Well, I've been using Ubuntu 12.04 LTS for a while now, and for my own sanity and security, I've configured my ufw firewall to deny all incoming, and for outgoing just allow these ports:
TCP 80, 443 for web browsing UDP 53 for dns
Now, the scenario is that sometimes, I want to turn my workstation into a wifi hotspot to allow internet sharing with my smartphone. To do that, I followed this howto article: http://www.howtogeek.com/116409/how-to-turn-your-ubuntu-laptop-into-a-wireless-access-point/
The hotsport works and wifi connection is established with the smartphone. However, with my default firewall setup, I'm unable to browse anything on my smartphone. Only if I turn off the firewall, I can browse. But I don't want this. I tried allowing UDP53 & TCP80 ports for incoming connections, but it still doesn't work. One more thing I've noted is that with my firewall turned on, the smartphone doesn't get a proper ip-address. It is allocated something like 169.256.x.x which I believe is insufficient to get an internet connection. However, with the firewall turned on, it gets something like 10.x.x.x and browsing is ok.
Do any of you know which ports this hotspot service uses or needs enabled in order for it to work properly? So, that I can share internet with smartphone, and at the same time also be secure by enabling only those ports on ufw that are required ?