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# IRC, freenode, #hurd, 2012-07-19
<nowhere_man> well, I really actively started last week, so I'm ironing my
various use cases and above all I'm taking my barings in Hurd's code
<nowhere_man> I'm currently reading boot/ and pfinet/
<braunr> sorry for asking but
<braunr> can you describe brielfy what you mean to achieve
<braunr> i know it sounds weird but the project description is a bit vague
for me
<nowhere_man> OK
<nowhere_man> the main goal is to be able to easily spawn a subhurd that's
connected in some way to its host
<braunr> ok
<nowhere_man> mainly connected by network, possibly sharing resources like
FS
<braunr> is it similar in spirit with something like linux containers ?
<nowhere_man> IIRC about them, yes
<braunr> ok
<braunr> that will do for me then
<tschwinge> Yes, so not complete virtualization, but instaed limitied to
several components.
<braunr> lxc with more runtime features to increase/decrease the level of
isolation
<nowhere_man> at first it would be static, at creation time only
<braunr> ok, i clearly understand the proposal now :)
<braunr> what kind of help could you need in the near future ?
<braunr> (except permanent access to youpi's brain?)
<tschwinge> Yes, that's my question, too -- what can we do to "get this
thing going".
<nowhere_man> by monday or tuesday I should be clear on what I understand
or not in the code
<nowhere_man> I'm still a bit up to my elbows in it
<nowhere_man> at that point I'll be happy to be able to pop a lot of
questions about it
<braunr> so you'll be ready for the next meeting
<nowhere_man> yeah
<tschwinge> Please do as soon as there are questions that you cannot
resolve in a reasonably short amount of time.
<tschwinge> So often a quick hint from someone else already helps to ge
un-stuck.
<nowhere_man> OK
<tschwinge> There is no problem with asking for help given this huge and
convoluted code-base, where often design decisions are not obvious, too.
<nowhere_man> I will
<tschwinge> Good. :-)
<antrik> nowhere_man: hm... what you said so far doesn't sound any
different than the work zhengda already did on boot years ago...
<antrik> (although none of it ever got upstream IIRC :-( )
<nowhere_man> antrik: wasn't aware of it, is there some code published?
<tschwinge> There are bits and pieces, but certainly there is enough work
left to be done, to put it all together.
<antrik> yes, his git repository should be up somewhere. it's quite
convoluted though, as he worked on several things, and also wasn't very
experienced with revision control in the beginning
<tschwinge> nowhere_man:
http://www.gnu.org/software/hurd/community/gsoc/2008.html
<tschwinge> nowhere_man: http://www.gnu.org/software/hurd/user/zhengda.html
<tschwinge> Second section of the latter one.
<antrik> well, my understanding of the proposal (and more or less what I
was driving at in the project idea, which is rather vague admittedly) is
something lighter than a real subhurd... rather some kind of thin
subenvironment that doesn't actually boot a complete system instance with
various daemons etc.
<tschwinge> nowhere_man: It is certainly valid for you to use pre-existing
code/patches, by the way.
<antrik> BTW, regarding the "full subhurd" thing, the missing pieces are
mostly virtual device implementations
<antrik> (that and some tough bug(s) remaining in zhengda's modified
boot...)
<nowhere_man> cool, I'll take a look
<antrik> in any case, getting a picture of the work zhengda did is, is
definitely the first thing to do :-)
<tschwinge> nowhere_man: I'll also try to locate some bits and stuff from
his verious repositories (I just fond a Subverision one; will convert to
Git).
<antrik> tschwinge: I'm pretty sure zhengda's git repository was converted
from the SVN one...
<tschwinge> antrik: Thanks for reminding us about this -- I failed to
remember all that.
<antrik> (which was in turn converted from CVS...)
<tschwinge> antrik: OK, will have a lot.
<tschwinge> Yeah, found a CVS tree, too. ;-)
<antrik> BTW, zhengda's work more exactly was about subhurd without root
privileges. but that lays a lot of the groundwork for all kinds of more
flexible subhurd usage
<antrik> (but it's still quite a different thing that thing
subenvironments, so don't get confused...)
<antrik> err... thin subenvironments
# IRC, freenode, #hurd, 2012-07-27
<nowhere_man> bddebian: I'm actually not progressing much while reading the
source, I'm jumping all over the place to grasp the various types and
functions used where I start
<nowhere_man> would there be a few starting points that could help me?
