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

[Amos Kong]

On 18/04/12 10:10, Michael Roth wrote:
> 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()?

Yes, connect error is got by 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.

We use Error to pass meaningful error, but we need to process original 
socket error,
which is got by socket_error().

In qemu, we used socket_error() to get socket error in many place. If 
you are confused
with how that would work, we need to fix socket_error. I don't want to 
fix this in the
migration patchset.

What's your opinion?

> > 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();


connect error is got here


> > +            }
> > +#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;

--
                        Amos.