Long queries on DNAME cause truncated response

Conditions:

• the zone contains DNAME with long target domain name
• a query matching DNAME is sent to server
• the length of the owner name of the synthesized CNAME exceeds maximal length for domain name

Current behavior:

• the response is marked as truncated (even for TCP)
• the response contains DNAME
• the response doesn't contain DNAME RRSIG
• the response doesn't contain CNAME

Expected behavior:

• the response is not marked as truncated
• the response contains DNAME
• the response doesn't contain CNAME
• the response contains DNAME RRSIG
• (or SERVFAIL)