<tschwinge> nowhere_man: So what exactly is your status; what are you
doing, what do you need help with? We surely can provide help, but need
to know where.
<nowhere_man> I'm starting from the source of boot/ and pfinet/ and as soon
as I encounter something that I don't understand, I find its definition
<nowhere_man> I'm kind of doing a depth-first search of what I need to
understand in the source code
<nowhere_man> I'm wondering if there are a few places in the source code
that I should start reading before anything else
<nowhere_man> well, I'll have to go in a few minutes
<nowhere_man> I'll continue my DFS ;-)
# IRC, freenode, #hurd, 2012-08-02
<nowhereman> well, I made a leap forward in understanding the code, when I
stopped my DFS
<nowhereman> in hindsight, I'd say my way of approaching the code was
probably one of the worst possible
<braunr> oh
<tschwinge> OK, so at least you learned something, which is good.
<tschwinge> So, what's the new approach? And what are you working on at
the moment
<tschwinge> ?
<nowhereman> I just remembered SICP, the idea of wishful thinking when you
code, and didn't bother with the fine details behind what I'm reading
<nowhereman> like, I don't really get what happens when a Mach port is
allocated, but I know approximately what a Mach port is
<tschwinge> So originally you worked on investigating all that, every line
of code?
<nowhereman> almost, yeah
<braunr> nowhereman: again, feel free to ask
<tschwinge> Yes indeed -- that's too complex for a single person to tackle
at one time.
<braunr> and quickly
<braunr> don't loose time
<tschwinge> Not even braunr and I have looked up all these things.
(Speaking for Richard here, but I'm quite sure he'll agree. Perhaps he
has in fact looked up all the Mach things, though.)
<tschwinge> nowhereman: ufc?
<nowhereman> BTW, last week I wanted to push my description of how the tool
could be used, the use cases
<nowhereman> ufs
<nowhereman> but flubber is not online
<tschwinge> nowhereman: Oh, why ufs specifically?
<braunr> don't waste time on ufs
<braunr> really
<tschwinge> nowhereman: Yes, flubber is down. But you can push directly to
the Savannah repository.
<tschwinge> nowhereman: Please immediatelly tell us if you're stuck on
something, like flubber not being available.
<tschwinge> We may not be able to help immediatelly, but we're the at least
aware of issues.
<braunr> and we may be able to help immediately :)
<tschwinge> As we're not sitting in a lab next to each other, we can't tell
otherwise what's going on.
<tschwinge> We may in fact even be able to tell you immediatelly to use
Savannah instead of flubber, indeed.
<tschwinge> nowhereman: So, back to ufs -- which you don't specifically
need to look at, I think -- ext2fs is what everyone uses. But even there
you shouldn't really need to know many details/internals.
<nowhereman> OK, I was looking into it has it appears in hurd.boot
<tschwinge> Ah, OK. Yeah, that's just an example/template, and should use
ext2fs nowadays.
<nowhereman> in fact, as far as FS are concerned, I suppose I will merely
need to know how to pass a port to the host's FS to some proxy FS in the
subhurd
<nowhereman> mmmh, Savannah only mentions a hurd.git
<tschwinge> Exactly that is the abstraction level you need, yes.
<nowhereman> I'm looking at http://savannah.gnu.org/git/?group=hurd
<tschwinge> Yeah, that's a known shortcoming -- look here instead:
http://git.savannah.gnu.org/cgit/hurd
<tschwinge> Here is some more up-to-date stuff on subhurds:
http://www.gnu.org/software/hurd/hurd/subhurd.html
<tschwinge> nowhereman: You know how to tell git to add a new remote to
your web pages checkout and such stuff?
<nowhereman> yeah, no problem with that
<braunr> have you prepared any question to ask us ?
<nowhereman> the only I have now is if you can tell me where to look in the
code about passing Mach ports
<braunr> you don't pass ports, you pass rights
<braunr> http://www.gnu.org/software/hurd/gnumach-doc/index.html is the
best location to have a look at
<braunr>
http://www.gnu.org/software/hurd/gnumach-doc/Exchanging-Port-Rights.html#Exchanging-Port-Rights
<braunr> i suppose the mig doc will help too, as you may be using a higher
level interface to exchange rights
<braunr> be careful about user references on port rights
<braunr> deallocate releases a reference, it doesn't immediately destroy a
resource
<braunr> portinfo -v can help monitoring a task's rights
<braunr> nowhereman: so what are you planning to do now ?
