xend: Add interface name definition support for xend-relocation-address

Add a new feature for xend-relocation-address option to support
definition by interface name which can be useful for people having
e.g. a cluster environment with multiple network interfaces on all of
the machines with only one reserved to be registered to a private
cluster network. This way they won't need to specify the relocation
address manually on all the machines but just simple providing the
interface name to get the IP address from would do the job (all the
machines have to have this interface named the same to make it
working, of course).

Technically it reads the interface name and gets its IP address using
ioctl call of SIOCGIFADDR and if the interface doesn't have the
address, i.e. if non-existing interface or hostname was provided the
original ifname is returned to preserve the old behaviour.

Signed-off-by: Michal Novotny <minovotn@redhat.com>

tools/examples/xend-config.sxp

@@ -110,6 +110,8 @@
 # Address xend should listen on for relocation-socket connections, if
 # xend-relocation-server is set.
 # Meaning and default as for xend-address above.
+# Also, interface name is allowed (e.g. eth0) there to get the
+# relocation address to be bound on.
 #(xend-relocation-address '')
 
 # The hosts allowed to talk to the relocation port.  If this is empty (the

tools/python/xen/web/tcp.py

@@ -21,6 +21,8 @@ import errno
 import re
 import socket
 import time
+import fcntl     # For get_interface_addr
+import struct    # For get_interface_addr
 
 import connection
 
@@ -35,6 +37,49 @@ class TCPListener(connection.SocketListener):
         self.hosts_allow = hosts_allow
         connection.SocketListener.__init__(self, protocol_class)
 
+    def isValidHex(self, word):
+        # If we have empty word we treat it as valid
+        if len(word) == 0:
+            return True
+        try:
+            int(word, 16)
+            return True
+        except ValueError:
+            return False
+
+    def isValidIP(self, ipaddr):
+        # Check for IPv4 address
+        numValid = 0
+        tmp = ipaddr.split('.')
+        for byte in tmp:
+            if byte.isdigit():
+                numValid += 1
+
+        if numValid == len(tmp):
+            return True
+
+        # Check for IPv6 address
+        numValid = 0
+        tmp = ipaddr.split(':')
+        for word in tmp:
+            if self.isValidHex(word):
+                numValid += 1
+
+        return numValid == len(tmp)
+
+    def getIfAddr(self, ifname):
+        s = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
+        try:
+            x = socket.inet_ntoa(fcntl.ioctl(
+                s.fileno(),
+                0x8915,  # SIOCGIFADDR
+                struct.pack('256s', ifname[:15])
+            )[20:24])
+            s.close()
+        except Exception, e:
+            x = ifname
+
+        return x
 
     def createSocket(self):
         sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
@@ -46,6 +91,9 @@ class TCPListener(connection.SocketListener):
         timeout = time.time() + 30
         while True:
             try:
+                if not self.isValidIP(self.interface):
+                    self.interface = self.getIfAddr(self.interface)
+                log.debug("Listening on %s:%s" % (self.interface, self.port))
                 sock.bind((self.interface, self.port))
                 return sock
             except socket.error, (_errno, strerrno):
@@ -78,6 +126,49 @@ class SSLTCPListener(TCPListener):
 
         TCPListener.__init__(self, protocol_class, port, interface, hosts_allow)
 
+    def isValidHex(self, word):
+        # If we have empty word we treat it as valid
+        if len(word) == 0:
+            return True
+        try:
+            int(word, 16)
+            return True
+        except ValueError:
+            return False
+
+    def isValidIP(self, ipaddr):
+        # Check for IPv4 address
+        numValid = 0
+        tmp = ipaddr.split('.')
+        for byte in tmp:
+            if byte.isdigit():
+                numValid += 1
+
+        if numValid == len(tmp):
+            return True
+
+        # Check for IPv6 address
+        numValid = 0
+        tmp = ipaddr.split(':')
+        for word in tmp:
+            if self.isValidHex(word):
+                numValid += 1
+
+        return numValid == len(tmp)
+
+    def getIfAddr(self, ifname):
+        s = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
+        try:
+            x = socket.inet_ntoa(fcntl.ioctl(
+                s.fileno(),
+                0x8915,  # SIOCGIFADDR
+                struct.pack('256s', ifname[:15])
+            )[20:24])
+            s.close()
+        except Exception, e:
+            x = ifname
+
+        return x
 
     def createSocket(self):
         from OpenSSL import SSL
@@ -97,6 +188,9 @@ class SSLTCPListener(TCPListener):
         timeout = time.time() + 30
         while True:
             try:
+                if not self.isValidIP(self.interface):
+                    self.interface = self.getIfAddr(self.interface)
+                log.debug("Listening on %s:%s" % (self.interface, self.port))
                 sock.bind((self.interface, self.port))
                 return sock
             except socket.error, (_errno, strerrno):