Re: [PATCH RFC net-next v4 1/8] vsock/dgram: generalize recvmsg and drop transport->dgram_dequeue

From: Bobby Eshleman
Date: Thu Jun 22 2023 - 19:37:57 EST

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In reply to: Bobby Eshleman: "Re: [PATCH RFC net-next v4 1/8] vsock/dgram: generalize recvmsg and drop transport->dgram_dequeue"
Next in thread: Stefano Garzarella: "Re: [PATCH RFC net-next v4 1/8] vsock/dgram: generalize recvmsg and drop transport->dgram_dequeue"
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On Thu, Jun 22, 2023 at 04:51:41PM +0200, Stefano Garzarella wrote:
> On Sun, Jun 11, 2023 at 11:43:15PM +0300, Arseniy Krasnov wrote:
> > Hello Bobby! Thanks for this patchset! Small comment below:
> >
> > On 10.06.2023 03:58, Bobby Eshleman wrote:
> > > This commit drops the transport->dgram_dequeue callback and makes
> > > vsock_dgram_recvmsg() generic. It also adds additional transport
> > > callbacks for use by the generic vsock_dgram_recvmsg(), such as for
> > > parsing skbs for CID/port which vary in format per transport.
> > >
> > > Signed-off-by: Bobby Eshleman <bobby.eshleman@xxxxxxxxxxxxx>
> > > ---
> > > drivers/vhost/vsock.c | 4 +-
> > > include/linux/virtio_vsock.h | 3 ++
> > > include/net/af_vsock.h | 13 ++++++-
> > > net/vmw_vsock/af_vsock.c | 51 ++++++++++++++++++++++++-
> > > net/vmw_vsock/hyperv_transport.c | 17 +++++++--
> > > net/vmw_vsock/virtio_transport.c | 4 +-
> > > net/vmw_vsock/virtio_transport_common.c | 18 +++++++++
> > > net/vmw_vsock/vmci_transport.c | 68 +++++++++++++--------------------
> > > net/vmw_vsock/vsock_loopback.c | 4 +-
> > > 9 files changed, 132 insertions(+), 50 deletions(-)
> > >
> > > diff --git a/drivers/vhost/vsock.c b/drivers/vhost/vsock.c
> > > index 6578db78f0ae..c8201c070b4b 100644
> > > --- a/drivers/vhost/vsock.c
> > > +++ b/drivers/vhost/vsock.c
> > > @@ -410,9 +410,11 @@ 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,
> > > + .dgram_get_cid = virtio_transport_dgram_get_cid,
> > > + .dgram_get_port = virtio_transport_dgram_get_port,
> > > + .dgram_get_length = virtio_transport_dgram_get_length,
> > >
> > > .stream_enqueue = virtio_transport_stream_enqueue,
> > > .stream_dequeue = virtio_transport_stream_dequeue,
> > > diff --git a/include/linux/virtio_vsock.h b/include/linux/virtio_vsock.h
> > > index c58453699ee9..23521a318cf0 100644
> > > --- a/include/linux/virtio_vsock.h
> > > +++ b/include/linux/virtio_vsock.h
> > > @@ -219,6 +219,9 @@ bool virtio_transport_stream_allow(u32 cid, u32 port);
> > > int virtio_transport_dgram_bind(struct vsock_sock *vsk,
> > > struct sockaddr_vm *addr);
> > > bool virtio_transport_dgram_allow(u32 cid, u32 port);
> > > +int virtio_transport_dgram_get_cid(struct sk_buff *skb, unsigned int *cid);
> > > +int virtio_transport_dgram_get_port(struct sk_buff *skb, unsigned int *port);
> > > +int virtio_transport_dgram_get_length(struct sk_buff *skb, size_t *len);
> > >
> > > int virtio_transport_connect(struct vsock_sock *vsk);
> > >
> > > diff --git a/include/net/af_vsock.h b/include/net/af_vsock.h
> > > index 0e7504a42925..7bedb9ee7e3e 100644
> > > --- a/include/net/af_vsock.h
> > > +++ b/include/net/af_vsock.h
> > > @@ -120,11 +120,20 @@ 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);
> > > + int (*dgram_get_cid)(struct sk_buff *skb, unsigned int *cid);
> > > + int (*dgram_get_port)(struct sk_buff *skb, unsigned int *port);
> > > + int (*dgram_get_length)(struct sk_buff *skb, size_t *length);
> > > +
> > > + /* The number of bytes into the buffer at which the payload starts, as
> > > + * first seen by the receiving socket layer. For example, if the
> > > + * transport presets the skb pointers using skb_pull(sizeof(header))
> > > + * than this would be zero, otherwise it would be the size of the
> > > + * header.
> > > + */
> > > + const size_t dgram_payload_offset;
> > >
> > > /* STREAM. */
> > > /* TODO: stream_bind() */
> > > diff --git a/net/vmw_vsock/af_vsock.c b/net/vmw_vsock/af_vsock.c
> > > index efb8a0937a13..ffb4dd8b6ea7 100644
> > > --- a/net/vmw_vsock/af_vsock.c
> > > +++ b/net/vmw_vsock/af_vsock.c
> > > @@ -1271,11 +1271,15 @@ 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);
> > > @@ -1286,7 +1290,52 @@ 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;
> > > +
> > > + err = transport->dgram_get_length(skb, &payload_len);
>
> What about ssize_t return value here?
>
> Or maybe a single callback that return both length and offset?
>
> .dgram_get_payload_info(skb, &payload_len, &payload_off)
>

