OS detection, hostname get/set, get ip address on all platforms

Preperation for fl0w network discovery.

Shared/Utils.py

@@ -1,6 +1,14 @@
 from traceback import print_exception
 from sys import exc_info
 import platform
+import os
+import struct
+import socket
+import fcntl
+
+class HostnameNotChangedError(PermissionError):
+	def __init__(self):
+		super(PermissionError, self).__init__("hostname could not be changed")	
 
 def capture_trace():
 	exc_type, exc_value, exc_traceback = exc_info()
@@ -8,4 +16,57 @@ def capture_trace():
 
 
 def is_wallaby():
-	return "3.18.21-custom" in platform.uname().release
+	return "3.18.21-custom" in platform.uname().release
+
+
+def is_linux():
+	return platform.uname().system == "Linux"
+
+
+def is_darwin():
+	return platform.uname().system == "Darwin"
+
+
+def is_windows():
+	return platform.uname().system == "Windows"	
+
+
+def set_hostname(hostname):
+	if is_linux():
+		if os.geteuid() == 0:
+			open("/etc/hostname", "w").write(hostname)
+		else:
+			raise HostnameNotChangedError()
+	elif is_darwin():
+		if os.geteuid() == 0:
+			subprocess.check_call(["scutil", "--set", "HostName", hostname])
+		else:
+			raise HostnameNotChangedError()
+	else:
+		raise HostnameNotChangedError()
+
+
+def get_hostname():
+	return platform.uname().node
+
+
+def get_ip_address(ifname=None):
+	if ifname:
+		if is_linux():
+			s = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
+			try:
+				return socket.inet_ntoa(fcntl.ioctl(
+				s.fileno(),
+				0x8915,  # SIOCGIFADDR
+				struct.pack('256s', ifname[:15].encode()))[20:24])
+			except OSError:
+				pass
+	else:
+		if is_darwin() or is_windows():
+			return socket.gethostbyname(socket.gethostname())
+		if is_linux():
+			sock = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
+			sock.connect(('8.8.8.8', 53))
+			ip_address = sock.getsockname()[0]
+			sock.close()
+			return ip_address