Update readme to reflect client documentation

Author: lvfrazao

README.md

@@ -4,8 +4,9 @@ Version 0.1.0
 
 A Python implementation of a DHCP client and the tools to manipulate DHCP packets. Includes:
 
-1. A parser of DHCP packets, returning Python objects - supports all DHCP options in RFC 2132
-2. A CLI DHCP client that is useful for debugging
+1. A parser of DHCP packets, returning Python objects
+2. Supports for all DHCP options in RFC 2132
+3. A rudimentary DHCP client
 
 ## Installation
 
@@ -17,7 +18,7 @@ A Python implementation of a DHCP client and the tools to manipulate DHCP packet
 
 **NOTE: This has been tested on Ubuntu 18.04 and Windows WSL. May or may not work on other platforms.**
 
-## Packet Parser
+## The Packet Parser
 
 Two files contribute to the packet parsing: `dhcppython.packet` and `dhcppython.options`. For most operations only `dhcppython.packet` will be required.
 
@@ -180,3 +181,24 @@ Hostname(code=12, length=9, data=b'Galaxy-S9')
 ParameterRequestList(code=55, length=10, data=b'\x01\x03\x06\x0f\x1a\x1c3:;+')
 MessageType(code=53, length=1, data=b'\x01')
 ```
+
+## The DHCP Client
+
+A very primitive DHCP client is included in this package in the `dhcppython.client` module. The client is able to negotiate a lease with a DHCP server and can be configured to use:
+
+* A given interface
+* Option to send broadcast packets or unicast packets to a specific server
+* Set a relay in the giaddr field
+* "Spoof" MAC addresses
+* Specify options to send with request
+
+The high level interface to negotiate a lease is the `get_lease` method of the `dhcppython.client.DHCPClient` object. This method goes through the DORA DHCP handshake and returns a `Lease` namedtuple which includes all the packets in the :
+
+```python
+>>> import dhcppython
+>>> client = dhcppython.client.DHCPClient(interface="enp0s8")
+>>> lease = client.get_lease(mac_addr="de:ad:be:ef:c0:de", broadcast=True, relay=None, server="255.255.255.255", options_list=None)
+Lease succesful: 192.168.56.3 -- DE:AD:BE:EF:C0:DE -- 3 ms elapsed
+>>> lease
+Lease(discover=DHCPPacket(op='BOOTREQUEST', htype='ETHERNET', hlen=6, hops=0, xid=2829179566, secs=0, flags=32768, ciaddr=IPv4Address('0.0.0.0'), yiaddr=IPv4Address('0.0.0.0'), siaddr=IPv4Address('0.0.0.0'), giaddr=IPv4Address('0.0.0.0'), chaddr='de:ad:be:ef:c0:de', sname=b'', file=b'', options=OptionList([MessageType(code=53, length=1, data=b'\x01')])), offer=DHCPPacket(op='BOOTREPLY', htype='ETHERNET', hlen=6, hops=0, xid=2829179566, secs=0, flags=32768, ciaddr=IPv4Address('0.0.0.0'), yiaddr=IPv4Address('192.168.56.3'), siaddr=IPv4Address('0.0.0.0'), giaddr=IPv4Address('0.0.0.0'), chaddr='DE:AD:BE:EF:C0:DE', sname=b'', file=b'', options=OptionList([SubnetMask(code=1, length=4, data=b'\xff\xff\xff\x00'), Router(code=3, length=4, data=b'\n\x97\x01\x01'), DNSServer(code=6, length=4, data=b'\nh\x01\x08'), Hostname(code=12, length=22, data=b'dhcp.-192-168-56-3.com'), DomainName(code=15, length=14, data=b'example.com'), IPAddressLeaseTime(code=51, length=4, data=b'\x00\x01Q\x80'), MessageType(code=53, length=1, data=b'\x02'), ServerIdentifier(code=54, length=4, data=b'\xc0\xa88\x02'), RenewalTime(code=58, length=4, data=b'\x00\x00T`'), RebindingTime(code=59, length=4, data=b'\x00\x00\xa8\xc0'), End(code=255, length=0, data=b'')])), request=DHCPPacket(op='BOOTREQUEST', htype='ETHERNET', hlen=6, hops=0, xid=2829179566, secs=0, flags=32768, ciaddr=IPv4Address('0.0.0.0'), yiaddr=IPv4Address('0.0.0.0'), siaddr=IPv4Address('0.0.0.0'), giaddr=IPv4Address('0.0.0.0'), chaddr='de:ad:be:ef:c0:de', sname=b'', file=b'', options=OptionList([MessageType(code=53, length=1, data=b'\x03')])), ack=DHCPPacket(op='BOOTREPLY', htype='ETHERNET', hlen=6, hops=0, xid=2829179566, secs=0, flags=32768, ciaddr=IPv4Address('0.0.0.0'), yiaddr=IPv4Address('192.168.56.3'), siaddr=IPv4Address('0.0.0.0'), giaddr=IPv4Address('0.0.0.0'), chaddr='DE:AD:BE:EF:C0:DE', sname=b'', file=b'', options=OptionList([SubnetMask(code=1, length=4, data=b'\xff\xff\xff\x00'), Router(code=3, length=4, data=b'\n\x97\x01\x01'), DNSServer(code=6, length=4, data=b'\nh\x01\x08'), Hostname(code=12, length=22, data=b'dhcp.-192-168-56-3.com'), DomainName(code=15, length=14, data=b'example.com'), IPAddressLeaseTime(code=51, length=4, data=b'\x00\x01Q\x80'), MessageType(code=53, length=1, data=b'\x05'), ServerIdentifier(code=54, length=4, data=b'\xc0\xa88\x02'), RenewalTime(code=58, length=4, data=b'\x00\x00T`'), RebindingTime(code=59, length=4, data=b'\x00\x00\xa8\xc0'), End(code=255, length=0, data=b'')])), time=0.0032514659978915006, server=('192.168.56.2', 67))
+```