Re: [PATCH v13 3/7] net/vmnet: implement shared mode (vmnet-shared)

[Akihiko Odaki]

On 2022/01/14 2:22, Vladislav Yaroshchuk wrote:
> Interaction with vmnet.framework in different modes
> differs only on configuration stage, so we can create
> common `send`, `receive`, etc. procedures and reuse them.
>
> vmnet.framework supports iov, but writing more than
> one iov into vmnet interface fails with
> 'VMNET_INVALID_ARGUMENT'. Collecting provided iovs into
> one and passing it to vmnet works fine. That's the
> reason why receive_iov() left unimplemented. But it still
> works with good enough performance having .receive()
> implemented only.
>
> Also, there is no way to unsubscribe from vmnet packages
> receiving except registering and unregistering event
> callback or simply drop packages just ignoring and
> not processing them when related flag is set. Here we do
> using the second way.
>
> Signed-off-by: Phillip Tennen <phillip@axleos.com>
> Signed-off-by: Vladislav Yaroshchuk <yaroshchuk2000@gmail.com>
> ---
>   net/vmnet-common.m | 313 +++++++++++++++++++++++++++++++++++++++++++++
>   net/vmnet-shared.c |  83 +++++++++++-
>   net/vmnet_int.h    |  23 ++++
>   3 files changed, 415 insertions(+), 4 deletions(-)
>
> diff --git a/net/vmnet-common.m b/net/vmnet-common.m
> index 532d152840..e780985891 100644
> --- a/net/vmnet-common.m
> +++ b/net/vmnet-common.m
> @@ -10,6 +10,8 @@
>    */
>   
>   #include "qemu/osdep.h"
> +#include "qemu/main-loop.h"
> +#include "qemu/log.h"
>   #include "qapi/qapi-types-net.h"
>   #include "vmnet_int.h"
>   #include "clients.h"
> @@ -17,4 +19,315 @@
>   #include "qapi/error.h"
>   
>   #include <vmnet/vmnet.h>
> +#include <dispatch/dispatch.h>
>   
> +#ifdef DEBUG
> +#define D(x) x
> +#define D_LOG(...) qemu_log(__VA_ARGS__)
> +#else
> +#define D(x) do { } while (0)
> +#define D_LOG(...) do { } while (0)
> +#endif
> +
> +typedef struct vmpktdesc vmpktdesc_t;
> +typedef struct iovec iovec_t;

The uses of these typedefs are inconsistent and some use struct 
vmpktdesc and struct iovec and the other use vmpktdesc_t and iovec_t. 
They should be at least consistent, and I also don't think adding 
typedefs for types provided by an external library is a good idea in 
general.

