Provide DNS Search List in DHCH6_Reply

In case of an IPv6 only VM we have to serve a Domain Search List
so that Windows VM can find the kms server by issuing:

nslookup -type=srv _vlmcs._tcp

An extra config option in ipv6 section is added; domains
This is a list of search domains included in DHCP6_Reply.
Since we validate it with force_list() there is no need for a
trailing comma.

This info could be passed in RAs but DNSSL options is not currently
supported by scapy's inet6.py.

Signed-off-by: Dimitris Aragiorgis <dimara@grnet.gr>

diff --git a/nfdhcpd b/nfdhcpd
index 0bb36ea..41980ce 100755 (executable)
--- a/nfdhcpd
+++ b/nfdhcpd
@@ -55,7 +55,7 @@ from scapy.layers.inet6 import IPv6, ICMPv6ND_RA, ICMPv6ND_NA, \
 from scapy.layers.dhcp import BOOTP, DHCP
 from scapy.layers.dhcp6 import DHCP6_Reply, DHCP6OptDNSServers, \
                                DHCP6OptServerId, DHCP6OptClientId, \
-                               DUID_LLT, DHCP6_InfoRequest
+                               DUID_LLT, DHCP6_InfoRequest, DHCP6OptDNSDomains
 
 
 DEFAULT_CONFIG = "/etc/nfdhcpd/nfdhcpd.conf"
@@ -96,6 +96,7 @@ rs_queue = integer(min=0, max=65535)
 ns_queue = integer(min=0, max=65535)
 dhcp_queue = integer(min=0, max=65535)
 nameservers = ip_addr_list(family=6)
+domains = force_list(default=None)
 """
 
 
@@ -356,9 +357,10 @@ class VMNetProxy(object):  # pylint: disable=R0902
                  rs_queue_num=None, ns_queue_num=None, dhcpv6_queue_num=None,
                  dhcp_lease_lifetime=DEFAULT_LEASE_LIFETIME,
                  dhcp_lease_renewal=DEFAULT_LEASE_RENEWAL,
-                 dhcp_domain='',
+                 dhcp_domain=None,
                  dhcp_server_ip=DHCP_DUMMY_SERVER_IP, dhcp_nameservers=None,
-                 ra_period=DEFAULT_RA_PERIOD, ipv6_nameservers=None):
+                 ra_period=DEFAULT_RA_PERIOD, ipv6_nameservers=None,
+                 dhcpv6_domains=None):
 
         try:
             getattr(nfqueue.payload, 'get_physindev')
@@ -381,6 +383,11 @@ class VMNetProxy(object):  # pylint: disable=R0902
         else:
             self.ipv6_nameservers = ipv6_nameservers
 
+        if dhcpv6_domains is None:
+            self.dhcpv6_domains = []
+        else:
+            self.dhcpv6_domains = dhcpv6_domains
+
         self.ipv6_enabled = False
 
         self.clients = {}
@@ -745,14 +752,23 @@ class VMNetProxy(object):  # pylint: disable=R0902
         logging.info(" - Generating DHCPv6 response for host %s (mac %s) on tap %s",
                       binding.hostname, binding.mac, binding.tap)
 
+        if self.dhcpv6_domains:
+            domains = self.dhcpv6_domains
+        else:
+            domains = [binding.hostname.split('.', 1)[-1]]
+
+        # We do this in order not to caclulate optlen ourselves
+        dnsdomains = str(DHCP6OptDNSDomains(dnsdomains=domains))
+        dnsservers = str(DHCP6OptDNSServers(dnsservers=self.ipv6_nameservers))
+
         resp = Ether(src=indevmac, dst=binding.mac)/\
                IPv6(tc=192, src=str(ifll), dst=str(ofll))/\
                UDP(sport=pkt.dport, dport=pkt.sport)/\
                DHCP6_Reply(trid=pkt[DHCP6_InfoRequest].trid)/\
                DHCP6OptClientId(duid=pkt[DHCP6OptClientId].duid)/\
                DHCP6OptServerId(duid=DUID_LLT(lladdr=indevmac, timeval=time.time()))/\
-               DHCP6OptDNSServers(dnsservers=self.ipv6_nameservers,
-                                  optlen=16 * len(self.ipv6_nameservers))
+               DHCP6OptDNSDomains(dnsdomains)/\
+               DHCP6OptDNSServers(dnsservers)
 
         try:
             binding.sendp(resp)
@@ -1186,6 +1202,7 @@ if __name__ == "__main__":
             "ns_queue_num": config["ipv6"].as_int("ns_queue"),
             "ra_period": config["ipv6"].as_int("ra_period"),
             "ipv6_nameservers": config["ipv6"]["nameservers"],
+            "dhcpv6_domains": config["ipv6"]["domains"],
         })
 
     # pylint: disable=W0142

diff --git a/nfdhcpd.conf b/nfdhcpd.conf
index d1d3a4f..84c6799 100644 (file)
--- a/nfdhcpd.conf
+++ b/nfdhcpd.conf
@@ -16,7 +16,7 @@ dhcp_queue = 42 # NFQUEUE number to listen on for DHCP requests
 # IPv4 nameservers to include in DHCP responses
 nameservers = 192.0.2.2, 192.0.2.3
 # Optional domain to serve with the replies
-#domain = example.com
+domain = example.com
 
 ## IPv6-related functionality
 [ipv6]
@@ -26,4 +26,7 @@ rs_queue = 43 # NFQUEUE number to listen on for router solicitations
 ns_queue = 44 # NFQUEUE number to listen on for neighbor solicitations
 dhcp_queue = 45 # NFQUEUE number to listen on for neighbor solicitations
 # IPv6 nameservers to send using the ICMPv6 RA RDNSS option (RFC 5006)
+# since it is not supported by several OS we serve them to DHCPv6 replies
 nameservers = 2001:db8:100::1, 2001:db8:200::2
+# Optional list of search domains to serve with DHCPv6 replies
+domains = example.com, synnefo.live