feat(src): add option to preserve hostname

wsdd now uses the lower case version of the hostname for domains and (as
before this commit) the upper case version for workgroup environments in
its default behavior. The added -p option preserves the case information
of the provided or detected hostname.

closes #16
see also #15

README.md

@@ -93,7 +93,8 @@ allowed.
 
      Assume that the host running wsdd joined an ADS domain. This will make
      wsdd report the host being a domain member. It disables workgroup
-     membership reporting.
+     membership reporting. The (provided) hostname is automatically converted
+     to lower case. Use the `-p` option to change this behavior.
 
  * `-n HOSTNAME`, `--hostname HOSTNAME`
 
@@ -103,10 +104,11 @@ allowed.
 
  * `-w WORKGROUP`, `--workgroup WORKGROUP`
 
-	 By default wsdd reports the host is a member of a workgroup rather than a
-	 domain (use the -d/--domain option to override this). With -w/--workgroup
-	 the default workgroup name can be changed. The default work group name is
-	 WORKGROUP.
+     By default wsdd reports the host is a member of a workgroup rather than a
+     domain (use the -d/--domain option to override this). With -w/--workgroup
+     the default workgroup name can be changed. The default work group name is
+     WORKGROUP. The (provided) hostname is automatically converted to upper
+     case. Use the `-p` option to change this behavior.
 
  * `-t`, `--nohttp`
 
@@ -125,11 +127,18 @@ allowed.
      This is useful in cases where the logging mechanism, like systemd on Linux,
      automatically prepend a date and process name plus ID to the log message.
 
+ * `-p`, `--preserve-case`
+
+     Preserve the hostname as it is. Without this option, the hostname is
+     converted as follows. For workgroup environments (see `-w`) the hostname
+     is made upper case by default. Vice versa it is made lower case for usage
+     in domains (see `-d`).
+
  * `-4`, `--ipv4only` (see below)
  * `-6`, `--ipv6only`
 
-	 Restrict to the given address family. If both options are specified no
-	 addreses will be available and wsdd will exit.
+     Restrict to the given address family. If both options are specified no
+     addreses will be available and wsdd will exit.
 
 ## Example Usage
 
@@ -176,6 +185,16 @@ reliably discovered. The reason appears to be that Windows is not always able
 to connect to the HTTP service for unknown reasons. As a workaround, run wsdd
 with IPv4 only.
 
+## Usage with NATs
+
+Do not use wssd on interfaces that are affected by NAT. According to the
+standard, the _ResolveMatch_ messages emitted by wsdd, contain the IP address
+("transport address" in standard parlance) of the interface(s) the application
+has been bound to into. When such messages are retrieved by a client (Windows
+hosts, e.g.) they are unlikely to be able to connect to the provided address
+which has been subject to NAT. To avoid this issue, use the `-i/--interface`
+option to bind wsdd to interfaces not affected by NAT.
+
 ## Tunnel/Bridge Interface
 
 If tunnel/bridge interfaces like those created by OpenVPN or Docker exist, they

man/wsdd.1

@@ -21,7 +21,8 @@ addreses will be available and wsdd will exit.
 \fB\-d \fIDOMAIN\fR, \fB\-\-domain \fIDOMAIN\fR
 Assume that the host running wsdd joined an ADS domain. This will make
 wsdd report the host being a domain member. It disables workgroup
-membership reporting.
+membership reporting. The (provided) hostname is automatically converted
+to lower case. Use the `-p` option to change this behavior.
 .TP
 \fB\-H \fIHOPLIMIT\fR, \fB\-\-hoplimit \fIHOPLIMIT\fR
 Set the hop limit for multicast packets. The default is 1 which should
@@ -40,6 +41,12 @@ Override the host name wsdd uses during discovery. By default the machine's
 host name is used (look at hostname(1)). Only the host name part of a
 possible FQDN will be used in the default case.
 .TP
+\fB\-p\fR, \fB\-\-preserve-case\fR
+Preserve the hostname as it is. Without this option, the hostname is
+converted as follows. For workgroup environments (see -w) the hostname
+is made upper case by default. Vice versa it is made lower case for usage
+in domains (see -d).
+.TP
 \fB\-s\fR, \fB\-\-shortlog\fR
 Use a shorter logging format that only includes the level and message.
 This is useful in cases where the logging mechanism, like systemd on Linux,
@@ -67,7 +74,8 @@ to DEBUG.
 By default wsdd reports the host is a member of a workgroup rather than a
 domain (use the -d/--domain option to override this). With -w/--workgroup
 the default workgroup name can be changed. The default work group name is
-WORKGROUP.
+WORKGROUP. The (provided) hostname is automatically converted to upper
+case. Use the `-p` option to change this behavior.
 .SH EXAMPLE USAGE
 .SS Handle traffic on eth0 and eth2 only, but only with IPv6 addresses
 

src/wsdd.py

@@ -354,14 +354,14 @@ def wsd_handle_get():
     ElementTree.SubElement(host, 'wsdp:ServiceId').text = args.uuid.urn
     if args.domain:
         ElementTree.SubElement(host, PUB_COMPUTER).text = (
-                '{0}/Domain:{1}'.format(
-                    args.hostname.upper(),
-                    args.domain))
+            '{0}/Domain:{1}'.format(
+                args.hostname if args.preserve_case else args.hostname.lower(),
+                args.domain))
     else:
         ElementTree.SubElement(host, PUB_COMPUTER).text = (
-                '{0}/Workgroup:{1}'.format(
-                    args.hostname.upper(),
-                    args.workgroup.upper()))
+            '{0}/Workgroup:{1}'.format(
+                args.hostname if args.preserve_case else args.hostname.upper(),
+                args.workgroup.upper()))
 
     return metadata
 
@@ -613,6 +613,10 @@ def parse_args():
         '-s', '--shortlog',
         help='log only level and message',
         action='store_true')
+    parser.add_argument(
+        '-p', '--preserve-case'
+        help='preserve case of the provided/detected hostname',
+        action='store_true')
 
     args = parser.parse_args(sys.argv[1:])