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

[Michael Roth]

On Wed, Apr 18, 2012 at 10:49:02AM +0800, Amos Kong wrote:
> 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().

Don't use Error as an indicator to check socket_error(). If we want to
pass back something akin to errno, it should be done via Error. Paolo
had some suggestions on how to do this, but I think the Errors you
introduced in patch #2 are sufficient for now. qmp_migrate() currently
just sets QERR_UNDEFINED_ERROR and ignores the actual value of
socket_error(), we only use it for DPRINTF(), so if you still want to
dump the output of socket_error()/errno to stderr, do it early in
inet_connect()/inet_listen() so we don't have to propagate anything
back tcp_start_outgoing_migration() other than **errp.

> 
> 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.
>