[SOLVED][Problem and Solution] RAZR XT910 tethering. - Motorola Droid RAZR

Problem:
Tethering problem with my RAZR XT910,PSHAsiaRetail.en
Findings:
Not NAT rule enabled in netfilter.
Solution: This is my simple solution.
0)
Code:
adb shell
1) Get root access.
Code:
$ su
2) Enable NAT in netfilter using iptables, by inserting the rule.
Code:
# iptables -t nat -F
# iptables -t nat -A POSTROUTING -o qmi0 -j MASQUERADE
3) Check with # iptables -t nat -nvL
Example
Code:
# iptables -t nat -nvL
0 0 MASQUERADE all -- * qmi0 0.0.0.0/0 0.0.0.0/0
Conclusion:
Very bad/immature tethering implementation by Motorola.
Updates: 2012--07-13
For ICS 4.0.4 Motorola had changed the FORWAD chain to DROP, and we need change it back to ACCPET to make successful tethering.
Code:
adb shell 'su -c "iptables -F; iptables -P FORWARD ACCEPT; iptables -t nat -A POSTROUTING -o qmi0 -j MASQUERADE"'
Update 2 2012-07-13
Finally ... the CORRECT way to set up tethering... goto post #21
http://forum.xda-developers.com/showpost.php?p=28698646&postcount=21
Thank you.

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Thanks for this! Works well.

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Hello to both of you,
this tip is very interesting!
Is there a way to make the same thing under Windows?
Thanks for your help!

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Windows? You even can run the commands without connecting to PC/Laptop.
If you want to use Windows, get adb and related driver for windows.
1) Connect your RAZR and let windows 'see' and install driver
2) Start-> Run -> cmd
3) cd \to\path\where\you\put\the\adb.exe
4) adb.exe shell
Now you should get command prompt $ and ready to run commands.
5) $ su
The prompt will change to #, which mean you are going to run commands using 'root' or supervisor power/authority.
6) Type or copy the commands in my previous post.
You also can use Andriod terminal emulator, such as Connectbot in local mode, and continue from step 5)
Good luck.
Thank you.

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Hello Bahathir,
I didn't remember the very useful android terminal emulator!
Your tip worked great! Thanks a lot man!
I wonder how Motorola can forget something like that...
Sent from my XT910 using XDA Premium App

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the problem turns back by restarting
Hi,
Thanks for your tip, it works very well but after I restart the phone same problem and I need to reenter the codes!
any comments?
Cheers,
Ardal

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Yes, I forgot to mention that, this method is temporary. You need to run the commands after reboot. But, it's still better than nothing.
Sent from my XT910 using XDA App

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unbelievable bug it this motorola (( hey, I have an idea but dont know how to make it (working on it):
to put these two line commands somewhere like autoexec.bat (I don't know what is equivalent in android)
So you guys know better than me about android, what do you think?
Cheers,
Ardal

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Yes ,and it's called init.d or rc.d.
Sent from my XT910 using XDA App

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Already done, by help of script manager. Set your commands as a script in etc/init.d/ with SU permission, boot.
I have also sent an email to Motorola Australia and asked them to release an update to solve this problem.

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Thank you for the follow up with Motorola. Please update and share us their responses.
Actually, the commands should be invoke when we start tethering ,and should be removed when we stop tethering for enhanced security.
Sent from my XT910 using XDA App

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Hi fellow!
Thanks for the tip! It really helped!
I don't know if Motorola "forgot" it, I think it was a way to block Tethering...
Anyway, I managed to permanently apply these modifications without need permanent root. BUT I'M NOT RESPONSIBLE FOR ANY DAMAGE YOUR DEVICE SHOULD HAVE! YOU MUST HAVE A MINIMUM LINUX KNOWLEDGE TO SAFELY EXECUTE THESE STEPS!
1) You will need adb working and the zip file with the scripts necessary to root Droid Razr on Linux / MAC (you can easily find it...)
2) From that zip, take zergRush and extract to a folder.
3) Plug the phone with USB debugging enable and execute:
adb shell 'cd /data/local/tmp/; rm *'
adb push zergRush /data/local/tmp/
adb shell './data/local/tmp/zergRush'
At this point, zergRush will try to obtain root.
After the execution, enter in shell (adb shell), you will see that you will be logged as root! The good point is that it is temporary, if you reboot your device and delete everything on /data/local/tmp/ your device will be exactly the same as it was before root.
4) So, with root access, get rc.local:
adb pull /etc/rc.local
REMEMBER TO BACKUP THIS FILE!
5) Be careful now: edit rc.local and add the following lines:
# Enable Tethering
# http://forum.xda-developers.com/showthread.php?t=1435619
iptables -t nat -F
iptables -t nat -A POSTROUTING -s 192.168.42.0/24 -o qmi0 -j MASQUERADE
at the end of file, just before:
exit 0
OBS.: look that I have modified the original rule and added '-s 192.168.42.0/24'. Here, all devices connected to my RAZR in tethering mode has an ip from LAN 192.168.42.0/24. So, the masquerading will only work when package is coming from this LAN. I think it should increase security and avoid some problems. But remember, if you set up wifi router to assign an IP from another LAN you will have to add another rule!
6) Save and push it back:
adb push rc.local /etc/
7) Enter in shell and gives rc.local permission to be executed:
adb shell
cd /etc
chmod 755 rc.local
exit
8) After it, reboot and the change should be persistent.
I have tested it and, even after a factory reset, the changes are persistent!
Now I can successfully use Wifi and USB tethering.
Thanks one more time for these great information!
Also, I want to thanks tophyr from freenode #android-dev, myn from EFnet #android, and rob0 from freenode #Netfilter.
Ronan

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Hi fellows,
EDITED: the problem was gone after I repositioned my router
I'm having a big trouble.
When I enable this, my Wifi connection becomes very unstable. It keeps disconnecting if I heavily use it. Any ideas?

