Proxy for HDHomeRun tuner discovery across VLANs (#337)

Co-authored-by: Jake-B <jake-b@users.noreply.github.com>

hdhomerun/README.md

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+# HDHomeRun VLAN Traversal
+
+## License
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell 
+copies of the Software, and to permit persons to whom the Software is 
+furnished to do so, subject to the following conditions:
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, 
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER 
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN 
+THE SOFTWARE.
+
+## Reference
+
+From https://community.ui.com/questions/Howto-HDHomerun-discovery-on-different-LAN-segment/97db52c6-4add-4ba1-ab0d-27ee6f43db8f
+
+## Purpose
+
+The HDHomeRun software sends a UDP broadcast out to the HDHomeRun tuner as part
+of the discovery process.  If your HDHomeRun is on a separate VLAN, you need 
+some sort of proxy to push this UDP broadcast out to the target network.
+
+Also `socat` is a useful tool and maybe you want to cross-compile it for your 
+UDMP(SE)
+
+## Compiling `socat`
+
+In the `build` directory, there is a Docker file to cross compile a socat 
+binary for the Dream Machine Pro.
+
+```docker build -t build_socat .```
+```docker run -v $PWD:/tmp/release build_socat```
+
+The first command builds the container, and the second runs the container.  The
+container will copy the binary inside the container to `/tmp/release`.  The -v
+volume mapping will case the file to apper in the current working directory of
+the host.
+
+Precompiled binary is provided.  Use at your own risk.
+
+## Setting up the on.boot script
+
+1. Update the `99-hdhomerun.sh` script with the IP address of your HDHomeRun
+   tuner.
+2. Place it in your `on_boot.d` folder and make it executable.
+3. Reboot your UDMP(SE) or restart the service with something like 
+   `systemctl restart udm-boot`
+4. You can verify the script is running with `ps aux | grep "socat"`
+5. The HDHomeRun software should now be able to discover the tuner on the 
+   other VLAN.
+
+## Testing
+
+This was tested with an HDHomeRun PRIME.  I do not know if it works with other
+hardware.

hdhomerun/build/Dockerfile

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+# Note: map a volume to /tmp/release to accept the binary.
+# ```
+# docker build -t build_socat .
+
+FROM aarch64/gcc
+
+ARG SOCAT_VERSION=1.7.4.3
+ARG READLINE_VERSION=7.0
+ARG OPENSSL_VERSION=1.0.2k
+
+# Make directories
+RUN mkdir -p /build && mkdir -p /tmp/release
+WORKDIR /build
+
+# Build readline
+RUN curl -k -LO ftp://ftp.cwru.edu/pub/bash/readline-${READLINE_VERSION}.tar.gz
+RUN tar xzvf readline-${READLINE_VERSION}.tar.gz
+WORKDIR  /build/readline-${READLINE_VERSION}
+RUN ./configure -disable-shared --enable-static -build=aarch64
+RUN make -j4
+RUN make install-static
+
+# Build OpenSSL
+WORKDIR /build
+RUN curl -k -LO https://www.openssl.org/source/openssl-${OPENSSL_VERSION}.tar.gz
+RUN tar zxvf openssl-${OPENSSL_VERSION}.tar.gz
+WORKDIR /build/openssl-${OPENSSL_VERSION}
+ENV CFLAGS='-fPIC -static'
+RUN ./Configure no-shared linux-aarch64
+RUN make -j4
+RUN make install
+
+# Build socat
+WORKDIR /build
+RUN curl -k -LO http://www.dest-unreach.org/socat/download/socat-${SOCAT_VERSION}.tar.gz
+RUN tar xzvf socat-${SOCAT_VERSION}.tar.gz
+WORKDIR /build/socat-${SOCAT_VERSION}
+ENV LDFLAGS='-static -ldl -ltinfo'
+RUN ./configure -build=linux-aarch64
+RUN make -j4
+
+# Copy the file to the release directory
+ENTRYPOINT cp socat /tmp/release

hdhomerun/on_boot.d/99-hdhomerun.sh

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+#!/bin/sh
+# Place cross compiled version of `socat` in /mnt/data/hdhomerun
+HDHOMERUN_IP=10.10.30.146
+
+/mnt/data/hdhomerun/socat -d -d -v udp4-recvfrom:65001,broadcast,fork udp4-sendto:{$HDHOMERUN_IP}:65001 &