Re: [Qemu-devel] [PATCH v1 09/22] migration: convert unix socket protocol to use QIOChannel

[Daniel P. Berrange]

On Tue, Feb 02, 2016 at 06:02:13PM +0000, Dr. David Alan Gilbert wrote:
> * Daniel P. Berrange (address@hidden) wrote:
> > Convert the unix socket migration protocol driver to use
> > QIOChannel and QEMUFileChannel, instead of plain sockets
> > APIs. It can be unconditionally built, since the socket
> > impl of QIOChannel will report a suitable error on platforms
> > where UNIX sockets are unavailable.
> > 
> > Signed-off-by: Daniel P. Berrange <address@hidden>
> > ---
> >  migration/Makefile.objs |   4 +-
> >  migration/migration.c   |   4 ++
> >  migration/unix.c        | 103 
> > +++++++++++++++++++++++++++++++-----------------
> >  3 files changed, 72 insertions(+), 39 deletions(-)
> > 
> > diff --git a/migration/Makefile.objs b/migration/Makefile.objs
> > index b357e2f..a5f8a03 100644
> > --- a/migration/Makefile.objs
> > +++ b/migration/Makefile.objs
> > @@ -1,11 +1,11 @@
> > -common-obj-y += migration.o tcp.o
> > +common-obj-y += migration.o tcp.o unix.o
> >  common-obj-y += vmstate.o
> >  common-obj-y += qemu-file.o qemu-file-buf.o qemu-file-unix.o 
> > qemu-file-stdio.o
> >  common-obj-y += qemu-file-channel.o
> >  common-obj-y += xbzrle.o postcopy-ram.o
> >  
> >  common-obj-$(CONFIG_RDMA) += rdma.o
> > -common-obj-$(CONFIG_POSIX) += exec.o unix.o fd.o
> > +common-obj-$(CONFIG_POSIX) += exec.o fd.o
> >  
> >  common-obj-y += block.o
> >  
> > diff --git a/migration/migration.c b/migration/migration.c
> > index e921b20..1c5f12e 100644
> > --- a/migration/migration.c
> > +++ b/migration/migration.c
> > @@ -312,8 +312,10 @@ void qemu_start_incoming_migration(const char *uri, 
> > Error **errp)
> >  #if !defined(WIN32)
> >      } else if (strstart(uri, "exec:", &p)) {
> >          exec_start_incoming_migration(p, errp);
> > +#endif
> >      } else if (strstart(uri, "unix:", &p)) {
> >          unix_start_incoming_migration(p, errp);
> > +#if !defined(WIN32)
> >      } else if (strstart(uri, "fd:", &p)) {
> >          fd_start_incoming_migration(p, errp);
> >  #endif
> > @@ -1017,8 +1019,10 @@ void qmp_migrate(const char *uri, bool has_blk, bool 
> > blk,
> >  #if !defined(WIN32)
> >      } else if (strstart(uri, "exec:", &p)) {
> >          exec_start_outgoing_migration(s, p, &local_err);
> > +#endif
> >      } else if (strstart(uri, "unix:", &p)) {
> >          unix_start_outgoing_migration(s, p, &local_err);
> > +#if !defined(WIN32)
> >      } else if (strstart(uri, "fd:", &p)) {
> >          fd_start_outgoing_migration(s, p, &local_err);
> >  #endif
> > diff --git a/migration/unix.c b/migration/unix.c
> > index b591813..4674640 100644
> > --- a/migration/unix.c
> > +++ b/migration/unix.c
> > @@ -1,10 +1,11 @@
> >  /*
> >   * QEMU live migration via Unix Domain Sockets
> >   *
> > - * Copyright Red Hat, Inc. 2009
> > + * Copyright Red Hat, Inc. 2009-2015
> 
> year++ ?
> 
> >   *
> >   * Authors:
> >   *  Chris Lalancette <address@hidden>
> > + *  Daniel P. Berrange <address@hidden>
> >   *
> >   * This work is licensed under the terms of the GNU GPL, version 2.  See
> >   * the COPYING file in the top-level directory.
> > @@ -17,11 +18,9 @@
> >  
> >  #include "qemu-common.h"
> >  #include "qemu/error-report.h"
> > -#include "qemu/sockets.h"
> > -#include "qemu/main-loop.h"
> >  #include "migration/migration.h"
> >  #include "migration/qemu-file.h"
> > -#include "block/block.h"
> > +#include "io/channel-socket.h"
> >  
> >  //#define DEBUG_MIGRATION_UNIX
> >  
> > @@ -33,71 +32,101 @@
> >      do { } while (0)
> >  #endif
> >  
> > -static void unix_wait_for_connect(int fd, Error *err, void *opaque)
