Re: [PATCH V8 36/39] chardev: cpr for sockets

[Peng Liang]

On 6/15/2022 10:52 PM, Steve Sistare wrote:
> Save accepted socket fds before cpr-save, and look for them after cpr-load.
> Block cpr-exec if a socket enables the TLS or websocket option.  Allow a
> monitor socket by closing it on exec.
> 
> Signed-off-by: Mark Kanda <mark.kanda@oracle.com>
> Signed-off-by: Steve Sistare <steven.sistare@oracle.com>
> ---
>  chardev/char-socket.c         | 45 
> +++++++++++++++++++++++++++++++++++++++++++
>  include/chardev/char-socket.h |  1 +
>  monitor/hmp.c                 |  3 +++
>  monitor/qmp.c                 |  3 +++
>  4 files changed, 52 insertions(+)
> 
> diff --git a/chardev/char-socket.c b/chardev/char-socket.c
> index dc4e218..3a1e36b 100644
> --- a/chardev/char-socket.c
> +++ b/chardev/char-socket.c
> @@ -26,6 +26,7 @@
>  #include "chardev/char.h"
>  #include "io/channel-socket.h"
>  #include "io/channel-websock.h"
> +#include "migration/cpr.h"
>  #include "qemu/error-report.h"
>  #include "qemu/module.h"
>  #include "qemu/option.h"
> @@ -33,6 +34,7 @@
>  #include "qapi/clone-visitor.h"
>  #include "qapi/qapi-visit-sockets.h"
>  #include "qemu/yank.h"
> +#include "sysemu/sysemu.h"
>  
>  #include "chardev/char-io.h"
>  #include "chardev/char-socket.h"
> @@ -358,6 +360,11 @@ static void tcp_chr_free_connection(Chardev *chr)
>      SocketChardev *s = SOCKET_CHARDEV(chr);
>      int i;
>  
> +    if (chr->cpr_enabled) {
> +        cpr_delete_fd(chr->label, 0);
> +    }
> +    cpr_del_blocker(&s->cpr_blocker);
> +
>      if (s->read_msgfds_num) {
>          for (i = 0; i < s->read_msgfds_num; i++) {
>              close(s->read_msgfds[i]);
> @@ -923,6 +930,10 @@ static void tcp_chr_accept(QIONetListener *listener,
>                                 QIO_CHANNEL(cioc));
>      }
>      tcp_chr_new_client(chr, cioc);
> +
> +    if (s->sioc && chr->cpr_enabled) {
> +        cpr_resave_fd(chr->label, 0, s->sioc->fd, NULL);
> +    }
>  }
>  
>  
> @@ -1178,6 +1189,26 @@ static gboolean socket_reconnect_timeout(gpointer 
> opaque)
>      return false;
>  }
>  
> +static int load_char_socket_fd(Chardev *chr, Error **errp)
> +{
> +    SocketChardev *sockchar = SOCKET_CHARDEV(chr);
> +    QIOChannelSocket *sioc;
> +    const char *label = chr->label;
> +    int fd = cpr_find_fd(label, 0);
> +
> +    if (fd != -1) {
> +        sockchar = SOCKET_CHARDEV(chr);
> +        sioc = qio_channel_socket_new_fd(fd, errp);
> +        if (sioc) {
> +            tcp_chr_accept(sockchar->listener, sioc, chr);
> +            object_unref(OBJECT(sioc));
> +        } else {
> +            error_setg(errp, "could not restore socket for %s", label);

If we go here, then qio_channel_socket_new_fd fails and errp should be set. So 
I think
error_prepend is more appropriate here.

> +            return -1;
> +        }
> +    }
> +    return 0;
> +}
>  
>  static int qmp_chardev_open_socket_server(Chardev *chr,
>                                            bool is_telnet,
> @@ -1388,6 +1419,18 @@ static void qmp_chardev_open_socket(Chardev *chr,
>      }
>      s->registered_yank = true;
>  
> +    if (!s->tls_creds && !s->is_websock) {
> +        qemu_chr_set_feature(chr, QEMU_CHAR_FEATURE_CPR);
> +    } else if (!chr->reopen_on_cpr) {
> +        s->cpr_blocker = NULL;
> +        error_setg(&s->cpr_blocker,
> +                   "error: socket %s is not cpr capable due to %s option",
> +                   chr->label, (s->tls_creds ? "TLS" : "websocket"));
> +        if (cpr_add_blocker(&s->cpr_blocker, errp, CPR_MODE_RESTART, 0)) {
> +            return;
> +        }
> +    }
> +
>      /* be isn't opened until we get a connection */
>      *be_opened = false;
>  
> @@ -1403,6 +1446,8 @@ static void qmp_chardev_open_socket(Chardev *chr,
>              return;
>          }
>      }
> +
> +    load_char_socket_fd(chr, errp);
>  }
>  
>  static void qemu_chr_parse_socket(QemuOpts *opts, ChardevBackend *backend,
> diff --git a/include/chardev/char-socket.h b/include/chardev/char-socket.h
> index 0708ca6..1c3abf7 100644
> --- a/include/chardev/char-socket.h
> +++ b/include/chardev/char-socket.h
> @@ -78,6 +78,7 @@ struct SocketChardev {
>      bool connect_err_reported;
>  
>      QIOTask *connect_task;
> +    Error *cpr_blocker;
>  };
>  typedef struct SocketChardev SocketChardev;
>  
> diff --git a/monitor/hmp.c b/monitor/hmp.c
> index 15ca047..75e6739 100644
> --- a/monitor/hmp.c
> +++ b/monitor/hmp.c
> @@ -1501,4 +1501,7 @@ void monitor_init_hmp(Chardev *chr, bool use_readline, 
> Error **errp)
>      qemu_chr_fe_set_handlers(&mon->common.chr, monitor_can_read, 
> monitor_read,
>                               monitor_event, NULL, &mon->common, NULL, true);
>      monitor_list_append(&mon->common);
> +
> +    /* monitor cannot yet be preserved across cpr */
> +    chr->reopen_on_cpr = true;
>  }
> diff --git a/monitor/qmp.c b/monitor/qmp.c
> index 092c527..0043459 100644
> --- a/monitor/qmp.c
> +++ b/monitor/qmp.c
> @@ -535,4 +535,7 @@ void monitor_init_qmp(Chardev *chr, bool pretty, Error 
> **errp)
>                                   NULL, &mon->common, NULL, true);
>          monitor_list_append(&mon->common);
>      }
> +
> +    /* Monitor cannot yet be preserved across cpr */
> +    chr->reopen_on_cpr = true;
>  }