confd: Remove -6 option from gen-interfaces

With the behavior introduced in the referenced commit, port
interfaces (i.e. all ports on many systems) no longer get any SLAAC
address, leaving the user with no way of reaching the system.

Comment says this is by design, but that seems like an awkward
default.

Remove the option, and simplify gen_interfaces to either
- Enable SLAAC, if the port is not going to be part of any bridge, or
- Disabel SLAAC, if the port is going to be part of a bridge

If necessary, we can add an inverse option at a later date.

Fixes: d0f3960 ("confd: add -6 option to gen-interfaces for SLACC on port interfaces")

src/confd/bin/gen-interfaces

@@ -22,13 +22,6 @@
 # can be used to enable IPv4 and DHCP on a single service interface if
 # needed.
 #
-# Note: interfaces classified as ports, i.e., switchcore interfaces, or
-#       have been classified 'group port' by other means will by default
-#       *not* get an IPv6 address.  This is by design, some may want to
-#       have port isolation and *no* IP communication by default.  But,
-#       if you want IPv6 SLAAC on your port interfaces by default, add
-#       the -6 option to GEN_IFACE_OPTS in your /etc/confdrc.local
-#
 ### Bridge Mode ########################################################
 # The '-b brname' option triggers the bridge mode, creating a 'brname'
 # bridge interface using all interfaces classified in 'group port' by
@@ -48,46 +41,49 @@ set -e
 
 bridge=
 ipv4=false
-ipv6=false
 dhcp=
 
 usage()
 {
     cat <<EOF
-Usage: gen-interfaces [-46d] [-b brN]
+Usage: gen-interfaces [-4d] [-b brN]
 
   -4      Enable IPv4 ZeroConf, only for brN in bridge mode
-  -6      Enable IPv6 SLACC on *port* interfaces too
   -b brN  Bridged mode, add all port interfaces to brN
   -d      Enable DHCPv4 client, only for brN in bridge mode
 
-IPv6 SLACC is default in non-bridged mode, but not for the port
-interfaces, i.e., switchcore interfaces or otherwise classifed
-as ports.  Hence, -6 is necessary for platforms that have all
-ports from a switchcore but do not want switching enabled.
-
 EOF
     exit 0
 }
 
+# shellcheck disable=SC3043
 gen_interface()
 {
+    local ifname="$1"
+    local br="$2"
+
     cat <<EOF
       ,{
-        "name": "$1",
+        "name": "$ifname",
         "type": "infix-if-type:ethernet",
-        "ietf-ip:ipv6": {
-	    "enabled": $2
 EOF
-    if [ -n "$3" ]; then
+
+    if [ -n "$br" ]; then
 	cat <<EOF
+        "ietf-ip:ipv6": {
+	    "enabled": false
 	},
 	"infix-interfaces:bridge-port": {
-	    "bridge": "$3"
+	    "bridge": "$br"
+	}
+EOF
+    else
+	cat <<EOF
+        "ietf-ip:ipv6": {}
 EOF
     fi
+
     cat <<EOF
-	}
       }
 EOF
 }
@@ -97,9 +93,6 @@ while [ "$1" != "" ]; do
 	-4)
 	    ipv4=true
 	    ;;
-	-6)
-	    ipv6=true
-	    ;;
 	-b)
 	    bridge="$2"
 	    shift
@@ -175,8 +168,8 @@ fi
 
 cat <<EOF
       }
-$(for iface in $ifaces; do gen_interface $iface true; done)
-$(for iface in $ports; do gen_interface $iface $ipv6 $bridge; done)
+$(for iface in $ifaces; do gen_interface $iface; done)
+$(for iface in $ports; do gen_interface $iface $bridge; done)
     ]
 EOF
 if [ "$dhcp" = "true" ] && [ -n "$bridge" ]; then