[syslinux] PXERETRY directive

[Ady]

> 
> > On Thu, Apr 21, 2016 at 10:30 PM, Ady via Syslinux <syslinux at zytor.com> wrote:
> > > Would someone please be so kind to explain / describe the PXERETRY
> > > directive?
> > 
> > $ git grep -ni pxeretry
> > com32/elflink/ldlinux/readconfig.c:1305:    else if (looking_at(p, "pxeretry"))
> > com32/elflink/ldlinux/readconfig.c:1306:        PXERetry =
> > atoi(skipspace(p + 8));
> > 
> > core/fs/pxe/pxe.c:275:    int i = PXERetry;
> > 
> > 
> > It's used in pxe_searchdir() to affect how many times it retries to
> > open a file and added in commit 4f989f247 for 4.03.
> > 
> > -- 
> > -Gene
>  
> If possible, I would appreciate some additional information, perhaps 
> aimed at common users?
> 
> Some of the following questions might sound strange to some readers, 
> but I have found no information nor examples (nor experiences by 
> others), at all, that could help describe the behavior for a common 
> user.
> 
> Some of the questions that come to mind...
> 
> _ Does it affect the initial configuration file (e.g., 
> "pxelinux.cfg/default")? At first sight, this question might seem to 
> have no sense, considering that the configuration file needs to be 
> found and be parsed first, before being able to act according to the 
> PXERETRY directive in it. But, as a common user, I am not sure whether 
> there could be some situation in which the / a configuration file is 
> re-read and/or re-parsed -- the CONFIG directive, the INCLUDE 
> directive, and the config.c32 module perhaps could be relevant for this 
> question.
> 
> _ Does it affect every single file? For instance, if the user tries to 
> execute a c32 module, does PXERETRY affect the command? And what about 
> kernel / initrd file(s)? What happens when using pxechn.c32 or when 
> loading a different network bootloader / NBP (for instance, with the 
> PXE directive)?
> 
> _ Does it have any effect when using (vesa)menu.c32? Could it (perhaps 
> unintentionally) affect the presentation of the boot menu itself (e.g. 
> by loading the menu on screen several times, according to the PXERETRY 
> value)?
> 
> _ Is the PXERETRY directive "sticky" (similarly to the SERIAL 
> directive)? Can it be reset or changed by loading a different 
> configuration file? Or perhaps, is it reset automatically after any 
> particular situation / action / behavior?
> 
> _ Is there a valid range of values? Are non-decimal values accepted?
> 
> _ Would I be correct by assuming this is a global directive?
> 
> _ Is it valid for pxelinux.0 only? What about lpxelinux.0? What about 
> syslinux.efi? Others?
> 
> _ Could someone please describe a usage case for this directive? Why 
> might it be needed? What for? In which circumstances? Which behavior 
> (or log's content) would trigger the need / desire for this directive? 
> Which advantage or positive consequence(s) would it provide?
> 
> 
> I wish I would have the means to actually test all these cases by 
> myself, instead of asking here.
> 
> I hope these questions might also trigger the curiosity of others to 
> test and report back, considering that this directive is not very 
> well-known.
> 
> I also hope the potential replies / answers would help users to find 
> this email thread as (initial) documentation for this PXERETRY 
> directive, considering that it is not documented anywhere else (or at 
> least, I couldn't find it).
> 
> TIA,
> Ady.
>  
Anyone?