bcp38: Add note about IPv6 to package description and help text

Fixes #3793.

net/bcp38/Makefile

@@ -7,7 +7,7 @@ include $(TOPDIR)/rules.mk
 
 PKG_NAME:=bcp38
 PKG_VERSION:=5
-PKG_RELEASE:=1
+PKG_RELEASE:=2
 PKG_LICENCE:=GPL-3.0+
 
 include $(INCLUDE_DIR)/package.mk
@@ -23,7 +23,11 @@ define Package/bcp38
 endef
 
 define Package/bcp38/description
- bcp38 implements IETF BCP38 for home routers. See https://tools.ietf.org/html/bcp38.
+ bcp38 implements IETF BCP38 for home routers.
+ See https://tools.ietf.org/html/bcp38.
+
+ This package provides BCP38 for IPv4 only - IPv6 uses source 
+ specific default routes, so no firewall configuration is needed.
 endef
 
 define Package/bcp38/conffiles

net/bcp38/files/bcp38.config

@@ -17,6 +17,10 @@ config bcp38
 #	There is a dhcp trigger to do this for the netmask of a 
 #	double natted connection needed
 
+#       You can only specify IPv4 addresses here - for IPv6, only source
+#       specific default routes will be installed, which achieves the same
+#       without needing any firewall routes.
+
 #	I will argue that this level of indirection doesn't scale
 # 	very well - see how to block china as an example
 #	http://www.okean.com/china.txt