I have a Raspberry Pi running the latest Raspberry Pi OS with Linux Kernel 6.6.
I have a Quectel EC25 modem with an active SIM card that successfully connects to the internet. I can ping 8.8.8.8 through this wwan0 interface, but not google.com. I have tried setting the nameserver entries in resolv.conf, however DNS seems to keep failing. I have disabled NetworkManager and systemd-resolved services so that they do not interface ( they did not improve the DNS situation when running ). I have tried nslookup and dig with the wwan0 interface inside a network namespace and they immediately succeed. I don't understand how dig/nslookup work, but not ping. How can I get DNS to work through the cellular modem?
Network namespace setup script:
root@raspberrypi:/home/pi/Desktop# cat create_and_enter_ns.sh
#!/bin/bash
MODEM_IF="wwan0"
ip netns add cellular
ip link set $MODEM_IF netns cellular
ip netns exec cellular bash
Connection script ran from inside the network namespace:
root@raspberrypi:/home/pi/Desktop# cat connect-cellular.sh
#!/bin/bash
MODEM_IF="wwan0"
echo "-------------------------------------------------------"
echo "*** Setting up cellular modem ..."
ip link set $MODEM_IF down
echo 'Y' | sudo tee /sys/class/net/wwan0/qmi/raw_ip
ip link set $MODEM_IF up
qmicli -p -d /dev/cdc-wdm0 --device-open-net='net-raw-ip|net-no-qos-header' --wds-start-network="apn='super',ip-type=4" --client-no-release-cid
echo "-------------------------------------------------------"
echo "*** Requesting IP Address for modem ..."
udhcpc -q -f -i wwan0
echo "-------------------------------------------------------"
echo "*** Displaying cellular connection details ..."
qmicli -d /dev/cdc-wdm0 --wds-get-current-settings
echo "-------------------------------------------------------"
echo "*** Setting nameservers in resolv.conf ..."
echo "nameserver 8.8.8.8" > /etc/resolv.conf
echo "nameserver 8.8.4.4" > /etc/resolv.conf
echo "-------------------------------------------------------"
echo "*** Displaying routes ..."
ip route
route
echo "-------------------------------------------------------"
echo "*** DNS Lookups ..."
nslookup google.com
dig google.com
echo "-------------------------------------------------------"
echo "*** Attempting pings ..."
echo "*** Pinging 8.8.8.8 ..."
ping -c 3 -W 3 8.8.8.8
echo "*** Pinging google.com ..."
ping -c 3 -W 3 google.com
echo "-------------------------------------------------------"
echo "*** Done ..."
Connection script output:
root@raspberrypi:/home/pi/Desktop# ./connect-cellular.sh
-------------------------------------------------------
*** Setting up cellular modem ...
Y
[/dev/cdc-wdm0] Network started
Packet data handle: '2269105392'
[/dev/cdc-wdm0] Client ID not released:
Service: 'wds'
CID: '18'
-------------------------------------------------------
*** Requesting IP Address for modem ...
udhcpc: started, v1.35.0
Dropped protocol specifier '.udhcpc' from 'wwan0.udhcpc'. Using 'wwan0' (ifindex=3).
Failed to revert interface configuration: Unit dbus-org.freedesktop.resolve1.service not found.
udhcpc: broadcasting discover
udhcpc: broadcasting select for 100.75.157.67, server 100.75.157.68
udhcpc: lease of 100.75.157.67 obtained from 100.75.157.68, lease time 7200
Dropped protocol specifier '.udhcpc' from 'wwan0.udhcpc'. Using 'wwan0' (ifindex=3).
Failed to set DNS configuration: Unit dbus-org.freedesktop.resolve1.service not found.
-------------------------------------------------------
*** Displaying cellular connection details ...
[/dev/cdc-wdm0] Current settings retrieved:
