Neighbour advertisement messages not coming from sub interface linux

I created a macvlan interface with eth0 as the parent interface. I can see NS for eth0 and NA msgs from eth0 but not for macvlan interface. However when I ping the gateway from macvlan, then NS msgs are seen for macvlan but macvlan is not responding with NA. What configuration would help resolve this? I want to see periodic NS and NA msgs for macvlan the way I am seeing for eth0 currently. There are no namespaces created. I am working in global namespace itself. Also in order to ping to the gateway from macvlan I had to put "iface lo inet6 loopback" in /etc/network/interfaces file. Otherwise, ping6 kept on changing source into whenever I tried to explicitly put macvlan using -I in ping6. Ping6 from macvlan to eth0 is also not working. Ping6 always changes the source address with msg like -> "Warning: source address might be selected on a device other than macvlan1." To reproduce the issue checkout below snippets:

ubuntu@vm0:~$ uname -r
3.13.0-36-generic

ubuntu@vm0:~$ ip -6 link                                                            
1: lo:  mtu 65536 qdisc noqueue state UNKNOWN mode DEFAULT group default 
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
2: eth0:  mtu 1500 qdisc pfifo_fast state UP mode DEFAULT group default qlen 1000
    link/ether 02:ec:39:e5:22:50 brd ff:ff:ff:ff:ff:ff
3: macvlan1@eth0:  mtu 1500 qdisc noqueue state UNKNOWN mode DEFAULT group default 
    link/ether ce:99:a8:33:1e:5d brd ff:ff:ff:ff:ff:ff

ubuntu@vm0:~$ ip -6 address
1: lo:  mtu 65536 
    inet6 ::1/128 scope host 
       valid_lft forever preferred_lft forever
2: eth0:  mtu 1500 qlen 1000
    inet6 2001:db8::3/64 scope global 
       valid_lft forever preferred_lft forever
    inet6 fe80::ec:39ff:fee5:2250/64 scope link 
       valid_lft forever preferred_lft forever
3: macvlan1@eth0:  mtu 1500 
    inet6 2001:db8::8/64 scope global 
       valid_lft forever preferred_lft forever
    inet6 fe80::cc99:a8ff:fe33:1e5d/64 scope link 
       valid_lft forever preferred_lft forever

ubuntu@vm0:~$ ip -6 route
2001:db8::/64 dev macvlan1  proto kernel  metric 256 
2001:db8::/64 dev eth0  proto kernel  metric 256 
2001:db8::/48 dev eth0  proto kernel  metric 256 
2001:db8::/48 dev macvlan1  proto kernel  metric 256 
fe80::/64 dev eth0  proto kernel  metric 256 
fe80::/64 dev macvlan1  proto kernel  metric 256 
default via 2001:db8::1 dev eth0  metric 1 
default via fe80::ec:39ff:fee5:22 dev eth0  metric 1024

ubuntu@vm0:~$ ip -6 neighbor
2001:db8::1 dev macvlan1 lladdr 00:00:5e:00:01:00 router REACHABLE
2001:db8::1 dev eth0 lladdr 00:00:5e:00:01:00 router STALE
2001:db8::2 dev macvlan1  router FAILED
fe80::5e00:100 dev macvlan1 lladdr 00:00:5e:00:01:00 router STALE
fe80::5e00:100 dev eth0 lladdr 00:00:5e:00:01:00 router STALE
2001:db8::2 dev eth0 lladdr 00:00:5e:00:01:00 router DELAY
2001:db8::9 dev macvlan1 lladdr 6a:25:a8:4e:23:5d STALE

When trying to ping eth0 from macvlan, ping6 changes the source with below warning:

ubuntu@vm0:~$ ping6 2001:db8::3 -I macvlan1
ping6: Warning: source address might be selected on device other than macvlan1.
PING 2001:db8::3(2001:db8::3) from 2001:db8::3 macvlan1: 56 data bytes
64 bytes from 2001:db8::3: icmp_seq=1 ttl=64 time=4.41 ms
64 bytes from 2001:db8::3: icmp_seq=2 ttl=64 time=0.548 ms
64 bytes from 2001:db8::3: icmp_seq=3 ttl=64 time=0.628 ms
64 bytes from 2001:db8::3: icmp_seq=4 ttl=64 time=0.546 ms
^C
--- 2001:db8::3 ping statistics ---
4 packets transmitted, 4 received, 0% packet loss, time 3053ms
rtt min/avg/max/mdev = 0.546/1.534/4.417/1.665 ms

Ping to gateway works from macvlan

ubuntu@vm0:~$ ping6 2001:db8::1 -I macvlan1
PING 2001:db8::1(2001:db8::1) from 2001:db8::8 macvlan1: 56 data bytes
64 bytes from 2001:db8::1: icmp_seq=2 ttl=255 time=3.50 ms
64 bytes from 2001:db8::1: icmp_seq=3 ttl=255 time=1.63 ms
64 bytes from 2001:db8::1: icmp_seq=4 ttl=255 time=2.54 ms
64 bytes from 2001:db8::1: icmp_seq=5 ttl=255 time=1.26 ms
^C
--- 2001:db8::1 ping statistics ---
5 packets transmitted, 4 received, 20% packet loss, time 4041ms
rtt min/avg/max/mdev = 1.261/2.237/3.501/0.867 ms

tcpdump on eth0 looks like this

ubuntu@vm0:~$ sudo tcpdump -eni eth0 ip6
11:45:39.281934 00:00:5e:00:01:00 > 33:33:00:00:00:01, ethertype IPv6 (0x86dd), length 110: fe80::5e00:100 > ff02::1: ICMP6, router advertisement, length 56
11:45:40.105204 00:00:5e:00:01:00 > 33:33:ff:00:00:03, ethertype IPv6 (0x86dd), length 86: 2001:db8::2 > ff02::1:ff00:3: ICMP6, neighbor solicitation, who has 2001:db8::3, length 32
11:45:40.105975 02:ec:39:e5:22:50 > 00:00:5e:00:01:00, ethertype IPv6 (0x86dd), length 86: 2001:db8::3 > 2001:db8::2: ICMP6, neighbor advertisement, tgt is 2001:db8::3, length 32

but no NS for macvlan

tcpdump: verbose output suppressed, use -v or -vv for full protocol decode
listening on macvlan1, link-type EN10MB (Ethernet), capture size 65535 bytes
11:48:09.316865 00:00:5e:00:01:00 > 33:33:00:00:00:01, ethertype IPv6 (0x86dd), length 110: fe80::5e00:100 > ff02::1: ICMP6, router advertisement, length 56
11:48:10.197974 00:00:5e:00:01:00 > 33:33:ff:00:00:03, ethertype IPv6 (0x86dd), length 86: 2001:db8::2 > ff02::1:ff00:3: ICMP6, neighbor solicitation, who has 2001:db8::3, length 32
11:48:20.220753 00:00:5e:00:01:00 > 33:33:ff:00:00:03, ethertype IPv6 (0x86dd), length 86: 2001:db8::2 > ff02::1:ff00:3: ICMP6, neighbor solicitation, who has 2001:db8::3, length 32