router: check for duplicate .list files across groups, document BIRD2

router/route-update.sh

@@ -90,6 +90,20 @@ TABLE RESOLUTION:
   Table number is auto-allocated in range 200-250 and registered in rt_tables.
   ip rule pref = table_number × 10.
 
+BIRD2 BGP INTEGRATION:
+  If BIRD2 is installed (birdc available), auto-generates
+  /etc/bird/route-tables.conf after each run. For each per-list table,
+  creates a protocol kernel (with learn) importing routes into a
+  per-list BIRD table, tagged with BGP community (65000:TABLE_NUM),
+  and a protocol pipe merging into master4/master6.
+
+  This allows egw to act as an iBGP route reflector, distributing
+  per-list routes to BGP clients. Clients filter by community to
+  receive only the lists they need.
+
+  Constants: BIRD_AS=65000, BIRD_CONF=/etc/bird/route-tables.conf
+  birdc configure is called only when the config actually changes.
+
 EXAMPLES:
   ./route-update.sh                    # normal run
   ./route-update.sh --resolve -v       # re-resolve DNS, verbose
@@ -756,10 +770,35 @@ EOF
     birdc configure >/dev/null 2>&1 && log "BIRD reconfigured" || log "WARNING: birdc configure failed"
 }
 
+# --- Check for duplicate .list files across groups ---
+check_list_duplicates()
+{
+    local routes_dir="$1" label="$2"
+    [ -d "$routes_dir" ] || return 0
+    local seen="" errors=0
+    for f in "$routes_dir"/*/*.list ; do
+        [ -f "$f" ] || continue
+        local bname=$(basename "$f")
+        local group=$(basename "$(dirname "$f")")
+        local prev=$(echo "$seen" | grep " ${bname} " | awk '{print $1}')
+        if [ -n "$prev" ] ; then
+            log "ERROR:$label $bname found in both $prev/ and $group/ — each .list must belong to one group only"
+            errors=$((errors + 1))
+        fi
+        seen="$seen${group} ${bname} "
+    done
+    return $errors
+}
+
 # --- Main ---
 [ -n "$SHOW" ] && log "Dry-run mode (no changes will be made)"
 [ -n "$VERBOSE" ] && log "Verbose mode, state_dir=$STATE_DIR"
 
+dup_errors=0
+check_list_duplicates "$ROUTES_DIR" "" || dup_errors=$((dup_errors + $?))
+check_list_duplicates "$ROUTES6_DIR" " (v6)" || dup_errors=$((dup_errors + $?))
+[ "$dup_errors" -gt 0 ] && fatal "Duplicate .list files detected — fix config before proceeding"
+
 check_extra_dns
 [ -n "$EXTRA_DNS" ] && vlog "Extra DNS: $EXTRA_DNS" || log "Extra DNS ($EXTRA_DNS_SERVER) unreachable, local resolver only"