Re: [Qemu-devel] [PATCH 1/1] Support abstract socket namespace in AF_UNIX socket family.

[Alexander Barabash]

Hi,

On 01/07/2013 04:07 PM, Anthony Liguori wrote:
> Alexander Barabash <address@hidden> writes:
>
> > The abstract socket namespace is a nonportable Linux extension.
> > The sockets' names in this namespace have no connection
> > with file system pathnames. To specify a named AF_UNIX socket
> > in the abstract socket namespace, start the socket's path option
> > with a backslash followed by zero: \0.
> >
> > Signed-off-by: Alexander Barabash <address@hidden>
> Magic interpretation of path names is a bad thing in general.
>
> I think it would be better to add a flag 'abstract=on' which
> indicates to use the abstract namespace.  As an example:
>
> qemu -chardev foo,path=bar,abstract=on
>
> vs:
>
> qemu -chardev foo,path="\\\\0bar"
>
> I think the former is quite a bit more user friendly.
OK

> Regards,
>
> Anthony Liguori
Regards,
Alex
> > ---
> >   qemu-sockets.c |   58 +++++++++++++++++++++++++++++++++++++++++++++++++++++---
> >   1 file changed, 55 insertions(+), 3 deletions(-)
> >
> > diff --git a/qemu-sockets.c b/qemu-sockets.c
> > index 3537bf3..70c8ad5 100644
> > --- a/qemu-sockets.c
> > +++ b/qemu-sockets.c
> > @@ -663,11 +663,50 @@ int inet_nonblocking_connect(const char *str,
> >   
> >   #ifndef _WIN32
> >   
> > +/*
> > + * The abstract socket namespace is a nonportable Linux extension.
> > + * The sockets' names in this namespace have no connection
> > + * with file system pathnames. To specify a named AF_UNIX socket
> > + * in the abstract socket namespace, start the socket's path option
> > + * with a backslash followed by zero: \0.
> > + */
> > +static
> > +char *get_abstract_namespace_path(const char *path, int *abstract_path_length)
> > +{
> > +    char *abstract_path;
> > +    char *inp;
> > +    char *outp;
> > +    char c;
> > +
> > +    *abstract_path_length = 0;
> > +    if ((path == NULL) || (path[0] != '\\') || (path[1] != '0')) {
> > +        return NULL;
> > +    }
> > +    abstract_path = g_strdup(path + 2);
> > +    for (inp = abstract_path, outp = abstract_path; (c = *inp); ++inp, ++outp) 
> > {
> > +        if (c == '\\') {
> > +            c = *++inp;
> > +            if (c == '\\') {
> > +                *outp = c;
> > +            } else if (c == '0') {
> > +                *outp = '\0';
> > +            }
> > +        } else {
> > +            *outp = c;
> > +        }
> > +    }
> > +    *abstract_path_length = outp - abstract_path;
> > +    return abstract_path;
> > +}
> > +
> >   int unix_listen_opts(QemuOpts *opts, Error **errp)
> >   {
> >       struct sockaddr_un un;
> >       const char *path = qemu_opt_get(opts, "path");
> > +    int abstract_path_length;
> > +    char *abstract_path;
> >       int sock, fd;
> > +    socklen_t addrlen = sizeof(un);
> >   
> >       sock = qemu_socket(PF_UNIX, SOCK_STREAM, 0);
> >       if (sock < 0) {
> > @@ -675,9 +714,18 @@ int unix_listen_opts(QemuOpts *opts, Error **errp)
> >           return -1;
> >       }
> >   
> > +    abstract_path = get_abstract_namespace_path(path, &abstract_path_length);
> > +
> >       memset(&un, 0, sizeof(un));
> >       un.sun_family = AF_UNIX;
> > -    if (path && strlen(path)) {
> > +    if (abstract_path != NULL) {
> > +        if (abstract_path_length > sizeof(un.sun_path) - 1) {
> > +            abstract_path_length = sizeof(un.sun_path) - 1;
> > +        }
> > +        memcpy(un.sun_path + 1, abstract_path, abstract_path_length);
> > +        addrlen =
> > +            offsetof(struct sockaddr_un, sun_path) + 1 + abstract_path_length;
> > +    } else if (path && strlen(path)) {
> >           snprintf(un.sun_path, sizeof(un.sun_path), "%s", path);
> >       } else {
> >           char *tmpdir = getenv("TMPDIR");
> > @@ -694,8 +742,10 @@ int unix_listen_opts(QemuOpts *opts, Error **errp)
> >           qemu_opt_set(opts, "path", un.sun_path);
> >       }
> >   
> > -    unlink(un.sun_path);
> > -    if (bind(sock, (struct sockaddr*) &un, sizeof(un)) < 0) {
> > +    if (abstract_path == NULL) {
> > +        unlink(un.sun_path);
> > +    }
> > +    if (bind(sock, (struct sockaddr *) &un, addrlen) < 0) {
> >           error_set_errno(errp, errno, QERR_SOCKET_BIND_FAILED);
> >           goto err;
> >       }
> > @@ -704,10 +754,12 @@ int unix_listen_opts(QemuOpts *opts, Error **errp)
> >           goto err;
> >       }
> >   
> > +    g_free(abstract_path);
> >       return sock;
> >   
> >   err:
> >       closesocket(sock);
> > +    g_free(abstract_path);
> >       return -1;
> >   }
> >   
> > --
> > 1.7.9.5