Re: [Qemu-devel] [PATCH 2/7] qemu-char: Allow a chardev to reconnect if disconnected

[Weidong Huang]

On 2014/3/5 8:38, address@hidden wrote:

> From: Corey Minyard <address@hidden>
> 
> Allow a socket that connects to reconnect on a periodic basis if it
> fails to connect at startup or if the connection drops while in use.
> 
> Signed-off-by: Corey Minyard <address@hidden>
> ---
>  include/sysemu/char.h |  16 ++++-
>  qemu-char.c           | 165 
> +++++++++++++++++++++++++++++++++++++++++++++-----
>  qemu-options.hx       |  11 +++-
>  3 files changed, 173 insertions(+), 19 deletions(-)
> 
> diff --git a/include/sysemu/char.h b/include/sysemu/char.h
> index f6844dd..1800c54 100644
> --- a/include/sysemu/char.h
> +++ b/include/sysemu/char.h
> @@ -53,6 +53,17 @@ typedef struct {
>  
>  typedef void IOEventHandler(void *opaque, int event);
>  
> +struct ReconData {
> +    void *opaque;
> +    uint64_t recon_time;
> +    struct ReconHandlers *handlers;
> +    void (*state_change)(void *open_opaque, int is_open);
> +    void *state_change_opaque;
> +    void (*reconnected)(struct ReconData *r);
> +    void (*connection_lost)(struct ReconData *r);
> +    void (*shutdown)(struct ReconData *r);
> +};
> +
>  struct CharDriverState {
>      void (*init)(struct CharDriverState *s);
>      int (*chr_write)(struct CharDriverState *s, const uint8_t *buf, int len);
> @@ -82,6 +93,8 @@ struct CharDriverState {
>      guint fd_in_tag;
>      QemuOpts *opts;
>      QTAILQ_ENTRY(CharDriverState) next;
> +    GSList *backend;
> +    struct ReconData *recon;
>  };
>  
>  /**
> @@ -293,7 +306,8 @@ CharDriverState *qemu_chr_find(const char *name);
>  QemuOpts *qemu_chr_parse_compat(const char *label, const char *filename);
>  
>  void register_char_driver(const char *name,
> -        CharDriverState *(*open)(CharDriverState *, QemuOpts *));
> +        CharDriverState *(*open)(CharDriverState *, QemuOpts *),
> +        int (*recon_setup)(CharDriverState *));
>  void register_char_driver_qapi(const char *name, ChardevBackendKind kind,
>          void (*parse)(QemuOpts *opts, ChardevBackend *backend, Error 
> **errp));
>  
> diff --git a/qemu-char.c b/qemu-char.c
> index fc688cf..d9838aa 100644
> --- a/qemu-char.c
> +++ b/qemu-char.c
> @@ -88,6 +88,44 @@
>  /***********************************************************/
>  /* character device */
>  
> +struct GenericReconData {
> +    QEMUTimer *recon_timer;
> +};
> +
> +static void generic_recon_timeout(void *opaque)
> +{
> +    struct ReconData *r = opaque;
> +    struct GenericReconData *d = r->opaque;
> +
> +    timer_mod(d->recon_timer,
> +              (get_clock() + (r->recon_time * get_ticks_per_sec())));
> +    r->state_change(r->state_change_opaque, 0);
> +}
> +
> +static void generic_reconnected(struct ReconData *r)
> +{
> +    struct GenericReconData *d = r->opaque;
> +
> +    timer_del(d->recon_timer);
> +}
> +
> +static void generic_connection_lost(struct ReconData *r)
> +{
> +    struct GenericReconData *d = r->opaque;
> +
> +    r->state_change(r->state_change_opaque, 1);
> +    timer_mod(d->recon_timer,
> +              (get_clock() + (r->recon_time * get_ticks_per_sec())));
> +}
> +
> +static void generic_recon_shutdown(struct ReconData *r)
> +{
> +    struct GenericReconData *d = r->opaque;
> +    timer_free(d->recon_timer);
> +    free(d);
> +    r->opaque = NULL;
> +}
> +
>  static QTAILQ_HEAD(CharDriverStateHead, CharDriverState) chardevs =
>      QTAILQ_HEAD_INITIALIZER(chardevs);
>  
> @@ -96,9 +134,15 @@ void qemu_chr_be_event(CharDriverState *s, int event)
>      /* Keep track if the char device is open */
