From 99344d28c8fe258de7fb72810ad5646ab62dbbc7 Mon Sep 17 00:00:00 2001
From: sebres <serg.brester@sebres.de>
Date: Mon, 24 Apr 2017 20:17:57 +0200
Subject: [PATCH 1/4] Introduces new tags with hostname: - `<fq-hostname>` -
 fully-qualified name of host (the same as `$(hostname -f)`) - `<sh-hostname>`
 - short hostname (the same as `$(uname -n)`)

Execution of `uname -n` replaced in all mail actions with most interesting fully-qualified `<fq-hostname>`.
---
 config/action.d/mail-buffered.conf            |  6 +++---
 config/action.d/mail-whois-lines.conf         |  6 +++---
 config/action.d/mail-whois.conf               |  6 +++---
 config/action.d/mail.conf                     |  6 +++---
 config/action.d/sendmail-buffered.conf        |  8 +++----
 config/action.d/sendmail-common.conf          |  4 ++--
 config/action.d/sendmail-geoip-lines.conf     |  2 +-
 .../sendmail-whois-ipjailmatches.conf         |  2 +-
 config/action.d/sendmail-whois-ipmatches.conf |  2 +-
 config/action.d/sendmail-whois-lines.conf     |  2 +-
 config/action.d/sendmail-whois-matches.conf   |  2 +-
 config/action.d/sendmail-whois.conf           |  2 +-
 config/action.d/sendmail.conf                 |  2 +-
 config/action.d/xarf-login-attack.conf        |  4 ++--
 config/jail.conf                              |  2 +-
 fail2ban/server/actions.py                    |  4 ++++
 fail2ban/server/ipdns.py                      | 21 +++++++++++++++++++
 17 files changed, 53 insertions(+), 28 deletions(-)

diff --git a/config/action.d/mail-buffered.conf b/config/action.d/mail-buffered.conf
index e74db9cc..88cd623f 100644
--- a/config/action.d/mail-buffered.conf
+++ b/config/action.d/mail-buffered.conf
@@ -17,7 +17,7 @@ actionstart = printf %%b "Hi,\n
               The jail <name> has been started successfully.\n
               Output will be buffered until <lines> lines are available.\n
               Regards,\n
-              Fail2Ban"|mail -s "[Fail2Ban] <name>: started on `uname -n`" <dest>
+              Fail2Ban"|mail -s "[Fail2Ban] <name>: started on <fq-hostname>" <dest>
 
 # Option:  actionstop
 # Notes.:  command executed once at the end of Fail2Ban
@@ -28,13 +28,13 @@ actionstop = if [ -f <tmpfile> ]; then
                  These hosts have been banned by Fail2Ban.\n
                  `cat <tmpfile>`
                  Regards,\n
-                 Fail2Ban"|mail -s "[Fail2Ban] <name>: Summary from `uname -n`" <dest>
+                 Fail2Ban"|mail -s "[Fail2Ban] <name>: Summary from <fq-hostname>" <dest>
                  rm <tmpfile>
              fi
              printf %%b "Hi,\n
              The jail <name> has been stopped.\n
              Regards,\n
-             Fail2Ban"|mail -s "[Fail2Ban] <name>: stopped on `uname -n`" <dest>
+             Fail2Ban"|mail -s "[Fail2Ban] <name>: stopped on <fq-hostname>" <dest>
 
 # Option:  actioncheck
 # Notes.:  command executed once before each actionban command
diff --git a/config/action.d/mail-whois-lines.conf b/config/action.d/mail-whois-lines.conf
index 7ebb8b9f..37e2d9b0 100644
--- a/config/action.d/mail-whois-lines.conf
+++ b/config/action.d/mail-whois-lines.conf
@@ -21,7 +21,7 @@ norestored = 1
 actionstart = printf %%b "Hi,\n
               The jail <name> has been started successfully.\n
               Regards,\n
-              Fail2Ban" | <mailcmd> "[Fail2Ban] <name>: started on `uname -n`" <dest>
+              Fail2Ban" | <mailcmd> "[Fail2Ban] <name>: started on <fq-hostname>" <dest>
 
 # Option:  actionstop
 # Notes.:  command executed once at the end of Fail2Ban
@@ -30,7 +30,7 @@ actionstart = printf %%b "Hi,\n
 actionstop = printf %%b "Hi,\n
              The jail <name> has been stopped.\n
              Regards,\n
-             Fail2Ban" | <mailcmd> "[Fail2Ban] <name>: stopped on `uname -n`" <dest>
+             Fail2Ban" | <mailcmd> "[Fail2Ban] <name>: stopped on <fq-hostname>" <dest>
 
