci_transport_dgram_dequeue,
> .dgram_enqueue = vmci_transport_dgram_enqueue,
> .dgram_allow = vmci_transport_dgram_allow,
> + .dgram_addr_init = vmci_transport_dgram_addr_init,
> .stream_dequeue = vmci_transport_stream_dequeue,
> .stream_enqueue = vmci_transport_stream_enqueue,
> .stream_has_data = vmci_transport_stream_has_data,
> diff --git a/net/vmw_vsock/vsock_loopback.c b/net/vmw_vsock/vsock_loopback.c
> index 5c6360df1f31..2a59dd177c74 100644
> --- a/net/vmw_vsock/vsock_loopback.c
> +++ b/net/vmw_vsock/vsock_loopback.c
> @@ -62,7 +62,6 @@ static struct virtio_transport loopback_transport = {
> .cancel_pkt = vsock_loopback_cancel_pkt,
>
> .dgram_bind = virtio_transport_dgram_bind,
> - .dgram_dequeue = virtio_transport_dgram_dequeue,
> .dgram_enqueue = virtio_transport_dgram_enqueue,
> .dgram_allow = virtio_transport_dgram_allow,
>
>