> +
> +static void vmnet_set_send_enabled(VmnetCommonState *s, bool enable)
> +{
> +    s->send_enabled = enable;
> +}
> +
> +
> +static void vmnet_send_completed(NetClientState *nc, ssize_t len)
> +{
> +    VmnetCommonState *s = DO_UPCAST(VmnetCommonState, nc, nc);
> +    vmnet_set_send_enabled(s, true);
> +}
> +
> +
> +static void vmnet_send(NetClientState *nc,
> +                       interface_event_t event_id,
> +                       xpc_object_t event)
> +{
> +    assert(event_id == VMNET_INTERFACE_PACKETS_AVAILABLE);
> +
> +    VmnetCommonState *s;
> +    uint64_t packets_available;
> +
> +    struct iovec *iov;
> +    struct vmpktdesc *packets;
> +    int pkt_cnt;
> +    int i;
> +
> +    vmnet_return_t if_status;
> +    ssize_t size;
> +
> +    s = DO_UPCAST(VmnetCommonState, nc, nc);
> +
> +    packets_available = xpc_dictionary_get_uint64(
> +        event,
> +        vmnet_estimated_packets_available_key
> +    );
> +
> +    pkt_cnt = (packets_available < VMNET_PACKETS_LIMIT) ?
> +              packets_available :
> +              VMNET_PACKETS_LIMIT;
> +
> +
> +    iov = s->iov_buf;
> +    packets = s->packets_buf;
> +
> +    for (i = 0; i < pkt_cnt; ++i) {
> +        packets[i].vm_pkt_size = s->max_packet_size;
> +        packets[i].vm_pkt_iovcnt = 1;
> +        packets[i].vm_flags = 0;
> +    }
> +
> +    if_status = vmnet_read(s->vmnet_if, packets, &pkt_cnt);
> +    if (if_status != VMNET_SUCCESS) {
> +        error_printf("vmnet: read failed: %s\n",
> +                     vmnet_status_map_str(if_status));
> +    }
> +    qemu_mutex_lock_iothread();
> +    for (i = 0; i < pkt_cnt; ++i) {
> +        size = qemu_send_packet_async(nc,
> +                                      iov[i].iov_base,
> +                                      packets[i].vm_pkt_size,
> +                                      vmnet_send_completed);
> +        if (size == 0) {
> +            vmnet_set_send_enabled(s, false);
> +        } else if (size < 0) {
> +            break;
> +        }
> +    }
> +    qemu_mutex_unlock_iothread();
> +
> +}
> +
> +
> +static void vmnet_register_event_callback(VmnetCommonState *s)
> +{
> +    dispatch_queue_t avail_pkt_q = dispatch_queue_create(
> +        "org.qemu.vmnet.if_queue",
> +        DISPATCH_QUEUE_SERIAL
> +    );
> +
> +    vmnet_interface_set_event_callback(
> +        s->vmnet_if,
> +        VMNET_INTERFACE_PACKETS_AVAILABLE,
> +        avail_pkt_q,
> +        ^(interface_event_t event_id, xpc_object_t event) {
> +          if (s->send_enabled) {
> +              vmnet_send(&s->nc, event_id, event);
> +          }
> +        });
> +}

avail_pkt_q leaks even after vmnet_cleanup_common. Note:
- that you can dynamically add and delete interfaces with HMP and QMP.
- that vmnet_interface_set_event_callback somehow does not manage the 
reference counter by itself so you cannot just call dispatch_release 
immediately after vmnet_interface_set_event_callback and you have to 
call it after making sure everything is done.

> +
> +
> +static void vmnet_bufs_init(VmnetCommonState *s)
> +{
> +    int i;
> +    struct vmpktdesc *packets;
> +    struct iovec *iov;
> +
> +    packets = s->packets_buf;
> +    iov = s->iov_buf;
> +
> +    for (i = 0; i < VMNET_PACKETS_LIMIT; ++i) {
> +        iov[i].iov_len = s->max_packet_size;
> +        iov[i].iov_base = g_malloc0(iov[i].iov_len);
> +        packets[i].vm_pkt_iov = iov + i;
> +    }
> +}
> +
> +
> +const char *vmnet_status_map_str(vmnet_return_t status)
> +{
> +    switch (status) {
> +    case VMNET_SUCCESS:
> +        return "success";
> +    case VMNET_FAILURE:
> +        return "general failure";
> +    case VMNET_MEM_FAILURE:
> +        return "memory allocation failure";
> +    case VMNET_INVALID_ARGUMENT:
> +        return "invalid argument specified";
> +    case VMNET_SETUP_INCOMPLETE:
> +        return "interface setup is not complete";
> +    case VMNET_INVALID_ACCESS:
> +        return "invalid access, permission denied";
> +    case VMNET_PACKET_TOO_BIG:
> +        return "packet size is larger than MTU";
> +    case VMNET_BUFFER_EXHAUSTED:
> +        return "buffers exhausted in kernel";
> +    case VMNET_TOO_MANY_PACKETS:
> +        return "packet count exceeds limit";
> +#if defined(MAC_OS_VERSION_11_0) && \
> +    MAC_OS_X_VERSION_MIN_REQUIRED >= MAC_OS_VERSION_11_0
> +    case VMNET_SHARING_SERVICE_BUSY:
> +        return "conflict, sharing service is in use";
> +#endif
> +    default:
> +        return "unknown vmnet error";
> +    }
> +}
> +
> +
> +int vmnet_if_create(NetClientState *nc,
> +                    xpc_object_t if_desc,
> +                    Error **errp,
> +                    void (*completion_callback)(xpc_object_t interface_param))

completion_callback parameter is apparently unused in this series and 
can be removed.

