mirror of
https://github.com/markqvist/tncattach.git
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129 lines
6.1 KiB
Markdown
129 lines
6.1 KiB
Markdown
TNC Attach
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==========
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Attach KISS TNC devices as network interfaces in Linux. This program allows you to attach TNCs or any KISS-compatible device as a network interface. This program does not need any kernel modules, and has no external dependencies outside the standard Linux and GNU C libraries.
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## Version edited
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Add capability of using TCP Kiss.
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## Installation
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Currently it is recommended to compile and install __tncattach__ from source with the below commands.
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If that is not possible for you, precompiled __amd64__ and __armhf__ (Raspberry Pi and similar) binaries have been provided in the releases section. You can [download the latest release here](https://github.com/markqvist/tncattach/releases).
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```sh
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# If you don't already have a compiler installed
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sudo apt install build-essential
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# Clone repository from GitHub
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git clone https://github.com/markqvist/tncattach.git
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# Move into source directory
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cd tncattach
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# Make program
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make
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# Install to system
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sudo make install
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```
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## Using tncattach
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Using __tncattach__ is simple. Run the program from the command line, specifying which serial port the TNC is connected to, and the serial port baud-rate, and __tncattach__ takes care of the rest. In most cases, depending on what you intend to do, you probably want to use some of the options, though. See the examples section below for usage examples.
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```
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Usage: tncattach [OPTION...] (serial_port|host) (baudrate|port)
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Attach TNC devices as system network interfaces
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-o, --kisstcp Use TCP Kiss (such as Direwolf port 8001)
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-d, --daemon Run tncattach as a daemon
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-e, --ethernet Create a full ethernet device
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-i, --ipv4=IP_ADDRESS Configure an IPv4 address on interface
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-m, --mtu=MTU Specify interface MTU
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-n, --noipv6 Filter IPv6 traffic from reaching TNC
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--noup Only create interface, don't bring it up
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-s, --id=CALLSIGN Station identification data
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-t, --interval=SECONDS Maximum interval between station identifications
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-v, --verbose Enable verbose output
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-?, --help Give this help list
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--usage Give a short usage message
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-V, --version Print program version
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```
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The program supports attaching TNCs as point-to-point tunnel devices, or generic ethernet devices. The ethernet mode is suitable for point-to-multipoint setups, and can be enabled with the corresponding command line switch. If you only need point-to-point links, it is advisable to just use the standard point-to-point mode, since it doesn't incur the ethernet header overhead on each packet.
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Additionally, it is worth noting that __tncattach__ can filter out IPv6 packets from reaching the TNC. Most operating systems attempts to autoconfigure IPv6 when an interface is brought up, which results in a substantial amount of IPv6 traffic generated by router solicitations and similar, which is usually unwanted for packet radio links and similar.
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If you intend to use __tncattach__ on a system with mDNS services enabled (avahi-daemon, for example), you may want to consider modifying your mDNS setup to exclude TNC interfaces, or turning it off entirely, since it will generate a lot of traffic that might be unwanted.
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## Station Identification
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You can configure tncattach to automatically transmit station identification beacons according to a given interval, by using the --id and --interval options. Identification will be transmitted as raw data frames with whatever content has been specified in the --id option. Useful for amateur radio use, or other areas where station identification is necessary.
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Identification beacons will be transmitted when:
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- There is outgoing data to send, and the specified interval has elapsed.
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- The specified interval elapses, and data has been sent since the last ID beacon.
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- The program exits, if any data frames have been transmitted since the last ID beacon.
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The above methodology should comply with station identification rules for amateur radio in most parts of the world, and complies with US Part 97 rules.
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## Examples
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Create an ethernet device with a USB-connected TNC, set the MTU, filter IPv6 traffic, and set an IPv4 address:
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```sh
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# Attach interface
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sudo tncattach /dev/ttyUSB0 115200 --ethernet --mtu 576 --noipv6 --ipv4 10.92.0.10/24
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sudo tncattach localhost 8001 -o --ethernet --mtu 576 --noipv6 --ipv4 10.92.0.10/24
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```
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You can interact with the interface like any other using the __ip__ or __ifconfig__ utilities:
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```sh
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# Check interface is running
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ifconfig
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tnc0: flags=579<UP,BROADCAST,RUNNING,ALLMULTI> mtu 576
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inet 10.92.0.10 netmask 255.255.255.0 broadcast 10.92.0.255
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ether 02:56:ad:f2:40:33 txqueuelen 1000 (Ethernet)
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RX packets 0 bytes 0 (0.0 B)
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RX errors 0 dropped 0 overruns 0 frame 0
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TX packets 0 bytes 0 (0.0 B)
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TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0
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```
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Create a point-to-point link:
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```sh
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# Attach interface
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sudo tncattach /dev/ttyUSB0 115200 --mtu 400 --noipv6 --noup
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sudo tncattach localhost 8001 -o --mtu 400 --noipv6 --noup
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# Configure IP addresses for point-to-point link
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sudo ifconfig tnc0 10.93.0.1 pointopoint 10.93.0.2
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# Check interface
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ifconfig
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tnc0: flags=4305<UP,POINTOPOINT,RUNNING,NOARP,MULTICAST> mtu 400
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inet 10.93.0.1 netmask 255.255.255.255 destination 10.93.0.2
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unspec 00-00-00-00-00-00-00-00-00-00-00-00-00-00-00-00 txqueuelen 500 (UNSPEC)
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RX packets 0 bytes 0 (0.0 B)
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RX errors 0 dropped 0 overruns 0 frame 0
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TX packets 0 bytes 0 (0.0 B)
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TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0
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```
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## Worth Knowing on Raspbian
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On some versions of Raspbian (and probably other operating systems), the DHCP client daemon _dhcpcd_ interferes with TNC interfaces, by overriding their MTU and trying to auto-configure link-local addresses. You probably don't want this, and it can be disabled by editing the __/etc/dhcpcd.conf__ file, adding a statement telling _dhcpcd_ to ignore your TNC interface:
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```
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# Add the following statement somewhere at the beginning
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# of /etc/dhcpcd.conf to prevent dhcpcd from changing MTU
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denyinterfaces tnc0
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``` |