[FROG] NHRP from FRR, cannot make it work!

[Vahid Gharaee]

Hello everyone,
would someone please help me with this:

I want to use nhrpd from FRR, to connect to a Cisco network.
I have an IPv4 network and want to use IPv6 with gre tunnels over IPv4.

the structure is as below:

  **Spoke1** ----- **Switch** ------**Spoke2** (gentoo PC with Frr running)
                       |
                    **HUB**

*Spoke1* : Cisco router configured with GRE and NHRP

*HUB*: Cisco router:
IP: 10.179.240.169
IPV6: 2a02:d20:e8:503::1

*Spoke2* : FRR with below config:

interface gre1
 description DSL-Payload-v6
 ipv6 address 2a02:d20:e8:503::c/128
 ipv6 nhrp holdtime 60
 ipv6 nhrp map 2a02:d20:e8:503::1 10.179.240.169
 ipv6 nhrp map multicast 10.179.240.169
 ipv6 nhrp network-id 99
 ipv6 nhrp nhs 2a02:d20:e8:503::1 nbma 10.179.240.169
 ipv6 nhrp registration no-unique
 ipv6 nhrp shortcut
 no link-detect
 tunnel source enp3s0
exit

also the interfaces on OS:

enp3s0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
        inet 192.168.201.202  netmask 255.255.252.0  broadcast 192.168.203.255
        inet6 fe80::e8f6:102d:1d27:d0ce  prefixlen 64  scopeid 0x20<link>
        ether 40:8d:5c:dd:09:cb  txqueuelen 1000  (Ethernet)
        RX packets 31262  bytes 23696880 (22.5 MiB)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 22327  bytes 3724978 (3.5 MiB)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

the tunnel:

gre1: flags=81<UP,POINTOPOINT,RUNNING>  mtu 1472
        inet6 2a02:d20:e8:503::c  prefixlen 128  scopeid 0x0<global>
        unspec 64-40-3C-67-00-00-00-00-00-00-00-00-00-00-00-00
txqueuelen 1000  (UNSPEC)
        RX packets 2949  bytes 566208 (552.9 KiB)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 2949  bytes 377472 (368.6 KiB)
        TX errors 62  dropped 0 overruns 0  carrier 62  collisions 0

gre1: gre/ip remote 10.179.240.169 local 100.64.60.103 ttl 64 key 503

logs:

2022/04/05 11:14:09 NHRP: [KHACV-6YE92] Send Registration-Request(3)
2a02:d20:e8:503::c -> 2a02:d20:e8:503::1
2022/04/05 11:14:09 NHRP: [WSA6E-5GM0H] PACKET: Send 100.64.60.103 ->
10.179.240.169


Wireshark says:
Linux cooked capture v1
Next Hop Resolution Protocol (NHRP Registration Reply)

0000   00 01 86 dd 00 00 00 00 00 ff 00 c0 b0 3f 00 6c
0010   01 04 04 00 10 10 80 02 00 00 00 01 64 40 3c 67
0020   2a 02 0d 20 00 e8 05 03 00 00 00 00 00 00 00 0c
0030   2a 02 0d 20 00 e8 05 03 00 00 00 00 00 00 00 01
0040   00 00 00 00 00 00 00 3c 00 00 00 00 00 00 00 00
0050   26 f4 00 3c 00 00 10 00 fe 80 00 00 00 00 00 00
0060   be e7 12 ff fe 41 53 80 0a b3 f0 a9 80 04 00 00
0070   80 05 00 00 80 03 00 20 00 00 00 00 26 f4 00 3c
0080   04 00 10 ff 0a b3 f0 a9 2a 02 0d 20 00 e8 05 03
0090   00 00 00 00 00 00 00 01 00 09 00 20 00 80 00 00
00a0   00 00 00 00 04 00 10 00 0a b3 f0 a9 2a 02 0d 20
00b0   00 e8 05 03 00 00 00 00 00 00 00 01 80 00 00 00


on the HUB we can see both request and reply.
and IPv4 networks also works.

*The Problem:*
the spoke1 can ping HUB through the tunnel, but on the Frr we cannot!

is this structure correct? should it work or we need different
configuration?

*Some more info*:
I looked into the code and it fails in function:
os_recvmsg(uint8_t *buf, size_t *len, int *ifindex, uint8_t *addr,
size_t *addrlen)

the addrlen should be 4 and it is 0 instead!!

the value of sockaddr_ll :

lladdr.sll_addr[] -> all zero ------------> this leads to addrlen be 0 later
lladdr.sll_family -> 0x11
lladdr.sll_protocol -> 0x120
lladdr.sll_ifindex -> 0x1a
lladdr.sll_hatype -> 0x30a
lladdr.sll_pkttype -> 0
lladdr.sll_halen -> 0
*addrlen -> 40
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