ericyan / docker-freetdm

Docker image for FreeTDM

docker-freetdm

Docker image for building FreeTDM and the mod_freetdm module for use with FreeSWITCH.

The ZapTel/DAHDI I/O module (ftmod_zt) along with the analog signaling modules (ftmod_analog and ftmod_analog_em) are compiled as well. So it should be able to work with DAHDI-compatible telephony cards offering integration with FXO/FXS or E&M lines.

Usage

The ericyan/freetdm image works as a builder only and is not awfully useful on its own. Another container (based on ericyan/freeswitch in this example) that actually do all the hard work can then copy and use the compiled modules from the builder like this:

FROM ericyan/freetdm as builder

FROM ericyan/freeswitch

# FreeTDM
COPY --from=builder /usr/local/freeswitch/lib/libfreetdm.so.1.0.0 /usr/lib/
RUN chmod 644 /usr/lib/libfreetdm.so.1.0.0 \
    && ln -s /usr/lib/libfreetdm.so.1.0.0 /usr/lib/libfreetdm.so.1 \
    && ln -s /usr/lib/libfreetdm.so.1.0.0 /usr/lib/libfreetdm.so
COPY --from=builder /usr/local/freeswitch/mod/*.so /usr/lib/freeswitch/mod/
RUN chmod 644 /usr/lib/freeswitch/mod/*.so

Make sure the drivers are properly installed on the host. Then, use the --device option to add host device to the container when starting the container with docker run. For example:

sudo docker run -d --name ftdm \
    --net=host \
    --cap-add SYS_NICE \
    --device /dev/dahdi/ \
    ericyan/freetdm

Configuration

In order to interface with FreeTDM from FreeSWITCH you must configure several different components:

• Hardware drivers (eg. DAHDI)
• The FreeTDM library
• FreeSWITCH module mod_freetdm

Sample configs is available at https://freeswitch.org/stash/projects/FS/repos/freeswitch/browse/libs/freetdm/conf

Driver configuration

On the host, the driver needs to be installed and properly configurated. For DAHDI devices, the config file is /etc/dahdi/system.conf. The user manual of the telephony card should have a chapter on how to configure the driver.

In the container, you need to make sure the freeswitch user has the permission to access the mounted device. For DAHDI devices, you may need to do something like this:

chown -R freeswitch:freeswitch /dev/dahdi

FreeTDM library configuration

The /etc/freeswitch/freetdm.conf file follows an INI-like format. This is where you declare your spans. For each span, you must specify the I/O module that will control that span and the span name, for example:

[span zt dahdi-1]
trunk_type => FXO
fxo-channel => 1:1-8

This specifies a span named dahdi-1 that will be controlled by the zt I/O module. Consult the FreeTDM documentation for details.

The I/O modules also have their own config files (for ftmod_zt, it is /etc/freeswitch/zt.conf), but you normally do not need them as the defaults are sensible.

The ftmod_analog module requires /etc/freeswitch/tones.conf for tone generation and detection. If you use analog interfaces and you want to dial out you must make sure the tone configuration is correct for your country.

FreeSWITCH configuration

Once the library is configured, we then tell FreeSWITCH which signaling settings to use and where to send the incoming calls to. This is done through /etc/freeswitch/autload_configs/freetdm.conf.xml.

Most of the time the span definitions will match those in the library config. However, you can have some spans defined in freetdm.conf but not in use in freetdm.conf.xml, but not the other way around.

Span definitions are declared inside an section for each signaling type. Inside each section, you can declare individual spans. The name of the span must match one of the names you used in the freetdm.conf file.

Please refer to the sample configuration file for documentation in all the span types and their respective XML sections.