gluon-mesh-batman-adv: get IPv6-addresses via netlink

[blocktrron]

Previously the content of "/proc/net/if_inet6" was parsed to acquire the
nodes IPv6 addresses. With this commit, IPv6 addresses are acquired
using getifaddrs() as proposed by neoraider in #1615.

Fixes #1615

[neocturne]

Did you already test if this change has any effect on the duplicate address issue?

[blocktrron]

@NeoRaider Testing if it has an affect on the duplicate IP issue is hard as i can't even reproduce it reliably. Maybe @mweinelt is with me testing these cahnges on the experimental nodes of Freifunk Darmstadt?

The cahnges itself are tested as in we have all 3 (Global, ULA, LL) IP-addresses in the respondd response.

[neocturne]

Found one more issue, and a whitespace nitpick.

[cmarxmeier]

https://forum.freifunk.net/t/neue-firmware-stable-3-0-1-im-testbetrieb/20064/5
used patch - works.

[blocktrron]

Updated to use netlink. Now looks for the tentative and deprecated flags

[blocktrron]

We've rolled out an image containing 71eb8ba. We have now 17 nodes running with this patch. The double-address issue occurred on 3 of them without the patch, with the patch no node sends duplicate IP-Addresses (Filter for FIrmware 1.3~20190115 on our map)

[neocturne]

I think it would make sense to use libnl-tiny or libmnl for the message parsing; that way we could also deal with replies spread over multiple recv calls and wouldn't need such a huge receive buffer. libnl-tiny is already included in our firmware (although I hope to switch most users over to libmnl eventually, as it has a nicer API, is maintained more actively, and is even smaller)

[blocktrron]

@NeoRaider So is it libnl-tiny or libmnl? I would like to overhaul it just once more.

[mweinelt]

Alot more stuff upstream also depends on libnl-tiny so I don't see it going anywhere without some huge effort. Meanwhile libmnl is nowhere to be found on our routers today.

root@64289-rocket-cloud:~# opkg whatdepends libnl-tiny
Root set:
  libnl-tiny
What depends on root set
	iw 4.14-1	depends on libnl-tiny
	gluon-mesh-batman-adv-15 1	depends on libnl-tiny
	swconfig 11	depends on libnl-tiny
	libiwinfo 2018-07-31-65b8333f-1	depends on libnl-tiny
	wpa-supplicant-mesh-wolfssl 2018-05-21-62566bc2-5	depends on libnl-tiny
	gluon-status-page 3	depends on libiwinfo
	netifd 2018-11-19-4b83102d-2	depends on libnl-tiny
	gluon-radv-filterd 1-1	depends on libnl-tiny
	libbatadv 1	depends on libnl-tiny
	gluon-ebtables-source-filter 1-1	depends on gluon-mesh-batman-adv
	respondd-module-airtime 1-2	depends on libnl-tiny
	simple-tc 1	depends on libnl-tiny
	gluon-ebtables-limit-arp 1-1	depends on gluon-mesh-batman-adv
	gluon-mesh-vpn-core 1	depends on simple-tc
	gluon-status-page-mesh-batman-adv 1	depends on gluon-status-page
	hostapd-wolfssl 2018-05-21-62566bc2-5	depends on libnl-tiny
	gluon-ebtables-filter-ra-dhcp 1-1	depends on gluon-mesh-batman-adv
	batctl 2018.1-1	depends on libnl-tiny
	gluon-ebtables-filter-multicast 1-1	depends on gluon-mesh-batman-adv
	kmod-cfg80211 4.14.95+2017-11-01-9	depends on iw
	gluon-config-mode-mesh-vpn 2	depends on gluon-mesh-vpn-core

[blocktrron]

Updated the PR to use libnl-tiny. Tested on one device (AVM 4020). Works flawlessly.

[neocturne]

Thanks, looking much better now! I've found two issues I'd like to see fixed.

[neocturne]

if_nametoindex should only be called once and passed into the callback (by making arg a struct containing the ifindex and the JSON array).

[blocktrron]

Good idea, will implement this.

[neocturne]

respondd.c: In function 'get_addresses':
respondd.c:125:14: error: invalid type argument of '->' (have 'struct ip_address_information')
   return info->addresses;
              ^~
respondd.c:146:13: error: invalid type argument of '->' (have 'struct ip_address_information')
  return info->addresses;
             ^~
respondd.c:147:1: warning: control reaches end of non-void function [-Wreturn-type]
 }
 ^
make[5]: *** [Makefile:35: respondd.so] Error 1

[blocktrron]

@NeoRaider yes i hope it's fixed now. will let you know when i run tested my latest change.

[blocktrron]

@NeoRaider should be fixed now- This node is running the patch: https://meshviewer.darmstadt.freifunk.net/#/en/map/5c49793001b4