TrafficVision

git strategy:

1. things that are in progress of development are to be committed and pushed into the deDICKated feature branch. After a feature is done and merged, the feature branch is to be deleted.
2. feature branches must have a continious PR for reviews.
3. never push and force push to master.
4. ALL COMMIT MESSAGES MUST BE PREPENDED BY yaaaaaaaas girrrrrrrrrrrrl!

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1. Major modules are to be separated into dynamically linked libraries.
2. Major modules are separated by features that they implement.
3. Codestyle c99, compilation standard -- c11
4. Codestyle guidline; -Wall -Werror

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reference list
1) https://gauravsarma1992.medium.com/packet-sniffer-and-parser-in-c-c86070081c38
2) This nice reference

TrafficVision design specification

• -A
  Print each packet (minus its link level header) in ASCII. Handy for capturing web pages.

• -b
  Print the AS number in BGP packets in ASDOT notation rather than ASPLAIN notation.

• -B buffer_size

• --buffer-size=buffer_size
  Set the operating system capture buffer size to buffer_size, in units of KiB (1024 bytes).

• -c count
  Exit after receiving count packets.

• --count
  Print only on stderr the packet count when reading capture file(s) instead of parsing/printing the packets. If a filter is specified on the command line, tcpdump counts only packets that were matched by the filter expression.

• -C file_size
  Before writing a raw packet to a savefile, check whether the file is currently larger than file_size and, if so, close the current savefile and open a new one. Savefiles after the first savefile will have the name specified with the -w flag, with a number after it, starting at 1 and continuing upward. The units of file_size are millions of bytes (1,000,000 bytes, not 1,048,576 bytes).

• -d
  Dump the compiled packet-matching code in a human readable form to standard output and stop.
  Please mind that although code compilation is always DLT-specific, typically it is impossible (and unnecessary) to specify which DLT to use for the dump because tcpdump uses either the DLT of the input pcap file specified with -r, or the default DLT of the network interface specified with -i, or the particular DLT of the network interface specified with -y and -i respectively. In these cases the dump shows the same exact code that would filter the input file or the network interface without -d.
  However, when neither -r nor -i is specified, specifying -d prevents tcpdump from guessing a suitable network interface (see -i). In this case the DLT defaults to EN10MB and can be set to another valid value manually with -y.

• --list-interfaces
  Print the list of the network interfaces available on the system and on which tcpdump can capture packets. For each network interface, a number and an interface name, possibly followed by a text description of the interface, are printed. The interface name or the number can be supplied to the -i flag to specify an interface on which to capture.
  This can be useful on systems that don't have a command to list them (e.g., Windows systems, or UNIX systems lacking ifconfig -a); the number can be useful on Windows 2000 and later systems, where the interface name is a somewhat complex string.
  The -D flag will not be supported if tcpdump was built with an older version of libpcap that lacks the pcap_findalldevs(3PCAP) function.

• -e
  Print the link-level header on each dump line. This can be used, for example, to print MAC layer addresses for protocols such as Ethernet and IEEE 802.11.

• -f
  Print foreign' IPv4 addresses numerically rather than symbolically (this option is intended to get around serious brain damage in Sun's NIS server --- usually it hangs forever translating non-local internet numbers). The test for foreign' IPv4 addresses is done using the IPv4 address and netmask of the interface on which capture is being done. If that address or netmask are not available, available, either because the interface on which capture is being done has no address or netmask or because the capture is being done on the Linux "any" interface, which can capture on more than one interface, this option will not work correctly.

• -F file
  Use file as input for the filter expression. An additional expression given on the command line is ignored.

• -G rotate_seconds
  If specified, rotates the dump file specified with the -w option every rotate_seconds seconds. Savefiles will have the name specified by -w which should include a time format as defined by strftime(3). If no time format is specified, each new file will overwrite the previous. Whenever a generated filename is not unique, tcpdump will overwrite the pre-existing data; providing a time specification that is coarser than the capture period is therefore not advised.
  If used in conjunction with the -C option, filenames will take the form of `file'.

• -h

• --help
  Print the tcpdump and libpcap version strings, print a usage message, and exit.

• --version
  Print the tcpdump and libpcap version strings and exit.

• -i interface

• --interface=interface
  Listen, report the list of link-layer types, report the list of time stamp types, or report the results of compiling a filter expression on interface. If unspecified and if the -d flag is not given, tcpdump searches the system interface list for the lowest numbered, configured up interface (excluding loopback), which may turn out to be, for example, eth0''. On Linux systems with 2.2 or later kernels, an interface argument of any'' can be used to capture packets from all interfaces. Note that captures on the ``any'' device will not be done in promiscuous mode.
  If the -D flag is supported, an interface number as printed by that flag can be used as the interface argument, if no interface on the system has that number as a name.

• -K

• --dont-verify-checksums
  Don't attempt to verify IP, TCP, or UDP checksums. This is useful for interfaces that perform some or all of those checksum calculation in hardware; otherwise, all outgoing TCP checksums will be flagged as bad.

• -n
  Don't convert addresses (i.e., host addresses, port numbers, etc.) to names.

• -N
  Don't print domain name qualification of host names. E.g., if you give this flag then tcpdump will print nic'' instead of nic.ddn.mil''.

• -#

• --number
  Print an optional packet number at the beginning of the line.

• -Q direction

• --direction=direction
  Choose send/receive direction direction for which packets should be captured. Possible values are in', out' and `inout'. Not available on all platforms.

• -q
  Quick (quiet?) output. Print less protocol information so output lines are shorter.

• -r file
  Read packets from file (which was created with the -w option or by other tools that write pcap or pcapng files). Standard input is used if file is ``-''.

• -S

• --absolute-tcp-sequence-numbers
  Print absolute, rather than relative, TCP sequence numbers.