IP Family: IPv4
IPv4 address: 100.75.157.67
IPv4 subnet mask: 255.255.255.248
IPv4 gateway address: 100.75.157.68
IPv4 primary DNS: 8.8.4.4
IPv4 secondary DNS: 8.8.8.8
MTU: 1360
Domains: none
-------------------------------------------------------
*** Setting nameservers in resolv.conf ...
-------------------------------------------------------
*** Displaying routes ...
default via 100.75.157.68 dev wwan0
100.75.157.64/29 dev wwan0 proto kernel scope link src 100.75.157.67
Kernel IP routing table
Destination Gateway Genmask Flags Metric Ref Use Iface
default 100.75.157.68 0.0.0.0 UG 0 0 0 wwan0
100.75.157.64 0.0.0.0 255.255.255.248 U 0 0 0 wwan0
-------------------------------------------------------
*** DNS Lookups ...
Server: 8.8.4.4
Address: 8.8.4.4#53
Non-authoritative answer:
Name: google.com
Address: 142.251.163.139
Name: google.com
Address: 142.251.163.101
Name: google.com
Address: 142.251.163.138
Name: google.com
Address: 142.251.163.102
Name: google.com
Address: 142.251.163.113
Name: google.com
Address: 142.251.163.100
Name: google.com
Address: 2607:f8b0:4004:c1b::8b
Name: google.com
Address: 2607:f8b0:4004:c1b::8a
Name: google.com
Address: 2607:f8b0:4004:c1b::64
Name: google.com
Address: 2607:f8b0:4004:c1b::71
; <<>> DiG 9.18.24-1-Debian <<>> google.com
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 7473
;; flags: qr rd ra; QUERY: 1, ANSWER: 6, AUTHORITY: 0, ADDITIONAL: 1
;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 512
;; QUESTION SECTION:
;google.com. IN A
;; ANSWER SECTION:
google.com. 15 IN A 142.251.163.100
google.com. 15 IN A 142.251.163.101
google.com. 15 IN A 142.251.163.138
google.com. 15 IN A 142.251.163.139
google.com. 15 IN A 142.251.163.102
google.com. 15 IN A 142.251.163.113
;; Query time: 132 msec
;; SERVER: 8.8.4.4#53(8.8.4.4) (UDP)
;; WHEN: Fri Apr 05 02:36:11 BST 2024
;; MSG SIZE rcvd: 135
*** Attempting pings ...
*** Pinging 8.8.8.8 ...
PING 8.8.8.8 (8.8.8.8) 56(84) bytes of data.
64 bytes from 8.8.8.8: icmp_seq=1 ttl=115 time=145 ms
64 bytes from 8.8.8.8: icmp_seq=2 ttl=115 time=183 ms
64 bytes from 8.8.8.8: icmp_seq=3 ttl=115 time=142 ms
--- 8.8.8.8 ping statistics ---
3 packets transmitted, 3 received, 0% packet loss, time 2003ms
rtt min/avg/max/mdev = 142.221/156.747/183.145/18.697 ms
*** Pinging google.com ...
PING google.com (142.251.163.139) 56(84) bytes of data.
--- google.com ping statistics ---
3 packets transmitted, 0 received, 100% packet loss, time 2056ms
*** Done ...
Update:
In fact, it seems DNS is working fine to resolve various domain names, but I can never ping them through wwan0.
root@raspberrypi:/home/pi/Desktop# dig stackoverflow.com
; <<>> DiG 9.18.24-1-Debian <<>> stackoverflow.com
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 3647
;; flags: qr rd ra; QUERY: 1, ANSWER: 2, AUTHORITY: 0, ADDITIONAL: 1
;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 512
;; QUESTION SECTION:
;stackoverflow.com. IN A
;; ANSWER SECTION:
stackoverflow.com. 300 IN A 104.18.32.7
stackoverflow.com. 300 IN A 172.64.155.249
;; Query time: 168 msec
;; SERVER: 8.8.8.8#53(8.8.8.8) (UDP)
;; WHEN: Fri Apr 05 14:05:58 BST 2024
;; MSG SIZE rcvd: 78
root@raspberrypi:/home/pi/Desktop# ping 104.18.32.7
PING 104.18.32.7 (104.18.32.7) 56(84) bytes of data.
^C
--- 104.18.32.7 ping statistics ---
6 packets transmitted, 0 received, 100% packet loss, time 5098ms
I also cannot seem to ping 1.1.1.1 ( Cloudflare public DNS ):
root@raspberrypi:/home/pi/Desktop# ping -W 3 -c 1 8.8.8.8
PING 8.8.8.8 (8.8.8.8) 56(84) bytes of data.
64 bytes from 8.8.8.8: icmp_seq=1 ttl=115 time=294 ms
--- 8.8.8.8 ping statistics ---
1 packets transmitted, 1 received, 0% packet loss, time 0ms
rtt min/avg/max/mdev = 294.368/294.368/294.368/0.000 ms
root@raspberrypi:/home/pi/Desktop# ping -W 3 -c 1 8.8.4.4
PING 8.8.4.4 (8.8.4.4) 56(84) bytes of data.
64 bytes from 8.8.4.4: icmp_seq=1 ttl=57 time=181 ms
--- 8.8.4.4 ping statistics ---
1 packets transmitted, 1 received, 0% packet loss, time 0ms
rtt min/avg/max/mdev = 181.163/181.163/181.163/0.000 ms
root@raspberrypi:/home/pi/Desktop# ping -W 3 -c 1 1.1.1.1
PING 1.1.1.1 (1.1.1.1) 56(84) bytes of data.
