Patchwork [13/18] vnc: add error propagation to vnc_display_open

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Submitter Paolo Bonzini
Date Oct. 3, 2012, 2:37 p.m.
Message ID <1349275025-5093-14-git-send-email-pbonzini@redhat.com>
Download mbox | patch
Permalink /patch/188801/
State New
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Paolo Bonzini - Oct. 3, 2012, 2:37 p.m.
Before:

    $ qemu-system-x86_64 -vnc foo.bar:12345
    getaddrinfo(foo.bar,18245): Name or service not known
    Failed to start VNC server on `foo.bar:12345'

    $ qemu-system-x86_64 -vnc localhost:12345,reverse=on
    inet_connect_opts: connect(ipv4,yakj.usersys.redhat.com,127.0.0.1,12345): Connection refused
    Failed to start VNC server on `localhost:12345,reverse=on'

After:

    $ x86_64-softmmu/qemu-system-x86_64 -vnc foo.bar:12345
    qemu-system-x86_64: address resolution failed for foo.bar:18245: Name or service not known
    Failed to start VNC server on `foo.bar:12345'

    $ x86_64-softmmu/qemu-system-x86_64 -vnc localhost:12345,reverse=on
    qemu-system-x86_64: Failed to connect to socket: Connection refused
    Failed to start VNC server on `localhost:12345,reverse=on'

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
 console.h |  2 +-
 qmp.c     |  6 ++----
 ui/vnc.c  | 67 +++++++++++++++++++++++++++++----------------------------------
 vl.c      |  5 ++++-
 4 file modificati, 38 inserzioni(+), 42 rimozioni(-)
Luiz Capitulino - Oct. 4, 2012, 8:29 p.m.
On Wed,  3 Oct 2012 16:37:00 +0200
Paolo Bonzini <pbonzini@redhat.com> wrote:

> Before:
> 
>     $ qemu-system-x86_64 -vnc foo.bar:12345
>     getaddrinfo(foo.bar,18245): Name or service not known
>     Failed to start VNC server on `foo.bar:12345'
> 
>     $ qemu-system-x86_64 -vnc localhost:12345,reverse=on
>     inet_connect_opts: connect(ipv4,yakj.usersys.redhat.com,127.0.0.1,12345): Connection refused
>     Failed to start VNC server on `localhost:12345,reverse=on'
> 
> After:
> 
>     $ x86_64-softmmu/qemu-system-x86_64 -vnc foo.bar:12345
>     qemu-system-x86_64: address resolution failed for foo.bar:18245: Name or service not known
>     Failed to start VNC server on `foo.bar:12345'
> 
>     $ x86_64-softmmu/qemu-system-x86_64 -vnc localhost:12345,reverse=on
>     qemu-system-x86_64: Failed to connect to socket: Connection refused
>     Failed to start VNC server on `localhost:12345,reverse=on'
> 
> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
> ---
>  console.h |  2 +-
>  qmp.c     |  6 ++----
>  ui/vnc.c  | 67 +++++++++++++++++++++++++++++----------------------------------
>  vl.c      |  5 ++++-
>  4 file modificati, 38 inserzioni(+), 42 rimozioni(-)
> 
> diff --git a/console.h b/console.h
> index f990684..fcf2fc5 100644
> --- a/console.h
> +++ b/console.h
> @@ -378,7 +378,7 @@ void cocoa_display_init(DisplayState *ds, int full_screen);
>  /* vnc.c */
>  void vnc_display_init(DisplayState *ds);
>  void vnc_display_close(DisplayState *ds);
> -int vnc_display_open(DisplayState *ds, const char *display);
> +int vnc_display_open(DisplayState *ds, const char *display, Error **errp);
>  void vnc_display_add_client(DisplayState *ds, int csock, int skipauth);
>  int vnc_display_disable_login(DisplayState *ds);
>  char *vnc_display_local_addr(DisplayState *ds);
> diff --git a/qmp.c b/qmp.c
> index 36c54c5..31bc3bf 100644
> --- a/qmp.c
> +++ b/qmp.c
> @@ -349,11 +349,9 @@ void qmp_change_vnc_password(const char *password, Error **errp)
>      }
>  }
>  
> -static void qmp_change_vnc_listen(const char *target, Error **err)
> +static void qmp_change_vnc_listen(const char *target, Error **errp)
>  {
> -    if (vnc_display_open(NULL, target) < 0) {
> -        error_set(err, QERR_VNC_SERVER_FAILED, target);
> -    }
> +    vnc_display_open(NULL, target, errp);
>  }
>  
>  static void qmp_change_vnc(const char *target, bool has_arg, const char *arg,
> diff --git a/ui/vnc.c b/ui/vnc.c
> index 235596e..0d92670 100644
> --- a/ui/vnc.c
> +++ b/ui/vnc.c
> @@ -2844,7 +2844,7 @@ char *vnc_display_local_addr(DisplayState *ds)
>      return vnc_socket_local_addr("%s:%s", vs->lsock);
>  }
>  
> -int vnc_display_open(DisplayState *ds, const char *display)
> +int vnc_display_open(DisplayState *ds, const char *display, Error **errp)