>      switch (event) {
>          case CHR_EVENT_OPENED:
> +            if (s->recon) {
> +                s->recon->reconnected(s->recon);
> +            }
>              s->be_open = 1;
>              break;
>          case CHR_EVENT_CLOSED:
> +            if (s->recon) {
> +                s->recon->connection_lost(s->recon);
> +            }
>              s->be_open = 0;
>              break;
>      }
> @@ -2582,6 +2626,7 @@ static void tcp_chr_close(CharDriverState *chr)
>          closesocket(s->listen_fd);
>      }
>      g_free(s);
> +    chr->opaque = NULL;
>      qemu_chr_be_event(chr, CHR_EVENT_CLOSED);
>  }
>  
> @@ -2641,8 +2686,6 @@ static CharDriverState 
> *qemu_chr_open_socket_fd(CharDriverState *chr,
>      chr->get_msgfd = tcp_get_msgfd;
>      chr->chr_add_client = tcp_chr_add_client;
>      chr->chr_add_watch = tcp_chr_add_watch;
> -    /* be isn't opened until we get a connection */
> -    chr->explicit_be_open = true;
>  
>      if (is_listen) {
>          s->listen_fd = fd;
> @@ -2680,6 +2723,9 @@ static CharDriverState 
> *qemu_chr_open_socket(CharDriverState *chr,
>      bool do_nodelay     = !qemu_opt_get_bool(opts, "delay", true);
>      bool is_unix        = qemu_opt_get(opts, "path") != NULL;
>  
> +    /* be isn't opened until we get a connection */
> +    chr->explicit_be_open = true;
> +
>      if (is_unix) {
>          if (is_listen) {
>              fd = unix_listen_opts(opts, &local_err);
> @@ -2716,8 +2762,9 @@ static CharDriverState 
> *qemu_chr_open_socket(CharDriverState *chr,
>      if (fd >= 0) {
>          closesocket(fd);
>      }
> -    if (chr) {
> +    if (chr && chr->opaque) {
>          g_free(chr->opaque);
> +        chr->opaque = NULL;
>      }
>      return NULL;
>  }
> @@ -3128,6 +3175,7 @@ static void qemu_chr_parse_mux(QemuOpts *opts, 
> ChardevBackend *backend,
>  
>  typedef struct CharDriver {
>      const char *name;
> +    int (*recon_setup)(CharDriverState *);
>      /* old, pre qapi */
>      CharDriverState *(*open)(CharDriverState *chr, QemuOpts *opts);
>      /* new, qapi-based */
> @@ -3138,13 +3186,15 @@ typedef struct CharDriver {
>  static GSList *backends;
>  
>  void register_char_driver(const char *name,
> -                          CharDriverState *(*open)(CharDriverState*,QemuOpts 
> *))
> +                          CharDriverState *(*open)(CharDriverState*,QemuOpts 
> *),
> +                          int (*recon_setup)(CharDriverState *))
>  {
>      CharDriver *s;
>  
>      s = g_malloc0(sizeof(*s));
>      s->name = g_strdup(name);
>      s->open = open;
> +    s->recon_setup = recon_setup;
>  
>      backends = g_slist_append(backends, s);
>  }
> @@ -3162,6 +3212,50 @@ void register_char_driver_qapi(const char *name, 
> ChardevBackendKind kind,
>      backends = g_slist_append(backends, s);
>  }
>  
> +static void generic_recon_state_change(void *opaque, int is_open)
> +{
> +    struct CharDriverState *chr = opaque;
> +
> +    if (!is_open) {
> +        struct CharDriver *cd = chr->backend->data;
> +
> +        if (chr->be_open) {
> +            return;
> +        }
> +
> +        cd->open(chr, chr->opts);
> +    } else {
> +        void (*chr_close)(struct CharDriverState *chr) = chr->chr_close;
> +
> +        if (chr_close) {
> +            chr->chr_close = NULL;
> +            chr_close(chr);
> +        }
> +    }
> +}
> +
> +static int generic_recon_setup(struct CharDriverState *chr)
> +{
> +    struct GenericReconData *d;
> +
> +    d = g_malloc(sizeof(*d));
> +    chr->recon->opaque = d;
> +
> +    chr->recon->reconnected = generic_reconnected;
