Re: [Qemu-devel] [PATCH v2 1/4] net/socket: Convert the non-blocking connection mechanism to QIOchannel

[Markus Armbruster]

Mao Zhongyi <address@hidden> writes:

> Currently, socket connection in net is realized by an old
> mechanism which is non-blocking.
>
> That old mechanism may cause net blocks on DNS lookups and
> QEmu has already replaced it with QIOchannel in many features,
> such as migration.
>
> Convert it to QIOchannel for net as well.
>
> CC: address@hidden, address@hidden, address@hidden
> Signed-off-by: Mao Zhongyi <address@hidden>
> ---
> The test steps like this:
>
>     $ qemu-system-x86_64 -net nic -net socket,listen=:1234 ~/img/test.img
>     $ qemu-system-x86_64 -net nic -net socket,connect=127.0.0.1:1234 
> ~/img/test.img
>
> No exception.
>
>  net/socket.c | 30 +++++++++++++++++++-----------
>  1 file changed, 19 insertions(+), 11 deletions(-)
>
> diff --git a/net/socket.c b/net/socket.c
> index b8c931e..52f9dce 100644
> --- a/net/socket.c
> +++ b/net/socket.c
> @@ -33,6 +33,7 @@
>  #include "qemu/sockets.h"
>  #include "qemu/iov.h"
>  #include "qemu/main-loop.h"
> +#include "io/channel-socket.h"
>  
>  typedef struct NetSocketState {
>      NetClientState nc;
> @@ -525,16 +526,22 @@ typedef struct {
>      char *name;
>  } socket_connect_data;
>  
> -static void socket_connect_data_free(socket_connect_data *c)
> +static void socket_connect_data_free(void *opaque)
>  {
> +    socket_connect_data *c = opaque;

Blank line between declarations and statements, please.

> +    if (!c) {
> +        return;
> +    }
> +
>      qapi_free_SocketAddress(c->saddr);
>      g_free(c->model);
>      g_free(c->name);
>      g_free(c);
>  }
>  
> -static void net_socket_connected(int fd, Error *err, void *opaque)
> +static void net_socket_connected(QIOTask *task, void *opaque)
>  {
> +    QIOChannelSocket *sioc = QIO_CHANNEL_SOCKET(qio_task_get_source(task));
>      socket_connect_data *c = opaque;
>      NetSocketState *s;
>      char *addr_str = NULL;
> @@ -543,13 +550,13 @@ static void net_socket_connected(int fd, Error *err, 
> void *opaque)
>      addr_str = socket_address_to_string(c->saddr, &local_error);
>      if (addr_str == NULL) {
>          error_report_err(local_error);
> -        closesocket(fd);
> +        closesocket(sioc->fd);
>          goto end;
>      }
>  
> -    s = net_socket_fd_init(c->peer, c->model, c->name, fd, true);
> +    s = net_socket_fd_init(c->peer, c->model, c->name, sioc->fd, true);
>      if (!s) {
> -        closesocket(fd);
> +        closesocket(sioc->fd);
>          goto end;
>      }
>  
> @@ -567,7 +574,7 @@ static int net_socket_connect_init(NetClientState *peer,
>                                     const char *host_str)
>  {
>      socket_connect_data *c = g_new0(socket_connect_data, 1);
> -    int fd = -1;
> +    QIOChannelSocket *sioc;
>      Error *local_error = NULL;
>  
>      c->peer = peer;
> @@ -578,11 +585,12 @@ static int net_socket_connect_init(NetClientState *peer,
       c->model = g_strdup(model);
       c->name = g_strdup(name);
       c->saddr = socket_parse(host_str, &local_error);
       if (c->saddr == NULL) {
>          goto err;
>      }
>  
> -    fd = socket_connect(c->saddr, net_socket_connected, c, &local_error);
> -    if (fd < 0) {
> -        goto err;
> -    }
> -
> +    sioc = qio_channel_socket_new();
> +    qio_channel_socket_connect_async(sioc,
> +                                     c->saddr,
> +                                     net_socket_connected,
> +                                     c,
> +                                     NULL);
>      return 0;
>  
>  err:
       error_report_err(local_error);
       socket_connect_data_free(c);
       return -1;
   }

Ignorant question: how does this change the reporting of errors?

Before the patch, errors from socket_connect() are reported with
error_report_err(), just like errors from socket_parse().

After the patch?

The next patch converts this function to Error.  Errors from
socket_parse() are then propagated to the caller.  What about errors
from socket_connect()?