Can't return void?

>  {
>      VncDisplay *vs = ds ? (VncDisplay *)ds->opaque : vnc_display;
>      const char *options;
> @@ -2863,13 +2863,12 @@ int vnc_display_open(DisplayState *ds, const char *display)
>      int lock_key_sync = 1;
>  
>      if (!vnc_display)
> -        return -1;
> +        goto fail;
>      vnc_display_close(ds);
>      if (strcmp(display, "none") == 0)
>          return 0;
>  
> -    if (!(vs->display = strdup(display)))
> -        return -1;
> +    vs->display = g_strdup(display);
>      vs->share_policy = VNC_SHARE_POLICY_ALLOW_EXCLUSIVE;
>  
>      options = display;
> @@ -2877,13 +2876,11 @@ int vnc_display_open(DisplayState *ds, const char *display)
>          options++;
>          if (strncmp(options, "password", 8) == 0) {
>              if (fips_get_state()) {
> -                fprintf(stderr,
> -                        "VNC password auth disabled due to FIPS mode, "
> -                        "consider using the VeNCrypt or SASL authentication "
> -                        "methods as an alternative\n");
> -                g_free(vs->display);
> -                vs->display = NULL;
> -                return -1;
> +                error_setg(errp,
> +                           "VNC password auth disabled due to FIPS mode, "
> +                           "consider using the VeNCrypt or SASL authentication "
> +                           "methods as an alternative\n");
> +                goto fail;
>              }
>              password = 1; /* Require password auth */
>          } else if (strncmp(options, "reverse", 7) == 0) {
> @@ -2913,18 +2910,14 @@ int vnc_display_open(DisplayState *ds, const char *display)
>  
>                  VNC_DEBUG("Trying certificate path '%s'\n", path);
>                  if (vnc_tls_set_x509_creds_dir(vs, path) < 0) {
> -                    fprintf(stderr, "Failed to find x509 certificates/keys in %s\n", path);
> +                    error_setg(errp, "Failed to find x509 certificates/keys in %s\n", path);
>                      g_free(path);
> -                    g_free(vs->display);
> -                    vs->display = NULL;
> -                    return -1;
> +                    goto fail;
>                  }
>                  g_free(path);
>              } else {
> -                fprintf(stderr, "No certificate path provided\n");
> -                g_free(vs->display);
> -                vs->display = NULL;
> -                return -1;
> +                error_setg(errp, "No certificate path provided\n");
> +                goto fail;
>              }
>  #endif
>  #if defined(CONFIG_VNC_TLS) || defined(CONFIG_VNC_SASL)
> @@ -2943,10 +2936,8 @@ int vnc_display_open(DisplayState *ds, const char *display)
>              } else if (strncmp(options+6, "force-shared", 12) == 0) {
>                  vs->share_policy = VNC_SHARE_POLICY_FORCE_SHARED;
>              } else {
> -                fprintf(stderr, "unknown vnc share= option\n");
> -                g_free(vs->display);
> -                vs->display = NULL;
> -                return -1;
> +                error_setg(errp, "unknown vnc share= option\n");
> +                goto fail;
>              }
>          }
>      }
> @@ -3047,11 +3038,9 @@ int vnc_display_open(DisplayState *ds, const char *display)
>  
>  #ifdef CONFIG_VNC_SASL
>      if ((saslErr = sasl_server_init(NULL, "qemu")) != SASL_OK) {
> -        fprintf(stderr, "Failed to initialize SASL auth %s",
> -                sasl_errstring(saslErr, NULL, NULL));
> -        g_free(vs->display);
> -        vs->display = NULL;
> -        return -1;
> +        error_setg(errp, "Failed to initialize SASL auth %s",
> +                   sasl_errstring(saslErr, NULL, NULL));
> +        goto fail;
>      }
>  #endif
>      vs->lock_key_sync = lock_key_sync;
> @@ -3059,13 +3048,11 @@ int vnc_display_open(DisplayState *ds, const char *display)
>      if (reverse) {
>          /* connect to viewer */
>          if (strncmp(display, "unix:", 5) == 0)
> -            vs->lsock = unix_connect(display+5, NULL);
> +            vs->lsock = unix_connect(display+5, errp);
>          else
> -            vs->lsock = inet_connect(display, NULL);
> +            vs->lsock = inet_connect(display, errp);
>          if (-1 == vs->lsock) {
> -            g_free(vs->display);
> -            vs->display = NULL;
> -            return -1;
> +            goto fail;
>          } else {
>              int csock = vs->lsock;
>              vs->lsock = -1;
> @@ -3079,20 +3066,28 @@ int vnc_display_open(DisplayState *ds, const char *display)
>          dpy = g_malloc(256);
>          if (strncmp(display, "unix:", 5) == 0) {
>              pstrcpy(dpy, 256, "unix:");
> -            vs->lsock = unix_listen(display+5, dpy+5, 256-5, NULL);
> +            vs->lsock = unix_listen(display+5, dpy+5, 256-5, errp);
>          } else {
>              vs->lsock = inet_listen(display, dpy, 256,
> -                                    SOCK_STREAM, 5900, NULL);
> +                                    SOCK_STREAM, 5900, errp);
>          }
>          if (-1 == vs->lsock) {
>              g_free(dpy);
> -            return -1;
> +            goto fail;
>          } else {
>              g_free(vs->display);
>              vs->display = dpy;
>          }
>      }
>      return qemu_set_fd_handler2(vs->lsock, NULL, vnc_listen_read, NULL, vs);
> +
> +fail:
> +    if (!error_is_set(errp)) {
> +        error_set(errp, QERR_VNC_SERVER_FAILED, display);

