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how to wait on network

I am setting up armtix runit on a rpi4; since the board has no rtc I have installed ntp and that works OK. I have a run that looks like

Code: [Select]
# cat /etc/runit/sv/ntpd/run
#!/bin/sh
ntpd -g -q	#run once and quit
exec ntpd -g -u ntp:ntp -n >/dev/null 2>&1

and this works, but leaves messages about not being able to connect.  I guess I need to wait on the network, but I'm not sure how to do that. Currently the network is setup OK using dhcpcd so  I could use

sv check dhcpcd >/dev/null || exit 1

but that will fail if I switch to another network setup. Are there more general ways to wait on the network?

Re: how to wait on network

Reply #1 –
I used this script
Code: [Select]
$ cat /bin/have-net
#/bin/sh
for d in /sys/class/net/*;do
	[ `basename $d` = lo ] && continue
	[ "`cat $d/operstate`" = "up" ] && echo "connected" && exit 0
done
echo "disconnected"
exit 1

and /bin/have-net > /dev/null || exit 1 in the scripts that need to wait on the network

Re: how to wait on network

Reply #2 –
That's a pretty clever idea. runit and s6 could definitely use a script like that. Thanks!

Re: how to wait on network

Reply #3 –
Quote from: Dudemanguy on
That's a pretty clever idea. runit and s6 could definitely use a script like that. Thanks!
I cannot claim too much credit. I think the idea of using /sys/class/net/eth0/operstate came from stack overflow. I just added the loop and this script is probably not robust enough against devices without operstate etc etc.
Also it's not obvious which  devices actually connect to the outside;


Re: how to wait on network

Reply #4 –
Quote from: replabrobin on
Also it's not obvious which  devices actually connect to the outside;
I have personal script for similar purpose, this is how i find actual interface inside it:
Code: [Select]
DEFAULT_ROUTE=
DEFAULT_ROUTE_IFACE=
while [ -z $DEFAULT_ROUTE -o -z $DEFAULT_ROUTE_IFACE ]; do
    DEFAULT_ROUTE=$(ip route|grep default|awk '{print $3}')
    DEFAULT_ROUTE_IFACE=$(ip route|grep default|awk '{print $5}')
    sleep 1
 done
ARMtix

Re: how to wait on network

Reply #5 –
So in the context of the runit loop that would just be

Code: [Select]
#/bin/sh
[ "`ip route|grep default|awk '{print ($3!="")+($5!="")}'`" = "2" ] && echo "connected" && exit 0
echo "disconnected"
exit 1

Re: how to wait on network

Reply #6 –
Depending on your actual need you can simplify regex. The part of script i've posted defines which interface to check. In my case its gateway address is obtained to periodically ping gateway later and check if connection is present (but sometimes it still fails). If you're only interested to check network on boot, just checking if default route is present could be enough
ARMtix
 

Re: how to wait on network

Reply #7 –
In the end following phoenix_king_rus' suggestion I made the have-net script look like

Code: [Select]
#/bin/sh
if [ -x /usr/bin/ip -a -x /usr/bin/awk ]; then
	[ "`ip route|awk '/^default/{print ($3!="")+($5!="")}'`" = "2" ] && echo "connected" && exit 0
else
	for d in /sys/class/net/*;do
		[ `basename $d` = lo ] && continue
		[ "`cat $d/operstate`" = "up" ] && echo "connected" && exit 0
	done
fi
echo "disconnected"
exit 1

Re: how to wait on network

Reply #8 –
If you don't mind, I can include it on our runit scripts that require network (instead of running separate bin) and give proper credits. I'm sure the ip route and awk is enough (although the shell for loop is actually neat) since Artix has iproute2 and awk in base anyway.

Thanks!
the runit guy on artix