 # Option:  actioncheck
 # Notes.:  command executed once before each actionban command
@@ -56,7 +56,7 @@ _ban_mail_content = ( printf %%b "Hi,\n
             Regards,\n
             Fail2Ban" )
 
-actionban = %(_ban_mail_content)s | <mailcmd> "[Fail2Ban] <name>: banned <ip> from  `uname -n`" <dest>
+actionban = %(_ban_mail_content)s | <mailcmd> "[Fail2Ban] <name>: banned <ip> from <fq-hostname>" <dest>
 
 # Option:  actionunban
 # Notes.:  command executed when unbanning an IP. Take care that the
diff --git a/config/action.d/mail-whois.conf b/config/action.d/mail-whois.conf
index 553bfb69..1f69f4c6 100644
--- a/config/action.d/mail-whois.conf
+++ b/config/action.d/mail-whois.conf
@@ -20,7 +20,7 @@ norestored = 1
 actionstart = printf %%b "Hi,\n
               The jail <name> has been started successfully.\n
               Regards,\n
-              Fail2Ban"|mail -s "[Fail2Ban] <name>: started on `uname -n`" <dest>
+              Fail2Ban"|mail -s "[Fail2Ban] <name>: started on <fq-hostname>" <dest>
 
 # Option:  actionstop
 # Notes.:  command executed once at the end of Fail2Ban
@@ -29,7 +29,7 @@ actionstart = printf %%b "Hi,\n
 actionstop = printf %%b "Hi,\n
              The jail <name> has been stopped.\n
              Regards,\n
-             Fail2Ban"|mail -s "[Fail2Ban] <name>: stopped on `uname -n`" <dest>
+             Fail2Ban"|mail -s "[Fail2Ban] <name>: stopped on <fq-hostname>" <dest>
 
 # Option:  actioncheck
 # Notes.:  command executed once before each actionban command
@@ -49,7 +49,7 @@ actionban = printf %%b "Hi,\n
             Here is more information about <ip> :\n
             `%(_whois_command)s`\n
             Regards,\n
-            Fail2Ban"|mail -s "[Fail2Ban] <name>: banned <ip> from `uname -n`" <dest>
+            Fail2Ban"|mail -s "[Fail2Ban] <name>: banned <ip> from <fq-hostname>" <dest>
 
 # Option:  actionunban
 # Notes.:  command executed when unbanning an IP. Take care that the
diff --git a/config/action.d/mail.conf b/config/action.d/mail.conf
index 4715ecc5..cfc1cf65 100644
--- a/config/action.d/mail.conf
+++ b/config/action.d/mail.conf
@@ -16,7 +16,7 @@ norestored = 1
 actionstart = printf %%b "Hi,\n
               The jail <name> has been started successfully.\n
               Regards,\n
-              Fail2Ban"|mail -s "[Fail2Ban] <name>: started  on `uname -n`" <dest>
+              Fail2Ban"|mail -s "[Fail2Ban] <name>: started  on <fq-hostname>" <dest>
 
 # Option:  actionstop
 # Notes.:  command executed once at the end of Fail2Ban
@@ -25,7 +25,7 @@ actionstart = printf %%b "Hi,\n
 actionstop = printf %%b "Hi,\n
              The jail <name> has been stopped.\n
              Regards,\n
-             Fail2Ban"|mail -s "[Fail2Ban] <name>: stopped on `uname -n`" <dest>
+             Fail2Ban"|mail -s "[Fail2Ban] <name>: stopped on <fq-hostname>" <dest>
 
 # Option:  actioncheck
 # Notes.:  command executed once before each actionban command
@@ -43,7 +43,7 @@ actionban = printf %%b "Hi,\n
             The IP <ip> has just been banned by Fail2Ban after
             <failures> attempts against <name>.\n
             Regards,\n
-            Fail2Ban"|mail -s "[Fail2Ban] <name>: banned <ip> from `uname -n`" <dest>
+            Fail2Ban"|mail -s "[Fail2Ban] <name>: banned <ip> from <fq-hostname>" <dest>
 
