On Thu, Jun 22, 2023 at 10:23:26PM +0300, Arseniy Krasnov wrote:

On 22.06.2023 17:51, Stefano Garzarella wrote:

quoted

On Sun, Jun 11, 2023 at 11:43:15PM +0300, Arseniy Krasnov wrote:

quoted

Hello Bobby! Thanks for this patchset! Small comment below:

On 10.06.2023 03:58, Bobby Eshleman wrote:

quoted

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 <redacted>
---
 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

quoted

quoted

quoted

+    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?

quoted

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

quoted

Thanks, Arseniy

quoted

+
+        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,