Get link local address when performing mdns service discovery #8967

fuxiaoming-lumi · 2023-04-17T07:12:42Z

fuxiaoming-lumi
Apr 17, 2023

When our device (Matter over Thread) is added to Google Nest Gen2, and our device try to perform mdns discovery for another LAN device but it get the link local address(fe80::e65f:1ff:fec5:9ceb) from Google Nest Gen2.

The link local address of this LAN device cannot establish a route for the thread node, causing the thread device to try to send a message to this ip address, and the message is unreachable. In fact, this LAN device also has a ULA address, but what I see is that Google Nest Gen2 does not inform the thread device of this ULA address(fd78:314c:785b:4546:e65f:1ff:fec5:9ceb). I believe ULA is the address that the thread device wants to obtain for mdns discovery(AAAA record).

Answered by fuxiaoming-lumi

May 10, 2023

Should be fixed.

View full answer

jwhui · 2023-04-17T22:45:37Z

jwhui
Apr 17, 2023
Maintainer

@fuxiaoming-lumi , can you provide a pcap file for the mDNS traffic on the LAN? I'd like to see the mDNS traffic between the Nest Hub and your LAN device.

0 replies

fuxiaoming-lumi · 2023-04-23T09:48:31Z

fuxiaoming-lumi
Apr 23, 2023
Author

Sorry for late reply. I try to let my raspberry pi connect to WiFi Router through wifi this time and still can reproduce this issue.

Network Topology:
raspberry pi (Register mdns service)<------> WiFi Router <------> nest hub gen 2 <------> matter over thread accessory

raspberry pi address:

wlan0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
        inet 192.168.1.104  netmask 255.255.255.0  broadcast 192.168.1.255
        inet6 fe80::dea6:32ff:fef3:954a  prefixlen 64  scopeid 0x20<link>
        inet6 fde2:124d:3efb:15d0:dea6:32ff:fef3:954a  prefixlen 64  scopeid 0x0<global>
        ether dc:a6:32:f3:95:4a  txqueuelen 1000  (Ethernet)
        RX packets 13535  bytes 2847162 (2.8 MB)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 5339  bytes 3047102 (3.0 MB)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

matter over thread accessory ip address:

OpenThread State Changed (Flags: 0x00000001)
   Thread Unicast Addresses:
        fdf6:a0b8:1d4a:1:9fc7:7cc7:e28e:80e7/64 valid preferred
        fdc2:3654:e743:0:0:ff:fe00:401/64 valid rloc
        fdc2:3654:e743:0:7b5c:76ab:1591:7355/64 valid
        fe80:0:0:0:f85a:20db:8c3e:ec0e/64 valid preferred

Capture the Wlan traffic log from Raspberry PI side: wlan_1251.pcapng
Capture the thread sniffer log: thread_11244_issue.pcapng
sniffer_log.zip

Thread Info:
PANID: 0x703D
Thread Network Key: A4D6078BDD1929443E9246CE7BC16C40

Check the No.11236 from Thread sniffer log.
It shows that the thread accessory is try to query SRV for mdns service(89075EE6A1383DCC-0000000000000001._matter._tcp)

Queries
    89075EE6A1383DCC-0000000000000001._matter._tcp.default.service.arpa: type SRV, class IN
        Name: 89075EE6A1383DCC-0000000000000001._matter._tcp.default.service.arpa
        [Name Length: 67]
        [Label Count: 6]
        Type: SRV (Server Selection) (33)
        Class: IN (0x0001)
    89075EE6A1383DCC-0000000000000001._matter._tcp.default.service.arpa: type TXT, class IN
        Name: 89075EE6A1383DCC-0000000000000001._matter._tcp.default.service.arpa
        [Name Length: 67]
        [Label Count: 6]
        Type: TXT (Text strings) (16)
        Class: IN (0x0001)

Check the No.11244 from Thread sniffer log.
But get the additional records as following and only link local address from Nest Hub Gen2 (Thread Border Router)

