Introduction
Requirement
Nearly all devices that connect to the Internet use networking hardware that conforms to
IEEE-802 standards, commonly termed the Ethernet standards. It is common for desktop
and laptop computers to have two Ethernet interfaces, one wired (the IEEE-802.3
standard) and one wireless (the IEEE-802.11 standard), while mobile devices and
smartphones will typically have a single wireless Ethernet interface and a Bluetooth
interface (the IEEE-802.15.1 standard).
To simplify communication between devices, each Ethernet interface has a unique
networking address, termed its Media Access Control (MAC) address. Each MAC address
is 6-bytes long but, to make them easier for humans to read and compare, they’re usually
written as a sequence of hexadecimal characters separated by colons or hyphens, as in
the example 74:e2:f5:20:f9:8b. When written this way, MAC addresses are case-
insensitive - that is to say that 74-E2-F5:20:F9:8B is the same address.
When devices communicate using WiFi (the IEEE-802.11 standard) they break their
communication into many small packets of data. Each packet contains MAC addresses to
identify the device which transmitted the packet (the transmitter’s address), and the device
for which the packet is intended (the receiver’s address). The special MAC address,
ff:ff:ff:ff:ff:ff, is termed the broadcast MAC address, and is used when all devices within
range should receive the packet.
Each 6-byte MAC address comprises two 3-byte pieces. The first 3-bytes are termed the
Organizationally Unique Identifier (OUI), and they identify the vendor of the Ethernet
interface. From the address 74:e2:f5:20:f9:8b, the 74:e2:f5 indicates that the interface
was made by Apple
The goal of this project is to write a C99 program, named wifistats, that reports the
number of bytes either transmitted or received by devices using WiFi. The program may
be requested to generate reports sorted by either the device MACs or by the vendors’
names, from the largest transmitter (most bytes transmitted) to the smallest.
Program requirements
- Your program’s single source file must be named wifistats.c
- Your program will be invoked in one of two ways:
1.
prompt> ./wifistats what packets
where what is either the single character ‘t’ or ‘r’ to request statistics about WiFi
transmitters, or receivers, respectively. For example, if the program is invoked as ./
wifistats t packets then the program should produce statistics about the data
transmissions of each transmitting device present in the packets file.
packets is the name of a text-file providing information about each WiFi packet, one
packet per line. Here is a sample packet file (the attached 1) . Each line consists of
4 fields, providing the time that each packet was captured (in seconds and
microseconds), the transmitter’s and receiver’s MAC addresses, and the length (in
bytes) of the packet. Each of the fields will be separated by a single TAB (‘\t’)
character.
if we ran:
prompt> ./wifistats t sample-packets
this would be :
00:8e:f2:c0:13:cc 951
84:1b:5e:a8:bf:7f 929
84:1b:5e:a8:bf:7c 259
74:e2:f5:17:96:89 138
If we ran:
prompt> ./wifistats r sample-packets
this would be :
00:11:d9:20:aa:4e 951
74:e2:f5:17:96:89 829
cc:3a:61:df:4b:61 259
68:94:23:4b:e8:35 100
84:1b:5e:a8:bf:7f 82
84:1b:5e:a8:bf:7c 56
2.
prompt> ./wifistats what packets OUIfile
where OUIfile is the name of a text-file providing the OUIs and names of Ethernet
hardware vendors. If an OUIfile is provided, the program should report its statistics
not on individual device MAC addresses but on the vendor that produced each
device. Here are two sample OUIfiles: OUIfile-small (40 entries) ?the attached 2?
and OUIfile-large (23,000 entries) (the attached 3). The 2 fields will be separated by
a single TAB (‘\t’) character, and the vendors’ names may contain spaces.
For example, if we ran:
prompt> ./wifistats t sample-packets sample-OUIfile-
small
this would be the required output:
84:1b:5e NETGEAR 1188
??:??:?? UNKNOWN-VENDOR 951
74:e2:f5 Apple 138
If we ran:
prompt> ./wifistats r sample-packets sample-OUIfile-
small
this would be the required output:
00:11:d9 TiVo 951
74:e2:f5 Apple 829
cc:3a:61 SAMSUNG ELECTRO MECHANICS CO., LTD. 259
84:1b:5e NETGEAR 138
??:??:?? UNKNOWN-VENDOR 100
- You may assume that all input data is in the correct format.
If your program encounters a broadcast MAC address, your program should ignore
that input line.
If your program encounters an OUI not found in a provided OUI file, it should use/
report the vendor’s name as UNKNOWN-VENDOR.
- Your program must support these limits (you may assume that the input data never
exceeds these limits):
maximum number of distinct MAC addresses - 500.
maximum number of distinct OUIs - 25000.
maximum length of any vendor name - 90 characters.
- Your program must invoke the standard utility program /usr/bin/sort to sort
the final results. Your program must use the system-calls fork() and execv() (and
possibly others) to invoke /usr/bin/sort. Your program must not just call the
C function system(). Note that the command-line options supported by /usr/
bin/sort on OS-X, Linux, and cygwin(Windows) are often different.
- If the data totals of two or more MAC addresses, or two or more vendors (via their
OUIs), are identical, then the MAC addresses or vendors with identical totals should
be printed in ascending alphabetical order.
- Your program must employ sound programming practices, including the use of
meaningful comments, well chosen identifier names, appropriate choice of basic
data-structures and data-types, and appropriate choice of control-flow constructs.