Re: netgraph: documentation issue? What kernel options? Where to find?

Am Sun, 16 Jul 2017 16:29:40 -0600
Ian Lepore <ian_at_freebsd.org> schrieb:

> On Sun, 2017-07-16 at 22:48 +0200, O. Hartmann wrote:
> > For a small SoC based system, I use a highly customised static kernel
> > and build the
> > system via NanoBSD with no kernel modules.
> > 
> > Tyring to track down some network issues with recent CURRENT I
> > figured out, that when
> > using the ppp client to connect via modem to the ISP and there is no 
> > 
> > options	NETGRAPH_ETHER
> > options	NETGRAPH_PPPOE
> > 
> > in the kernel configuration, the resulting system fails to establish
> > a ppp session. The
> > man page states, that a netgraph node is established, but as hard as
> > I look, I can not
> > find any(!) information in the man pages what options are
> > necessary/optional to provide
> > the correct module statically.
> > 
> > The same is for many other NETGRAPH_XXX features. Starting from man
> > page "man 4
> > netgraph", section "SEE ALSO", I started tweaking the kernel with
> > NETGRAPH_XXX, i.e.
> > ng_vlan -> NETGRAPH_VLAN until the compiler bails out with an error,
> > for instance
> > ng_car -> NETGRAPH_CAR.
> > 
> > I tried to find out what options cover which netgraph module but
> > there is - right,
> > nothing I can find on a direct route.
> > 
> > Since netgraph isn't so brand new (I guess ~ 2000 from the PDFs I
> > found on the network),
> > there must be some documentation other than "reading the source
> > code".
> > 
> > Please give me some hints where to find the entry point for the
> > appropriate documented
> > options for netgraph modules.
> > 
> > Obviously, some ng_xxx modules are prerequisite for some services to
> > work properly, as
> > ppp - but I can't find any hints for "options NETGRAPH_ETHER" or
> > "options NETGRAPH_PPPOE"
> > in the manpages (looked at ppp, pppoed). 
> > 
> > Thanks in advance,
> > kind regards
> > 
> > Oliver
> >   
> 
> I can't help with anything specific to netgraph or its [lack of] docs.
> 
> For the general question "How do I know what undocumented device or
> option statement to put in my kernel config to get xxxxx" a good place
> to start is /usr/src/sys/conf/NOTES.  It's supposed to contain all the
> options and devices (except some machine/arch-specific stuff).  If you
> don't find it in NOTES, try "grep -i xxxxx *" in that dir, you may find
> the thing you're looking for in 'options' or 'files' and get some clues
> that way.

Yes, correct and I did this, too, but pulling in all of the options resulted in failues,
as far as I know NETGRAPH_CAR bailed out (with -DNO_CLEAN, I must confess).

> 
> For the netgraph stuff, I see that in NOTES it tells you how to find
> the manpages for netgraph things, so I guess I accidentally did answer
> that part too.  :)

No, not exactly,
it doesn't tell me which NETGRAPH_XXX I need for a certain service so I have to do
experiments: starting the service with a full install of all modules and see what modules
gets kloaded and then put the appropriate option into the kernel.

In my situation, using ppp/pppoe failed silently when disabling options NETGRAPH_ETHER,
NETGRAPH_PPPOE and the refering kernel modules weren't present.

Since I fight a problem with VLANs and routing on CURRENT, I'd appreciate a more dense
documentation - or a hint.

> 
> -- Ian


Thank you very much for the patience,

kind regards

Oliver

-- 
O. Hartmann

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