Domain Name System (response)
    Transaction ID: 0x9907
    Flags: 0x8000 Standard query response, No error
    Questions: 2
    Answer RRs: 2
    Authority RRs: 0
    Additional RRs: 1
    Queries
        89075EE6A1383DCC-0000000000000001._matter._tcp.default.service.arpa: type SRV, class IN
        89075EE6A1383DCC-0000000000000001._matter._tcp.default.service.arpa: type TXT, class IN
    Answers
        89075EE6A1383DCC-0000000000000001._matter._tcp.default.service.arpa: type SRV, class IN, priority 0, weight 0, port 5540, target DCA632F3954A0000.default.service.arpa
        89075EE6A1383DCC-0000000000000001._matter._tcp.default.service.arpa: type TXT, class IN
    Additional records
        DCA632F3954A0000.default.service.arpa: type AAAA, class IN, addr fe80::dea6:32ff:fef3:954a
            Name: DCA632F3954A0000.default.service.arpa
            Type: AAAA (IPv6 Address) (28)
            Class: IN (0x0001)
            Time to live: 10 (10 seconds)
            Data length: 16
            AAAA Address: fe80::dea6:32ff:fef3:954a
    [Request In: 11236]
    [Time: 0.066649000 seconds]

While the raspberry pi do have ULA (fde2:124d:3efb:15d0:dea6:32ff:fef3:954a) but it look like it don't include in additional records.

Check the No.1251 from Wlan sniffer log.

Frame 1251: 266 bytes on wire (2128 bits), 266 bytes captured (2128 bits)
Ethernet II, Src: Raspberr_f3:95:4a (dc:a6:32:f3:95:4a), Dst: IPv6mcast_fb (33:33:00:00:00:fb)
Internet Protocol Version 6, Src: fe80::dea6:32ff:fef3:954a, Dst: ff02::fb
User Datagram Protocol, Src Port: 5353, Dst Port: 5353
Multicast Domain Name System (response)
    Transaction ID: 0x0000
    Flags: 0x8400 Standard query response, No error
    Questions: 0
    Answer RRs: 1
    Authority RRs: 0
    Additional RRs: 4
    Answers
        _matter._tcp.local: type PTR, class IN, 89075EE6A1383DCC-0000000000000001._matter._tcp.local
            Name: _matter._tcp.local
            Type: PTR (domain name PoinTeR) (12)
            .000 0000 0000 0001 = Class: IN (0x0001)
            0... .... .... .... = Cache flush: False
            Time to live: 120 (2 minutes)
            Data length: 36
            Domain Name: 89075EE6A1383DCC-0000000000000001._matter._tcp.local
    Additional records
        89075EE6A1383DCC-0000000000000001._matter._tcp.local: type SRV, class IN, cache flush, priority 0, weight 0, port 5540, target DCA632F3954A0000.local
            Service: 89075EE6A1383DCC-0000000000000001
            Protocol: _matter
            Name: _tcp.local
            Type: SRV (Server Selection) (33)
            .000 0000 0000 0001 = Class: IN (0x0001)
            1... .... .... .... = Cache flush: True
            Time to live: 120 (2 minutes)
            Data length: 25
            Priority: 0
            Weight: 0
            Port: 5540
            Target: DCA632F3954A0000.local
        89075EE6A1383DCC-0000000000000001._matter._tcp.local: type TXT, class IN, cache flush
            Name: 89075EE6A1383DCC-0000000000000001._matter._tcp.local
            Type: TXT (Text strings) (16)
            .000 0000 0000 0001 = Class: IN (0x0001)
            1... .... .... .... = Cache flush: True
            Time to live: 4500 (1 hour, 15 minutes)
            Data length: 21
            TXT Length: 7
            TXT: SII=300
            TXT Length: 8
            TXT: SAI=2000
            TXT Length: 3
            TXT: T=1
        DCA632F3954A0000.local: type AAAA, class IN, cache flush, addr fde2:124d:3efb:15d0:dea6:32ff:fef3:954a
            Name: DCA632F3954A0000.local
            Type: AAAA (IPv6 Address) (28)
            .000 0000 0000 0001 = Class: IN (0x0001)
            1... .... .... .... = Cache flush: True
            Time to live: 120 (2 minutes)
            Data length: 16
            AAAA Address: fde2:124d:3efb:15d0:dea6:32ff:fef3:954a
        DCA632F3954A0000.local: type AAAA, class IN, cache flush, addr fe80::dea6:32ff:fef3:954a
            Name: DCA632F3954A0000.local
            Type: AAAA (IPv6 Address) (28)
            .000 0000 0000 0001 = Class: IN (0x0001)
            1... .... .... .... = Cache flush: True
            Time to live: 120 (2 minutes)
            Data length: 16
            AAAA Address: fe80::dea6:32ff:fef3:954a
    [Unsolicited: True]

BTW, if I replace nest with otbr, the accessory can obtain the ULA address of raspberry pi and everything work fine.