 # Option:  actionunban
 # Notes.:  command executed when unbanning an IP. Take care that the
diff --git a/config/action.d/sendmail-buffered.conf b/config/action.d/sendmail-buffered.conf
index a91a6957..37bc642d 100644
--- a/config/action.d/sendmail-buffered.conf
+++ b/config/action.d/sendmail-buffered.conf
@@ -17,7 +17,7 @@ norestored = 1
 # Notes.:  command executed once at the start of Fail2Ban.
 # Values:  CMD
 #
-actionstart = printf %%b "Subject: [Fail2Ban] <name>: started on `uname -n`
+actionstart = printf %%b "Subject: [Fail2Ban] <name>: started on <fq-hostname>
               From: <sendername> <<sender>>
               To: <dest>\n
               Hi,\n
@@ -31,7 +31,7 @@ actionstart = printf %%b "Subject: [Fail2Ban] <name>: started on `uname -n`
 # Values:  CMD
 #
 actionstop = if [ -f <tmpfile> ]; then
-                 printf %%b "Subject: [Fail2Ban] <name>: summary from `uname -n`
+                 printf %%b "Subject: [Fail2Ban] <name>: summary from <fq-hostname>
                  From: <sendername> <<sender>>
                  To: <dest>\n
                  Hi,\n
@@ -41,7 +41,7 @@ actionstop = if [ -f <tmpfile> ]; then
                  Fail2Ban" | /usr/sbin/sendmail -f <sender> <dest>
                  rm <tmpfile>
              fi
-             printf %%b "Subject: [Fail2Ban] <name>: stopped  on `uname -n`
+             printf %%b "Subject: [Fail2Ban] <name>: stopped  on <fq-hostname>
              From: Fail2Ban <<sender>>
              To: <dest>\n
              Hi,\n
@@ -64,7 +64,7 @@ actioncheck =
 actionban = printf %%b "`date`: <ip> (<failures> failures)\n" >> <tmpfile>
             LINE=$( wc -l <tmpfile> | awk '{ print $1 }' )
             if [ $LINE -ge <lines> ]; then
-                printf %%b "Subject: [Fail2Ban] <name>: summary from `uname -n`
+                printf %%b "Subject: [Fail2Ban] <name>: summary from <fq-hostname>
                 From: <sendername> <<sender>>
                 To: <dest>\n
                 Hi,\n
diff --git a/config/action.d/sendmail-common.conf b/config/action.d/sendmail-common.conf
index 1475dedb..46eca9ca 100644
--- a/config/action.d/sendmail-common.conf
+++ b/config/action.d/sendmail-common.conf
@@ -14,7 +14,7 @@ after = sendmail-common.local
 # Notes.:  command executed once at the start of Fail2Ban.
 # Values:  CMD
 #
-actionstart = printf %%b "Subject: [Fail2Ban] <name>: started on `uname -n`
+actionstart = printf %%b "Subject: [Fail2Ban] <name>: started on <fq-hostname>
               Date: `LC_ALL=C date +"%%a, %%d %%h %%Y %%T %%z"`
               From: <sendername> <<sender>>
               To: <dest>\n
@@ -27,7 +27,7 @@ actionstart = printf %%b "Subject: [Fail2Ban] <name>: started on `uname -n`
 # Notes.:  command executed once at the end of Fail2Ban
 # Values:  CMD
 #
-actionstop = printf %%b "Subject: [Fail2Ban] <name>: stopped on `uname -n`
+actionstop = printf %%b "Subject: [Fail2Ban] <name>: stopped on <fq-hostname>
              Date: `LC_ALL=C date +"%%a, %%d %%h %%Y %%T %%z"`
              From: <sendername> <<sender>>
              To: <dest>\n
diff --git a/config/action.d/sendmail-geoip-lines.conf b/config/action.d/sendmail-geoip-lines.conf
index decf2c05..b7c1bf36 100644
--- a/config/action.d/sendmail-geoip-lines.conf
+++ b/config/action.d/sendmail-geoip-lines.conf
@@ -23,7 +23,7 @@ norestored = 1
 # Tags:    See jail.conf(5) man page
 # Values:  CMD
 #
-actionban = ( printf %%b "Subject: [Fail2Ban] <name>: banned <ip> from `uname -n`
+actionban = ( printf %%b "Subject: [Fail2Ban] <name>: banned <ip> from <fq-hostname>
             Date: `LC_ALL=C date +"%%a, %%d %%h %%Y %%T %%z"`
             From: <sendername> <<sender>>
             To: <dest>\n
diff --git a/config/action.d/sendmail-whois-ipjailmatches.conf b/config/action.d/sendmail-whois-ipjailmatches.conf
index 5bcefe89..06ea3a3e 100644
--- a/config/action.d/sendmail-whois-ipjailmatches.conf
+++ b/config/action.d/sendmail-whois-ipjailmatches.conf
@@ -19,7 +19,7 @@ norestored = 1
