Re: [Qemu-devel] [PATCH v3] qapi: Add InetSocketAddress member keep-alive

[Markus Armbruster <armbru@redhat.com>]

I apologize for dragging my feet on this review.

Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com> writes:

> It's needed to provide keepalive for nbd client to track server
> availability.
>
> Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
> ---
>
> v3: [by Markus's comments]
>
> - Fix commit subject
> - Add comment to qapi and restrict server-side connections
> - Fix s/"keep-alive="/",keep-alive"/
>
>
>  qapi/sockets.json   |  6 +++++-
>  util/qemu-sockets.c | 28 ++++++++++++++++++++++++++++
>  2 files changed, 33 insertions(+), 1 deletion(-)
>
> diff --git a/qapi/sockets.json b/qapi/sockets.json
> index fc81d8d5e8..c44af481a1 100644
> --- a/qapi/sockets.json
> +++ b/qapi/sockets.json
> @@ -53,6 +53,9 @@
>  #
>  # @ipv6: whether to accept IPv6 addresses, default try both IPv4 and IPv6
>  #
> +# @keep-alive: enable keep-alive when connecting to this socket. Not supported
> +#              for server-side connections. (Since 4.1)
> +#

Is "server-side connection" is an established term?

For what it's worth, "passive socket" is, see listen(2).

>  # Since: 1.3
>  ##
>  { 'struct': 'InetSocketAddress',
> @@ -61,7 +64,8 @@
>      '*numeric':  'bool',
>      '*to': 'uint16',
>      '*ipv4': 'bool',
> -    '*ipv6': 'bool' } }
> +    '*ipv6': 'bool',
> +    '*keep-alive': 'bool' } }
>  
>  ##
>  # @UnixSocketAddress:
> diff --git a/util/qemu-sockets.c b/util/qemu-sockets.c
> index 8850a280a8..813063761b 100644
> --- a/util/qemu-sockets.c
> +++ b/util/qemu-sockets.c
> @@ -438,6 +438,12 @@ int inet_connect_saddr(InetSocketAddress *saddr, Error **errp)
>      struct addrinfo *res, *e;
>      int sock = -1;
>  
> +    if (saddr->keep_alive) {
> +        error_setg(errp, "keep-alive options is not supported for server-side "
> +                   "connection");
> +        return -1;
> +    }
> +
>      res = inet_parse_connect_saddr(saddr, errp);
>      if (!res) {
>          return -1;

I'm afraid you added this to the wrong function; ...

> @@ -457,6 +463,19 @@ int inet_connect_saddr(InetSocketAddress *saddr, Error **errp)
>      }
>  
>      freeaddrinfo(res);
> +
> +    if (saddr->keep_alive) {

... it renders this code unreachable.

I guess the "not supported for passive sockets" check should go into
inet_listen_saddr() instead.

> +        int val = 1;
> +        int ret = qemu_setsockopt(sock, SOL_SOCKET, SO_KEEPALIVE,
> +                                  &val, sizeof(val));
> +
> +        if (ret < 0) {
> +            error_setg_errno(errp, errno, "Unable to set KEEPALIVE");
> +            close(sock);
> +            return -1;
> +        }
> +    }
> +
>      return sock;
>  }
>  
> @@ -652,6 +671,15 @@ int inet_parse(InetSocketAddress *addr, const char *str, Error **errp)
>          }
>          addr->has_ipv6 = true;
>      }
> +    begin = strstr(optstr, ",keep-alive");
> +    if (begin) {
> +        if (inet_parse_flag("keep-alive", begin + strlen(",keep-alive"),
> +                            &addr->keep_alive, errp) < 0)
> +        {
> +            return -1;
> +        }
> +        addr->has_keep_alive = true;
> +    }
>      return 0;
>  }