> +    chr->recon->connection_lost = generic_connection_lost;
> +    chr->recon->shutdown = generic_recon_shutdown;
> +    chr->recon->state_change = generic_recon_state_change;
> +    chr->recon->state_change_opaque = chr;
> +
> +    d->recon_timer = timer_new(QEMU_CLOCK_REALTIME, SCALE_NS,
> +                               generic_recon_timeout, chr->recon);
> +
> +    /* Make sure it connects in time. */
> +    timer_mod(d->recon_timer,
> +              (get_clock() + (chr->recon->recon_time * 
> get_ticks_per_sec())));
> +    return 1;
> +}
> +
>  CharDriverState *qemu_chr_new_from_opts(QemuOpts *opts,
>                                      void (*init)(struct CharDriverState *s),
>                                      Error **errp)
> @@ -3169,6 +3263,7 @@ CharDriverState *qemu_chr_new_from_opts(QemuOpts *opts,
>      CharDriver *cd;
>      CharDriverState *chr;
>      GSList *i;
> +    uint64_t recon_time;
>  
>      if (qemu_opts_id(opts) == NULL) {
>          error_setg(errp, "chardev: no id specified");
> @@ -3244,11 +3339,41 @@ CharDriverState *qemu_chr_new_from_opts(QemuOpts 
> *opts,
>      }
>  
>      chr = g_malloc0(sizeof(CharDriverState));
> -    chr = cd->open(chr, opts);
> -    if (!chr) {
> -        error_setg(errp, "chardev: opening backend \"%s\" failed",
> -                   qemu_opt_get(opts, "backend"));
> -        goto err;
> +
> +    chr->backend = i;
> +    recon_time = qemu_opt_get_number(opts, "reconnect", 0);
> +    if (recon_time) {
> +        CharDriver *d = chr->backend->data;
> +        if (!d->recon_setup) {
> +            g_free(chr);
> +            fprintf(stderr, "chardev: reconnect not supported on %s\n",
> +                    qemu_opt_get(opts, "backend"));
> +            return NULL;
> +        }
> +        if (qemu_opt_get_bool(opts, "server", 0)) {
> +            g_free(chr);
> +            fprintf(stderr, "chardev: server device cannot reconnect\n");
> +            return NULL;
> +        }
> +        chr->opts = opts;
> +        chr->recon = g_malloc(sizeof(*chr->recon));
> +        chr->recon->recon_time = recon_time;
> +        if (!d->recon_setup(chr)) {
> +            g_free(chr->recon);
> +            g_free(chr);
> +            fprintf(stderr, "chardev: Unable to set up reconnect\n");
> +            return NULL;
> +        }
> +    }
> +
> +    if (!cd->open(chr, opts)) {
> +        if (!chr->recon) {
> +            /* Reconnect is not enabled, give up */
> +            fprintf(stderr, "chardev: opening backend \"%s\" failed\n",
> +                    qemu_opt_get(opts, "backend"));
> +            g_free(chr);
> +            return NULL;
> +        }
>      }
>  
>      if (!chr->filename)
> @@ -3267,7 +3392,8 @@ CharDriverState *qemu_chr_new_from_opts(QemuOpts *opts,
>          int len = strlen(qemu_opts_id(opts)) + 6;
>          base->label = g_malloc(len);
>          snprintf(base->label, len, "%s-base", qemu_opts_id(opts));
> -        chr = qemu_chr_open_mux(chr, base);
> +        chr = g_malloc0(sizeof(CharDriverState));
> +        qemu_chr_open_mux(chr, base);
>          chr->filename = base->filename;
>          chr->avail_connections = MAX_MUX;
>          QTAILQ_INSERT_TAIL(&chardevs, chr, next);
> @@ -3275,7 +3401,6 @@ CharDriverState *qemu_chr_new_from_opts(QemuOpts *opts,
>          chr->avail_connections = 1;
>      }
>      chr->label = g_strdup(qemu_opts_id(opts));
> -    chr->opts = opts;
>      return chr;
>  
>  err:
> @@ -3378,9 +3503,16 @@ void qemu_chr_fe_release(CharDriverState *s)
>  
>  void qemu_chr_delete(CharDriverState *chr)
>  {