Please, use error_setg() instead. QERR_ macros are deprecated.

> +    }
> +    g_free(vs->display);
> +    vs->display = NULL;
> +    return -1;
>  }
>  
>  void vnc_display_add_client(DisplayState *ds, int csock, int skipauth)
> diff --git a/vl.c b/vl.c
> index 53917c9..45a5ba5 100644
> --- a/vl.c
> +++ b/vl.c
> @@ -3692,8 +3692,11 @@ int main(int argc, char **argv, char **envp)
>  #ifdef CONFIG_VNC
>      /* init remote displays */
>      if (vnc_display) {
> +        Error *local_err = NULL;
>          vnc_display_init(ds);
> -        if (vnc_display_open(ds, vnc_display) < 0) {
> +        if (vnc_display_open(ds, vnc_display, &local_err) < 0) {
> +            qerror_report_err(local_err);
> +            error_free(local_err);
>              fprintf(stderr, "Failed to start VNC server on `%s'\n",
>                      vnc_display);
>              exit(1);

Why do you need to call qerror_report_err()? I'd just do:

fprintf(stderr, "Failed to start VNC server on display '%s': %s\n",
                vnc_display, error_get_pretty(local_err));
Paolo Bonzini - Oct. 5, 2012, 6:28 a.m.
Il 04/10/2012 22:29, Luiz Capitulino ha scritto:
> On Wed,  3 Oct 2012 16:37:00 +0200
> Paolo Bonzini <pbonzini@redhat.com> wrote:
> 
>> Before:
>>
>>     $ qemu-system-x86_64 -vnc foo.bar:12345
>>     getaddrinfo(foo.bar,18245): Name or service not known
>>     Failed to start VNC server on `foo.bar:12345'
>>
>>     $ qemu-system-x86_64 -vnc localhost:12345,reverse=on
>>     inet_connect_opts: connect(ipv4,yakj.usersys.redhat.com,127.0.0.1,12345): Connection refused
>>     Failed to start VNC server on `localhost:12345,reverse=on'
>>
>> After:
>>
>>     $ x86_64-softmmu/qemu-system-x86_64 -vnc foo.bar:12345
>>     qemu-system-x86_64: address resolution failed for foo.bar:18245: Name or service not known
>>     Failed to start VNC server on `foo.bar:12345'
>>
>>     $ x86_64-softmmu/qemu-system-x86_64 -vnc localhost:12345,reverse=on
>>     qemu-system-x86_64: Failed to connect to socket: Connection refused
>>     Failed to start VNC server on `localhost:12345,reverse=on'
>>
>> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
>> ---
>>  console.h |  2 +-
>>  qmp.c     |  6 ++----
>>  ui/vnc.c  | 67 +++++++++++++++++++++++++++++----------------------------------
>>  vl.c      |  5 ++++-
>>  4 file modificati, 38 inserzioni(+), 42 rimozioni(-)
>>
>> diff --git a/console.h b/console.h
>> index f990684..fcf2fc5 100644
>> --- a/console.h
>> +++ b/console.h
>> @@ -378,7 +378,7 @@ void cocoa_display_init(DisplayState *ds, int full_screen);
>>  /* vnc.c */
>>  void vnc_display_init(DisplayState *ds);
>>  void vnc_display_close(DisplayState *ds);
>> -int vnc_display_open(DisplayState *ds, const char *display);
>> +int vnc_display_open(DisplayState *ds, const char *display, Error **errp);
>>  void vnc_display_add_client(DisplayState *ds, int csock, int skipauth);
>>  int vnc_display_disable_login(DisplayState *ds);
>>  char *vnc_display_local_addr(DisplayState *ds);
>> diff --git a/qmp.c b/qmp.c
>> index 36c54c5..31bc3bf 100644
>> --- a/qmp.c
>> +++ b/qmp.c
>> @@ -349,11 +349,9 @@ void qmp_change_vnc_password(const char *password, Error **errp)
>>      }
>>  }
>>  
>> -static void qmp_change_vnc_listen(const char *target, Error **err)
>> +static void qmp_change_vnc_listen(const char *target, Error **errp)
>>  {
>> -    if (vnc_display_open(NULL, target) < 0) {
>> -        error_set(err, QERR_VNC_SERVER_FAILED, target);
>> -    }
>> +    vnc_display_open(NULL, target, errp);
>>  }
>>  
>>  static void qmp_change_vnc(const char *target, bool has_arg, const char *arg,
>> diff --git a/ui/vnc.c b/ui/vnc.c
>> index 235596e..0d92670 100644
>> --- a/ui/vnc.c
>> +++ b/ui/vnc.c
>> @@ -2844,7 +2844,7 @@ char *vnc_display_local_addr(DisplayState *ds)
>>      return vnc_socket_local_addr("%s:%s", vs->lsock);
>>  }
>>  
>> -int vnc_display_open(DisplayState *ds, const char *display)
>> +int vnc_display_open(DisplayState *ds, const char *display, Error **errp)
> 
> Can't return void?

Ok.

