Workaround for crashes when called from hotplug

Author: rickkatquanzadotnet

README.md

@@ -78,4 +78,8 @@ If it's working the output from tc should look something like this:
     * ECN marking is not supported
 * The script does not does anything with the Link Layer Adaptation fields. 
 * On kernel 5.10 the script does not remove the nssifb interface if it's stopped, because removing or even bringing down the interface frequently crashed my router. This could cause problems if you're switching to a script which set up regular ifb4ethX interfaces. You probably need to reboot if you want to switch to another SQM script. On kernel 5.15 this problem has been resolved. 
+* In some cases, the router crashes on ip link up of nssifb, *especially* when called from hotplug. Because of this, there's workaround in the script that prevents the script from executing when it's called from hotplug.  
+
+
+
 

files/usr/lib/sqm/nss-rk.qos

@@ -1,20 +1,20 @@
 ################################################################################
 # nss-rk.qos (HW Accelerated Simple Traffic Shaper)
-# version 20230313a
+# version 20230314a
 #
 # sqm script to use the NSS accelerated nssfq_codel qdisc 
 #
 # Based on simple.qos and nss.qos by ricsc.
 # Modified by rickk to allow configuration via (l)uci and play nicely with
 # the standard sqm scripts without throwing all kinds of errors.
-# 
+#
 # This script should be placed in your /usr/lib/sqm directory together with
 # nss-rk.qos.help.
 # 
 # To use it, select fq_codel as a queue discipline in (l)uci and nss.qos 
 # for the script. 
 #
-# Works on my machine (R7800 with OpenWRT 22.03.3) certified. 
+# Works on my machine (R7800 with OpenWRT master kernel 5.15) certified. 
 #
 # Original can be found at https://github.com/rickkdotnet/sqm-scripts-nss
 #
@@ -24,6 +24,20 @@
 
 ################################################################################
 
+# BAILOUT WHEN CALLED FROM HOTPLUG
+# 
+# Restarting SQM from hotplug tends to crash the router on boot, probably because it quickly brings up, down and up again 
+# the nssifb interface (it crashes on the last ip link up). Even worse when you have alias interfaces. Workaround that problem here. 
+#
+# /etc/hotplug.d/iface/11-sqm reloads SQM whenever an interface (i.e: wan) associated with the device (i.e.: eth0) 
+# changes state. This might be useful for dynamic interfaces, but with NSS you're always using a hardware interface 
+# and it's no problem if the NSS SQM config remains in place during ifup/downs. 
+
+if [ ! -z ${ACTION} ] && [ ! -z ${INTERFACE} ] && [ ! -z ${DEVICE} ]; then 
+  sqm_warn "By the looks of the ENV vars it looks like hotplug has triggered us. This is not necessary, quitting script to prevent crashes." 
+  exit 0
+fi 
+
 # this is needed here for sqm_stop to find and delete the correct ifb interface
 CUR_IFB=nssifb
 
@@ -48,6 +62,7 @@ else
    sqm_debug "Kernel version 5.10 found, will not delete nssifb on reload/stop"
 fi
 
+
 ipt_setup() {
 
     # unfortunately, mangle doesn't work well with NSS, nor are tc filters implemented
@@ -78,8 +93,8 @@ egress() {
     sqm_debug "Uplink speed is below 100Mb, setting codel quantum to 300"
     	EQUANTUM=300
     else
-        # use the interface mtu, this seems to work well in almost all cases
-        EQUANTUM=1514
+      # use the interface mtu, this seems to work well in almost all cases
+      EQUANTUM=1514
     fi
 
     # this allows you to set the codel interval via (l)uci eqdisc_opts
@@ -161,6 +176,7 @@ sqm_prepare_script() {
         return 1
     fi
 
+    # nssifb does not like me doing this 
     printf ${IFACE} > /sys/module/nss_ifb/parameters/nss_dev_name
 
     # the default sqm-stop script deletes the nssifb interface
@@ -218,6 +234,7 @@ sqm_start() {
 # custom sqm_stop, because the standard function deletes the ifb which
 # causes nssifb to crash if the interface is recreated and enabled
 sqm_stop() {
+
     if [ "${DOWNLINK}" -ne 0 ]; then
        $TC qdisc del dev $IFACE ingress
        $TC qdisc del dev $IFACE root
@@ -239,9 +256,9 @@ sqm_stop() {
         sqm_debug "${0}: Not deleting $CUR_IFB because variable DELETENSSIFB is not set"
     fi
 
-    # Under high load and reloading SQM nssifb tends to crash 
-    # sleep a little, hopefully this helps
-    sleep 2
+    # sleep a little, hopefully this prevents the system from crashing on restart of sqm  
+    sqm_debug "Sleeping for a second.. " 
+    sleep 1
 
     return 0
 }