Give Workspace sessions their address back after a restart

readme-vars.yml

@@ -132,6 +132,7 @@ init_diagram: |
   "kasm:latest" <- Base Images
 # changelog
 changelogs:
+  - {date: "23.09.26:", desc: "Give Workspace sessions their address back after a container restart."}
   - {date: "07.08.26:", desc: "Fix NVIDIA passthrough to Workspace containers by generating a CDI specification inside the DinD layer."}
   - {date: "04.08.26:", desc: "Give kasm_manager a healthcheck start period so a cold start does not leave kasm_proxy created but never started."}
   - {date: "16.04.26:", desc: "Update for 1.18.1 release. Use rolling service images. Bump docker to v29."}

root/etc/s6-overlay/s6-rc.d/svc-kasm/finish

@@ -1,4 +1,8 @@
 #!/usr/bin/with-contenv bash
 # shellcheck shell=bash
 
+# Kasm routes to a session by the address its container was created with
+# shellcheck disable=SC2016
+docker ps -q --filter "label=kasm.kasmid" | xargs -r docker inspect --format '{{.Id}} {{.State.Status}}{{range $network, $settings := .NetworkSettings.Networks}} {{$network}}={{$settings.IPAddress}}{{end}}' > /opt/kasm_sessions.state
+
 /opt/kasm/bin/stop

root/etc/s6-overlay/s6-rc.d/svc-kasm/run

@@ -8,6 +8,18 @@ done
 # Stop any running containers that shouldn't be
 docker ps -q | xargs docker stop &> /dev/null
 
+# Docker gives a starting container the lowest free address, not its previous one
+if [[ -f /opt/kasm_sessions.state ]]; then
+  while read -r id _ networks; do
+    for network in ${networks}; do
+      [[ -n "${network#*=}" ]] || continue
+      docker network disconnect --force "${network%%=*}" "${id}"
+      docker network connect --ip "${network#*=}" "${network%%=*}" "${id}" || docker network connect "${network%%=*}" "${id}"
+    done
+  done < /opt/kasm_sessions.state
+  rm -f /opt/kasm_sessions.state
+fi
+
 if [[ -f /opt/kasm/bin/start ]]; then
   /opt/kasm/bin/start
 fi