Re: [PATCH for-9.1 6/9] block/nbd: Use URI parsing code from glib

["Richard W.M. Jones" <rjones@redhat.com>]

On Mon, Sep 23, 2024 at 06:38:27PM +0200, Daniel P. Berrangé wrote:
> On Mon, Sep 23, 2024 at 11:03:08AM -0500, Eric Blake wrote:
> > On Sun, Sep 22, 2024 at 08:51:22PM GMT, Richard W.M. Jones wrote:
> > > On Thu, Mar 28, 2024 at 02:13:42PM +0000, Richard W.M. Jones wrote:
> > > > On Thu, Mar 28, 2024 at 03:06:03PM +0100, Thomas Huth wrote:
> > > > > Since version 2.66, glib has useful URI parsing functions, too.
> > > > > Use those instead of the QEMU-internal ones to be finally able
> > > > > to get rid of the latter. The g_uri_get_host() also takes care
> > > > > of removing the square brackets from IPv6 addresses, so we can
> > > > > drop that part of the QEMU code now, too.
> > > > > 
> > 
> > > > >  
> > > > > -    p = uri->path ? uri->path : "";
> > > > > +    p = g_uri_get_path(uri) ?: "";
> > > > >      if (p[0] == '/') {
> > > > >          p++;
> > > > >      }
> > 
> > > > Looks ok,
> > > >
> > > > Reviewed-by: Richard W.M. Jones <rjones@redhat.com>
> > > 
> > > Or maybe not.  This caused a regression in the nbdkit test suite (when
> > > we use qemu-img from 9.1).  It seems the exportname part of the NBD
> > > URI gets munged:
> > > 
> > > https://gitlab.com/qemu-project/qemu/-/issues/2584
> > 
> > To be more specific, it looks like
> > g_uri_get_path("./name//with//..//slashes") is getting munged to
> > "name/slashes".  That is, glib is blindly assuming that ./ and XXX/../
> > can be dropped, and // can be simplified to /, which may be true for
> > arbitrary file names but not true for abitrary URIs (since URIs have
> > application-specific semantics, which may not match path name
> > traversal semantics).  Looks like we need to report a bug to glib,
> > and/or see if glib's URI functions have a flag for turning off this
> > unwanted munging.
> 
> The source code indicates it is doing some normalization
> based on this:
> 
>   https://datatracker.ietf.org/doc/html/rfc3986#section-5.2.4

I wrote a bit about this in the bug:

https://gitlab.com/qemu-project/qemu/-/issues/2584#note_2125192404

Rich.

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