Re: [Qemu-devel] [PATCH v6 1/5] sockets: change inet_connect() to support nonblock socket

[Michael Roth]

On Tue, Apr 17, 2012 at 10:54:01PM +0800, Amos Kong wrote:
> Add a bool argument to inet_connect() to assign if set socket
> to block/nonblock, and delete original argument 'socktype'
> that is unused.
> 
> Retry to connect when following errors are got:
>   -EINTR
>   -EWOULDBLOCK (win32)
> Connect's successful for nonblock socket when following
> errors are got, user should wait for connecting by select():
>   -EINPROGRESS
>   -WSAEALREADY (win32)

How does the user access these? Via errno/socket_error()? I'm not sure
how that would work, I don't think we can rely on the value of errno
unless a function indicates an error, so for the case where we're
successful but have an EINPROGRESS, I don't think we have a way of
reliably obtaining that (errno value might be stale) except maybe
something like getsockopt().

I think it would be better to just merge this with your patch #3, which
handles all this nicely via Error.
> 
> Change nbd, vnc to use new interface.
> 
> Signed-off-by: Amos Kong <address@hidden>
> ---
>  nbd.c          |    2 +-
>  qemu-sockets.c |   58 
> +++++++++++++++++++++++++++++++++++++++++++-------------
>  qemu_socket.h  |    2 +-
>  ui/vnc.c       |    2 +-
>  4 files changed, 48 insertions(+), 16 deletions(-)
> 
> diff --git a/nbd.c b/nbd.c
> index 406e555..b4e68a9 100644
> --- a/nbd.c
> +++ b/nbd.c
> @@ -146,7 +146,7 @@ int tcp_socket_outgoing(const char *address, uint16_t 
> port)
> 
>  int tcp_socket_outgoing_spec(const char *address_and_port)
>  {
> -    return inet_connect(address_and_port, SOCK_STREAM);
> +    return inet_connect(address_and_port, true);
>  }
> 
>  int tcp_socket_incoming(const char *address, uint16_t port)
> diff --git a/qemu-sockets.c b/qemu-sockets.c
> index 6bcb8e3..e886195 100644
> --- a/qemu-sockets.c
> +++ b/qemu-sockets.c
> @@ -51,6 +51,9 @@ static QemuOptsList dummy_opts = {
>          },{
>              .name = "ipv6",
>              .type = QEMU_OPT_BOOL,
> +        },{
> +            .name = "block",
> +            .type = QEMU_OPT_BOOL,
>          },
>          { /* end if list */ }
>      },
> @@ -201,7 +204,8 @@ int inet_connect_opts(QemuOpts *opts)
>      const char *port;
>      char uaddr[INET6_ADDRSTRLEN+1];
>      char uport[33];
> -    int sock,rc;
> +    int sock, rc, err;
> +    bool block;
> 
>      memset(&ai,0, sizeof(ai));
>      ai.ai_flags = AI_CANONNAME | AI_ADDRCONFIG;
> @@ -210,6 +214,7 @@ int inet_connect_opts(QemuOpts *opts)
> 
>      addr = qemu_opt_get(opts, "host");
>      port = qemu_opt_get(opts, "port");
> +    block = qemu_opt_get_bool(opts, "block", 0);
>      if (addr == NULL || port == NULL) {
>          fprintf(stderr, "inet_connect: host and/or port not specified\n");
>          return -1;
> @@ -241,21 +246,44 @@ int inet_connect_opts(QemuOpts *opts)
>              continue;
>          }
>          setsockopt(sock,SOL_SOCKET,SO_REUSEADDR,(void*)&on,sizeof(on));
> -
> +        if (!block) {
> +            socket_set_nonblock(sock);
> +        }
>          /* connect to peer */
> -        if (connect(sock,e->ai_addr,e->ai_addrlen) < 0) {
> -            if (NULL == e->ai_next)
> -                fprintf(stderr, "%s: connect(%s,%s,%s,%s): %s\n", 
> __FUNCTION__,
> -                        inet_strfamily(e->ai_family),
> -                        e->ai_canonname, uaddr, uport, strerror(errno));
> -            closesocket(sock);
> -            continue;
> +        do {
> +            err = 0;
> +            if (connect(sock, e->ai_addr, e->ai_addrlen) < 0) {
> +                err = -socket_error();
> +            }
> +#ifndef _WIN32
> +        } while (err == -EINTR || err == -EWOULDBLOCK);
> +#else
> +        } while (err == -EINTR);
> +#endif
> +
> +        if (err >= 0) {
> +            goto success;
> +        } else if (!block && err == -EINPROGRESS) {
> +            goto success;
> +#ifdef _WIN32
> +        } else if (!block && err == -WSAEALREADY) {
> +            goto success;
> +#endif
>          }
> -        freeaddrinfo(res);
> -        return sock;
> +
> +        if (NULL == e->ai_next) {
> +            fprintf(stderr, "%s: connect(%s,%s,%s,%s): %s\n", __FUNCTION__,
> +                    inet_strfamily(e->ai_family),
> +                    e->ai_canonname, uaddr, uport, strerror(errno));
> +        }
> +        closesocket(sock);
>      }
>      freeaddrinfo(res);
>      return -1;
> +
> +success:
> +    freeaddrinfo(res);
> +    return sock;
>  }
> 
>  int inet_dgram_opts(QemuOpts *opts)
> @@ -449,14 +477,18 @@ int inet_listen(const char *str, char *ostr, int olen,
>      return sock;
>  }
> 
> -int inet_connect(const char *str, int socktype)
> +int inet_connect(const char *str, bool block)
>  {
>      QemuOpts *opts;
>      int sock = -1;
> 
>      opts = qemu_opts_create(&dummy_opts, NULL, 0);
> -    if (inet_parse(opts, str) == 0)
> +    if (inet_parse(opts, str) == 0) {
> +        if (block) {
> +            qemu_opt_set(opts, "block", "on");
> +        }
>          sock = inet_connect_opts(opts);
> +    }
>      qemu_opts_del(opts);
>      return sock;
>  }
> diff --git a/qemu_socket.h b/qemu_socket.h
> index a5d0a84..f73e26d 100644
> --- a/qemu_socket.h
> +++ b/qemu_socket.h
> @@ -41,7 +41,7 @@ int inet_listen_opts(QemuOpts *opts, int port_offset);
>  int inet_listen(const char *str, char *ostr, int olen,
>                  int socktype, int port_offset);
>  int inet_connect_opts(QemuOpts *opts);
> -int inet_connect(const char *str, int socktype);
> +int inet_connect(const char *str, bool block);
>  int inet_dgram_opts(QemuOpts *opts);
>  const char *inet_strfamily(int family);
> 
> diff --git a/ui/vnc.c b/ui/vnc.c
> index deb9ecd..4a96153 100644
> --- a/ui/vnc.c
> +++ b/ui/vnc.c
> @@ -3068,7 +3068,7 @@ int vnc_display_open(DisplayState *ds, const char 
> *display)
>          if (strncmp(display, "unix:", 5) == 0)
>              vs->lsock = unix_connect(display+5);
>          else
> -            vs->lsock = inet_connect(display, SOCK_STREAM);
> +            vs->lsock = inet_connect(display, true);
>          if (-1 == vs->lsock) {
>              g_free(vs->display);
>              vs->display = NULL;
> 
>