> +{
> +    VmnetCommonState *s;
> +
> +    dispatch_queue_t if_create_q;
> +    dispatch_semaphore_t if_created_sem
> +
> +    __block vmnet_return_t if_status;
> +
> +    if_create_q = dispatch_queue_create("org.qemu.vmnet.create",
> +                                        DISPATCH_QUEUE_SERIAL);
> +    if_created_sem = dispatch_semaphore_create(0);

if_created_sem leaks. Add dispatch_release(if_created_sem); later.

> +
> +    xpc_dictionary_set_bool(
> +        if_desc,
> +        vmnet_allocate_mac_address_key,
> +        false
> +    );
> +
> +    D(D_LOG("vmnet.start.interface_desc:\n");
> +    xpc_dictionary_apply(if_desc,
> +                         ^bool(const char *k, xpc_object_t v) {
> +                           char *desc = xpc_copy_description(v);
> +                           D_LOG("  %s=%s\n", k, desc);
> +                           free(desc);
> +                           return true;
> +                         }));
> +
> +    s = DO_UPCAST(VmnetCommonState, nc, nc);
> +    s->vmnet_if = vmnet_start_interface(
> +        if_desc,
> +        if_create_q,
> +        ^(vmnet_return_t status, xpc_object_t interface_param) {
> +          if_status = status;
> +          if (status != VMNET_SUCCESS || !interface_param) {
> +              dispatch_semaphore_signal(if_created_sem);
> +              return;
> +          }
> +
> +          D(D_LOG("vmnet.start.interface_param:\n");
> +                xpc_dictionary_apply(interface_param,
> +                                     ^bool(const char *k, xpc_object_t v) {
> +                                       char *desc = xpc_copy_description(v);
> +                                       D_LOG("  %s=%s\n", k, desc);
> +                                       free(desc);
> +                                       return true;
> +                                     }));

The indents in `D()` in this function is inconsistent. In my opinion, 
having a few statements in `()` is inherently confusing and just using 
`#ifdef DEBUG` is preferred.

Using a normal `if` instead of #ifdef would be even better, but you 
don't have to do that because apparently QEMU doesn't have a common 
infrastructure for this. c.f. 
https://www.kernel.org/doc/html/latest/process/coding-style.html#conditional-compilation

> +
> +          s->mtu = xpc_dictionary_get_uint64(
> +              interface_param,
> +              vmnet_mtu_key);
> +          s->max_packet_size = xpc_dictionary_get_uint64(
> +              interface_param,
> +              vmnet_max_packet_size_key);
> +
> +          if (completion_callback) {
> +              completion_callback(interface_param);
> +          }
> +          dispatch_semaphore_signal(if_created_sem);
> +        });
> +
> +    if (s->vmnet_if == NULL) {
> +        error_setg(errp, "unable to create interface with requested params");
> +        return -1;

if_create_q leaks here. You may just use a global queue here to entirely 
eliminate the need of calling dispatch_release(if_create_q).

