auto-detection of IPv6 subsystem availability (important for not on-demand actions or jails, like pass2allow)

fail2ban/server/action.py

@@ -45,8 +45,8 @@ logSys = getLogger(__name__)
 # Create a lock for running system commands
 _cmd_lock = threading.Lock()
 
-# Todo: make it configurable resp. automatically set, ex.: `[ -f /proc/net/if_inet6 ] && echo 'yes' || echo 'no'`:
-allowed_ipv6 = True
+# Specifies whether IPv6 subsystem is available:
+allowed_ipv6 = DNSUtils.IPv6IsAllowed
 
 # capture groups from filter for map to ticket data:
 FCUSTAG_CRE = re.compile(r'<F-([A-Z0-9_\-]+)>'); # currently uppercase only
@@ -459,7 +459,7 @@ class CommandAction(ActionBase):
 			v = splitwords(v)
 		elif self._hasCondSection: # all conditional families:
 			# todo: check it is needed at all # common (resp. ipv4) + ipv6 if allowed:
-			v = ['inet4', 'inet6'] if allowed_ipv6 else ['inet4']
+			v = ['inet4', 'inet6'] if allowed_ipv6() else ['inet4']
 		else: # all action tags seems to be the same
 			v = ['']
 		self._properties['__families'] = v

fail2ban/server/ipdns.py

@@ -202,6 +202,11 @@ class DNSUtils:
 		DNSUtils.CACHE_nameToIp.set(key, ips)
 		return ips
 
+	@staticmethod
+	def IPv6IsAllowed():
+		# return os.path.exists("/proc/net/if_inet6") || any((':' in ip) for ip in DNSUtils.getSelfIPs())
+		return any((':' in ip.ntoa) for ip in DNSUtils.getSelfIPs())
+
 
 ##
 # Class for IP address handling.