variables in loader(8) and other libstand applications.
Sometimes a dhcp server provides incorrect information along with the IP
address. It would be useful to have a way to override this with
locally-supplied information, such as command line parameters passed from a
prior-stage bootloader. This change allows pre-existing env vars to take
precedence over values delivered by the dhcp or bootp server.
The bootp/dhcp code in libstand automatically creates environment variables
from the data provided by the server (dhcp.root-path, dhcp.domain-name,
etc). It also transcribes the values to some global variables such as
'rootpath' and 'hostname'.
This change does two things:
When adding dhcp.* vars to the environment, don't replace existing
vars/values.
When setting the global vars rootpath and hostname, use the
dhcp.root-path and dhcp.host-name env var values if they exist.
This allows the platform-specific part of loader(8) to obtain override
values in some platform-specific way and store them in the environment
before opening the network device. The set of values that can be overriden
is currently limited to just string options. The values that are delivered
as binary data are things that probably shouldn't be overridden (IP,
netmask, gateway, etc).
The original patch this evolved from was submitted by martymac@
PR: 202098
Differential Revision: https://reviews.freebsd.org/D4559
The index() and rindex() functions were marked LEGACY in the 2001
revision of POSIX and were subsequently removed from the 2008 revision.
The strchr() and strrchr() functions are part of the C standard.
This makes the source code a lot more consistent, as most of these C
files also call into other str*() routines. In fact, about a dozen
already perform strchr() calls.
revised/modified by me) to store dhcp options into kenv variables,
so the information is available to the boot loader and can be used
to customize the boot process.
The change is totally unintrusive, essentially made of a single
function to be called while parsing a dhcp response, and a couple
of tables to classify options. The values extracted from dhcp
options are stored in the kenv environment in one of these forms:
+ options whose name and type is known are saved as
dhcp.name = value (string, or number/ip addresses lists)
+ unknown options are assumed to be strings and saved as
dhcp.option-NNN = "value"
+ options listed as '__INDIR' and sent on the wire as e.g.
option unknown-252 "some.name=the actual value"
are saved as
some.name = "the actual value"
+ options listed as '__ILIST' and sent on the wire as e.g.
option unknown-249 "a.b=foo bar; c.d= 123; e.f=done"
are saved as multiple values
a.b="foo bar"
c.d="123"
e.f="done"
As you can see there is quite a bit of flexibility on what can
be passed to the loader or the kernel.
For the time being the vendor-specific table is mostly disabled,
because there is no standard set of options for FreeBSD, and I don't
know all the pxe-specific vendor options.
Also, applications using libstand may live in memory-constrained
environments, so it makes sense to keep these tables as small as
possible, especially considering that one can generate arbitrary
name=value pairs using site-specific options of type __INDIR or
__ILIST (there are 4 __ILIST and 5 __INDIR in the table, numbered
246..249 and 250..254).
Actually, considering that probably 75% of the standard dhcp options
are totally useless, it might make sense to remove them as well.
Submitted by: Danny Braniss
MFC after: 4 weeks
identifier to the DHCP server. Now you can check for this string
in your dhcp configuration to decide whether you will hand out a
lease to the client or not.
