https://github.com/ogd09/nic_sharing

This Bash script enables and disables internet connection sharing on Linux by setting up a Wi-Fi access point. It configures `dnsmasq` for DHCP and optional DNS, adds NAT and forwarding rules with `iptables`, and ensures IP traffic is routed between a specified internet-connected interface and a Wi-Fi interface. When disabled, it restores original
https://github.com/ogd09/nic_sharing

bash-script dhcp dnsmasq forwarding hostapd hotspot internet-connection-sharing internet-sharing iptables linux nat network-routing temporary-network wi-fi-access-point

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This Bash script enables and disables internet connection sharing on Linux by setting up a Wi-Fi access point. It configures `dnsmasq` for DHCP and optional DNS, adds NAT and forwarding rules with `iptables`, and ensures IP traffic is routed between a specified internet-connected interface and a Wi-Fi interface. When disabled, it restores original

• Host: GitHub
• URL: https://github.com/ogd09/nic_sharing
• Owner: OGD09
• Created: 2024-11-05T20:43:23.000Z (about 2 months ago)
• Default Branch: main
• Last Pushed: 2024-11-05T22:04:56.000Z (about 2 months ago)
• Last Synced: 2024-11-05T22:37:08.314Z (about 2 months ago)
• Topics: bash-script, dhcp, dnsmasq, forwarding, hostapd, hotspot, internet-connection-sharing, internet-sharing, iptables, linux, nat, network-routing, temporary-network, wi-fi-access-point
• Language: Shell
• Homepage:
• Size: 2.93 KB
• Stars: 0
• Watchers: 1
• Forks: 0
• Open Issues: 0
• Metadata Files:
  • Readme: README.md

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README

        
# Internet Sharing Script

This script enables internet sharing from one network interface (e.g., connected to the internet or VPN) to another (e.g., a Wi-Fi access point). It dynamically configures IP forwarding, sets up `iptables` rules for NAT, configures `dnsmasq` for DHCP services, and generates a `hostapd` configuration file to create a Wi-Fi access point. The script allows optional configuration for a DNS server, automatically unblocks the Wi-Fi interface if it is blocked, and checks if the Wi-Fi interface is connected to any other network prior to setup. It uses `nmcli` (from `NetworkManager`) to manage and ensure Wi-Fi disconnection and reverts the interface to its previous state once internet sharing is disabled.

## Requirements

- `dnsmasq`: Used to provide DHCP services.

- `hostapd`: Used to create a Wi-Fi access point.

- `iptables`: For configuring NAT (Network Address Translation) rules.

- `rfkill`: Used to unblock the Wi-Fi interface if needed.

- `NetworkManager` (`nmcli`): Manages Wi-Fi connections and restores the Wi-Fi interface to its original state when sharing is disabled.

## Installation

Ensure `dnsmasq`, `hostapd`, `rfkill`, and `NetworkManager` are installed on your system:

```bash

sudo apt update

sudo apt install dnsmasq hostapd rfkill network-manager

```

## Usage

```bash

./nic_sharing.sh    --ssid  --pass  [--dns ]

```

- ``: Enables or disables internet sharing.

- ``: Network interface connected to the internet or VPN (e.g., `eth0`, `wg0`, or `tun0`).

- ``: Network interface to act as the access point (e.g., `wlan0`).

- `--ssid `: The SSID name for the Wi-Fi access point.

- `--pass `: The password for the Wi-Fi access point.

- `--dns `: (Optional) Sets a custom DNS server (e.g., for an Active Directory DNS) for clients connecting to the Wi-Fi access point.

### Example Commands

#### Enabling Internet Sharing

To enable internet sharing from the source interface `eth0` to Wi-Fi interface `wlan0` with a custom SSID, password, and DNS server:

```bash

./nic_sharing.sh on eth0 wlan0 --ssid "MyAccessPoint" --pass "MySecurePassword" --dns 192.168.x.x

```

#### Disabling Internet Sharing

To disable internet sharing and revert configurations:

```bash

./nic_sharing.sh off eth0 wlan0

```

## Features

- **Automatic DHCP and Gateway Configuration**: Configures `dnsmasq` to provide DHCP services on the specified Wi-Fi interface with a predefined IP range.