What are your thoughts on Arseniy's idea of using skb->len and adding a
skb_pull() just before vmci adds the skb to the sk receive queue?

> > > + if (err)
> > > + goto out;
> > > +
> > > + 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, transport->dgram_payload_offset, 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);
> > > + unsigned int cid, port;
> > > +
> > > + err = transport->dgram_get_cid(skb, &cid);
> > > + if (err)
> > > + goto out;
> > > +
> > > + err = transport->dgram_get_port(skb, &port);
> > > + if (err)
> > > + goto out;
> >
> > Maybe we can merge 'dgram_get_cid' and 'dgram_get_port' to a single callback? Because I see that this is
> > the only place where both are used (correct me if i'm wrong) and logically both operates with addresses:
> > CID and port. E.g. something like that: dgram_get_cid_n_port().
>
> What about .dgram_addr_init(struct sk_buff *skb, struct sockaddr_vm *addr)
> and the transport can set cid and port?
>

LGTM!

> >
> > Moreover, I'm not sure, but is it good "tradeoff" here: remove transport specific callback for dgram receive
> > where we already have 'msghdr' with both data buffer and buffer for 'sockaddr_vm' and instead of it add new
> > several fields (callbacks) to transports like dgram_get_cid(), dgram_get_port()? I agree, that in each transport
> > specific callback we will have same copying logic by calling 'skb_copy_datagram_msg()' and filling address
> > by using 'vsock_addr_init()', but in this case we don't need to update transports too much. For example HyperV
> > still unchanged as it does not support SOCK_DGRAM. For VMCI You just need to add 'vsock_addr_init()' logic
> > to it's dgram dequeue callback.
> >
> > What do You think?
>
> Honestly, I'd rather avoid duplicate code than reduce changes in
> transports that don't support dgram.
>
> One thing I do agree on though is minimizing the number of callbacks
> to call to reduce the number of indirection (more performance?).
>
> Thanks,
> Stefano
>

Thanks!

