Re: [PATCH v9 08/16] net: stream: add unix socket

[David Gibson]

On Mon, Sep 26, 2022 at 09:50:40PM +0200, Laurent Vivier wrote:
> Signed-off-by: Laurent Vivier <lvivier@redhat.com>
> Reviewed-by: Stefano Brivio <sbrivio@redhat.com>
> ---
>  net/stream.c    | 108 +++++++++++++++++++++++++++++++++++++++++++++---
>  qapi/net.json   |   2 +-
>  qemu-options.hx |   1 +
>  3 files changed, 105 insertions(+), 6 deletions(-)
> 
> diff --git a/net/stream.c b/net/stream.c
> index 3fb899df5d2d..02967c284efc 100644
> --- a/net/stream.c
> +++ b/net/stream.c
> @@ -235,7 +235,7 @@ static NetStreamState 
> *net_stream_fd_init_stream(NetClientState *peer,
>  static void net_stream_accept(void *opaque)
>  {
>      NetStreamState *s = opaque;
> -    struct sockaddr_in saddr;
> +    struct sockaddr_storage saddr;
>      socklen_t len;
>      int fd;
>  
> @@ -253,9 +253,27 @@ static void net_stream_accept(void *opaque)
>      s->fd = fd;
>      s->nc.link_down = false;
>      net_stream_connect(s);
> -    snprintf(s->nc.info_str, sizeof(s->nc.info_str),
> -             "connection from %s:%d",
> -             inet_ntoa(saddr.sin_addr), ntohs(saddr.sin_port));
> +    switch (saddr.ss_family) {
> +    case AF_INET: {
> +        struct sockaddr_in *saddr_in = (struct sockaddr_in *)&saddr;
> +
> +        snprintf(s->nc.info_str, sizeof(s->nc.info_str),
> +                 "connection from %s:%d",
> +                 inet_ntoa(saddr_in->sin_addr), ntohs(saddr_in->sin_port));

So, here you print the address from which the connection has come -
the remote address.

> +        break;
> +    }
> +    case AF_UNIX: {
> +        struct sockaddr_un saddr_un;
> +
> +        len = sizeof(saddr_un);
> +        getsockname(s->listen_fd, (struct sockaddr *)&saddr_un, &len);
> +        snprintf(s->nc.info_str, sizeof(s->nc.info_str),
> +                 "connect from %s", saddr_un.sun_path);

Here you print the bound address - the local address.  Does that make
sense?  I mean, in almost every occasion the remote Unix socket will
be anonymous, so it probably doesn't make sense to display that, but
is the bound address actually a useful substitute?

Maybe it should just be "connect from Unix socket".

> +        break;
> +    }
> +    default:
> +        g_assert_not_reached();
> +    }
>  }
>  
>  static int net_stream_server_init(NetClientState *peer,
> @@ -295,6 +313,43 @@ static int net_stream_server_init(NetClientState *peer,
>          }
>          break;
>      }
> +    case SOCKET_ADDRESS_TYPE_UNIX: {
> +        struct sockaddr_un saddr_un;
> +
> +        ret = unlink(addr->u.q_unix.path);
> +        if (ret < 0 && errno != ENOENT) {
> +            error_setg_errno(errp, errno, "failed to unlink socket %s",
> +                             addr->u.q_unix.path);
> +            return -1;
> +        }
> +
> +        saddr_un.sun_family = PF_UNIX;
> +        ret = snprintf(saddr_un.sun_path, sizeof(saddr_un.sun_path), "%s",
> +                       addr->u.q_unix.path);
> +        if (ret < 0 || ret >= sizeof(saddr_un.sun_path)) {
> +            error_setg(errp, "UNIX socket path '%s' is too long",
> +                       addr->u.q_unix.path);
> +            error_append_hint(errp, "Path must be less than %zu bytes\n",
> +                              sizeof(saddr_un.sun_path));
> +            return -1;
> +        }

Not necessarily in scope here, but I do wonder if we want a common
helper to convert the QAPI SocketAddress to a struct sockaddr, which
supports both inet and Unix - and one day IPv6, one hopes - with all
the appropriate error handling.