> +    void (*chr_close)(struct CharDriverState *chr) = chr->chr_close;
> +
>      QTAILQ_REMOVE(&chardevs, chr, next);
> -    if (chr->chr_close) {
> -        chr->chr_close(chr);
> +    if (chr_close) {
> +        chr->chr_close = NULL;
> +        chr_close(chr);
> +    }
> +    if (chr->recon) {
> +        chr->recon->shutdown(chr->recon);
> +        g_free(chr->recon);
>      }
>      g_free(chr->filename);
>      g_free(chr->label);
> @@ -3515,6 +3647,9 @@ QemuOptsList qemu_chardev_opts = {
>              .name = "mux",
>              .type = QEMU_OPT_BOOL,
>          },{
> +            .name = "reconnect",
> +            .type = QEMU_OPT_NUMBER,
> +        },{
>              .name = "signal",
>              .type = QEMU_OPT_BOOL,
>          },{
> @@ -3811,8 +3946,8 @@ void qmp_chardev_remove(const char *id, Error **errp)
>  static void register_types(void)
>  {
>      register_char_driver_qapi("null", CHARDEV_BACKEND_KIND_NULL, NULL);
> -    register_char_driver("socket", qemu_chr_open_socket);
> -    register_char_driver("udp", qemu_chr_open_udp);
> +    register_char_driver("socket", qemu_chr_open_socket, 
> generic_recon_setup);
> +    register_char_driver("udp", qemu_chr_open_udp, NULL);
>      register_char_driver_qapi("ringbuf", CHARDEV_BACKEND_KIND_RINGBUF,
>                                qemu_chr_parse_ringbuf);
>      register_char_driver_qapi("file", CHARDEV_BACKEND_KIND_FILE,
> diff --git a/qemu-options.hx b/qemu-options.hx
> index 56e5fdf..1002a3d 100644
> --- a/qemu-options.hx
> +++ b/qemu-options.hx
> @@ -1787,8 +1787,9 @@ ETEXI
>  DEF("chardev", HAS_ARG, QEMU_OPTION_chardev,
>      "-chardev null,id=id[,mux=on|off]\n"
>      "-chardev 
> socket,id=id[,host=host],port=host[,to=to][,ipv4][,ipv6][,nodelay]\n"
> -    "         [,server][,nowait][,telnet][,mux=on|off] (tcp)\n"
> -    "-chardev socket,id=id,path=path[,server][,nowait][,telnet],[mux=on|off] 
> (unix)\n"
> +    "         [,server][,nowait][,telnet][,mux=on|off][,reconnect=seconds] 
> (tcp)\n"
> +    "-chardev 
> socket,id=id,path=path[,server][,nowait][,telnet][,mux=on|off]\n"
> +    "         [,reconnect=seconds] (unix)\n"
>      "-chardev udp,id=id[,host=host],port=port[,localaddr=localaddr]\n"
>      "         [,localport=localport][,ipv4][,ipv6][,mux=on|off]\n"
>      "-chardev msmouse,id=id[,mux=on|off]\n"
> @@ -1860,7 +1861,7 @@ Options to each backend are described below.
>  A void device. This device will not emit any data, and will drop any data it
>  receives. The null backend does not take any options.
>  
> address@hidden -chardev socket ,address@hidden address@hidden options} or 
> @var{unix options}] [,server] [,nowait] [,telnet]
> address@hidden -chardev socket ,address@hidden address@hidden options} or 
> @var{unix options}] [,server] [,nowait] [,telnet] [,address@hidden
>  
>  Create a two-way stream socket, which can be either a TCP or a unix socket. A
>  unix socket will be created if @option{path} is specified. Behaviour is
> @@ -1874,6 +1875,10 @@ connect to a listening socket.
>  @option{telnet} specifies that traffic on the socket should interpret telnet
>  escape sequences.
>  
> address@hidden specifies that if the client socket does not connect at
> +startup, or if the client socket is closed for some reason (like the other
> +end exited), wait the given number of seconds and attempt to reconnect.
> +
>  TCP and unix socket options are given below:
>  
>  @table @option

The client will reconnect for ever when the server is dead. Is it better that 
try to reconnect several times?
Or add a option which specifies times of reconnect?