USB Internet

A phone running postmarketOS can connect to the Internet through a USB cable plugged onto another Internet-connected device. For this to work you set your host machine as gateway for your phone and let your host machine do for the phone or a guest machine.
== On your phone or guest machine ==
These instructions assume the relevant interface is named usb0. On some devices (those running [android-based] downstream kernels?), it may be rndis0. Check first with e.g., ifconfig, and use the interface that has the line inet addr:172.16.42.1.
# ip route add default via 172.16.42.2 dev usb0
# echo nameserver 1.1.1.1 > /etc/resolv.conf
If neither of those work or run correctly, try route add default gw 172.16.42.2
To make the configuration persistent after reboot do:
# echo 'ip route add default via 172.16.42.2 dev usb0' > /etc/local.d/usb_internet.start
# chmod +x /etc/local.d/usb_internet.start
# rc-update add local
Disable it if you plug the USB cable out and want to use WiFi, because it can interfere with routing (packets would try to use the USB networking, even though it's disconnected)
== On the host machine ==
First, enable IP forwarding:
# sysctl net.ipv4.ip_forward=1
Then follow the instructions according to the distribution or firewall you use.
=== iptables (Ubuntu/Arch/Alpine) ===
# iptables -A FORWARD -m conntrack --ctstate ESTABLISHED,RELATED -j ACCEPT
# iptables -A FORWARD -s 172.16.42.0/24 -j ACCEPT
# iptables -A POSTROUTING -t nat -j MASQUERADE -s 172.16.42.0/24
# iptables-save #Save changes
This will enable IPv4 forwarding on your host machine which basically lets it function as a router. The postrouting command will make the kernel on the host translate the packets between the phone network
and your normal network on the host machine.
=== firewalld (RHEL/CentOS/Fedora/Rocky/SLE/openSUSE) ===
# firewall-cmd --get-active-zone 
# nmcli connection modify ethX_other connection.zone external
# nmcli connection modify ethX_to_phone connection.zone internal
# firewall-cmd --get-active-zone 
# firewall-cmd --zone=external --add-masquerade
# firewall-cmd --zone=external --list-all
# firewall-cmd --zone=internal --list-all
Use the --permanent and --reload options for a persistent configuration.https://www.server-world.info/en/note?os=CentOS_7&p=firewalld&f=2
=== nftables (postmarketOS) ===
# nft add table inet nat
# nft 'add chain inet nat postrouting { type nat hook postrouting priority 100 ; }'
# nft add rule inet nat postrouting iifname "usb*" masquerade
postmarketOS has chain forward configured for USB interfaces by default.https://gitlab.postmarketos.org/postmarketOS/pmaports/-/blob/master/main/postmarketos-config-nftables/rules/51_usb_inet.nft
If using other distributions or the following lines are missing, add them manually.
# nft add rule inet filter forward ct state { established, related } accept
# nft add rule inet filter forward iifname "usb*" accept
You can now verify the Internet connection on your phone by pinging something. If this does not work it means you need to compile the kernel with CONFIG_USB_ETH setting enabled in menuconfig.
=== ufw ===
In the file /etc/default/ufw, change DEFAULT_FORWARD_POLICY to ACCEPT.
DEFAULT_FORWARD_POLICY="ACCEPT"
In the file /etc/ufw/sysctl.conf, uncomment net/ipv4/ip_forward=1.
net/ipv4/ip_forward=1
#net/ipv6/conf/default/forwarding=1
#net/ipv6/conf/all/forwarding=1
Add the following rule to /etc/ufw/before.rules BEFORE the *filter table rules.
# NAT table rules
*nat
:POSTROUTING ACCEPT [0:0]
# Forward traffic for 172.16.42.0/24
-A POSTROUTING -j MASQUERADE -s 172.16.42.0/24
# don't delete the 'COMMIT' line or these rules won't be processed
COMMIT
Restart ufw to make changes take effect.
# ufw disable && ufw enable
== See also ==
* USB Tethering
== Notes ==
Category:Guide