--- 1.1.1.1 ping statistics ---
1 packets transmitted, 0 received, 100% packet loss, time 0ms
root@raspberrypi:/home/pi/Desktop#
Here are the traceroute results:
root@raspberrypi:/home/pi/Desktop# traceroute 8.8.8.8
traceroute to 8.8.8.8 (8.8.8.8), 30 hops max, 60 byte packets
1 * * *
2 * * *
3 * * *
4 * * *
5 * * *
6 * * *
7 * * *
8 * * dns.google (8.8.8.8) 571.410 ms
root@raspberrypi:/home/pi/Desktop# traceroute google.com
traceroute to google.com (142.251.163.100), 30 hops max, 60 byte packets
1 * * *
2 * * *
3 * * *
4 * * *
5 * * *
6 * * *
7 * * *
8 * * *
9 * * *
10 * * *
11 * * *
12 * * *
13 * * *
14 * * *
15 * * *
16 * * *
17 * * *
18 * * *
19 * * *
20 * * *
21 * * *
22 * * *
23 * * *
24 * * *
25 * * *
26 * * *
27 * * *
28 * * *
29 * * *
30 * * *
root@raspberrypi:/home/pi/Desktop# traceroute -n google.com
traceroute to google.com (142.251.163.101), 30 hops max, 60 byte packets
1 * * *
2 * * *
3 * * *
4 * * *
5 * * *
6 * * *
7 * * *
8 * * *
9 * * *
10 * * *
11 * * *
12 * * *
13 * * *
14 * * *
15 * * *
16 * * *
17 * * *
18 * * *
19 * * *
20 * * *
21 * * *
22 * * *
23 * * *
24 * * *
25 * * *
26 * * *
27 * * *
28 * * *
29 * * *
30 * * *
root@raspberrypi:/home/pi/Desktop#
Update 2:
I tried a different board that I had with a PCIe Quectel EC25 modem and it can ping google through that interface. I double checked everything I could think of between that one and the Sixfab hat - and found no errors. But the Sixfab one cannot ping google ( please see the output below as a comparison of the routes and everything else between the two ).
Could this be a service level DNS thing not related to the actual Linux configuration?
Working other board:
root@iot-gate-imx8plus:~# qmicli -d /dev/cdc-wdm0 --wds-get-current-settings
[/dev/cdc-wdm0] Current settings retrieved:
IP Family: IPv4
IPv4 address: 10.204.79.165
IPv4 subnet mask: 255.255.255.252
IPv4 gateway address: 10.204.79.166
IPv4 primary DNS: 8.8.8.8
IPv4 secondary DNS: 8.8.4.4
MTU: 1500
Domains: none
root@iot-gate-imx8plus:~#
root@iot-gate-imx8plus:~# ifconfig wwan0
wwan0: flags=4305<UP,POINTOPOINT,RUNNING,NOARP,MULTICAST> mtu 1500
inet 10.204.79.165 netmask 255.255.255.252 destination 10.204.79.165
unspec 00-00-00-00-00-00-00-00-00-00-00-00-00-00-00-00 txqueuelen 1000 (UNSPEC)
RX packets 1538 bytes 197923 (193.2 KiB)
RX errors 0 dropped 0 overruns 0 frame 0
TX packets 1374 bytes 171063 (167.0 KiB)
TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0
root@iot-gate-imx8plus:~# ip route
default via 10.204.79.166 dev wwan0 metric 10
10.2.0.0/16 dev wg0 scope link
10.204.79.164/30 dev wwan0 proto kernel scope link src 10.204.79.165
root@iot-gate-imx8plus:~#
root@iot-gate-imx8plus:~# ping google.com
PING google.com (142.250.180.14) 56(84) bytes of data.
64 bytes from lhr25s32-in-f14.1e100.net (142.250.180.14): icmp_seq=1 ttl=112 time=236 ms
64 bytes from lhr25s32-in-f14.1e100.net (142.250.180.14): icmp_seq=2 ttl=112 time=275 ms
64 bytes from lhr25s32-in-f14.1e100.net (142.250.180.14): icmp_seq=3 ttl=112 time=243 ms
64 bytes from lhr25s32-in-f14.1e100.net (142.250.180.14): icmp_seq=4 ttl=112 time=274 ms
^C
--- google.com ping statistics ---
4 packets transmitted, 4 received, 0% packet loss, time 3003ms
rtt min/avg/max/mdev = 236.348/257.205/275.411/17.489 ms
root@iot-gate-imx8plus:~# cat /etc/resolv.conf
This is /run/systemd/resolve/resolv.conf managed by man:systemd-resolved(8).
Do not edit.
This file might be symlinked as /etc/resolv.conf. If you're looking at
/etc/resolv.conf and seeing this text, you have followed the symlink.
This is a dynamic resolv.conf file for connecting local clients directly to
all known uplink DNS servers. This file lists all configured search domains.
