Contiki: "No response to client initiated bootstrap"

[mkowalczyk88]

I'm observing "No response to client initiated bootstrap" error during client-initiated bootstrap on Contiki 6lowpan clicker board. Although the error message is displayed, the bootstrap process completes successfully. I was using global IPv6 addresses.

From my investigation it seems the UDP packet with bootstrap request is not sent because uIP stack is doing Neighbor Solicitation procedure. Instead of sending actual UDP packet after neighbor is discovered, the packet is dropped by network stack. Only after couple of re-tries, when UDP packet is requested to be sent when Neighbor Discovery is completed, the actual UDP data is in the air. Unfortunately, the uIP API doesn't provide return result of UDP send function, so it's really hard to know from app point of view if packet was actually sent. All in all this seems like a Contiki issue, but I'm reporting it here for the record (if someone see the same error) or if you have any idea of workaround/fix it.
Maybe the error should be just a warning? Generally, it's ok if UDP packet doesn't reach a target and it's common practice to re-try UDP communication.
Also note, there is open pull request on Contiki github regarding ND: contiki-os/contiki#1765.