- **Custom DNS Option**: Allows specifying a custom DNS server with the `--dns` option, such as a DNS server in an Active Directory environment.

- **Dynamic Wi-Fi Configuration**: Generates a temporary `hostapd.conf` file based on specified SSID and password. This file is deleted upon deactivation.

- **Wi-Fi Interface Unblocking**: Checks if the Wi-Fi interface is blocked and unblocks it if necessary.

- **Automatic Disconnection Check and Restoration**: If the Wi-Fi interface is connected to a network before activation, the script uses `nmcli` to disconnect it. Upon deactivation, the interface’s previous state is restored, reconnecting it if it was connected previously.

- **Reverts to Original State**: When disabled, all configurations, including IP forwarding, iptables rules, and DHCP settings, are restored to their original state.

## How It Works

1. **Enabling Sharing (`on`)**:

   - Ensures the Wi-Fi interface is disconnected from any active networks.

   - Enables IP forwarding.

   - Configures NAT for internet sharing through iptables.

   - Configures `dnsmasq` to provide DHCP and (optionally) a custom DNS server.

   - Generates an `hostapd.conf` file with the specified SSID and password, and starts `hostapd` to create a Wi-Fi access point.

2. **Disabling Sharing (`off`)**:

   - Disables IP forwarding.

   - Removes NAT and iptables rules.

   - Restores the original `dnsmasq` configuration.

   - Stops `hostapd` and deletes the generated `hostapd.conf` file.

   - Restores the Wi-Fi interface to its previous connection state using `nmcli`.

### Important Notes

- **Wi-Fi Interface Management**: If the Wi-Fi interface is blocked by `rfkill`, the script will automatically unblock it. The script also uses `nmcli` to disconnect any active Wi-Fi connections before setting up the access point and reconnects it when sharing is disabled, if it was connected beforehand.

- **Permissions**: Ensure to run the script with `sudo` to apply system-wide network configurations.

- **File Restoration**: The script automatically backs up the original `dnsmasq.conf` and restores it upon disabling, ensuring the system returns to its prior state.

### Example Output

When enabling sharing:

```plaintext

Activating Internet sharing from eth0 to wlan0...

IP forwarding enabled.

NAT MASQUERADE rule added for eth0.

FORWARD rule for RELATED,ESTABLISHED added.

FORWARD rule for outgoing traffic added.

Wi-Fi interface wlp0s20f3 configured with IP 192.168.60.1.

Creating hostapd configuration for SSID 'MyAccessPoint'...

hostapd configuration created with SSID 'MyAccessPoint'.

hostapd started with SSID 'MyAccessPoint'.

dnsmasq restarted.

Internet sharing enabled.

```

When disabling sharing:

```plaintext

Deactivating Internet sharing...

IP forwarding disabled.

NAT MASQUERADE rule removed for eth0.

FORWARD rule for RELATED,ESTABLISHED removed.

FORWARD rule for outgoing traffic removed.

Wi-Fi interface wlan0 down.

hostapd stopped and configuration removed.

Restoring Wi-Fi interface wlan0 to previous connection state...

dnsmasq restarted.

Internet sharing disabled.

```

## Troubleshooting

If the Wi-Fi access point is not visible or cannot connect to the internet:

- Ensure the Wi-Fi adapter supports AP mode and is not blocked by hardware or software.

- Confirm that `hostapd`, `dnsmasq`, and `iptables` are installed and configured correctly.

- Check `hostapd` and `dnsmasq` logs for any errors with:

  ```bash

  sudo journalctl -u hostapd

  sudo journalctl -u dnsmasq

  ```

- Use `nmcli device status` to ensure that the Wi-Fi interface is managed by NetworkManager.

## License

This project is licensed under the MIT License.