shell: sc_icmpv6_echo: only allow unicast ping for now

[miri64]

Currently the ping shell command is too simple to handle multicast ping, so the simplest solution for now is to not allow it at all.

[cgundogan]

Could you also PR this against the RC branch? Otherwise, I do not understand why you tagged this as Release 2015.09

[miri64]

Will do, just forgot about it yesterday.

[OlegHahm]

Hm, to me that still seems to be a workaround for an underlying problem. What about changing the netapi IPC send call to non-blocking? Since all layers have their message queues, the default behavior shouldn't change (messages are delivered), but the system won't get stuck any more in cases like this. (I checked with ping 100 ff02::1 0 0 and msg_try_send() in the corresponding netapi call and the system isn't hanging any more.)

[OlegHahm]

With #4005 the problem seems to be solved in a less intrusive way then switching to non-blocking netapi calls.

[miri64]

@OlegHahm did you check the state of the packet buffer, too?

[OlegHahm]

No, but since the application hung after some time without the release and now doesn't hang any more, I assume it to be okay, but I will check.

[miri64]

So with #4009 and #4013 this is not necessary anymore right? Then close?

[OlegHahm]

I think so, yes.