Best,
Bobby

> >
> > Thanks, Arseniy
> >
> > > +
> > > + vsock_addr_init(vm_addr, cid, port);
> > > + 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..ff6e87e25fa0 100644
> > > --- a/net/vmw_vsock/hyperv_transport.c
> > > +++ b/net/vmw_vsock/hyperv_transport.c
> > > @@ -556,8 +556,17 @@ 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)
> > > +static int hvs_dgram_get_cid(struct sk_buff *skb, unsigned int *cid)
> > > +{
> > > + return -EOPNOTSUPP;
> > > +}
> > > +
> > > +static int hvs_dgram_get_port(struct sk_buff *skb, unsigned int *port)
> > > +{
> > > + return -EOPNOTSUPP;
> > > +}
> > > +
> > > +static int hvs_dgram_get_length(struct sk_buff *skb, size_t *len)
> > > {
> > > return -EOPNOTSUPP;
> > > }
> > > @@ -833,7 +842,9 @@ static struct vsock_transport hvs_transport = {
> > > .shutdown = hvs_shutdown,
> > >
> > > .dgram_bind = hvs_dgram_bind,
> > > - .dgram_dequeue = hvs_dgram_dequeue,
> > > + .dgram_get_cid = hvs_dgram_get_cid,
> > > + .dgram_get_port = hvs_dgram_get_port,
> > > + .dgram_get_length = hvs_dgram_get_length,
> > > .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..5763cdf13804 100644
> > > --- a/net/vmw_vsock/virtio_transport.c
> > > +++ b/net/vmw_vsock/virtio_transport.c
> > > @@ -429,9 +429,11 @@ 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,
> > > + .dgram_get_cid = virtio_transport_dgram_get_cid,
> > > + .dgram_get_port = virtio_transport_dgram_get_port,
> > > + .dgram_get_length = virtio_transport_dgram_get_length,
> > >
> > > .stream_dequeue = virtio_transport_stream_dequeue,
> > > .stream_enqueue = virtio_transport_stream_enqueue,
> > > diff --git a/net/vmw_vsock/virtio_transport_common.c b/net/vmw_vsock/virtio_transport_common.c
> > > index b769fc258931..e6903c719964 100644
> > > --- a/net/vmw_vsock/virtio_transport_common.c
> > > +++ b/net/vmw_vsock/virtio_transport_common.c
> > > @@ -797,6 +797,24 @@ int virtio_transport_dgram_bind(struct vsock_sock *vsk,
> > > }
> > > EXPORT_SYMBOL_GPL(virtio_transport_dgram_bind);
> > >
> > > +int virtio_transport_dgram_get_cid(struct sk_buff *skb, unsigned int *cid)
> > > +{
> > > + return -EOPNOTSUPP;
> > > +}
> > > +EXPORT_SYMBOL_GPL(virtio_transport_dgram_get_cid);
> > > +
> > > +int virtio_transport_dgram_get_port(struct sk_buff *skb, unsigned int *port)
> > > +{
> > > + return -EOPNOTSUPP;
> > > +}
> > > +EXPORT_SYMBOL_GPL(virtio_transport_dgram_get_port);
> > > +
> > > +int virtio_transport_dgram_get_length(struct sk_buff *skb, size_t *len)
> > > +{
> > > + return -EOPNOTSUPP;
> > > +}
> > > +EXPORT_SYMBOL_GPL(virtio_transport_dgram_get_length);
> > > +
> > > bool virtio_transport_dgram_allow(u32 cid, u32 port)
> > > {
> > > return false;
> > > diff --git a/net/vmw_vsock/vmci_transport.c b/net/vmw_vsock/vmci_transport.c
> > > index b370070194fa..bbc63826bf48 100644
> > > --- a/net/vmw_vsock/vmci_transport.c
> > > +++ b/net/vmw_vsock/vmci_transport.c
> > > @@ -1731,57 +1731,40 @@ 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 int vmci_transport_dgram_get_cid(struct sk_buff *skb, unsigned int *cid)
> > > {
> > > - int err;
> > > struct vmci_datagram *dg;
> > > - size_t payload_len;
> > > - struct sk_buff *skb;
> > >
> > > - if (flags & MSG_OOB || flags & MSG_ERRQUEUE)
> > > - return -EOPNOTSUPP;
> > > + dg = (struct vmci_datagram *)skb->data;
> > > + if (!dg)
> > > + return -EINVAL;
> > >
> > > - /* 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;
> > > + *cid = dg->src.context;
> > > + return 0;
> > > +}
> > > +
> > > +static int vmci_transport_dgram_get_port(struct sk_buff *skb, unsigned int *port)
> > > +{
> > > + struct vmci_datagram *dg;
> > >
> > > 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;
> > > - }
> > > + return -EINVAL;
> > >
> > > - if (payload_len > len) {
> > > - payload_len = len;
> > > - msg->msg_flags |= MSG_TRUNC;
> > > - }
> > > + *port = dg->src.resource;
> > > + return 0;
> > > +}
> > >
> > > - /* Place the datagram payload in the user's iovec. */
> > > - err = skb_copy_datagram_msg(skb, sizeof(*dg), msg, payload_len);
> > > - if (err)
> > > - goto out;
> > > +static int vmci_transport_dgram_get_length(struct sk_buff *skb, size_t *len)
> > > +{
> > > + struct vmci_datagram *dg;
> > >
> > > - 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;
> > > + dg = (struct vmci_datagram *)skb->data;
> > > + if (!dg)
> > > + return -EINVAL;
> > >
> > > -out:
> > > - skb_free_datagram(&vsk->sk, skb);
> > > - return err;
> > > + *len = dg->payload_size;
> > > + return 0;
> > > }
> > >
> > > static bool vmci_transport_dgram_allow(u32 cid, u32 port)
> > > @@ -2040,9 +2023,12 @@ 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_get_cid = vmci_transport_dgram_get_cid,
> > > + .dgram_get_port = vmci_transport_dgram_get_port,
> > > + .dgram_get_length = vmci_transport_dgram_get_length,
> > > + .dgram_payload_offset = sizeof(struct vmci_datagram),
> > > .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..2f3cabc79ee5 100644
> > > --- a/net/vmw_vsock/vsock_loopback.c
> > > +++ b/net/vmw_vsock/vsock_loopback.c
> > > @@ -62,9 +62,11 @@ 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,
> > > + .dgram_get_cid = virtio_transport_dgram_get_cid,
> > > + .dgram_get_port = virtio_transport_dgram_get_port,
> > > + .dgram_get_length = virtio_transport_dgram_get_length,
> > >
> > > .stream_dequeue = virtio_transport_stream_dequeue,
> > > .stream_enqueue = virtio_transport_stream_enqueue,
> > >
> >
>
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