fix agent networking

configure.d/lib/mdns.sh

@@ -0,0 +1,48 @@
+#!/bin/bash
+#
+# Purpose : Find what's on the local network over mDNS (Avahi), for the
+#           configure.d items that set up servers, printers and storage on it.
+#           Source this file.
+
+# Every service Avahi can see, or only those of type $1 (e.g. _ipp._tcp), one
+# per line after waiting a few seconds for answers:
+# "name|type|host|address|port|txt". IPv4 only, so a machine isn't listed once
+# per address family. The name has Avahi's escapes decoded.
+mdns_services() {
+  local name type host address port txt
+  timeout 15 avahi-browse "${1:---all}" --resolve --terminate --parsable --no-db-lookup 2> /dev/null \
+    | awk -F';' '$1 == "=" && $3 == "IPv4"' \
+    | while IFS=';' read -r _ _ _ name type _ host address port txt; do
+        printf '%s|%s|%s|%s|%s|%s\n' "$(mdns_unescape "$name")" "$type" "$host" "$address" "$port" "$txt"
+      done | sort -u
+}
+
+# Avahi writes a space as \032 and a dot in a name as \. (decimal escapes)
+mdns_unescape() {
+  local s="$1" out="" ch code escape='^([^\\]*)\\([0-9][0-9][0-9]|.)(.*)$'
+  while [[ "$s" =~ $escape ]]; do
+    out+="${BASH_REMATCH[1]}"
+    code="${BASH_REMATCH[2]}"
+    s="${BASH_REMATCH[3]}"
+    if [[ "$code" == [0-9][0-9][0-9] ]]; then
+      # shellcheck disable=SC2059
+      printf -v ch "\\$(printf %03o "$((10#$code))")"
+      out+="$ch"
+    else
+      out+="$code"
+    fi
+  done
+  echo "$out$s"
+}
+
+# This machine's own .local name, which mdns_hosts leaves out
+mdns_own_host() {
+  echo "$(hostnamectl hostname 2> /dev/null || cat /etc/hostname).local"
+}
+
+# The other machines on the network: one .local name per line
+mdns_hosts() {
+  local own
+  own="$(mdns_own_host)"
+  mdns_services | cut -d'|' -f3 | grep -vixF "$own" | sort -u
+}