where do I find the NTP server address with 'dhcpc -O ntpsrv'

[Lambrecht Jürgen]

Hello,

The NTP server ip is distributed via DHCP in my case.
So I want to do 'ntpd -p $NTP_SERVER'.
But that variable $NTP_SERVER is empty, and also /etc/ntp.conf does not
exist.

Does anybody know where to find the NTP server's IP address received
with 'dhcpc -O ntpsrc' ?

Regards,
J?rgen

P.S.: when I try to search the mailing list on busybox.net, google gives
an error that the site may be sending spam..

[Laurent Bercot]

Post by Lambrecht Jürgen
The NTP server ip is distributed via DHCP in my case.
So I want to do 'ntpd -p $NTP_SERVER'.
But that variable $NTP_SERVER is empty, and also /etc/ntp.conf does not
exist.
Does anybody know where to find the NTP server's IP address received
with 'dhcpc -O ntpsrc' ?

If I understand the udhcpc.c code correctly, result of unknown options
listed with "-O foobar" are put into the environment via the line
ofs = sprintf(*curr, "opt%u=", i);

So if you start your client with "udhcpc -O ntpsrv", if my guess is
correct, you should get the NTP server address in the "opt0" environment
variable.

[Lambrecht Jürgen]

Post by Laurent Bercot

Post by Lambrecht Jürgen
The NTP server ip is distributed via DHCP in my case.
So I want to do 'ntpd -p $NTP_SERVER'.
But that variable $NTP_SERVER is empty, and also /etc/ntp.conf does not
exist.
Does anybody know where to find the NTP server's IP address received
with 'dhcpc -O ntpsrc' ?

If I understand the udhcpc.c code correctly, result of unknown options
listed with "-O foobar" are put into the environment via the line
ofs = sprintf(*curr, "opt%u=", i);
So if you start your client with "udhcpc -O ntpsrv", if my guess is
correct, you should get the NTP server address in the "opt0" environment
variable.

...

thanks for the hint, but 'env | grep -i opt' gives nothing.
I must say, the dhcp server sends out the ntp server IP address by
default, so it is not necessary to ask.
With wireshark, I see the DHCP offer, and it contains the NTP server IP
address.

J?rgen

Post by Laurent Bercot
--
Laurent

[Lambrecht Jürgen]

Post by Laurent Bercot

Post by Lambrecht Jürgen
The NTP server ip is distributed via DHCP in my case.
So I want to do 'ntpd -p $NTP_SERVER'.
But that variable $NTP_SERVER is empty, and also /etc/ntp.conf does not
exist.
Does anybody know where to find the NTP server's IP address received
with 'dhcpc -O ntpsrc' ?

If I understand the udhcpc.c code correctly, result of unknown options
listed with "-O foobar" are put into the environment via the line
ofs = sprintf(*curr, "opt%u=", i);
So if you start your client with "udhcpc -O ntpsrv", if my guess is
correct, you should get the NTP server address in the "opt0" environment
variable.

...

Indeed, but there are bugs in the code.
For the 256 options, only 32 bits are allocated, and 1<<42 assignments
to an unsigned happen..
I fixed the bugs, and will try today if it works.

J?rgen

Post by Laurent Bercot
--
Laurent

[Denys Vlasenko]

Post by Laurent Bercot

Post by Lambrecht Jürgen
The NTP server ip is distributed via DHCP in my case.
So I want to do 'ntpd -p $NTP_SERVER'.
But that variable $NTP_SERVER is empty, and also /etc/ntp.conf does not
exist.
Does anybody know where to find the NTP server's IP address received
with 'dhcpc -O ntpsrc' ?

I suppose you meant "ntpsrv".

Post by Laurent Bercot
If I understand the udhcpc.c code correctly, result of unknown options
listed with "-O foobar" are put into the environment via the line
ofs = sprintf(*curr, "opt%u=", i);

But ntpsrv is a *known* option, therefore it is exported as $ntpsrv
environment variable to the udhcpc script, a-la

ntpsrv='10.4.2.125 10.4.5.7'

See examples/var_service/dhcp_if/* for an example.