> +
> +        fd = qemu_socket(PF_UNIX, SOCK_STREAM, 0);
> +        if (fd < 0) {
> +            error_setg_errno(errp, errno, "can't create stream socket");
> +            return -1;
> +        }
> +        qemu_socket_set_nonblock(fd);
> +
> +        ret = bind(fd, (struct sockaddr *)&saddr_un, sizeof(saddr_un));
> +        if (ret < 0) {
> +            error_setg_errno(errp, errno, "can't create socket with path: 
> %s",
> +                             saddr_un.sun_path);
> +            closesocket(fd);
> +            return -1;
> +        }
> +        break;
> +    }
>      case SOCKET_ADDRESS_TYPE_FD:
>          fd = monitor_fd_param(monitor_cur(), addr->u.fd.str, errp);
>          if (fd == -1) {
> @@ -380,6 +435,49 @@ static int net_stream_client_init(NetClientState *peer,
>                                     ntohs(saddr_in.sin_port));
>          break;
>      }
> +    case SOCKET_ADDRESS_TYPE_UNIX: {
> +        struct sockaddr_un saddr_un;
> +
> +        saddr_un.sun_family = PF_UNIX;
> +        ret = snprintf(saddr_un.sun_path, sizeof(saddr_un.sun_path), "%s",
> +                       addr->u.q_unix.path);
> +        if (ret < 0 || ret >= sizeof(saddr_un.sun_path)) {
> +            error_setg(errp, "UNIX socket path '%s' is too long",
> +                       addr->u.q_unix.path);
> +            error_append_hint(errp, "Path must be less than %zu bytes\n",
> +                              sizeof(saddr_un.sun_path));
> +            return -1;
> +        }
> +
> +        fd = qemu_socket(PF_UNIX, SOCK_STREAM, 0);
> +        if (fd < 0) {
> +            error_setg_errno(errp, errno, "can't create stream socket");
> +            return -1;
> +        }
> +        qemu_socket_set_nonblock(fd);
> +
> +        connected = 0;
> +        for (;;) {
> +            ret = connect(fd, (struct sockaddr *)&saddr_un, 
> sizeof(saddr_un));
> +            if (ret < 0) {
> +                if (errno == EINTR || errno == EWOULDBLOCK) {
> +                    /* continue */
> +                } else if (errno == EAGAIN ||
> +                           errno == EALREADY) {
> +                    break;
> +                } else {
> +                    error_setg_errno(errp, errno, "can't connect socket");
> +                    closesocket(fd);
> +                    return -1;
> +                }
> +            } else {
> +                connected = 1;
> +                break;
> +            }
> +        }
> +        info_str = g_strdup_printf(" connect to %s", saddr_un.sun_path);
> +        break;
> +    }
>      case SOCKET_ADDRESS_TYPE_FD:
>          fd = monitor_fd_param(monitor_cur(), addr->u.fd.str, errp);
>          if (fd == -1) {
> @@ -395,7 +493,7 @@ static int net_stream_client_init(NetClientState *peer,
>          info_str = g_strdup_printf("connect to fd %d", fd);
>          break;
>      default:
> -        error_setg(errp, "only support inet or fd type");
> +        error_setg(errp, "only support inet, unix or fd type");
>          return -1;
>      }
>  
> diff --git a/qapi/net.json b/qapi/net.json
> index e02e8001a000..bb96701a49a7 100644
> --- a/qapi/net.json
> +++ b/qapi/net.json
> @@ -583,7 +583,7 @@
>  #        or connect to (server=false)
>  # @server: create server socket (default: true)
>  #
> -# Only SocketAddress types 'inet' and 'fd' are supported.
> +# Only SocketAddress types 'unix', 'inet' and 'fd' are supported.
>  #
>  # Since: 7.1
>  ##
> diff --git a/qemu-options.hx b/qemu-options.hx
> index 8c765f345da8..7a34022ac651 100644
> --- a/qemu-options.hx
> +++ b/qemu-options.hx
> @@ -2735,6 +2735,7 @@ DEF("netdev", HAS_ARG, QEMU_OPTION_netdev,
>      "                configure a network backend to connect to another 
> network\n"
>      "                using an UDP tunnel\n"
>      "-netdev 
> stream,id=str[,server=on|off],addr.type=inet,addr.host=host,addr.port=port\n"
> +    "-netdev stream,id=str[,server=on|off],addr.type=unix,addr.path=path\n"
>      "-netdev stream,id=str[,server=on|off],addr.type=fd,addr.str=h\n"
>      "                configure a network backend to connect to another 
> network\n"
>      "                using a socket connection in stream mode.\n"

-- 
David Gibson                    | I'll have my music baroque, and my code
david AT gibson.dropbear.id.au  | minimalist, thank you.  NOT _the_ _other_
                                | _way_ _around_!
http://www.ozlabs.org/~dgibson

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