BROADCAST WITH MULTIPLE NETWORK INTERFACES

```
Description: There is currently no mechanism to send a broadcast packet
out through several network interfaces. Currently packets
can be sent to only one device. Logic in netdev_findby_ipvXaddr()
currently just selects the first device in the list of
devices; only that device will receive broadcast packets.
Status: Open
Priority: High if you require broadcast on multiple networks. There is
no simple solution known at this time, however. Perhaps
netdev_findby_ipvXaddr() should return a list of devices rather
than a single device? All upstream logic would then have to
deal with a list of devices. That would be a huge effect and
certainly doesn't dount as a "simple solution".
```

Start by tracing netdev_findby_ipvXaddr() and the upstream logic that sends broadcast packets. Determine how device selection currently stops at the first interface and assess the impact of supporting several interfaces. Done means a broadcast packet can be sent through multiple network interfaces without breaking existing callers.

Written by the indexing model from the issue text.