 # Tags:    See jail.conf(5) man page
 # Values:  CMD
 #
-actionban = printf %%b "Subject: [Fail2Ban] <name>: banned <ip> from `uname -n`
+actionban = printf %%b "Subject: [Fail2Ban] <name>: banned <ip> from <fq-hostname>
             Date: `LC_ALL=C date +"%%a, %%d %%h %%Y %%T %%z"`
             From: <sendername> <<sender>>
             To: <dest>\n
diff --git a/config/action.d/sendmail-whois-ipmatches.conf b/config/action.d/sendmail-whois-ipmatches.conf
index 4a8edcb7..83bff1b4 100644
--- a/config/action.d/sendmail-whois-ipmatches.conf
+++ b/config/action.d/sendmail-whois-ipmatches.conf
@@ -19,7 +19,7 @@ norestored = 1
 # Tags:    See jail.conf(5) man page
 # Values:  CMD
 #
-actionban = printf %%b "Subject: [Fail2Ban] <name>: banned <ip> from `uname -n`
+actionban = printf %%b "Subject: [Fail2Ban] <name>: banned <ip> from <fq-hostname>
             Date: `LC_ALL=C date +"%%a, %%d %%h %%Y %%T %%z"`
             From: <sendername> <<sender>>
             To: <dest>\n
diff --git a/config/action.d/sendmail-whois-lines.conf b/config/action.d/sendmail-whois-lines.conf
index e3a1c974..4b947cb2 100644
--- a/config/action.d/sendmail-whois-lines.conf
+++ b/config/action.d/sendmail-whois-lines.conf
@@ -20,7 +20,7 @@ norestored = 1
 # Tags:    See jail.conf(5) man page
 # Values:  CMD
 #
-actionban = ( printf %%b "Subject: [Fail2Ban] <name>: banned <ip> from `uname -n`
+actionban = ( printf %%b "Subject: [Fail2Ban] <name>: banned <ip> from <fq-hostname>
             Date: `LC_ALL=C date +"%%a, %%d %%h %%Y %%T %%z"`
             From: <sendername> <<sender>>
             To: <dest>\n
diff --git a/config/action.d/sendmail-whois-matches.conf b/config/action.d/sendmail-whois-matches.conf
index fc4ba061..01520135 100644
--- a/config/action.d/sendmail-whois-matches.conf
+++ b/config/action.d/sendmail-whois-matches.conf
@@ -19,7 +19,7 @@ norestored = 1
 # Tags:    See jail.conf(5) man page
 # Values:  CMD
 #
-actionban = printf %%b "Subject: [Fail2Ban] <name>: banned <ip> from `uname -n`
+actionban = printf %%b "Subject: [Fail2Ban] <name>: banned <ip> from <fq-hostname>
             Date: `LC_ALL=C date +"%%a, %%d %%h %%Y %%T %%z"`
             From: <sendername> <<sender>>
             To: <dest>\n
diff --git a/config/action.d/sendmail-whois.conf b/config/action.d/sendmail-whois.conf
index b8d99423..2fb01ed3 100644
--- a/config/action.d/sendmail-whois.conf
+++ b/config/action.d/sendmail-whois.conf
@@ -19,7 +19,7 @@ norestored = 1
 # Tags:    See jail.conf(5) man page
 # Values:  CMD
 #
-actionban = printf %%b "Subject: [Fail2Ban] <name>: banned <ip> from `uname -n`
+actionban = printf %%b "Subject: [Fail2Ban] <name>: banned <ip> from <fq-hostname>
             Date: `LC_ALL=C date +"%%a, %%d %%h %%Y %%T %%z"`
             From: <sendername> <<sender>>
             To: <dest>\n
diff --git a/config/action.d/sendmail.conf b/config/action.d/sendmail.conf
index 62c94439..cf420915 100644
--- a/config/action.d/sendmail.conf
+++ b/config/action.d/sendmail.conf
@@ -19,7 +19,7 @@ norestored = 1
 # Tags:    See jail.conf(5) man page
 # Values:  CMD
 #
-actionban = printf %%b "Subject: [Fail2Ban] <name>: banned <ip> from `uname -n`
+actionban = printf %%b "Subject: [Fail2Ban] <name>: banned <ip> from <fq-hostname>
             Date: `LC_ALL=C date +"%%a, %%d %%h %%Y %%T %%z"`
             From: <sendername> <<sender>>
             To: <dest>\n
diff --git a/config/action.d/xarf-login-attack.conf b/config/action.d/xarf-login-attack.conf
index 5274cdaf..9d441aa3 100644
--- a/config/action.d/xarf-login-attack.conf
+++ b/config/action.d/xarf-login-attack.conf
@@ -46,7 +46,7 @@ actionban = oifs=${IFS}; IFS=.;SEP_IP=( <ip> ); set -- ${SEP_IP}; ADDRESSES=$(di
             FROM=<sender>
             SERVICE=<service>
             FAILURES=<failures>
-            REPORTID=<time>@`uname -n`
+            REPORTID=<time>@<fq-hostname>
             TLP=<tlp>
             PORT=<port>
             DATE=`LC_ALL=C date --date=@<time> +"%%a, %%d %%h %%Y %%T %%z"`
@@ -119,7 +119,7 @@ logpath = /dev/null
 
