[riot-notifications] [RIOT-OS/RIOT] gnrc_netif: centralize device-type-specific functions (#10524)

Gunar Schorcht notifications at github.com
Fri Jan 4 17:27:44 CET 2019


@miri64 
> * Pinging from one node the other node with `ping6 2001:db8::32ae:a4ff:fe18:7a3d` doesnt work. The reason seems to be that the source node is using rather its link local address than its global unicast address. On the router, I can ovserve the following message:
>   ```
>   ipv6: Received (src = fe80::32ae:a4ff:fe41:60f9, dst = 2001:db8::32ae:a4ff:fe18:7a3d, next header = 58, length = 12)
>   ```
>   So it is probably the a problem of `esp_now`.

It tried to figure out what exactly happens, but I need some guidance due the complexity. Probably, you can tell the reason in less than 1 min while I'm having to surf through the source code for several hours to figure out the how it works.

It seems that `2001:db8::32ae:a4ff:fe41:60f9` is not used as source address since it is not added to the candidate set here https://github.com/RIOT-OS/RIOT/blob/3af28369a8d49d7e18a0766ceb93098dd42c712e/sys/net/gnrc/netif/gnrc_netif.c#L970-L972. Therefore, it is later skipped here https://github.com/RIOT-OS/RIOT/blob/3af28369a8d49d7e18a0766ceb93098dd42c712e/sys/net/gnrc/netif/gnrc_netif.c#L1029-L1032 and the link local address is used:
```
gathering source address candidates
Checking address: fe80::32ae:a4ff:fe41:60f9
add to candidate set
Checking address: 2001:db8::32ae:a4ff:fe41:60f9
```
```
finding the best match within the source address candidates
Checking address: fe80::32ae:a4ff:fe41:60f9
winner for rule 2 (smaller scope) found
Checking address: 2001:db8::32ae:a4ff:fe41:60f9
Not part of the candidate set - skipping
```
My question is, why is it important how many `duplicate address detection transmissions` already         performed for an address?

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