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 - 19:34:37 EST
On Thu, Jun 22, 2023 at 10:23:26PM +0300, Arseniy Krasnov wrote:
>
>
> On 22.06.2023 17:51, 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)
>
> Just architectural question:
>
> May be we can avoid this callback for length? IIUC concept of skbuff is that
> current level of network stack already have pointer to its data 'skb->data' and
> length of the payload 'skb->len' (both are set by previous stack handler - transport in
> this case), so here we can use just 'skb->len' and thats all. There is no need to ask
> lower level of network stack for length of payload? I see that VMCI stores metadata
> with payload in 'data' buffer, but may be it is more correctly to do 'skb_pull()'
> in vmci before inserting skbuff to sockets queue? In this case field with dgram payload
> offset could be removed from transport.
>
> Thanks, Arseniy
>
I agree, I think introducing the skb_pull() to vmci would honestly be
best. I don't think it should break anything based on my reading of the
code if it is called just prior to sk_receive_skb().
Thanks,
Bobby
> >
> >>> + 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?
> >
> >>
> >> 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, 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,
> >>>
> >>
> >