Re: Some issues in examples/udhcp/simple.script
On Thu, 5 Sep 2019, Rolf Eike Beer wrote: > > Busybox ash: > > # command ip > -sh: command: not found > # ip a > 1: lo: mtu 65536 qdisc noqueue qlen 1000 > link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00 You're probably missing: CONFIG_ASH_CMDCMD=y in your .config. Cheers, -- Cristian ___ busybox mailing list busybox@busybox.net http://lists.busybox.net/mailman/listinfo/busybox
Re: Some issues in examples/udhcp/simple.script
Am Donnerstag, 5. September 2019, 14:57:15 CEST schrieb Denys Vlasenko:
> On Wed, Aug 14, 2019 at 9:50 AM Rolf Eike Beer wrote:
> > Hi all,
> >
> > I have discovered some problems with examples/udhcp/simple.script. I know,
> > it's an example, and a simplified one. Most people will still just use it
> > because it works, so I would like to point out at least some things.
> >
> > First, it does not really use ip. At least not if "command" does not
> > exist.
>
> "command" is a mandatory shell builtin.
>
> https://pubs.opengroup.org/onlinepubs/9699919799/utilities/command.html
>
> https://pubs.opengroup.org/onlinepubs/9699919799/utilities/V3_chap02.html
> section "Command Search and Execution" specifically mentions it.
>
> The reason for this mention is that its function
> can not reasonably be implemented as a separate external tool,
> since external tools don't know what functions are defined
> in current shell's invocation, thus "command FUNCNAME"
> won't work.
>
> Since it's an internal builtin, using it should be a fastest way to test
> whether "ip" can be executed, without assuming a path
> ("test -x /usr/bin/ip") or forking a possibly external tool
> ("which ip").
>
> Which shell do you use so that you don't have "command"?
Busybox ash:
# command ip
-sh: command: not found
# ip a
1: lo: mtu 65536 qdisc noqueue qlen 1000
link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
…
> > The difference between both cases is: ifconfig brings up the interface, ip
> > with this command does not. So if you are using ip this will just send
> > DHCP
> > request to a network interface that has link down, which will not get you
> > anywhere.
>
> Yes, this is different. How about:
>
> echo "Clearing IP addresses on $interface, upping it"
> if command -v ip >/dev/null; then
> ip addr flush dev $interface
> ip link set dev $interface up
> else
> ifconfig $interface 0.0.0.0
> fi
Which is basically what I'm using now, just different order of commands.
Thanks,
Eike
--
Rolf Eike Beer, emlix GmbH, http://www.emlix.com
Fon +49 551 30664-0, Fax +49 551 30664-11
Gothaer Platz 3, 37083 Göttingen, Germany
Sitz der Gesellschaft: Göttingen, Amtsgericht Göttingen HR B 3160
Geschäftsführung: Heike Jordan, Dr. Uwe Kracke – Ust-IdNr.: DE 205 198 055
emlix - smart embedded open source
signature.asc
Description: This is a digitally signed message part.
___
busybox mailing list
busybox@busybox.net
http://lists.busybox.net/mailman/listinfo/busybox
Re: Some issues in examples/udhcp/simple.script
On Wed, Aug 14, 2019 at 9:50 AM Rolf Eike Beer wrote:
> Hi all,
>
> I have discovered some problems with examples/udhcp/simple.script. I know,
> it's an example, and a simplified one. Most people will still just use it
> because it works, so I would like to point out at least some things.
>
> First, it does not really use ip. At least not if "command" does not exist.
"command" is a mandatory shell builtin.
https://pubs.opengroup.org/onlinepubs/9699919799/utilities/command.html
https://pubs.opengroup.org/onlinepubs/9699919799/utilities/V3_chap02.html
section "Command Search and Execution" specifically mentions it.
The reason for this mention is that its function
can not reasonably be implemented as a separate external tool,
since external tools don't know what functions are defined
in current shell's invocation, thus "command FUNCNAME"
won't work.
Since it's an internal builtin, using it should be a fastest way to test
whether "ip" can be executed, without assuming a path
("test -x /usr/bin/ip") or forking a possibly external tool
("which ip").
Which shell do you use so that you don't have "command"?
> Fair enough, I know I have ip, so I just deleted the checks and the ifconfig
> lines.
>
> This makes it do nothing. As I found out the culprit is this:
>
> if command -v ip >/dev/null; then
> ip addr flush dev $interface
> else
> ifconfig $interface 0.0.0.0
> fi
>
> The difference between both cases is: ifconfig brings up the interface, ip
> with this command does not. So if you are using ip this will just send DHCP
> request to a network interface that has link down, which will not get you
> anywhere.
Yes, this is different. How about:
echo "Clearing IP addresses on $interface, upping it"
if command -v ip >/dev/null; then
ip addr flush dev $interface
ip link set dev $interface up
else
ifconfig $interface 0.0.0.0
fi
___
busybox mailing list
busybox@busybox.net
http://lists.busybox.net/mailman/listinfo/busybox
Some issues in examples/udhcp/simple.script
Hi all, I have discovered some problems with examples/udhcp/simple.script. I know, it's an example, and a simplified one. Most people will still just use it because it works, so I would like to point out at least some things. First, it does not really use ip. At least not if "command" does not exist. Fair enough, I know I have ip, so I just deleted the checks and the ifconfig lines. This makes it do nothing. As I found out the culprit is this: if command -v ip >/dev/null; then ip addr flush dev $interface else ifconfig $interface 0.0.0.0 fi The difference between both cases is: ifconfig brings up the interface, ip with this command does not. So if you are using ip this will just send DHCP request to a network interface that has link down, which will not get you anywhere. Greetings, Eike -- Rolf Eike Beer, emlix GmbH, http://www.emlix.com Fon +49 551 30664-0, Fax +49 551 30664-11 Gothaer Platz 3, 37083 Göttingen, Germany Sitz der Gesellschaft: Göttingen, Amtsgericht Göttingen HR B 3160 Geschäftsführung: Heike Jordan, Dr. Uwe Kracke – Ust-IdNr.: DE 205 198 055 emlix - smart embedded open source signature.asc Description: This is a digitally signed message part. ___ busybox mailing list busybox@busybox.net http://lists.busybox.net/mailman/listinfo/busybox