>>  {
>>      VncDisplay *vs = ds ? (VncDisplay *)ds->opaque : vnc_display;
>>      const char *options;
>> @@ -2863,13 +2863,12 @@ int vnc_display_open(DisplayState *ds, const char *display)
>>      int lock_key_sync = 1;
>>  
>>      if (!vnc_display)
>> -        return -1;
>> +        goto fail;
>>      vnc_display_close(ds);
>>      if (strcmp(display, "none") == 0)
>>          return 0;
>>  
>> -    if (!(vs->display = strdup(display)))
>> -        return -1;
>> +    vs->display = g_strdup(display);
>>      vs->share_policy = VNC_SHARE_POLICY_ALLOW_EXCLUSIVE;
>>  
>>      options = display;
>> @@ -2877,13 +2876,11 @@ int vnc_display_open(DisplayState *ds, const char *display)
>>          options++;
>>          if (strncmp(options, "password", 8) == 0) {
>>              if (fips_get_state()) {
>> -                fprintf(stderr,
>> -                        "VNC password auth disabled due to FIPS mode, "
>> -                        "consider using the VeNCrypt or SASL authentication "
>> -                        "methods as an alternative\n");
>> -                g_free(vs->display);
>> -                vs->display = NULL;
>> -                return -1;
>> +                error_setg(errp,
>> +                           "VNC password auth disabled due to FIPS mode, "
>> +                           "consider using the VeNCrypt or SASL authentication "
>> +                           "methods as an alternative\n");
>> +                goto fail;
>>              }
>>              password = 1; /* Require password auth */
>>          } else if (strncmp(options, "reverse", 7) == 0) {
>> @@ -2913,18 +2910,14 @@ int vnc_display_open(DisplayState *ds, const char *display)
>>  
>>                  VNC_DEBUG("Trying certificate path '%s'\n", path);
>>                  if (vnc_tls_set_x509_creds_dir(vs, path) < 0) {
>> -                    fprintf(stderr, "Failed to find x509 certificates/keys in %s\n", path);
>> +                    error_setg(errp, "Failed to find x509 certificates/keys in %s\n", path);
>>                      g_free(path);
>> -                    g_free(vs->display);
>> -                    vs->display = NULL;
>> -                    return -1;
>> +                    goto fail;
>>                  }
>>                  g_free(path);
>>              } else {
>> -                fprintf(stderr, "No certificate path provided\n");
>> -                g_free(vs->display);
>> -                vs->display = NULL;
>> -                return -1;
>> +                error_setg(errp, "No certificate path provided\n");
>> +                goto fail;
>>              }
>>  #endif
>>  #if defined(CONFIG_VNC_TLS) || defined(CONFIG_VNC_SASL)
>> @@ -2943,10 +2936,8 @@ int vnc_display_open(DisplayState *ds, const char *display)
>>              } else if (strncmp(options+6, "force-shared", 12) == 0) {
