[Dnsmasq-discuss] dnsmasq 2.78 is failing to respond to dhcpv6 requests forwarded via relay agent

[Sandeep K M]

Hi All,



I have a simple setup with a relay agent as shown below:


+----------+-------------+
|    dnsmasq server |

|         (ubuntu)         |

+-------------------------+
                | m1s1p7 (1040::2/120)
                | (IP route : 2020::/120 via 1040::1 dev m1s1p7  proto
static  metric 512  pref medium)
                |
                |
                | 1/1/2 (1040::1/120)
+----------+------------+
|        Switch            |
|     (Relay Agent )  |
+-----------------------+
                | 1/1/1 (2020::1/120)
                |
                |
                | eth1
+----------+--------------+
|     Client (Ubuntu)  |
+--------------------------+


It is exactly the same as explained in the video :
https://www.youtube.com/watch?v=2Lt1aXpCzvQ


Whenever the client is requesting an IPv6 address dnsmasq is failing to
respond with “DHCPADVERTISE” message. The “DHCPADVERTISE” has not been sent
via the interface. The tcpdump clearly shows that “DHCPADVERTISE” message
has not gone through the interface (m1s1p7), its only showing the
“DHCPSOLICIT” message which has been received:



*root at 8320:~# tcpdump -i m1s1p7 udp port 547 or 546 -vvv -n*

*tcpdump: listening on m1s1p7, link-type EN10MB (Ethernet), capture size
262144 bytes*



*06:32:37.214798 IP6 (hlim 64, next-header UDP (17) payload length: 110)
2020::1.547 > 1040::2.547: [udp sum ok] dhcp6 relay-fwd (linkaddr=2020::1
peeraddr=fe80::250:56ff:febd:7c93 (relay-message (dhcp6 solicit (xid=1894f2
(client-ID hwaddr/time type 1 time 599811159 005056bd7c93) (option-request
DNS-server DNS-search-list Client-FQDN SNTP-servers) (elapsed-time 0)
(IA_NA IAID:1455258771 T1:3600 T2:5400))) (interface-ID 00000024...))*



But the dnsmasq logs shows that it is trying to send the “DHCPADVERTISE”
message but for some reason it’s not been sent via the interface *m1s1p7. *



*root at 8320:~# tail -f /var/log/dnsmasq_swns/dnsmasq6.log*

*Jan  3 06:11:20 dnsmasq[4151]: started, version 2.78 DNS disabled*

*Jan  3 06:11:20 dnsmasq[4151]: compile time options: IPv6 GNU-getopt
no-DBus no-i18n no-IDN DHCP DHCPv6 no-Lua TFTP no-conntrack ipset auth
no-DNSSEC loop-detect inotify*
* Jan  3 06:11:20 dnsmasq-dhcp[4151]: DHCPv6, IP range 2020::10 --
2020::20, lease time 1h*

*Jan  3 06:12:38 dnsmasq-dhcp[4151]: DHCPSOLICIT(m1s1p7)
00:01:00:01:23:c0:64:57:00:50:56:bd:7c:93*

*Jan  3 06:12:38 dnsmasq-dhcp[4151]: DHCPADVERTISE(m1s1p7) 2020::12
00:01:00:01:23:c0:64:57:00:50:56:bd:7c:93*



*Does anyone has any clue on what is going on here ? Am I missing something
? Here is my dnsmasq config file contents:*



*root at 8320:~# cat /var/run/dnsmasq_swns/dnsmasq6.conf*

*enable-ra*

*log-dhcp*

*log-queries*

*log-facility=/var/log/dnsmasq_swns/dnsmasq6.log*

*port=0*

*dhcp-script=/usr/bin/dhcp_server_leases*

*leasefile-ro*

*dhcp-lease-max=64000*

*dhcp-range=set:default+test,2020::10,2020::20,120*



Thanks
-Sandeep
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