[openwrt] can not get the new Mesh Local Prefix,help,thanks

[haitao52198]

I use openthread-br with OpenWrt 21.02.07

ot-ctl dataset init new
ot-ctl dataset channel 15
ot-ctl dataset panid 0x76d7
ot-ctl dataset extpanid 9b636d580129ea60
ot-ctl dataset networkkey 9b636d580129ea60a95e419904e031af
ot-ctl dataset meshlocalprefix fd2d:19fc:af4f:e7dc:: 
ot-ctl dataset networkname WHZY-6d7
ot-ctl dataset commit active
ot-ctl ifconfig up
ot-ctl thread start
ot-ctl netdata register

device I used nrf52840 ncs sdk, first time erase all the flash and download, it will work ok. after upgrade the openwrt firmwave，dataset meshlocalprefix will change, the device can attach the new thread net, but it still keep the old meshlocalprefix, how to fix it?

on openwrt

ot-ctl dataset active
Active Timestamp: 1
Channel: 15
Channel Mask: 0x07fff800
Ext PAN ID: 9b636d580129ea60
Mesh Local Prefix: fd0d:193d:97d7:d093::/64
Network Key: 9b636d580129ea60a95e419904e031af
Network Name: WHZY-6d7
PAN ID: 0x76d7
PSKc: a0c477a887b0419b66b652570ac8548a
Security Policy: 672 onrc 0
Done
root@OpenWrt:~# ot-ctl prefix
fdec:fc69:e16b:1::/64 paos low ec00
Done
root@OpenWrt:~# ot-ctl prefix meshlocal
fd0d:193d:97d7:d093::/64
Done
root@OpenWrt:~# ot-ctl netdata show
Prefixes:
fdec:fc69:e16b:1::/64 paos low ec00
Routes:
fdec:fc69:e16b:2:0:0::/96 sn low ec00
fc00::/7 s med ec00
Services:
44970 01 1d000500000e10 s ec00
44970 5d fd0d193d97d7d093145fe65df9984ecfd120 s ec00
Contexts:
fdec:fc69:e16b:1::/64 1 c
Commissioning:
7339 - - -
Done
root@OpenWrt:~# ot-ctl ipaddr
fd0d:193d:97d7:d093:0:ff:fe00:fc11
fdec:fc69:e16b:1:b70b:671f:a995:8de1
fd0d:193d:97d7:d093:0:ff:fe00:fc10
fd0d:193d:97d7:d093:0:ff:fe00:fc38
fd0d:193d:97d7:d093:0:ff:fe00:fc00
fd0d:193d:97d7:d093:0:ff:fe00:ec00
fd0d:193d:97d7:d093:145f:e65d:f998:4ecf
fe80:0:0:0:5c98:c14a:d84:7d23
Done

on nrf52840

 ot netdata show
Prefixes:
fdec:fc69:e16b:1::/64 paos low fffe
Routes:
fdec:fc69:e16b:2:0:0::/96 sn low fffe
fc00::/7 s med fffe
Services:
44970 01 1d000500000e10 s fc10
44970 5d fd0d193d97d7d093145fe65df9984ecfd120 s fc11
Contexts:
fdec:fc69:e16b:1::/64 1 c
Done
uart:~$ ot dataset active
Active Timestamp: 1
Channel: 15
Channel Mask: 0x07fff800
Ext PAN ID: 9b636d580129ea60
Mesh Local Prefix: fd93:3c3a:9300:df63::/64
Network Key: 9b636d580129ea60a95e419904e031af
Network Name: WHZY-6d7
PAN ID: 0x76d7
PSKc: 06dac050d3119482a41155d1f798c1ab
Security Policy: 672 onrc 0
Done

 ot ipaddr
fdec:fc69:e16b:1:ae1b:682a:a6b2:80b7
fd93:3c3a:9300:df63:0:ff:fe00:ec01
fd93:3c3a:9300:df63:549:e140:efe8:67fd
fe80:0:0:0:48d1:d855:59c0:1fcd
Done

when I use nrf52840 to ping ff03::1 tcpdum will show fd0d:193d:97d7:d093:549:e140:efe8:67fd > ff03::1: [bad icmp6 cksum 0x8e23 -> 0xbb9f!] ICMP6, echo request, seq 1, I think the Mesh Local Prefix cause the problem. the devce still used old Mesh Local Prefix fd93:3c3a:9300:df63::/64

tcpdump -i wpan0 -v -vv
tcpdump: listening on wpan0, link-type RAW (Raw IP), capture size 262144 bytes
06:50:19.046535 IP6 (hlim 255, next-header UDP (17) payload length: 50) fe80::5c98:c14a:d84:7d23.19788 > ip6-allnodes.19788: [udp sum ok] UDP, length 42
06:50:25.327222 IP6 (hlim 64, next-header ICMPv6 (58) payload length: 16) fd0d:193d:97d7:d093:549:e140:efe8:67fd > ff03::1: [bad icmp6 cksum 0x8e23 -> 0xbb9f!] ICMP6, echo request, seq 1
06:50:27.496928 IP6 (hlim 255, next-header UDP (17) payload length: 50) fe80::5c98:c14a:d84:7d23.19788 > ip6-allnodes.19788: [udp sum ok] UDP, length 42
06:50:38.756416 IP6 (hlim 255, next-header UDP (17) payload length: 50) fe80::5c98:c14a:d84:7d23.19788 > ip6-allnodes.19788: [udp sum ok] UDP, length 42

[jwhui]

Can you provide details on how you are joining the nrf52840 device?

[haitao52198]

Thans for reply, Config thread in prj.conf by nordic ncs sdk, I have find the answer from "https://github.com/orgs/openthread/discussions/7876"
But I still want to know why it need to rely on this timestamp,? because there is no rtc on my hardware. If the openwrt system ota does not retain the configuration, I have no way of knowing how to generate an updated timestamp. Is there any way to allow device forcibly updates the dataset information?

[jwhui]

Active Timestamp simply allows devices to determine which one is newer.

If you always want a device to adopt whatever network it initially joins, set the Active Timestamp value to 0.

See this quick start guide for more details.