Syslinux - Jun 2013 - [5.10] PXE + dhcp opts 209, 210 and path issues in tftp/http

On 06/07/2013 03:34 PM, Ady wrote:
> 
> If I may...
> 
> Most Linux distros are not using 5.xx yet. From the point of view of 
> the final user, there are still few new features in 5.xx in 
> comparison with 4.xx. Before this issue affects more users, and 
> perhaps even turning into more difficult maintenance and patches, it 
> may be better to suffer a relatively "small" break now than
later,
> when more users and more distros might adopt newer versions (6.xx).
> 
> I would guess that even those (relatively few) users already using 
> 5.xx would rather correct a couple of cfg files (if they are using 
> the PATH directive with multiple paths), instead of potentially 
> having more serious issues in the future (or making maintenance more 
> difficult because of strange needed patches).
> 
> I would also guess that those users that are using 5.xx with multiple 
> paths listed in the PATH directive are probably following the 
> development closely enough.
> 
> IMHO, this seems to be a case where there is no "clean" solution;
> rather "suffer" from a break now (by choosing a different 
> path-separator for the PATH directive), or it might generate much 
> more problems in the future. Well, at least this is my (very humble) 
> impression. Not being a developer myself, I could be completely and 
> absolutely wrong about it.
> 
The only other alternative I can think of is to allow quoted strings in
PATH.  Backslash-escapes are not really usable as some OSes use them and
TFTP needs to use the host filename syntax, but quotes are very rare in
filenames and probably wouldn't cause too much trouble.

	-hpa

On Jun 8, 2013 11:48 AM, "H. Peter Anvin" <hpa at zytor.com>
wrote:
>
> On 06/07/2013 03:34 PM, Ady wrote:
> >
> > If I may...
> >
> > Most Linux distros are not using 5.xx yet. From the point of view of
> > the final user, there are still few new features in 5.xx in
> > comparison with 4.xx. Before this issue affects more users, and
> > perhaps even turning into more difficult maintenance and patches, it
> > may be better to suffer a relatively "small" break now than
later,
> > when more users and more distros might adopt newer versions (6.xx).
> >
> > I would guess that even those (relatively few) users already using
> > 5.xx would rather correct a couple of cfg files (if they are using
> > the PATH directive with multiple paths), instead of potentially
> > having more serious issues in the future (or making maintenance more
> > difficult because of strange needed patches).
> >
> > I would also guess that those users that are using 5.xx with multiple
> > paths listed in the PATH directive are probably following the
> > development closely enough.
> >
> > IMHO, this seems to be a case where there is no "clean"
solution;
> > rather "suffer" from a break now (by choosing a different
> > path-separator for the PATH directive), or it might generate much
> > more problems in the future. Well, at least this is my (very humble)
> > impression. Not being a developer myself, I could be completely and
> > absolutely wrong about it.
> >
>
> The only other alternative I can think of is to allow quoted strings in
> PATH.  Backslash-escapes are not really usable as some OSes use them and
> TFTP needs to use the host filename syntax, but quotes are very rare in
> filenames and probably wouldn't cause too much trouble.
To minimize impact and convey the extent of the change, perhaps change to
';' immediately and make another release, probably 5.20 and this week.

--Gene

> To minimize impact and convey the extent of the change, perhaps change to
> ';' immediately and make another release, probably 5.20 and this
week.
> 
> --Gene
I would hope that using ";" as path separator in the PATH directive 
would not be a problem for ISO9660 fs and ISOLINUX, where the ";" is 
used in the standard specification to indicate the 'Version Number' 
of files (";1"). In practice, this Version Number is not always used, 
yet it is still part of the standard.

Additionally, ";" is still a valid character for directory names in 
several fs.

My apologies if this is not at all a concern and thus not relevant. 
I'd rather just mention it now in case it happens to be relevant, 
than to see a new potential conflict with a new possible 
path-separator.

Best Regards,
Ady.

On Sat, 08 Jun, at 11:57:34AM, Gene Cumm wrote:
> To minimize impact and convey the extent of the change, perhaps change to
> ';' immediately and make another release, probably 5.20 and this
week.
 
This chunk of ftp_readdir() caught my eye,

		} else if ((p = strchr(buf, ';'))) {
		    /* VMS/Multinet format */
		    if (p > buf+4 && !memcmp(p-4, ".DIR", 4)) {
			type = 'd';
			p -= 4;
		    } else {
			type = 'f';
		    }
		    *p = '\0';
		    name = buf;

Now, I admit to knowing absolutely nothing about VMS pathnames, so is it
possible that someone may want to specify an ftp path that includes a
semi-colon in their PATH directive?

-- 
Matt Fleming, Intel Open Source Technology Center