• -s snaplen

• --snapshot-length=snaplen
  Snarf snaplen bytes of data from each packet rather than the default of 262144 bytes. Packets truncated because of a limited snapshot are indicated in the output with ``[|proto]'', where proto is the name of the protocol level at which the truncation has occurred.
  Note that taking larger snapshots both increases the amount of time it takes to process packets and, effectively, decreases the amount of packet buffering. This may cause packets to be lost. Note also that taking smaller snapshots will discard data from protocols above the transport layer, which loses information that may be important. NFS and AFS requests and replies, for example, are very large, and much of the detail won't be available if a too-short snapshot length is selected.
  If you need to reduce the snapshot size below the default, you should limit snaplen to the smallest number that will capture the protocol information you're interested in. Setting snaplen to 0 sets it to the default of 262144, for backwards compatibility with recent older versions of tcpdump.

• -t
  Don't print a timestamp on each dump line.

• -tt
  Print the timestamp, as seconds since January 1, 1970, 00:00:00, UTC, and fractions of a second since that time, on each dump line.

• -ttt
  Print a delta (microsecond or nanosecond resolution depending on the --time-stamp-precision option) between current and previous line on each dump line. The default is microsecond resolution.

• -tttt
  Print a timestamp, as hours, minutes, seconds, and fractions of a second since midnight, preceded by the date, on each dump line.

• -ttttt
  Print a delta (microsecond or nanosecond resolution depending on the --time-stamp-precision option) between current and first line on each dump line. The default is microsecond resolution.

• -u
  Print undecoded NFS handles.

• -U

• --packet-buffered
  If the -w option is not specified, or if it is specified but the --print flag is also specified, make the printed packet output packet-buffered''; i.e., as the description of the contents of each packet is printed, it will be written to the standard output, rather than, when not writing to a terminal, being written only when the output buffer fills. If the -w option is specified, make the saved raw packet output packet-buffered''; i.e., as each packet is saved, it will be written to the output file, rather than being written only when the output buffer fills.
  The -U flag will not be supported if tcpdump was built with an older version of libpcap that lacks the pcap_dump_flush(3PCAP) function.

• -v
  When parsing and printing, produce (slightly more) verbose output. For example, the time to live, identification, total length and options in an IP packet are printed. Also enables additional packet integrity checks such as verifying the IP and ICMP header checksum.
  When writing to a file with the -w option and at the same time not reading from a file with the -r option, report to stderr, once per second, the number of packets captured. In Solaris, FreeBSD and possibly other operating systems this periodic update currently can cause loss of captured packets on their way from the kernel to tcpdump.

• -vv
  Even more verbose output. For example, additional fields are printed from NFS reply packets, and SMB packets are fully decoded.

• -vvv
  Even more verbose output. For example, telnet SB ... SE options are printed in full. With -X Telnet options are printed in hex as well.

• -w file
  Write the raw packets to file rather than parsing and printing them out. They can later be printed with the -r option. Standard output is used if file is ``-''.
  This output will be buffered if written to a file or pipe, so a program reading from the file or pipe may not see packets for an arbitrary amount of time after they are received. Use the -U flag to cause packets to be written as soon as they are received.
  The MIME type application/vnd.tcpdump.pcap has been registered with IANA for pcap files. The filename extension .pcap appears to be the most commonly used along with .cap and .dmp. Tcpdump itself doesn't check the extension when reading capture files and doesn't add an extension when writing them (it uses magic numbers in the file header instead). However, many operating systems and applications will use the extension if it is present and adding one (e.g. .pcap) is recommended.
  See pcap-savefile(5) for a description of the file format.

• -W filecount
  Used in conjunction with the -C option, this will limit the number of files created to the specified number, and begin overwriting files from the beginning, thus creating a 'rotating' buffer. In addition, it will name the files with enough leading 0s to support the maximum number of files, allowing them to sort correctly.
  Used in conjunction with the -G option, this will limit the number of rotated dump files that get created, exiting with status 0 when reaching the limit.
  If used in conjunction with both -C and -G, the -W option will currently be ignored, and will only affect the file name.

• -x
  When parsing and printing, in addition to printing the headers of each packet, print the data of each packet (minus its link level header) in hex. The smaller of the entire packet or snaplen bytes will be printed. Note that this is the entire link-layer packet, so for link layers that pad (e.g. Ethernet), the padding bytes will also be printed when the higher layer packet is shorter than the required padding. In the current implementation this flag may have the same effect as -xx if the packet is truncated.

• -xx
  When parsing and printing, in addition to printing the headers of each packet, print the data of each packet, including its link level header, in hex.

• -X
  When parsing and printing, in addition to printing the headers of each packet, print the data of each packet (minus its link level header) in hex and ASCII. This is very handy for analysing new protocols. In the current implementation this flag may have the same effect as -XX if the packet is truncated.

• -XX
  When parsing and printing, in addition to printing the headers of each packet, print the data of each packet, including its link level header, in hex and ASCII.

• -z postrotate-command
  Used in conjunction with the -C or -G options, this will make tcpdump run " postrotate-command file " where file is the savefile being closed after each rotation. For example, specifying -z gzip or -z bzip2 will compress each savefile using gzip or bzip2.
  Note that tcpdump will run the command in parallel to the capture, using the lowest priority so that this doesn't disturb the capture process.
  And in case you would like to use a command that itself takes flags or different arguments, you can always write a shell script that will take the savefile name as the only argument, make the flags & arguments arrangements and execute the command that you want.

• -Z user

• --relinquish-privileges=user
  If tcpdump is running as root, after opening the capture device or input savefile, but before opening any savefiles for output, change the user ID to user and the group ID to the primary group of user.
  This behavior can also be enabled by default at compile time.