 # Option:  sender
 # Notes.:  This is the sender that is included in the XARF report
-sender = fail2ban@`uname -n`
+sender = fail2ban@<fq-hostname>
 
 # Option:  port
 # Notes.:  This is the port number that received the login-attack
diff --git a/config/jail.conf b/config/jail.conf
index 7e5cc9b7..135c9a2b 100644
--- a/config/jail.conf
+++ b/config/jail.conf
@@ -134,7 +134,7 @@ filter = %(__name__)s
 destemail = root@localhost
 
 # Sender email address used solely for some actions
-sender = root@localhost
+sender = root@<fq-hostname>
 
 # E-mail action. Since 0.8.1 Fail2Ban uses sendmail MTA for the
 # mailing. Change mta configuration parameter to mail if you want to
diff --git a/fail2ban/server/actions.py b/fail2ban/server/actions.py
index c33359c9..f8f8d4e1 100644
--- a/fail2ban/server/actions.py
+++ b/fail2ban/server/actions.py
@@ -35,6 +35,7 @@ except ImportError:
 	OrderedDict = dict
 
 from .banmanager import BanManager
+from .ipdns import DNSUtils
 from .jailthread import JailThread
 from .action import ActionBase, CommandAction, CallingMap
 from .mytime import MyTime
@@ -306,6 +307,9 @@ class Actions(JailThread, Mapping):
 			"ipjailmatches":	lambda self: "\n".join(self._mi4ip().getMatches()),
 			"ipfailures":			lambda self: self._mi4ip(True).getAttempt(),
 			"ipjailfailures":	lambda self: self._mi4ip().getAttempt(),
+			# system-information:
+			"fq-hostname":	lambda self: DNSUtils.getHostname(fqdn=True),
+			"sh-hostname":	lambda self: DNSUtils.getHostname(fqdn=False)
 		}
 
 		__slots__ = CallingMap.__slots__ + ('__ticket', '__jail', '__mi4ip')
diff --git a/fail2ban/server/ipdns.py b/fail2ban/server/ipdns.py
index bda32ae8..e1aa1920 100644
--- a/fail2ban/server/ipdns.py
+++ b/fail2ban/server/ipdns.py
@@ -118,6 +118,27 @@ class DNSUtils:
 
 		return ipList
 
+	@staticmethod
+	def getHostname(fqdn=True):
+		"""Get short hostname or fully-qualified hostname of host self"""
+		# try find cached own hostnames (this tuple-key cannot be used elsewhere):
+		key = ('self','hostname', fqdn)
+		name = DNSUtils.CACHE_ipToName.get(key)
+		# get it using different ways (hostname, fully-qualified or vice versa):
+		if name is None:
+			name = ''
+			for hostname in (
+				(socket.getfqdn, socket.gethostname) if fqdn else (socket.gethostname, socket.getfqdn)
+			):
+				try:
+					name = hostname()
+					break
+				except Exception as e: # pragma: no cover
+					logSys.warning("Retrieving own hostnames failed: %s", e)
+		# cache and return :
+		DNSUtils.CACHE_ipToName.set(key, name)
+		return name
+
 	@staticmethod
 	def getSelfNames():
 		"""Get own host names of self"""

From db16b4c22add97b619d24d5e1a1fa5bb60b4cdd8 Mon Sep 17 00:00:00 2001
From: sebres <serg.brester@sebres.de>
Date: Mon, 24 Apr 2017 20:54:08 +0200
Subject: [PATCH 2/4] testComplexMailActionMultiLog: better echo mock-up
 replacement for "...) | mail -s ..."