[Lambrecht Jürgen]

Post by Lambrecht Jürgen

Post by Laurent Bercot

Post by Lambrecht Jürgen
The NTP server ip is distributed via DHCP in my case.
So I want to do 'ntpd -p $NTP_SERVER'.
But that variable $NTP_SERVER is empty, and also /etc/ntp.conf

does not

Post by Laurent Bercot

Post by Lambrecht Jürgen
exist.
Does anybody know where to find the NTP server's IP address received
with 'dhcpc -O ntpsrc' ?

I suppose you meant "ntpsrv".

indeed

Post by Lambrecht Jürgen

Post by Laurent Bercot
If I understand the udhcpc.c code correctly, result of unknown options
listed with "-O foobar" are put into the environment via the line
ofs = sprintf(*curr, "opt%u=", i);

But ntpsrv is a *known* option, therefore it is exported as $ntpsrv

indeed, found that out in the mean time..

Post by Lambrecht Jürgen
environment variable to the udhcpc script, a-la

indeed, "to the udhcpc script", and not to the shell environment
variables as I thought wrongly
(http://stackoverflow.com/questions/6981033/why-setenv-does-not-work)

Post by Lambrecht Jürgen
ntpsrv='10.4.2.125 10.4.5.7'
See examples/var_service/dhcp_if/* for an example.

ok, I will check this. Thanks. I thought that the "putenv(..)" code was
useless, and should be removed from dhcpc.c.

Regards,
J?rgen

Post by Lambrecht Jürgen
--
vda

[Lambrecht Jürgen]

Post by Lambrecht Jürgen

Post by Lambrecht Jürgen

Post by Laurent Bercot

Post by Lambrecht Jürgen
The NTP server ip is distributed via DHCP in my case.
So I want to do 'ntpd -p $NTP_SERVER'.
But that variable $NTP_SERVER is empty, and also /etc/ntp.conf

does not

Post by Laurent Bercot

Post by Lambrecht Jürgen
exist.
Does anybody know where to find the NTP server's IP address received
with 'dhcpc -O ntpsrc' ?

I suppose you meant "ntpsrv".

indeed

Post by Lambrecht Jürgen

Post by Laurent Bercot
If I understand the udhcpc.c code correctly, result of unknown

options

Post by Lambrecht Jürgen

Post by Laurent Bercot
listed with "-O foobar" are put into the environment via the line
ofs = sprintf(*curr, "opt%u=", i);

But ntpsrv is a *known* option, therefore it is exported as $ntpsrv

indeed, found that out in the mean time..

Post by Lambrecht Jürgen
environment variable to the udhcpc script, a-la

indeed, "to the udhcpc script", and not to the shell environment
variables as I thought wrongly
(http://stackoverflow.com/questions/6981033/why-setenv-does-not-work)

Post by Lambrecht Jürgen
ntpsrv='10.4.2.125 10.4.5.7'
See examples/var_service/dhcp_if/* for an example.

ok, I will check this. Thanks. I thought that the "putenv(..)" code was
useless, and should be removed from dhcpc.c.

...

In busybox config for dhcp client, you can specify a script, and I
copied the default script and added 'ntpd -P $ntpsrv'.
Thanks,
J?rgen

Post by Lambrecht Jürgen
Regards,
J?rgen

Post by Lambrecht Jürgen
--
vda

--
J?rgen Lambrecht
R&D Associate
Tel: [phone] Fax: [phone]
http://www.televic-rail.com
Televic Rail NV - Leo Bekaertlaan 1 - 8870 Izegem - Belgium
Company number 0825.539.581 - RPR Kortrijk
_______________________________________________
busybox mailing list
busybox at busybox.net
http://lists.busybox.net/mailman/listinfo/busybox