Re: [Libcdio-devel] Rock Ridge and libisofs/xorriso 'AL' extension

[Pete Batard]

Hi Thomas,

On 2017.07.25 08:21, Thomas Schmitt wrote:
> AL is my invention.

Without trying to sound passive-aggressive, if you create a Rock Ridge 
extension and produce a relatively popular utility that uses it can you 
at least try to add a mention of it on the relevant Wikipedia page, 
especially after it's been in use for a few years? Considering that you 
are basically trying to establish a new standard, it may help trying not 
to keep it too "hidden" into one's project.

Even if libcdio should not have been choking on 'AL', I must say it took 
me quite while to figure out where exactly that extension came from, as 
the people who made use of it weren't that eager to point me out in the 
right direction [1], and, more annoyingly, Google was no help at all in 
linking 'AL' usage in Rock Ridge with the AAIP proposal.

I have since edited the Wikipedia Rock Ridge page [2] to list 'AL' and 
point to the AAIP documentation. But I think this edit should probably 
have happened a lot sooner. ..

On 2017.07.25 09:36, Thomas Schmitt wrote:
> In this case a preliminary fix could be to add "AL" to the list of
> allowed SUSP+RR entries.

Yeah, that's basically what I did in Rufus, since I want to be able to 
process the Kali ISOs. I guess what we want to do on the default case is 
add a cdio_warn() about using an unsupported Rock Ridge extension, and 
continue instead of erroring out.

I'm attaching a patch proposal for review, which I'll be happy to commit 
to libcdio if everyone agrees. Note that, even though we wouldn't 
technically need to add 'AL' to the case list in this proposal, and let 
the default warn case handle it, what I've seen from testing against the 
Kali ISOs is that this will generate a lot of warnings. So I think we 
probably want to avoid the warning for extensions that we are already 
aware of, even if we don't formally support them in libcdio.

Regards,

/Pete

[1] https://bugs.kali.org/view.php?id=4109
[2] https://en.wikipedia.org/wiki/Rock_Ridge

From e8289ce885e692dbbc64ec57da9bb879ffa7bcc8 Mon Sep 17 00:00:00 2001
From: Pete Batard <address@hidden>
Date: Tue, 25 Jul 2017 10:37:40 +0100
Subject: [PATCH] Warn but don't bail out on unsupported Rock Ridge SUSPs

* This reverts part of the new behaviour from commit 8b96bd3f ("Guard against 
malformed rockridge iso")
  as SUSP 1.12, paragraph 6.3 states that "Any System Use Entry which the 
receiving system does not
  recognize shall be ignored and skipped."
---
 lib/iso9660/rock.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/lib/iso9660/rock.c b/lib/iso9660/rock.c
index 00a22e8..2879fd3 100644
--- a/lib/iso9660/rock.c
+++ b/lib/iso9660/rock.c
@@ -182,10 +182,12 @@ get_rock_ridge_filename(iso9660_dir_t * p_iso9660_dir,
       case SIG('P','L'):
       case SIG('T','F'):
       case SIG('Z','F'):
+      case SIG('A','L'): /* libburnia's AAIP extension */
        break;
       default:
-        /* Something got screwed up here */
-       goto out;
+       /* Warn about unsupported SUSPs */
+       cdio_warn("Unsupported Rock Ridge extension: '%c%c'\n", *chr, *(chr+1));
+       break;
       }
 
       if (rr->len == 0) goto out; /* Something got screwed up here */
-- 
2.9.3.windows.2