gnrc_ndp_router: Initial import of router behavior of router discovery

[miri64]

This imports router behavior for NDP router discovery. This encompasses:

• building and sending of (periodic) router advertisement (including all available options specified in RFC 4861)
• handling of router solicitations and their options

Depends on:

• gnrc_ndp: add support for address-less link-layers #3628: address-less link-layer handling for NDP (merged)
• gnrc_ipv6_netif: prepare for router discovery #3745: gnrc_ipv6_netif adaptations for router discovery (merged)
• gnrc_ndp_host: Initial import of host behavior of router discovery #3746: host-behavior for router discovery (merged)

[x3ro]

Is #2770 really the PR this should be tested with? Asking because it is closed and seems to be superseded by #2776

[miri64]

Yes of course, sorry about that.

[x3ro]

I haven't managed to get this working yet, mainly because I don't know how the setup works, I suppose :s So I tried the following, as described by @kaspar030:

[snip]

1. actually there's no need for bridging. I precreate the tap using openvpn:
   # sudo openvpn --mktun --dev tap0
   Then setup the linux side of it (e.g., using ip to give it an address)
2. I start the resulting binary directly:
   # <path>/bin/native/driver_netdev_eth.elf tap0

To test pinging,

1. give the RIOT side an ipv6 address using, e.g., ifconfig <n> add 2001:db8::1/64
2. add the linux side to the neighbour cache: ```ncache add 2001:db8::2
3. do the opposite on the Linux side, make sure the tap is UP
4. ping from Linux side should succeed

Adding the interface to the RIOT side worked fine. But the "do the opposite on the Linux side and make sure the tap is up" part is not quite clear to me. What interface do I have add the IPv6 address to? (I've tried this command:)

sudo ip -6 address add 2001:db8::2/64 dev eth0

This will, however, result in ping6 not actually sending over the tap anything over the tap0 interface, which, due to the openvpn thingy, it should do if I've understood things correctly.

Can anyone help me on what I have to do on the linux side to get things working?

[miri64]

@x3ro if you want to configure your linux device as router you need to (a) install radvd (router advertisement daemon) and (b) enable forwarding on the interface, so Linux (a) sends router advertisements and (b) acts as a router. I haven't looked into the documentation for that too much however, because I find it far to complicated for a simple PR-test set up. Just configure two virtual RIOT nodes as router and host and let them ping it out. ;-)

[Lotterleben]

Mhm, but isn't a RIOT-RIOT test kind of... incomplete? Especially since we don't have a border router (yet!), an NDP implementation that doesn't play well with Linux could be a serious hindrance (it cost us many headaches with watr.li, at least ^^). Aaaaanyhow, I'm curious to see @x3ro s results. Fingers crossed! :)

[miri64]

I'm not saying you should test it if you want to, for me it was just too much of a hassle. Linux responds to router advertisements, that was everything I tested :D

[miri64]

Rebased to current master

[x3ro]

Ah, I think I've misunderstood the scope of this PR. This does not respond to neighbour solicitations, right?

[miri64]

Nope, that was #2910

[x3ro]

Okay, but that one is merged and RIOT does not seem to be responding to the neighbour solicitations that Linux is sending to ff02::1:ff00:2. Do I have to enable some special for it to work?

[x3ro]

Also, when starting radvd, RIOT seems to receive the router advertisements but does not display anything when I query the routers table in the shell

[miri64]

When we tested #2910 it worked and I tested it here to. Let me test it again, when I come home. Now that ng_nativenet is merged, it'll be a breeze :D

[miri64]

Rebased to current master and squashed fixes.

[OlegHahm]

Node hangs at _send_rtr_adv().

[miri64]

Might be a locked mutex?

[OlegHahm]

Yepp.

[OlegHahm]

Got an idea or should I continue to debug?

[miri64]

No I'm just commenting. Go on.

[OlegHahm]

For some reason https://github.com/RIOT-OS/RIOT/pull/3049/files#diff-f9bf85cb337616822921e4230ede1572R257 is not reached when adding the additional address (though it seems to work for the first (the link local) address).

[OlegHahm]

I guess it's because the router advertisement is sent from the same thread.

[miri64]

Ah, of course. So we have to unlock it for a short moment there :/

[OlegHahm]

Like

diff --git a/sys/net/gnrc/network_layer/ipv6/netif/gnrc_ipv6_netif.c b/sys/net/gnrc/network_layer/ipv6/netif/gnrc_ipv6_netif.c
index 319f626..bd4403c 100644
--- a/sys/net/gnrc/network_layer/ipv6/netif/gnrc_ipv6_netif.c
+++ b/sys/net/gnrc/network_layer/ipv6/netif/gnrc_ipv6_netif.c
@@ -108,7 +108,9 @@ static ipv6_addr_t *_add_addr_to_entry(gnrc_ipv6_netif_t *entry, const ipv6_addr
             if ((entry->flags & GNRC_IPV6_NETIF_FLAGS_ROUTER) &&
                 (entry->flags & GNRC_IPV6_NETIF_FLAGS_RTR_ADV)) {
                 entry->rtr_adv_count = GNRC_NDP_MAX_INIT_RTR_ADV_NUMOF;
+                mutex_unlock(&entry->mutex);
                 gnrc_ndp_router_retrans_rtr_adv(entry);
+                mutex_lock(&entry->mutex);
             }
 #endif
         }

?

[miri64]

Tell me what you think about my fixup (which I pushed while seeing your comment)

[OlegHahm]

You can squash immediately. Tested the diff successfully.

[miri64]

Squashed.

[OlegHahm]

Now RPL seems to be not working any more. (Cannot ping any more.)

[OlegHahm]

Was maybe just a hickup. Seems to be working again.

[OlegHahm]

ACK, merge as soon as Travis green like the sky on Qo'noS.

[miri64]

Welp, the goal of this PR wasn't certainly to make it stable (ad lib @emmanuelsearch "Get it done on sunday, don't test it; just get it done") ;-P

[OlegHahm]

Well, I would say that meant the additional features - the already working stuff shouldn't be broken.

[miri64]

Yes of course, but when a new feature (router advertisements in this case) is destroying something, then already working stuff might fall victim, too.

[OlegHahm]

Whatever, I can confirm that my usual quick'n'dirty tests on IoT-LAB with 5 nodes and RPL are working. That should be good enough for now.

[miri64]

ACK, merge as soon as Travis green like the sky on Qo'noS.

You should have ACK'd with "MAJ!" then ;-P

[OlegHahm]

/home/travis/build/RIOT-OS/RIOT/sys/net/gnrc/network_layer/ipv6/netif/gnrc_ipv6_netif.c:231:1: error: expected identifier or '(' before '{' token

 {

 ^

/home/travis/build/RIOT-OS/RIOT/sys/net/gnrc/network_layer/ipv6/netif/gnrc_ipv6_netif.c:238:1: error: expected identifier or '(' before '{' token

 {

 ^

[miri64]

Already fixed :-)