dhcpcd-discuss

Hi, Jeremy. I had the same problem except it worked with 6.11.5 until I 
did apt-get upgrade and THEN it started to fail, still with 6.11.5. I 
never did figure out what changed to break it.

What I did to resolve the issue is a workaround on a later version so I 
had RPi 3 B+ support. I went back to the /etc/network/interfaces 
configuration method and turned off dhcpcd. My GUESS is that dhcpcd is 
"waiting for carrier" because when I send it "dhcpcd -n wwan0" it again 
says "waiting for carrier" but the "interfaces" method SEEMS to just 
look for something else and its dhcp does the job, looking at the 
interface every 5 minutes and completes the dhcp so that ifconfig wwan0 
shows the correct stuff that modem manager logged when the modem was 
connected. From then on, everything works great. Also, I can issue a 
command and make it happen without waiting for the 5 minutes.

I've just come to this conclusion and NEVER asked Roy about it since we 
exchanged messages early last month, so he's not had a chance before to 
comment on my Wild A** Guess.

I'm in the North Woods(tm) planting 1,000 pine trees and can't access 
the "whatIdid" file on that particular RPi from here since it's powered 
down, so I can't give you specifics of my configuration files or the 
commands that I use to speed things up. They do work on my latest 
Raspbian copy that started with a 2018-04-18-raspbian-stretch download. 
I'll be home this weekend and if Roy hasn't helped by then I'll send you 
what works for me.

On 5/23/2018 7:05 PM, Jeremy K wrote:
> I'm running Raspbian on the Raspberry Pi and have been encountering DHCP 
> issues with my USB 3G modem.
>
> The previous discussion for this issue is here 
> https://github.com/raspberrypi/linux/issues/2544, but to summarise, 
> dhcpcd 6.10.1 works as expected, but dhcpcd 6.11.5 does not.
>
> The modem driver (sierra_net) exposes a wwan0 interface, and on dhcpcd 
> 6.10.1, the interface successfully gets the IPv4 address and the 
> interface works as expected.
>
> Using dhcpcd 6.11.5, the wwan0 interface does not get an IP address, so 
> I can't use it. If I downgrade back to 6.10.1, then the interface gets 
> the IP address and starts working again.
>
> Here is the syslog snippet using 6.10.1 (good)
>
> |Sep 7 15:54:40 raspberrypi dhcpcd[250]: wwan0: waiting for carrier Sep 7 
> 15:54:40 raspberrypi kernel: [ 21.042350] IPv6: ADDRCONF(NETDEV_UP): 
> wwan0: link is not ready Sep 7 15:54:41 raspberrypi systemd[1]: Started 
> Raise network interfaces. Sep 7 15:54:42 raspberrypi kernel: [ 
> 22.660424] IPv6: ADDRCONF(NETDEV_CHANGE): wwan0: link becomes ready Sep 
> 7 15:54:42 raspberrypi dhcpcd[250]: wwan0: carrier acquired Sep 7 
> 15:54:42 raspberrypi dhcpcd[250]: wwan0: adding address 
> fe80::1e09:995:5f42:fa48 Sep 7 15:54:43 raspberrypi dhcpcd[250]: DUID 
> 00:01:00:01:21:44:28:43:26:46:ee:43:01:07 Sep 7 15:54:43 raspberrypi 
> dhcpcd[250]: wwan0: IAID ee:43:01:07 Sep 7 15:54:43 raspberrypi 
> dhcpcd[250]: wwan0: soliciting a DHCP lease Sep 7 15:54:43 raspberrypi 
> dhcpcd[250]: wwan0: soliciting an IPv6 router Sep 7 15:54:43 raspberrypi 
> dhcpcd[250]: wwan0: offered 100.113.23.172 from 100.113.23.253 Sep 7 
> 15:54:43 raspberrypi dhcpcd[250]: wwan0: probing address 
> 100.113.23.172/32 <http://100.113.23.172/32>|
>
> and the same for 6.11.5 (bad):
>
> |Nov 29 02:37:27 raspberrypi dhcpcd[238]: wwan0: waiting for carrier Nov 
> 29 02:37:27 raspberrypi dhcpcd[238]: wwan0: carrier acquired Nov 29 
> 02:37:27 raspberrypi dhcpcd[238]: wwan0: IAID 17:fa:01:07 Nov 29 
> 02:37:27 raspberrypi dhcpcd[238]: wwan0: adding address 
> fe80::3cc3:cfbd:f6e4:82ec Nov 29 02:37:27 raspberrypi dhcpcd[238]: 
> wwan0: carrier lost Nov 29 02:37:27 raspberrypi dhcpcd[238]: wwan0: 
> deleting address fe80::3cc3:cfbd:f6e4:82ec |
>
>
> Can anyone help me to figure out why 6.11.5 isn't working as expected, 
> and if there is a configuration I can change to resolve the issue?
>
>
> Regards,
>
> Jeremy