> +    }
> +
> +    dispatch_semaphore_wait(if_created_sem, DISPATCH_TIME_FOREVER);
> +    dispatch_release(if_create_q);
> +
> +    if (if_status != VMNET_SUCCESS) {
> +        error_setg(errp,
> +                   "cannot create vmnet interface: %s",
> +                   vmnet_status_map_str(if_status));
> +        return -1;
> +    }
> +
> +    vmnet_register_event_callback(s);
> +    vmnet_bufs_init(s);
> +    vmnet_set_send_enabled(s, true);
> +
> +    return 0;
> +}
> +
> +
> +ssize_t vmnet_receive_common(NetClientState *nc,
> +                             const uint8_t *buf,
> +                             size_t size)
> +{
> +    VmnetCommonState *s;
> +    vmpktdesc_t packet;
> +    iovec_t iov;
> +    int pkt_cnt;
> +    vmnet_return_t if_status;
> +
> +    s = DO_UPCAST(VmnetCommonState, nc, nc);
> +
> +    if (size > s->max_packet_size) {
> +        warn_report("vmnet: packet is too big, %zu > %llu\n",
> +                    packet.vm_pkt_size,
> +                    s->max_packet_size);
> +        return -1;
> +    }
> +
> +    iov.iov_base = (char *) buf;
> +    iov.iov_len = size;
> +
> +    packet.vm_pkt_iovcnt = 1;
> +    packet.vm_flags = 0;
> +    packet.vm_pkt_size = size;
> +    packet.vm_pkt_iov = &iov;
> +
> +    pkt_cnt = 1;
> +    if_status = vmnet_write(s->vmnet_if, &packet, &pkt_cnt);
> +
> +    if (if_status != VMNET_SUCCESS) {
> +        error_report("vmnet: write error: %s\n",
> +                     vmnet_status_map_str(if_status));
> +    }
> +
> +    if (if_status == VMNET_SUCCESS && pkt_cnt) {
> +        return size;
> +    }
> +    return 0;
> +}
> +
> +
> +void vmnet_cleanup_common(NetClientState *nc)
> +{
> +    VmnetCommonState *s;
> +    dispatch_queue_t if_destroy_q;
> +
> +    s = DO_UPCAST(VmnetCommonState, nc, nc);
> +
> +    qemu_purge_queued_packets(nc);
> +    vmnet_set_send_enabled(s, false);
> +
> +    if (s->vmnet_if == NULL) {
> +        return;
> +    }
> +
> +    if_destroy_q = dispatch_queue_create(
> +        "org.qemu.vmnet.destroy",
> +        DISPATCH_QUEUE_SERIAL
> +    );
> +
> +    vmnet_stop_interface(
> +        s->vmnet_if,
> +        if_destroy_q,
> +        ^(vmnet_return_t status) {
> +        });
> +
> +    for (int i = 0; i < VMNET_PACKETS_LIMIT; ++i) {
> +        g_free(s->iov_buf[i].iov_base);
> +    }

Not sure it is safe to free things without waiting the callback of 
vmnet_stop_interface. I think a semaphore should be added as it is in 
vmnet_if_create.

> +}
> diff --git a/net/vmnet-shared.c b/net/vmnet-shared.c
> index f8c4a4f3b8..61f3e9201f 100644
> --- a/net/vmnet-shared.c
> +++ b/net/vmnet-shared.c
> @@ -10,16 +10,91 @@
>   
>   #include "qemu/osdep.h"
>   #include "qapi/qapi-types-net.h"
> +#include "qapi/error.h"
>   #include "vmnet_int.h"
>   #include "clients.h"
> -#include "qemu/error-report.h"
> -#include "qapi/error.h"
>   
>   #include <vmnet/vmnet.h>
>   
> +typedef struct VmnetSharedState {
> +  VmnetCommonState cs;
> +} VmnetSharedState;
> +
> +
> +static xpc_object_t create_if_desc(const Netdev *netdev, Error **errp)
> +{
> +    const NetdevVmnetSharedOptions *options = &(netdev->u.vmnet_shared);
> +    xpc_object_t if_desc = xpc_dictionary_create(NULL, NULL, 0);
> +
> +    xpc_dictionary_set_uint64(
> +        if_desc,
> +        vmnet_operation_mode_key,
> +        VMNET_SHARED_MODE
> +    );
> +
> +#if defined(MAC_OS_VERSION_11_0) && \
> +    MAC_OS_X_VERSION_MIN_REQUIRED >= MAC_OS_VERSION_11_0
> +    xpc_dictionary_set_bool(
> +        if_desc,
> +        vmnet_enable_isolation_key,
> +        options->isolated
> +    );
> +#else
> +    if (options->has_isolated) {
> +        error_setg(errp,
> +                   "vmnet-shared.isolated feature is "
> +                   "unavailable: outdated vmnet.framework API");
> +    }
> +#endif
> +
> +    if (options->has_nat66_prefix) {
> +        xpc_dictionary_set_string(if_desc,
> +                                  vmnet_nat66_prefix_key,
> +                                  options->nat66_prefix);
> +    }
> +
> +    if (options->has_start_address ||
> +        options->has_end_address ||
> +        options->has_subnet_mask) {
> +
> +        if (options->has_start_address &&
> +            options->has_end_address &&
> +            options->has_subnet_mask) {
> +
> +            xpc_dictionary_set_string(if_desc,
> +                                      vmnet_start_address_key,
> +                                      options->start_address);
> +            xpc_dictionary_set_string(if_desc,
> +                                      vmnet_end_address_key,
> +                                      options->end_address);
> +            xpc_dictionary_set_string(if_desc,
> +                                      vmnet_subnet_mask_key,
> +                                      options->subnet_mask);
> +        } else {
> +            error_setg(
> +                errp,
> +                "'start-address', 'end-address', 'subnet-mask' "
> +                "should be provided together"
> +            );
> +        }
> +    }