>>                  vs->share_policy = VNC_SHARE_POLICY_FORCE_SHARED;
>>              } else {
>> -                fprintf(stderr, "unknown vnc share= option\n");
>> -                g_free(vs->display);
>> -                vs->display = NULL;
>> -                return -1;
>> +                error_setg(errp, "unknown vnc share= option\n");
>> +                goto fail;
>>              }
>>          }
>>      }
>> @@ -3047,11 +3038,9 @@ int vnc_display_open(DisplayState *ds, const char *display)
>>  
>>  #ifdef CONFIG_VNC_SASL
>>      if ((saslErr = sasl_server_init(NULL, "qemu")) != SASL_OK) {
>> -        fprintf(stderr, "Failed to initialize SASL auth %s",
>> -                sasl_errstring(saslErr, NULL, NULL));
>> -        g_free(vs->display);
>> -        vs->display = NULL;
>> -        return -1;
>> +        error_setg(errp, "Failed to initialize SASL auth %s",
>> +                   sasl_errstring(saslErr, NULL, NULL));
>> +        goto fail;
>>      }
>>  #endif
>>      vs->lock_key_sync = lock_key_sync;
>> @@ -3059,13 +3048,11 @@ int vnc_display_open(DisplayState *ds, const char *display)
>>      if (reverse) {
>>          /* connect to viewer */
>>          if (strncmp(display, "unix:", 5) == 0)
>> -            vs->lsock = unix_connect(display+5, NULL);
>> +            vs->lsock = unix_connect(display+5, errp);
>>          else
>> -            vs->lsock = inet_connect(display, NULL);
>> +            vs->lsock = inet_connect(display, errp);
>>          if (-1 == vs->lsock) {
>> -            g_free(vs->display);
>> -            vs->display = NULL;
>> -            return -1;
>> +            goto fail;
>>          } else {
>>              int csock = vs->lsock;
>>              vs->lsock = -1;
>> @@ -3079,20 +3066,28 @@ int vnc_display_open(DisplayState *ds, const char *display)
>>          dpy = g_malloc(256);
>>          if (strncmp(display, "unix:", 5) == 0) {
>>              pstrcpy(dpy, 256, "unix:");
>> -            vs->lsock = unix_listen(display+5, dpy+5, 256-5, NULL);
>> +            vs->lsock = unix_listen(display+5, dpy+5, 256-5, errp);
>>          } else {
>>              vs->lsock = inet_listen(display, dpy, 256,
>> -                                    SOCK_STREAM, 5900, NULL);
>> +                                    SOCK_STREAM, 5900, errp);
>>          }
>>          if (-1 == vs->lsock) {
>>              g_free(dpy);
>> -            return -1;
>> +            goto fail;
>>          } else {
>>              g_free(vs->display);
>>              vs->display = dpy;
>>          }
>>      }
>>      return qemu_set_fd_handler2(vs->lsock, NULL, vnc_listen_read, NULL, vs);
>> +
>> +fail:
>> +    if (!error_is_set(errp)) {
>> +        error_set(errp, QERR_VNC_SERVER_FAILED, display);
> 
> Please, use error_setg() instead. QERR_ macros are deprecated.