<braunr> during the next week
<nowhereman> documenting what I understand from the boot process and where
things can be changed to fit my various use cases
<braunr> do you expect that to take the whole week ?
<nowhereman> and doing some first modifications to servers for the simplest
cases
<braunr> ok
<braunr> well i hope you're able to really start working on it soon, and
won't face weird issues in the meantime
<braunr> i'm a bit disappointed that you don't have more questions
<braunr> my feeling is you either did understand everything (except passing
port rights), or you didn't attempt to seriously understand the code
<braunr> or you don't dare ask questions
<braunr> this is something that must change
<braunr> or these meetings won't be as useful as they could be
<tschwinge> Yes. But also please don't wait for the meetings, but ask
questions throughout the week, too.
# IRC, freenode, #hurd, 2012-08-09
<nowhere_man> hey, does anyone knows the network device interface well?
<nowhere_man> I don't get it by reading net_io.c/h in gnumach
<braunr> nowhere_man: ask your question
<braunr> nowhere_man: http://www.sceen.net/~rbraun/pcap-hurd.c <- this may
help
<nowhere_man> I don't see what the entry point is
<nowhere_man> I finally understood that I actually don't need to touch
pfinet for gsoc project
<nowhere_man> but I should do a replacement network device instead
<nowhere_man> is the net_io_init function called at start?
<braunr> what entry point ?
<braunr> and you should perhaps have a look at the eth-multiplexer by
zhengda
<braunr> yes net_io_init is called at startup
<braunr> nowhere_man: did you find your answers about networking ?
<nowhere_man> no, I'm still digging in mach's code
<braunr> nowhere_man: well keep asking :/
<braunr> you left conversation without notice :/
<braunr> nowhere_man: and why mach ?
<nowhere_man> I thought hardware devices are there
<tschwinge> nowhere_man: You wanted to push your documentation one/two
weeks ago. Why has that not yet happened?
<youpi> nowhere_man: they used to be there, they are now in netdde, but in
both case it's just a matter of the same RPC interface
<nowhere_man> tschwinge: I spent very few time this week on gsoc, and
completely forgot about the push on savannah
<braunr> nowhere_man: i told you to look at the work by zhengda concerning
eth-multiplexer, did you do that ?
<tschwinge> nowhere_man: You realize GSoC is meant to be a full-time job?
<tschwinge> Or, next to full-time?
<braunr> it's full-time normally
<braunr> the payment is justified by that
<youpi> nowhere_man: most RPC operations you need to know about network can
be seen at work in pfinet/ethernet.c, wherever "ether_port" appears
<youpi> i.e. device_open, set_filter, write, set/get_status
<braunr> again, http://www.sceen.net/~rbraun/pcap-hurd.c should guide you
pretty well
<braunr> since it's the very least necessary to use that interface
<tschwinge> nowhere_man: How, roughly but realistically, are your plans to
continue this task?
<tschwinge> nowhere_man: What has been blocking you this week so you
couldn't work on your task?
<nowhere_man> tschwinge: mostly a previous work that was supposed to end at
the beginning of the summer and only went online now, for which I'm
basically sysadmin
<braunr> 21:25 < tschwinge> nowhere_man: How, roughly but realistically,
are your plans to continue this task?
<braunr> this question is really more interesting actually
<nowhere_man> right now, I want to write a netword device that just sends
its frames by IPC
<braunr> why ?
<nowhere_man> as I never wrote any program using Mach's IPC, that seems the
easiest to get them right
<braunr> you won't have time
<braunr> 21:22 < braunr> nowhere_man: i told you to look at the work by
zhengda concerning eth-multiplexer, did you do that ?
<nowhere_man> braunr: not yet, no
<braunr> well that's your best chance to make some progress
<nowhere_man> braunr: is writing the virtal network device that hard?
<braunr> basically, it allows "bridgind" the pfinet instances of various
subhurds
<braunr> the virtual network device you want *is* eth-multiplexer
<tschwinge> nowhere_man: GSoC is nearly over. That's why I'm asking how
this task is going to continue. I'm sorry but I reckon you have not
spend anywhere near the amount of hours that are meant to be spent on it.
<braunr> and from what antrik told me, yes it's hard, and moreover, why
rewrite it if it already exists and you're late
<braunr> i agree
<nowhere_man> tschwinge: I know, I've started way too late because of my
second round of exams
<tschwinge> nowhere_man: OK, that's how you started. But how is it going
to continue...
