Unable to get ipv6 dynamically allocated via udhcpc6

For Developers
1

I have enabled udhcpc6 in bluebox via below configurations
CONFIG_UDHCPC6=y
CONFIG_FEATURE_UDHCP_RFC3397=y

When I run the command manually I do not get the ipv6 address assigned

# udhcpc6 -i br-lan
udhcpc6: started, v1.31.1
udhcpc6: sending discover
udhcpc6: sending select
udhcpc6: IPv6 obtained, lease time 86400
Error: any valid prefix is expected rather than "/".
No DNS servers specified, refusing operation.
# dmesg | grep uhcp
#
# ifconfig br-lan
br-lan    Link encap:Ethernet  HWaddr A6:2A:76:44:90:C0
          inet6 addr: fe80::a42a:76ff:fe44:90c0/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:231 errors:0 dropped:0 overruns:0 frame:0
          TX packets:223 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000
          RX bytes:21778 (21.2 KiB)  TX bytes:26561 (25.9 KiB)

Let me know if my udhcpc6 command is correct or not

2

Run a packet capture to see what is being exchanged:
opkg update; opkg install tcpdump; tcpdump -i br-lan -vn udp port 547

3 
# udhcpc6 -i br-lan
udhcpc6: started, v1.31.1
udhcpc6: sending discover
15:59:59.127230 IP6 (hlim 1, next-header UDP (17) payload length: 42) fe80::a42a:76ff:fe44:90c0.546 > ff02::1:2.547: [udp sum ok] dhcp6 solicit (xid=df813b (client-ID hwaddr type 1 a62a764490c0) (IA_NA IAID:165447014 T1:0 T2:0))
15:59:59.127705 IP6 (hlim 64, next-header UDP (17) payload length: 84) fe80::acbb:ccff:fe00:0.547 > fe80::a42a:76ff:fe44:90c0.546: [udp sum ok] dhcp6 advertise (xid=df813b (client-ID hwaddr type 1 a62a764490c0) (server-ID hwaddr type 1 aebbcc000000) (IA_NA IAID:165447014 T1:34560 T2:55296 (IA_ADDR 2001::5 pltime:69120 vltime:86400)))
udhcpc6: sending select
15:59:59.227220 IP6 (hlim 1, next-header UDP (17) payload length: 56) fe80::a42a:76ff:fe44:90c0.546 > ff02::1:2.547: [udp sum ok] dhcp6 request (xid=df813b (client-ID hwaddr type 1 a62a764490c0) (server-ID hwaddr type 1 aebbcc000000) (IA_NA IAID:165447014 T1:0 T2:0))
15:59:59.227588 IP6 (hlim 64, next-header UDP (17) payload length: 84) fe80::acbb:ccff:fe00:0.547 > fe80::a42a:76ff:fe44:90c0.546: [udp sum ok] dhcp6 reply (xid=df813b (client-ID hwaddr type 1 a62a764490c0) (server-ID hwaddr type 1 aebbcc000000) (IA_NA IAID:165447014 T1:34560 T2:55296 (IA_ADDR 2001::5 pltime:69120 vltime:86400)))
udhcpc6: IPv6 obtained, lease time 86400
Error: any valid prefix is expected rather than "/".
No DNS servers specified, refusing operation.

Running the command in background

4

Can you try to request for DNS as well?

5

I checking the reason for this error
Error: any valid prefix is expected rather than "/".

6

Running ip route get / causes exactly that error anyway, if you use ip from iproute2/ip-full, not from busybox which gives you another error.