I'm not introducing a new one.  One thing at a time, please.

>> +    }
>> +    g_free(vs->display);
>> +    vs->display = NULL;
>> +    return -1;
>>  }
>>  
>>  void vnc_display_add_client(DisplayState *ds, int csock, int skipauth)
>> diff --git a/vl.c b/vl.c
>> index 53917c9..45a5ba5 100644
>> --- a/vl.c
>> +++ b/vl.c
>> @@ -3692,8 +3692,11 @@ int main(int argc, char **argv, char **envp)
>>  #ifdef CONFIG_VNC
>>      /* init remote displays */
>>      if (vnc_display) {
>> +        Error *local_err = NULL;
>>          vnc_display_init(ds);
>> -        if (vnc_display_open(ds, vnc_display) < 0) {
>> +        if (vnc_display_open(ds, vnc_display, &local_err) < 0) {
>> +            qerror_report_err(local_err);
>> +            error_free(local_err);
>>              fprintf(stderr, "Failed to start VNC server on `%s'\n",
>>                      vnc_display);
>>              exit(1);
> 
> Why do you need to call qerror_report_err()? I'd just do:
> 
> fprintf(stderr, "Failed to start VNC server on display '%s': %s\n",
>                 vnc_display, error_get_pretty(local_err));
> 
> 

Ok.
Paolo Bonzini - Oct. 5, 2012, 6:29 a.m.
Il 05/10/2012 08:28, Paolo Bonzini ha scritto:
>>>  void vnc_display_add_client(DisplayState *ds, int csock, int skipauth)
>>> diff --git a/vl.c b/vl.c
>>> index 53917c9..45a5ba5 100644
>>> --- a/vl.c
>>> +++ b/vl.c
>>> @@ -3692,8 +3692,11 @@ int main(int argc, char **argv, char **envp)
>>>  #ifdef CONFIG_VNC
>>>      /* init remote displays */
>>>      if (vnc_display) {
>>> +        Error *local_err = NULL;
>>>          vnc_display_init(ds);
>>> -        if (vnc_display_open(ds, vnc_display) < 0) {
>>> +        if (vnc_display_open(ds, vnc_display, &local_err) < 0) {
>>> +            qerror_report_err(local_err);
>>> +            error_free(local_err);
>>>              fprintf(stderr, "Failed to start VNC server on `%s'\n",
>>>                      vnc_display);
>>>              exit(1);
>>
>> Why do you need to call qerror_report_err()? I'd just do:
>>
>> fprintf(stderr, "Failed to start VNC server on display '%s': %s\n",
>>                 vnc_display, error_get_pretty(local_err));
> 
> Ok.

