This ICMP DestinationUnreachable code 0x7. This message means that the LinkLayer? can tell that a host authoratively does not exist, as opposed to DestinationHostUnreachable which means that it is simply unreachable.
Linux converts this to a EHOSTDOWN error return.
This is defined in 
RFC:1812 Section 5.2.7.1
One page links to DestinationHostUnknown:
