Unable to access internet using android wi-fi tethering

Question

Not sure this is the right place to post this question.

My issue is actually simple, I have my android device using a data connection, and a hotspot setup on this device.

I connect my linux box to this hotspot, no problem.
My pc gets the address 192.168.1.234 on wlan0
My android device is 192.168.1.1 on wlan0
=> wlan0 UP 192.168.1.1/24

I can ping the local wifi addresses from both side. However, I cant ping a server located on internet from my pc.

I know there is something about forwarding the traffic from 1 side to the other but I cant figure out how to do it.

I did so far : On the android device

$ echo 1 > /proc/sys/net/ipv4/ip_forward
$ iptables -t nat -F
$ iptables -t nat -A POSTROUTING -j MASQUERADE

Nothing special on the pc except adding a route for a special server I want the traffic to go through the wlan0.

Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
default         10.162.105.1    0.0.0.0         UG    0      0        0 eth0
10.162.105.0    *               255.255.255.0   U     0      0        0 eth0
158.x.x.x       192.168.1.1     255.255.255.255 UGH   0      0        0 wlan0
192.168.1.0     *               255.255.255.0   U     0      0        0 wlan0
192.168.25.0    *               255.255.255.0   U     0      0        0 vmnet1
192.168.29.0    *               255.255.255.0   U     0      0        0 vmnet8

On the android side, I can see the traffic coming from my pc ie.

03:50:17.426155 IP 192.168.1.234 > 158.x.x.x: ICMP echo request, id 5782, seq 634, length 64
03:50:18.427529 IP 192.168.1.234 > 158.x.x.x: ICMP echo request, id 5782, seq 635, length 64
03:50:19.428445 IP 192.168.1.234 > 158.x.x.x: ICMP echo request, id 5782, seq 636, length 64
03:50:20.425667 IP 192.168.1.234 > 158.x.x.x: ICMP echo request, id 5782, seq 637, length 64
03:50:21.426491 IP 192.168.1.234 > 158.x.x.x: ICMP echo request, id 5782, seq 638, length 64
03:50:22.425759 IP 192.168.1.234 > 158.x.x.x: ICMP echo request, id 5782, seq 639, length 64
03:50:23.425759 IP 192.168.1.234 > 158.x.x.x: ICMP echo request, id 5782, seq 640, length 64

but never see a reply, like the packets would never go out of the android device.

What am i doing wrong?

Thanks for the help.

Answer 1

I got the answer by myself.

The issue was with the iptables command. It was necessary to specify the output device and also set the forward policy.

iptables -t nat -A POSTROUTING -o rmnet_usb0 -j MASQUERADE
iptables -P FORWARD ACCEPT

After that internet becomes accessible on the linux box side. Hope this helps somebody in the same situation.