Third party programs should typically not access this file directly, but only
through the symlink at /etc/resolv.conf. To manage man:resolv.conf(5) in a
different way, replace this symlink by a static file or a different symlink.
See man:systemd-resolved.service(8) for details about the supported modes of
operation for /etc/resolv.conf.
nameserver 8.8.8.8
nameserver 8.8.4.4
search .
Sixfab HAT failing DNS:
root@raspberrypi:/home/pi/Desktop# qmicli -d /dev/cdc-wdm0 --wds-get-current-settings
[/dev/cdc-wdm0] Current settings retrieved:
IP Family: IPv4
IPv4 address: 100.75.157.67
IPv4 subnet mask: 255.255.255.248
IPv4 gateway address: 100.75.157.68
IPv4 primary DNS: 8.8.4.4
IPv4 secondary DNS: 8.8.8.8
MTU: 1360
Domains: none
root@raspberrypi:/home/pi/Desktop#
root@raspberrypi:/home/pi/Desktop# ifconfig wwan0
wwan0: flags=4305<UP,POINTOPOINT,RUNNING,NOARP,MULTICAST> mtu 1360
inet 100.75.157.67 netmask 255.255.255.248 destination 100.75.157.67
inet6 fe80::b750:b71f:6494:4e58 prefixlen 64 scopeid 0x20<link>
unspec 00-00-00-00-00-00-00-00-00-00-00-00-00-00-00-00 txqueuelen 1000 (UNSPEC)
RX packets 153 bytes 16644 (16.2 KiB)
RX errors 0 dropped 0 overruns 0 frame 0
TX packets 47348 bytes 8168507 (7.7 MiB)
TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0
root@raspberrypi:/home/pi/Desktop#
root@raspberrypi:/home/pi/Desktop# ip route
default via 100.75.157.68 dev wwan0 metric 10
100.75.157.64/29 dev wwan0 proto kernel scope link src 100.75.157.67
root@raspberrypi:/home/pi/Desktop#
root@raspberrypi:/home/pi/Desktop# ping -I wwan0 -W 3 -C 3 google.com
PING google.com (142.251.163.100) from 100.75.157.67 wwan0: 56(124) bytes of data.
^C
--- google.com ping statistics ---
19 packets transmitted, 0 received, 100% packet loss, time 18431ms
root@raspberrypi:/home/pi/Desktop#
root@raspberrypi:/home/pi/Desktop# ping 8.8.8.8
PING 8.8.8.8 (8.8.8.8) 56(84) bytes of data.
64 bytes from 8.8.8.8: icmp_seq=1 ttl=115 time=118 ms
64 bytes from 8.8.8.8: icmp_seq=2 ttl=115 time=116 ms
64 bytes from 8.8.8.8: icmp_seq=3 ttl=115 time=115 ms
^C
--- 8.8.8.8 ping statistics ---
3 packets transmitted, 3 received, 0% packet loss, time 2003ms
rtt min/avg/max/mdev = 115.051/116.219/117.650/1.077 ms
root@raspberrypi:/home/pi/Desktop# cat /etc/resolv.conf
nameserver 8.8.8.8
nameserver 8.8.4.4
search .
root@raspberrypi:/home/pi/Desktop#
Update 3:
I installed tshark, and then monitored wwan0 while I tried to ping google in a different terminal. It is interesting that the DNS response is received on the interface, but the ping then is never responded to.
root@raspberrypi:/home/pi/Desktop# tshark -i wwan0
Running as user "root" and group "root". This could be dangerous.
Capturing on 'wwan0'
** (tshark:456216) 20:56:56.160995 [Main MESSAGE] -- Capture started.
** (tshark:456216) 20:56:56.161146 [Main MESSAGE] -- File: "/tmp/wireshark_wwan05F4ZL2.pcapng"
1 0.000000000 100.75.157.67 → 8.8.8.8 DNS 56 Standard query 0x4501 A google.com
2 0.000025703 100.75.157.67 → 8.8.8.8 DNS 56 Standard query 0x6c0c AAAA google.com
3 0.287190564 8.8.8.8 → 100.75.157.67 DNS 168 Standard query response 0x6c0c AAAA google.com AAAA 2607:f8b0:4004:c1b::8b AAAA 2607:f8b0:4004:c1b::71 AAAA 2607:f8b0:4004:c1b::66 AAAA 2607:f8b0:4004:c1b::8a
4 0.287191675 8.8.8.8 → 100.75.157.67 DNS 152 Standard query response 0x4501 A google.com A 142.251.163.138 A 142.251.163.102 A 142.251.163.101 A 142.251.163.100 A 142.251.163.113 A 142.251.163.139
5 0.287529002 100.75.157.67 → 142.251.163.138 ICMP 84 Echo (ping) request id=0xb5fb, seq=1/256, ttl=64