---
 fail2ban/tests/servertestcase.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fail2ban/tests/servertestcase.py b/fail2ban/tests/servertestcase.py
index 1644d895..32f794a6 100644
--- a/fail2ban/tests/servertestcase.py
+++ b/fail2ban/tests/servertestcase.py
@@ -1748,7 +1748,7 @@ class ServerConfigReaderTests(LogCaptureTestCase):
 		def _executeMailCmd(self, realCmd, timeout=60):
 			# replace pipe to mail with pipe to cat:
 			realCmd = re.sub(r'\)\s*\|\s*mail\b([^\n]*)',
-				r' echo mail \1 ) | cat', realCmd)
+				r') | cat; printf "\\n... | "; echo mail \1', realCmd)
 			# replace abuse retrieving (possible no-network), just replace first occurrence of 'dig...':
 			realCmd = re.sub(r'\bADDRESSES=\$\(dig\s[^\n]+',
 				lambda m: 'ADDRESSES="abuse-1@abuse-test-server, abuse-2@abuse-test-server"',

From f75c3d8a0243550b440393cab40077e74ced7da2 Mon Sep 17 00:00:00 2001
From: sebres <serg.brester@sebres.de>
Date: Mon, 24 Apr 2017 21:12:01 +0200
Subject: [PATCH 3/4] code review and ChangeLog entry

---
 ChangeLog                | 2 ++
 fail2ban/server/ipdns.py | 7 ++-----
 2 files changed, 4 insertions(+), 5 deletions(-)

diff --git a/ChangeLog b/ChangeLog
index 9e722608..1978bf8b 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -69,6 +69,8 @@ TODO: implementing of options resp. other tasks from PR #1346
   - `<ip-rev>` - PTR reversed representation of IP address
   - `<ip-host>` - host name of the IP address
   - `<F-...>` - interpolates to the corresponding filter group capture `...`
+  - `<fq-hostname>` - fully-qualified name of host (the same as `$(hostname -f)`)
+  - `<sh-hostname>` - short hostname (the same as `$(uname -n)`)
 * Allow to use filter options by `fail2ban-regex`, example:
   fail2ban-regex text.log "sshd[mode=aggressive]"
 * Samples test case factory extended with filter options - dict in JSON to control 
diff --git a/fail2ban/server/ipdns.py b/fail2ban/server/ipdns.py
index e1aa1920..567a7f7d 100644
--- a/fail2ban/server/ipdns.py
+++ b/fail2ban/server/ipdns.py
@@ -148,11 +148,8 @@ class DNSUtils:
 		# get it using different ways (a set with names of localhost, hostname, fully qualified):
 		if names is None:
 			names = set(['localhost'])
-			for hostname in (socket.gethostname, socket.getfqdn):
-				try:
-					names |= set([hostname()])
-				except Exception as e: # pragma: no cover
-					logSys.warning("Retrieving own hostnames failed: %s", e)
+			for fqdn in (False, True):
+				names.add(DNSUtils.getHostname(fqdn=fqdn))
 		# cache and return :
 		DNSUtils.CACHE_ipToName.set(key, names)
 		return names

From e4ccbe728633fd12b90e1cf60a13de961ac53442 Mon Sep 17 00:00:00 2001
From: sebres <serg.brester@sebres.de>
Date: Mon, 24 Apr 2017 21:32:40 +0200
Subject: [PATCH 4/4] code review: getHostname can return ''

---
 fail2ban/server/ipdns.py | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/fail2ban/server/ipdns.py b/fail2ban/server/ipdns.py
index 567a7f7d..6ef36888 100644
--- a/fail2ban/server/ipdns.py
+++ b/fail2ban/server/ipdns.py
@@ -147,9 +147,9 @@ class DNSUtils:
 		names = DNSUtils.CACHE_ipToName.get(key)
 		# get it using different ways (a set with names of localhost, hostname, fully qualified):
 		if names is None:
-			names = set(['localhost'])
-			for fqdn in (False, True):
-				names.add(DNSUtils.getHostname(fqdn=fqdn))
+			names = set([
+				'localhost', DNSUtils.getHostname(False), DNSUtils.getHostname(True)
+			]) - set(['']) # getHostname can return ''
 		# cache and return :
 		DNSUtils.CACHE_ipToName.set(key, names)
 		return names