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

[Amos Kong]

On 18/04/12 14:52, Orit Wasserman wrote:
> On 04/17/2012 05:54 PM, 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)
> >
> > 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
>
> We shouldn't retry to connect for a blocking socket, please add a check for 
> !block.
> According to msn docs in WIN32 if we get EWOULDBLOCK , we should do select
> http://msdn.microsoft.com/en-us/library/windows/desktop/ms737625(v=vs.85).aspx
> so I think we only need to retry for -EINTR.

Hi Orit, thanks for your review.

In 
http://msdn.microsoft.com/en-us/library/windows/desktop/ms740668%28v=vs.85%29.aspx,
for 'EWOULDBLOCK': the operation should be retried later."

However, the two methods all works.  I would not re-try for EWOULDBLOCK 
(posix & win32).

> > +
> > +        if (err>= 0) {
> > +            goto success;
> > +        } else if (!block&&  err == -EINPROGRESS) {
> > +            goto success;
> > +#ifdef _WIN32
> > +        } else if (!block&&  err == -WSAEALREADY) {
>
> Also EWOULDBLOCK
> This is more a style comment as I feel to code doesn't need the go to.

Ok.

> Check for an error path so the rest of the function looks like:
>
> if (err<  0) {
>         if ( block ||
> #ifndef __WIN32
>          err != -EINPROGRESS ) {
> #else
>         (err != -EWOULDBLOCK&&  err != -WASALREADY) ) {
> #endif


EINPROGRESS and EWOULDBLOCK are for posix and win32,

  if (err <  0) {
        if (block || (err != -EINPROGRESS && err != -EWOULDBLOCK
  #ifndef __WIN32
         )) {
  #else
        &&  err != -WASALREADY)) {
  #endif


>         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);
>         sock = -1;
> }
>
> freeaddrinfo(res);
> return sock;
> }

...

--
                        Amos.