Block all DDS off the Pi and bring up PipeWire behind the firewall

ROS never leaves the robot, by the owner's decision: the firewall drops domain
42's DDS ports on every interface but loopback (usb0 included), discovery is
pinned to LOCALHOST, and hermes_mcp is the only bridge to the outside. PipeWire
1.0.5 runs as hermes's user services with its network server on TCP 4713; the
firewall, loaded at boot before it, is the protection. Verified from talos: 4713
connects over usb0 and times out over Wi-Fi.

CONTEXT.md brought up to date: the face service, gaze, recognition, the firewall,
and what is left.

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01AFN8nRRCiDiMN7ChBpHJhs

pi/nftables-robot.nft

@@ -1,9 +1,10 @@
 #!/usr/sbin/nft -f
 # The robot's audio (4713), MCP (8765) and face webhook (8766) ports are reachable only over the
 # USB link, and only from the host at 10.55.0.1. Every other interface, Wi-Fi included, is dropped.
-# ROS 2's DDS has no authentication, and /camera/* and /vision/faces carry video and recognised
-# names, so its ports (domain 42: 17900-18149 with Fast DDS's default offsets) are dropped on every
-# interface but usb0 and loopback too.
+# ROS 2 never leaves the robot: its DDS has no authentication, and /camera/* and /vision/faces
+# carry video and recognised names. Domain 42's ports (17900-18149 with Fast DDS's default offsets)
+# are dropped on every interface but loopback, usb0 included. The only way in or out is hermes_mcp,
+# which talks to the ROS graph locally and to the host over MCP.
 # SSH and everything else are left alone: that policy is the owner's call.
 
 table inet robot
@@ -15,6 +16,6 @@ table inet robot {
         iif "lo" accept
         iifname "usb0" ip saddr 10.55.0.1 tcp dport { 4713, 8765, 8766 } accept
         tcp dport { 4713, 8765, 8766 } drop
-        iifname != { "lo", "usb0" } udp dport 17900-18149 drop
+        iifname != "lo" udp dport 17900-18149 drop
     }
 }

pi/pipewire/50-network-server.conf

@@ -1,11 +1,13 @@
 # ~/.config/pipewire/pipewire-pulse.conf.d/50-network-server.conf  (on the Pi)
 #
-# Lets your Omarchy machine reach the robot's microphone and speaker over the
-# network, using the PulseAudio protocol that pipewire-pulse speaks.
+# Lets the host reach the robot's microphone and speaker over the USB link, using the
+# PulseAudio protocol that pipewire-pulse speaks.
 #
 # This replaces the default address list, so "unix:native" must stay in it.
-# Anyone on the LAN who can reach port 4713 could listen to the microphone;
-# the nftables rules installed alongside restrict it to your machine's IP.
+# It listens on every interface and is unauthenticated: anyone who can reach port 4713 could
+# listen to the microphone. The protection is the firewall (pi/nftables-robot.nft, loaded at boot
+# by robot-firewall.service), which accepts 4713 only on usb0 from 10.55.0.1 and drops it on every
+# other interface, Wi-Fi included. Do not enable this without that firewall loaded.
 
 pulse.properties = {
     server.address = [

pi/robot-env.sh

@@ -3,14 +3,14 @@
 #  - the Raspberry Pi libcamera fork ahead of ROS's own copy (same soname, but ROS's crashes in the
 #    Pi image plugin: see CONTEXT.md)
 #  - ~/venv's site-packages first: Blinka/Adafruit for the display, OpenCV 4.10 for YuNet
-#  - a fixed ROS domain (42), discovery on this machine only. DDS has no authentication and the
-#    camera and recognised names travel on it: set ROBOT_ROS_DISCOVERY=SUBNET only to
-#    reach it from a host over the USB link (the firewall drops DDS ports on every other interface)
+#  - a fixed ROS domain (42), discovery on this machine only. ROS never leaves the robot: DDS has
+#    no authentication and carries the camera and recognised names, so the firewall drops its ports
+#    on every interface but loopback. hermes_mcp is the only bridge to the outside world.
 source /opt/ros/jazzy/setup.bash
 [ -f "$HOME/camera_ws/install/setup.bash" ] && source "$HOME/camera_ws/install/setup.bash"
 [ -f "$HOME/ros_ws/install/setup.bash" ] && source "$HOME/ros_ws/install/setup.bash"
 export LD_LIBRARY_PATH="/opt/libcamera-rpi/lib/aarch64-linux-gnu:${LD_LIBRARY_PATH:-}"
 export PYTHONPATH="$HOME/venv/lib/python3.12/site-packages:${PYTHONPATH:-}"
 export ROS_DOMAIN_ID="${ROS_DOMAIN_ID:-42}"
-# ROS's own setup script exports SUBNET, so a ${VAR:-default} on the ROS variable would never apply
-export ROS_AUTOMATIC_DISCOVERY_RANGE="${ROBOT_ROS_DISCOVERY:-LOCALHOST}"
+# ROS's own setup script exports SUBNET, so this must be assigned, not defaulted
+export ROS_AUTOMATIC_DISCOVERY_RANGE=LOCALHOST