If you find the Internet tethering option is missing after blackra1n jailbreak, try to follow these procedures to bring it back. For those haven’t heard of Internet Tethering, it’s a feature on iPhone that lets you share the 3G connection with your laptop (PC or Mac) to connect to the Internet. With tethering, your iPhone acts just like a wireless modem to provide your laptop with Internet connection.

1. Make sure you’re using blackra1n to jailbreak your iPhone. If you haven’t done that, check out this jailbreak guide (iPhone 2G / iPhone 3G and 3GS) for details.

2. Next, on your iPhone, launch Safari and point it to http://help.benm.at.

3. Scroll down and tap on “Mobileconfigs”.

4. Select your country and then your existing carrier. For example, you’re using AT&T, select “U.S.A.” and “AT&T”.

5. Tap “Install” and then select “Install Now” to confirm the installation of carrier profile.

6. After installation, restart your iPhone (i.e. Power it off and then start it up again)

7. Go to “Settings” -> “General” -> “Network”. The Internet Tethering option should appear.

8. When you need to use Internet Tethering, switch the option to ON to enable it.

Note: This is a workaround to enable tethering on your iPhone. Some carriers have intended to disable this option on iPhone. If you have anything uncertain, you may further check out with your carrier.

Note: if internet tethering option still does not appear after your restart you iPhone: Go to Settings–> General —> Reset—> Reset Network settings..hope this could help you..enjoy.