Domain Name System client library

[zephyrbot]

Reported by Flavio Santes:

aaU, I want to be able to communicate with other network devices by means of their name instead of an IP address.

(Imported from Jira ZEP-500)

[zephyrbot]

by Mark Linkmeyer:

Juan Manuel Cruz Alcaraz , proceed without netz approach.

[zephyrbot]

by Lei Liu:

DNS client log
{code:title=Bar.java|borderStyle=solid}
shell> test_dns_query www.baidu.com

---

Domain name: www.baidu.com
[_test_dns_query:148] DNS Create Query: 0, ID: 2

****** DNS ANSWER: 0 ******
Response: CNAME NO IP address Size: 15: 3 119 119 119 1 97 6 115 104 105 102 101 110 192 22 CNAME: www.a.shifen.com
****** DNS ANSWER: 1 ******
Response: IP address Size: 4: 61 135 169 125
****** DNS ANSWER: 2 ******
Response: IP address Size: 4: 61 135 169 121
[_test_dns_query:164] DNS response: 0
shell> test_dns_query www.google.com

---

Domain name: www.google.com
[_test_dns_query:148] DNS Create Query: 0, ID: 3

****** DNS ANSWER: 0 ******
Response: IP address Size: 4: 203 98 7 65
[_test_dns_query:164] DNS response: 0
{code}
Linux net tool
{code:title=nslookup log|borderStyle=solid}
root@alvin:/home/alvin/Downloads/mqtt-1.5-rc1-test/testlib/net/test_iot_protocol# nslookup www.baidu.com
Server: 10.248.2.5
Address: 10.248.2.5#53

Non-authoritative answer:
www.baidu.com canonical name = www.a.shifen.com.
Name: www.a.shifen.com
Address: 61.135.169.125
Name: www.a.shifen.com
Address: 61.135.169.121

root@alvin:/home/alvin/Downloads/mqtt-1.5-rc1-test/testlib/net/test_iot_protocol# nslookup www.google.com
Server: 10.248.2.5
Address: 10.248.2.5#53

Non-authoritative answer:
Name: www.google.com
Address: 203.98.7.65
{code}

Compare above logs, DNS client works.
Zephyr: v1.5.0-rc1