Hmm, qerror_report_err is more consistent (it prints the program name).

Paolo

Patch

diff --git a/console.h b/console.h
index f990684..fcf2fc5 100644
--- a/console.h
+++ b/console.h
@@ -378,7 +378,7 @@  void cocoa_display_init(DisplayState *ds, int full_screen);
 /* vnc.c */
 void vnc_display_init(DisplayState *ds);
 void vnc_display_close(DisplayState *ds);
-int vnc_display_open(DisplayState *ds, const char *display);
+int vnc_display_open(DisplayState *ds, const char *display, Error **errp);
 void vnc_display_add_client(DisplayState *ds, int csock, int skipauth);
 int vnc_display_disable_login(DisplayState *ds);
 char *vnc_display_local_addr(DisplayState *ds);
diff --git a/qmp.c b/qmp.c
index 36c54c5..31bc3bf 100644
--- a/qmp.c
+++ b/qmp.c
@@ -349,11 +349,9 @@  void qmp_change_vnc_password(const char *password, Error **errp)
     }
 }
 
-static void qmp_change_vnc_listen(const char *target, Error **err)
+static void qmp_change_vnc_listen(const char *target, Error **errp)
 {
-    if (vnc_display_open(NULL, target) < 0) {
-        error_set(err, QERR_VNC_SERVER_FAILED, target);
-    }
+    vnc_display_open(NULL, target, errp);
 }
 
 static void qmp_change_vnc(const char *target, bool has_arg, const char *arg,
diff --git a/ui/vnc.c b/ui/vnc.c
index 235596e..0d92670 100644
--- a/ui/vnc.c
+++ b/ui/vnc.c
@@ -2844,7 +2844,7 @@  char *vnc_display_local_addr(DisplayState *ds)
     return vnc_socket_local_addr("%s:%s", vs->lsock);
 }
 
-int vnc_display_open(DisplayState *ds, const char *display)
+int vnc_display_open(DisplayState *ds, const char *display, Error **errp)
 {
     VncDisplay *vs = ds ? (VncDisplay *)ds->opaque : vnc_display;
     const char *options;
@@ -2863,13 +2863,12 @@  int vnc_display_open(DisplayState *ds, const char *display)
     int lock_key_sync = 1;
 
     if (!vnc_display)
-        return -1;
+        goto fail;
     vnc_display_close(ds);
     if (strcmp(display, "none") == 0)
         return 0;
 
-    if (!(vs->display = strdup(display)))
-        return -1;
+    vs->display = g_strdup(display);
     vs->share_policy = VNC_SHARE_POLICY_ALLOW_EXCLUSIVE;
 
     options = display;
@@ -2877,13 +2876,11 @@  int vnc_display_open(DisplayState *ds, const char *display)
         options++;
         if (strncmp(options, "password", 8) == 0) {
             if (fips_get_state()) {
-                fprintf(stderr,
-                        "VNC password auth disabled due to FIPS mode, "
-                        "consider using the VeNCrypt or SASL authentication "
-                        "methods as an alternative\n");
-                g_free(vs->display);
-                vs->display = NULL;
-                return -1;
+                error_setg(errp,
+                           "VNC password auth disabled due to FIPS mode, "
+                           "consider using the VeNCrypt or SASL authentication "
+                           "methods as an alternative\n");
+                goto fail;
             }
             password = 1; /* Require password auth */
         } else if (strncmp(options, "reverse", 7) == 0) {
@@ -2913,18 +2910,14 @@  int vnc_display_open(DisplayState *ds, const char *display)
 