0 replies

fuxiaoming-lumi · 2023-04-28T05:56:02Z

fuxiaoming-lumi
Apr 28, 2023
Author

Update my test result with Nest Hub Gen2.
1.Thread Accessory(SRP Client) Query Request (Sniffer Log No.32117)

Queries
    11DA090384C9CFB4-0000000000000001._matter._tcp.default.service.arpa: type SRV, class IN
    11DA090384C9CFB4-0000000000000001._matter._tcp.default.service.arpa: type TXT, class IN

2.Nest Hub(SRP Server) Query Response with LLA (Sniffer Log No.32127)

Queries
    11DA090384C9CFB4-0000000000000001._matter._tcp.default.service.arpa: type SRV, class IN
    11DA090384C9CFB4-0000000000000001._matter._tcp.default.service.arpa: type TXT, class IN
Answers
    11DA090384C9CFB4-0000000000000001._matter._tcp.default.service.arpa: type SRV, class IN, priority 0, weight 0, port 5540, target DCA632F3954A0000.default.service.arpa
    11DA090384C9CFB4-0000000000000001._matter._tcp.default.service.arpa: type TXT, class IN
Additional records
    DCA632F3954A0000.default.service.arpa: type AAAA, class IN, addr fe80::dea6:32ff:fef3:954a
        Name: DCA632F3954A0000.default.service.arpa
        Type: AAAA (IPv6 Address) (28)
        Class: IN (0x0001)
        Time to live: 10 (10 seconds)
        Data length: 16
        AAAA Address: fe80::dea6:32ff:fef3:954a

3.Let Thread Accessory Query Request for AAAA (Sniffer Log No.32129)

Queries
    DCA632F3954A0000.default.service.arpa: type AAAA, class IN
        Name: DCA632F3954A0000.default.service.arpa
        [Name Length: 37]
        [Label Count: 4]
        Type: AAAA (IPv6 Address) (28)
        Class: IN (0x0001)

Nest Hub(SRP Server) Query Response with ULA (Sniffer Log No.32161)

Queries
    DCA632F3954A0000.default.service.arpa: type AAAA, class IN
Answers
    DCA632F3954A0000.default.service.arpa: type AAAA, class IN, addr fddc:3740:f4b5:4ff4:dea6:32ff:fef3:954a
        Name: DCA632F3954A0000.default.service.arpa
        Type: AAAA (IPv6 Address) (28)
        Class: IN (0x0001)
        Time to live: 10 (10 seconds)
        Data length: 16
        AAAA Address: fddc:3740:f4b5:4ff4:dea6:32ff:fef3:954a

5.Network is Reachable now

Thread Info:
PANID: 0x703D
Thread Network Key: A4D6078BDD1929443E9246CE7BC16C40
Sniffer log: google_thread_srp_AAAA_issue.zip

0 replies

fuxiaoming-lumi · 2023-05-10T03:30:29Z

fuxiaoming-lumi
May 10, 2023
Author

Should be fixed.

0 replies

jwhui · 2023-05-10T03:31:56Z

jwhui
May 10, 2023
Maintainer

Nest Hub returning link-local address is a bug that's specific to the product. That should be addressed in an upcoming software update.

0 replies

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Get link local address when performing mdns service discovery #8967

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OpenThread

Get link local address when performing mdns service discovery #8967

fuxiaoming-lumi Apr 17, 2023

Replies: 5 comments

jwhui Apr 17, 2023 Maintainer

fuxiaoming-lumi Apr 23, 2023 Author

fuxiaoming-lumi Apr 28, 2023 Author

fuxiaoming-lumi May 10, 2023 Author

jwhui May 10, 2023 Maintainer

fuxiaoming-lumi
Apr 17, 2023

jwhui
Apr 17, 2023
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fuxiaoming-lumi
Apr 23, 2023
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fuxiaoming-lumi
Apr 28, 2023
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fuxiaoming-lumi
May 10, 2023
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jwhui
May 10, 2023
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