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Ronis_BR said:
Hi fellows,
EDITED: the problem was gone after I repositioned my router
I'm having a big trouble.
When I enable this, my Wifi connection becomes very unstable. It keeps disconnecting if I heavily use it. Any ideas?
Click to expand...
Click to collapse
Android Wifi Tether 3.1-beta11, now available for download... http://android-wifi-tether.googlecode.com
Requires root, though... Don't you need root to run iptables anyway? Definitely needed to edit the rc file.

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tekahuna said:
Android Wifi Tether 3.1-beta11, now available for download... http://android-wifi-tether.googlecode.com
Requires root, though... Don't you need root to run iptables anyway? Definitely needed to edit the rc file.
Click to expand...
Click to collapse
Yes, you need root to edit rc.local, but, after pushing it back, you don't need it anymore.

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Ronis_BR said:
Hi fellow!
Thanks for the tip! It really helped!
I don't know if Motorola "forgot" it, I think it was a way to block Tethering...
Click to expand...
Click to collapse
FYI, my RAZR XT910 is contract free and not from VZW. It also has Hotspot and tethering features. That why I said, the it is the bad implementation at the first place.
# Enable Tethering
# http://forum.xda-developers.com/showthread.php?t=1435619
iptables -t nat -F
iptables -t nat -A POSTROUTING -s 192.168.42.0/24 -o qmi0 -j MASQUERADE
Click to expand...
Click to collapse
Yes, but, to be sure the FORWARDING is enabled, add this line
Code:
echo 1 > /proc/sys/net/ipv4/ip_forward
# Enable IP Forwarding in kernel
The ip_forward is 1, when you enabled the Hotspot/tethering, but just in case, if Motorola also disable the IP Forwarding in kernel. Yes, the netfilter's rules NEEDs the ip_froward value to be 1, to make the NATting to works.
BTW, I did not add the '-s 192.168.2.0/24' because, the NATting will not work if user change the hotspot default IP to other than 192.168.2.xxx.
Thank you and great job. I think this is not only for RAZR, but also for most Android smartphones which has 'iptables' command.
Good luck.

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Great
bahathir said:
Problem:
Tethering problem with my RAZR XT910,PSHAsiaRetail.en
Findings:
Not NAT rule enabled in netfilter.
Solution: This is my simple solution.
1) Get root access.
2) Enable NAT in netfilter using iptables, by inserting the rule.
Code:
# iptables -t nat -F
# iptables -t nat -A POSTROUTING -o qmi0 -j MASQUERADE
3) Check with # iptables -t nat -nvL
Example
Code:
# iptables -t nat -nvL
0 0 MASQUERADE all -- * qmi0 0.0.0.0/0 0.0.0.0/0
Conclusion:
Very bad/immature tethering implementation by Motorola.
Thank you.
Click to expand...
Click to collapse
Working great on 2.3.6 Stock, thank you!!!!!

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ichi go said:
Hello Bahathir,
I didn't remember the very useful android terminal emulator!
Your tip worked great! Thanks a lot man!
I wonder how Motorola can forget something like that...
Sent from my XT910 using XDA Premium App
Click to expand...
Click to collapse
you can save to a shell script, let say mytether and execute ./mytether.sh later on...
but the init file is much convenient.

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Any idea why doesn't work on Asia.03 ICS was what fixed issue in Asia.03 GB.
Sent from my XT910 using xda premium

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Yes.
It is because Motorla had changed the default FORWARD chain policy to DROP, and all packets which going out from other IPs going through it will be dropped and ignored. So no connections for client's.
Here is the default rules.
Code:
$ adb shell 'su -c "iptables -nvL"'
Chain INPUT (policy ACCEPT 460 packets, 282K bytes)
pkts bytes target prot opt in out source destination
0 0 all -- !lo+ * 0.0.0.0/0 0.0.0.0/0 ! quota globalAlert: 2097152 bytes
145 8251 ACCEPT all -- lo * 0.0.0.0/0 0.0.0.0/0
343 270K all -- * * 0.0.0.0/0 0.0.0.0/0 owner socket exists
Chain FORWARD (policy DROP 0 packets, 0 bytes)
pkts bytes target prot opt in out source destination
Chain OUTPUT (policy ACCEPT 325 packets, 34323 bytes)
pkts bytes target prot opt in out source destination
0 0 all -- * !lo+ 0.0.0.0/0 0.0.0.0/0 ! quota globalAlert: 2097152 bytes
145 8251 ACCEPT all -- * lo 0.0.0.0/0 0.0.0.0/0
319 34011 all -- * * 0.0.0.0/0 0.0.0.0/0 owner socket exists
Chain costly_shared (0 references)
pkts bytes target prot opt in out source destination
0 0 penalty_box all -- * * 0.0.0.0/0 0.0.0.0/0
0 0 all -- * * 0.0.0.0/0 0.0.0.0/0 owner socket exists
0 0 ACCEPT all -- * * 0.0.0.0/0 0.0.0.0/0
Chain penalty_box (1 references)
pkts bytes target prot opt in out source destination
Look at the FORWARD chain and other bizarre rules. We can change it to a more cleaner rules.
Code:
adb shell 'su -c "iptables -F; iptables -P FORWARD ACCEPT; iptables -t nat -A POSTROUTING -o qmi0 -j MASQUERADE"'
1) iptables -F : Flush/remove all rules
2) iptables -P FORWARD ACCEPT : Change the default FORWARD chain policy to ACCEPT, which allow all traffic goes through
3) iptables -t nat -A POSTROUTING -o qmi0 -j MASQUERADE : Enable the NAT rule.
Enjoy the tethering and good luck.
Thank you.