                 VNC_DEBUG("Trying certificate path '%s'\n", path);
                 if (vnc_tls_set_x509_creds_dir(vs, path) < 0) {
-                    fprintf(stderr, "Failed to find x509 certificates/keys in %s\n", path);
+                    error_setg(errp, "Failed to find x509 certificates/keys in %s\n", path);
                     g_free(path);
-                    g_free(vs->display);
-                    vs->display = NULL;
-                    return -1;
+                    goto fail;
                 }
                 g_free(path);
             } else {
-                fprintf(stderr, "No certificate path provided\n");
-                g_free(vs->display);
-                vs->display = NULL;
-                return -1;
+                error_setg(errp, "No certificate path provided\n");
+                goto fail;
             }
 #endif
 #if defined(CONFIG_VNC_TLS) || defined(CONFIG_VNC_SASL)
@@ -2943,10 +2936,8 @@  int vnc_display_open(DisplayState *ds, const char *display)
             } else if (strncmp(options+6, "force-shared", 12) == 0) {
                 vs->share_policy = VNC_SHARE_POLICY_FORCE_SHARED;
             } else {
-                fprintf(stderr, "unknown vnc share= option\n");
-                g_free(vs->display);
-                vs->display = NULL;
-                return -1;
+                error_setg(errp, "unknown vnc share= option\n");
+                goto fail;
             }
         }
     }
@@ -3047,11 +3038,9 @@  int vnc_display_open(DisplayState *ds, const char *display)
 
 #ifdef CONFIG_VNC_SASL
     if ((saslErr = sasl_server_init(NULL, "qemu")) != SASL_OK) {
-        fprintf(stderr, "Failed to initialize SASL auth %s",
-                sasl_errstring(saslErr, NULL, NULL));
-        g_free(vs->display);
-        vs->display = NULL;
-        return -1;
+        error_setg(errp, "Failed to initialize SASL auth %s",
+                   sasl_errstring(saslErr, NULL, NULL));
+        goto fail;
     }
 #endif
     vs->lock_key_sync = lock_key_sync;
@@ -3059,13 +3048,11 @@  int vnc_display_open(DisplayState *ds, const char *display)
     if (reverse) {
         /* connect to viewer */
         if (strncmp(display, "unix:", 5) == 0)
-            vs->lsock = unix_connect(display+5, NULL);
+            vs->lsock = unix_connect(display+5, errp);
         else
-            vs->lsock = inet_connect(display, NULL);
+            vs->lsock = inet_connect(display, errp);
         if (-1 == vs->lsock) {
-            g_free(vs->display);
-            vs->display = NULL;
-            return -1;
+            goto fail;
         } else {
             int csock = vs->lsock;
             vs->lsock = -1;
@@ -3079,20 +3066,28 @@  int vnc_display_open(DisplayState *ds, const char *display)
         dpy = g_malloc(256);
         if (strncmp(display, "unix:", 5) == 0) {
             pstrcpy(dpy, 256, "unix:");
-            vs->lsock = unix_listen(display+5, dpy+5, 256-5, NULL);
+            vs->lsock = unix_listen(display+5, dpy+5, 256-5, errp);
         } else {
             vs->lsock = inet_listen(display, dpy, 256,
-                                    SOCK_STREAM, 5900, NULL);
+                                    SOCK_STREAM, 5900, errp);
         }
         if (-1 == vs->lsock) {
             g_free(dpy);
-            return -1;
+            goto fail;
         } else {
             g_free(vs->display);
             vs->display = dpy;
         }
     }
     return qemu_set_fd_handler2(vs->lsock, NULL, vnc_listen_read, NULL, vs);
+
+fail:
+    if (!error_is_set(errp)) {
+        error_set(errp, QERR_VNC_SERVER_FAILED, display);
+    }
+    g_free(vs->display);
+    vs->display = NULL;
+    return -1;
 }
 
 void vnc_display_add_client(DisplayState *ds, int csock, int skipauth)
diff --git a/vl.c b/vl.c
index 53917c9..45a5ba5 100644
--- a/vl.c
+++ b/vl.c
@@ -3692,8 +3692,11 @@  int main(int argc, char **argv, char **envp)
 #ifdef CONFIG_VNC
     /* init remote displays */
     if (vnc_display) {
+        Error *local_err = NULL;
         vnc_display_init(ds);
-        if (vnc_display_open(ds, vnc_display) < 0) {
+        if (vnc_display_open(ds, vnc_display, &local_err) < 0) {
+            qerror_report_err(local_err);
+            error_free(local_err);
             fprintf(stderr, "Failed to start VNC server on `%s'\n",
                     vnc_display);
             exit(1);