<nowhere_man> tschwinge: in short, I write a prototype that just starts a
subhurd, and when that works correctly I add the network
<tschwinge> nowhere_man: I mean from an organizational point of view.
<nowhere_man> well, between now and the beginning of september, I'll work
full-time on this
<nowhere_man> up until september 8th
# IRC, freenode, #hurd, 2012-08-09
<antrik> nowhere_man: you do *not* have to do a replacement network
device. zhengda did that years ago.
<antrik> nowhere_man: also note that zhengda also implemented the support
for *using* the virtual network device (in fact any replacement devices
-- except that no others actually exist yet) in boot
<youpi> which is already in, actually, isn't it?
<antrik> youpi: hm, yes... it was the patch that zhengda posted on the list
once, but later updated, and at some later point you merged the outdated
variant from the list...
<youpi> outdated?
<youpi> ah, but he never posted the updated one, and it got lost in git
repos, right?
<youpi> (what was updated actually?)
<antrik> he changed the option name and description later for more
clarity. don't remember whether there were other changes
<antrik> -f, --device=device_name=device_file
<antrik> Specify a device file used by subhurd
and its
<antrik> virtual name.
<antrik> that's the one from the Debian package
<antrik> -m, --device-map=DEBICENAME=DEVICEFILE
<antrik> Map the device in subhurd to the
device in the
<antrik> main Hurd.
<antrik> that's the one I have locally built from his tree
<youpi> so you actually have access to his tree?
<antrik> uhm... I used to... it was on flubber
# IRC, freenode, #hurd, 2012-08-18
<nowhere_man> so, this week I discovered how fun it is to work on a
non-mainstream OS
<nowhere_man> I hoped to start coding the tool itself, put together the
skeleton, but every Lisp implementation I tried had problems
<braunr> ah you want to write it in lisp ?
<nowhere_man> ECL, that I had ported a few years ago, actually FTBFS since
<nowhere_man> I hoped to be able, it would be easier for me
<nowhere_man> and when I tried Scheme, I started with Guile (it's GNU's own
Scheme implementation, after all)
<nowhere_man> and when I execute the FFI functions, to access functions in
libmachdec
<nowhere_man> I get SIGILL
<braunr> i can't advise you about anything lisp related
<braunr> the most reliable thing you'll find on the hurd is C
<nowhere_man> I tried to debug that, but running Guile in GDB gets me a
SIGSEV
<nowhere_man> I'll try to make ECL to build again
<braunr> this seems like a waste of time to me
<braunr> avoid spending time on anything that isn't directly related to
your goal if you still hope to finish it
<nowhere_man> I'm ten times more comfortable coding in Lisp
<braunr> it doesn't matter, you're late
<nowhere_man> yeah, I know, so taking the time to correct that problem
won't change the fact that I won't finish in time
<nowhere_man> so I'll finish anyway, and in Lisp
<braunr> and if you lack something else, like some mach/hurd specific lisp
bindings, you'll have to spend more time on that
<braunr> ok
<nowhere_man> do you know if someone had a SIGILL situation on Hurd in the
past?
<nowhere_man> I'm wondering if that's a known kind of issue
<braunr> there are lots of issues
<braunr> especially when it comes to other languages and runtime
environments
<nowhere_man> but is it like MAX_PATH_LEN, something that is known to
happen when porting something on Hurd?
<braunr> i'm not sure how comparable it is
<braunr> i'd say it's often before of the conformance issues of the hurd
<braunr> because*
<nowhere_man> like missing bits of POSIX ?
<braunr> or simple wrong for some corner cases
<braunr> simply*
<bubu^> nowhere_man, I was able to run guile on my hurd image through qemu
<bubu^> but I didn't make any complexe programms to check if everything
works fine
<nowhere_man> yeah, it runs fine
<nowhere_man> FFI functions get you a SIGILL
<nowhere_man>
http://www.gnu.org/software/guile/manual/html_node/Dynamic-FFI.html
<nowhere_man> the define-module form at the beginning triggers the signal
<antrik> nowhere_man: what do you want to implement in Lisp?
<antrik> BTW, the guy working on Lisp bindings a couple of years ago used
Clisp
<antrik> it was working back then
<nowhere_man> antrik: the program that sets up a subhurd
<nowhere_man> I always forget about clisp, I'll try it right away