> > +
> > +static SocketAddress *unix_build_address(const char *path)
> > +{
> > +    SocketAddress *saddr;
> > +
> > +    saddr = g_new0(SocketAddress, 1);
> > +    saddr->type = SOCKET_ADDRESS_KIND_UNIX;
> > +    saddr->u.q_unix = g_new0(UnixSocketAddress, 1);
> > +    saddr->u.q_unix->path = g_strdup(path);
> > +
> > +    return saddr;
> > +}
> > +
> > +
> > +static void unix_outgoing_migration(Object *src,
> > +                                    Error *err,
> > +                                    gpointer opaque)
> >  {
> >      MigrationState *s = opaque;
> > +    QIOChannel *sioc = QIO_CHANNEL(src);
> >  
> > -    if (fd < 0) {
> > +    if (err) {
> >          DPRINTF("migrate connect error: %s\n", error_get_pretty(err));
> >          s->file = NULL;
> >          migrate_fd_error(s);
> >      } else {
> >          DPRINTF("migrate connect success\n");
> > -        s->file = qemu_fopen_socket(fd, "wb");
> > +        s->file = qemu_fopen_channel_output(sioc);
> >          migrate_fd_connect(s);
> >      }
> > +    object_unref(src);
> >  }
> >  
> > +
> >  void unix_start_outgoing_migration(MigrationState *s, const char *path, 
> > Error **errp)
> >  {
> > -    unix_nonblocking_connect(path, unix_wait_for_connect, s, errp);
> > +    SocketAddress *saddr = unix_build_address(path);
> > +    QIOChannelSocket *sioc;
> > +    sioc = qio_channel_socket_new();
> > +    qio_channel_socket_connect_async(sioc,
> > +                                     saddr,
> > +                                     unix_outgoing_migration,
> > +                                     s,
> > +                                     NULL);
> > +    qapi_free_SocketAddress(saddr);
> 
> It took me a bit of digging to see that qio_channel_socket_connect_async
> takes a copy of the address; it's not mentioned in channel-socket.h
> 
> >  }
> >  
> > -static void unix_accept_incoming_migration(void *opaque)
> > +
> > +static gboolean unix_accept_incoming_migration(QIOChannel *ioc,
> > +                                               GIOCondition condition,
> > +                                               gpointer opaque)
> >  {
> > -    struct sockaddr_un addr;
> > -    socklen_t addrlen = sizeof(addr);
> > -    int s = (intptr_t)opaque;
> >      QEMUFile *f;
> > -    int c, err;
> > -
> > -    do {
> > -        c = qemu_accept(s, (struct sockaddr *)&addr, &addrlen);
> > -        err = errno;
> > -    } while (c < 0 && err == EINTR);
> > -    qemu_set_fd_handler(s, NULL, NULL, NULL);
> > -    close(s);
> > +    QIOChannelSocket *cioc;
> 
> (not important but...) why is that a cioc not a sioc?

IIRC an earlier version of this patch had already used sioc for another
variable. I'll change this now though.

> 
> > +    Error *err = NULL;
> >  
> > -    DPRINTF("accepted migration\n");
> > -
> > -    if (c < 0) {
> > +    cioc = qio_channel_socket_accept(QIO_CHANNEL_SOCKET(ioc),
> > +                                     &err);
> > +    if (!cioc) {
> >          error_report("could not accept migration connection (%s)",
> > -                     strerror(err));
> > -        return;
> > -    }
> > -
> > -    f = qemu_fopen_socket(c, "rb");
> > -    if (f == NULL) {
> > -        error_report("could not qemu_fopen socket");
> > +                     error_get_pretty(err));
> >          goto out;
> >      }
> >  
> > +    DPRINTF("accepted migration\n");
> 
> Feel free to replace any DPRINTF's by trace_ entries.

Rather than change all my patches in this regard, I'll create an
add-on patch to introduce some useful trace_ entries across all
the migration backends in one go.

Regards,
Daniel
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