I think the following is simpler and the intention is still clear:
// if you have all the options...
if (options->has_start_address &&
    options->has_end_address &&
    options->has_subnet_mask) {
  // ... set relevant entries in the dictionary
// otherwise, if you still have some of the options...
} else if (options->has_start_address ||
           options->has_end_address ||
           options->has_subnet_mask) {
  // error
}

> +
> +    return if_desc;
> +}
> +
> +static NetClientInfo net_vmnet_shared_info = {
> +    .type = NET_CLIENT_DRIVER_VMNET_SHARED,
> +    .size = sizeof(VmnetSharedState),
> +    .receive = vmnet_receive_common,
> +    .cleanup = vmnet_cleanup_common,
> +};
> +
>   int net_init_vmnet_shared(const Netdev *netdev, const char *name,
>                             NetClientState *peer, Error **errp)
>   {
> -  error_setg(errp, "vmnet-shared is not implemented yet");
> -  return -1;
> +    NetClientState *nc = qemu_new_net_client(&net_vmnet_shared_info,
> +                                             peer, "vmnet-shared", name);
> +    xpc_object_t if_desc = create_if_desc(netdev, errp);
> +
> +    return vmnet_if_create(nc, if_desc, errp, NULL);

if_desc leaks here. Add xpc_release(if_desc);

qemu_del_net_client(nc) should also be called if the interface creation 
failed.

>   }
> diff --git a/net/vmnet_int.h b/net/vmnet_int.h
> index c5982259a4..3979fe4678 100644
> --- a/net/vmnet_int.h
> +++ b/net/vmnet_int.h
> @@ -16,10 +16,33 @@
>   
>   #include <vmnet/vmnet.h>
>   
> +#define VMNET_PACKETS_LIMIT 50 > +

This value has no reasoning. I found this:
https://developer.apple.com/documentation/vmnet
> Each read/write call allows up to 200 packets to be read or written
> for a maximum of 256KB.

If 200 is the correct value for this, the URI to the page should also 
added as a comment.

>   typedef struct VmnetCommonState {
>     NetClientState nc;
> +  interface_ref vmnet_if;
> +
> +  bool send_enabled;
> +
> +  uint64_t mtu;
> +  uint64_t max_packet_size;
> +
> +  struct vmpktdesc packets_buf[VMNET_PACKETS_LIMIT];
> +  struct iovec iov_buf[VMNET_PACKETS_LIMIT];
>   
>   } VmnetCommonState;
>   
> +const char *vmnet_status_map_str(vmnet_return_t status);
> +
> +int vmnet_if_create(NetClientState *nc,
> +                    xpc_object_t if_desc,
> +                    Error **errp,
> +                    void (*completion_callback)(xpc_object_t interface_param));
> +
> +ssize_t vmnet_receive_common(NetClientState *nc,
> +                             const uint8_t *buf,
> +                             size_t size);
> +
> +void vmnet_cleanup_common(NetClientState *nc);
>   
>   #endif /* VMNET_INT_H */