sqm-scripts: change default for qdisc target parameter

Alan Jenkins noted a bug in the smq luci GUI that effectively
erased several configuration paramters if two checkboxes were deselected.
This behaviour seems consistent in luci but certainly has the potential
to confuse users. While confusion can not really be avoided generally
it seems wise to change the default interpretation for empty or non-existent
itarget and etarget variables from the qdisc's default (5ms in the case of
one of the codels) to automatic determination of tghis variable dependent on
the configured bandwidth, as codels target variable should be large enough
to contain at least one full packet. With this change sqm-scripts will
do the right thing by default, but will yet allow the user to specify
over-ridding values (as long as the user does not un-check the
entry-field exposing check boxes). Survives light testing...
This change set also changes the sqm-scripts luci gui to note the user
of the change. For compatibility with existing setups sqm-scripts
will still honor "auto" as an alternative explicit way of requesting
automatic target selection. This might turn into a warning in the future
and might be phased out...

Signed-off-by: Sebastian Moeller <moeller0@gmx.de>

net/luci-app-sqm/files/sqm-cbi.lua

@@ -89,7 +89,7 @@ sc.default = "simple.qos"
 sc.rmempty = false
 sc.description = qos_desc
 
-ad = s:taboption("tab_qdisc", Flag, "qdisc_advanced", translate("Show Advanced Configuration"))
+ad = s:taboption("tab_qdisc", Flag, "qdisc_advanced", translate("Show and Use Advanced Configuration"))
 ad.default = false
 ad.rmempty = true
 
@@ -121,7 +121,7 @@ eecn.default = "NOECN"
 eecn.rmempty = true
 eecn:depends("qdisc_advanced", "1")
 
-ad2 = s:taboption("tab_qdisc", Flag, "qdisc_really_really_advanced", translate("Show Dangerous Configuration"))
+ad2 = s:taboption("tab_qdisc", Flag, "qdisc_really_really_advanced", translate("Show and Use Dangerous Configuration"))
 ad2.default = false
 ad2.rmempty = true
 ad2:depends("qdisc_advanced", "1")
@@ -140,12 +140,12 @@ elim.rmempty = true
 elim:depends("qdisc_really_really_advanced", "1")
 
 
-itarg = s:taboption("tab_qdisc", Value, "itarget", translate("Latency target for ingress, e.g 5ms [units: s, ms, or  us]; leave empty for default, or auto for automatic selection."))
+itarg = s:taboption("tab_qdisc", Value, "itarget", translate("Latency target for ingress, e.g 5ms [units: s, ms, or  us]; leave empty for automatic selection, put in the word default for the qdisc's default."))
 itarg.datatype = "string"
 itarg.rmempty = true
 itarg:depends("qdisc_really_really_advanced", "1")
 
-etarg = s:taboption("tab_qdisc", Value, "etarget", translate("Latency target for egress, e.g. 5ms [units: s, ms, or  us]; leave empty for default, or auto for automatic selection."))
+etarg = s:taboption("tab_qdisc", Value, "etarget", translate("Latency target for egress, e.g. 5ms [units: s, ms, or  us]; leave empty for automatic selection, put in the word default for the qdisc's default."))
 etarg.datatype = "string"
 etarg.rmempty = true
 etarg:depends("qdisc_really_really_advanced", "1")

net/sqm-scripts/files/usr/lib/sqm/functions.sh

@@ -253,8 +253,8 @@ get_target() {
 	# either e.g. 100ms or auto
 	CUR_TARGET_VALUE=$( echo ${CUR_TARGET} | grep -o -e \^'[[:digit:]]\+' )
 	CUR_TARGET_UNIT=$( echo ${CUR_TARGET} | grep -o -e '[[:alpha:]]\+'\$ )
-#	[ ! -z "$CUR_TARGET" ] && sqm_logger "CUR_TARGET_VALUE: $CUR_TARGET_VALUE"
-#	[ ! -z "$CUR_TARGET" ] && sqm_logger "CUR_TARGET_UNIT: $CUR_TARGET_UNIT"
+	#[ ! -z "$CUR_TARGET" ] && sqm_logger "CUR_TARGET_VALUE: $CUR_TARGET_VALUE"
+	#[ ! -z "$CUR_TARGET" ] && sqm_logger "CUR_TARGET_UNIT: $CUR_TARGET_UNIT"
 	
 	AUTO_TARGET=
 	UNIT_VALID=
@@ -271,14 +271,42 @@ get_target() {
 					;;
 			    esac
 			fi
-			case ${CUR_TARGET_UNIT} in
-			    auto|Auto|AUTO) 
+			# empty field in GUI or undefined GUI variable now defaults to auto
+			if [ -z "${CUR_TARGET_VALUE}" -a -z "${CUR_TARGET_UNIT}" ];
+    			then			
 				if [ ! -z "${CUR_LINK_KBPS}" ];
 				then
 				    TMP_TARGET_US=$( adapt_target_to_slow_link $CUR_LINK_KBPS )
 				    TMP_INTERVAL_STRING=$( adapt_interval_to_slow_link $TMP_TARGET_US )
 				    CUR_TARGET_STRING="target ${TMP_TARGET_US}us ${TMP_INTERVAL_STRING}"
 				    AUTO_TARGET="1"
+				    sqm_logger "get_target defaulting to auto." 
+			    	else
+				    sqm_logger "required link bandwidth in kbps not passed to get_target()." 
+				fi
+			fi
+			# but still allow explicit use of the keyword auto for backward compatibility
+                        case ${CUR_TARGET_UNIT} in
+                            auto|Auto|AUTO)
+                                if [ ! -z "${CUR_LINK_KBPS}" ];
+                                then
+                                    TMP_TARGET_US=$( adapt_target_to_slow_link $CUR_LINK_KBPS )
+                                    TMP_INTERVAL_STRING=$( adapt_interval_to_slow_link $TMP_TARGET_US )
+                                    CUR_TARGET_STRING="target ${TMP_TARGET_US}us ${TMP_INTERVAL_STRING}"
+                                    AUTO_TARGET="1"
+                                else
+                                    sqm_logger "required link bandwidth in kbps not passed to get_target()."
+                                fi
+                            ;;
+                        esac
+			
+			case ${CUR_TARGET_UNIT} in
+			    default|Default|DEFAULT) 
+				if [ ! -z "${CUR_LINK_KBPS}" ];
+				then
+				    CUR_TARGET_STRING=""	# return nothing so the default target is not over-ridden...
+				    AUTO_TARGET="1"
+				    #sqm_logger "get_target using qdisc default, no explicit target string passed."
 			    	else
 			    	    sqm_logger "required link bandwidth in kbps not passed to get_target()." 
 			        fi
@@ -288,7 +316,7 @@ get_target() {
 			    then
 			    if [ -z "${CUR_TARGET_VALUE}" -o -z "${UNIT_VALID}" ];
 			    then 
-				[ -z "$AUTO_TARGET" ] && sqm_logger "${CUR_TARGET} is not a well formed tc target specifier; e.g.: 5ms (or s, us), or the string auto."
+				[ -z "$AUTO_TARGET" ] && sqm_logger "${CUR_TARGET} is not a well formed tc target specifier; e.g.: 5ms (or s, us), or one of the strings auto or default."
 			    fi
 			fi
 		    ;;