udp::packet Class Reference

A UDP Packet. More...

#include <udp.h>

Public Member Functions
	packet (const connection &dst, const std::string &data)
	Create a packet from a string.
	packet (const std::string &in)
	Construct a packet from a string buffer.
template<typename T >
	packet (const connection &dst, const T &data, const size_t &size)
	Construct a packet from any variable data, and its size.
std::string	str () const
	Print the packet.
template<typename T >
const T	cast () const
	Cast the content of the packet as a type.
std::string	data () const
	Return the data.
std::string	buffer () const
	Create a buffer of the packet that can be sent across the network.
connection	destination () const
	Get the address and port of the destination.
connection	source () const
	Get the address and port of the source.

Static Public Member Functions
static packet	empty (const connection &dst)
	An empty packet.

Friends
void	network::thread (port_t, wireguard::config wg)

Detailed Description

A UDP Packet.

Remarks

The entire UDP Packet contains 2 parts: a Header, and the Data. Looking at the structure, you may be slightly confused by this "pseudo-header". TCP/UDP operates at the Transport Layer, which deals with Ports; the Network Layer deals with IP. UDP/TCP should not need to deal with addresses, yet this pseudo-header contains them. Why is this? The creator of UDP, David Reed, explains why the pseudo-header exists: https://www.postel.org/pipermail/end2end-interest/2005-February/004616.html and it boils down to historical reasons. TCP used to be one big protocol that encompassed both IP and TCP. When TCP was split, we still wanted to include address within the checksum, and rather than include that information both within an IP header, and a TCP/UDP header, we have this pseudo-header that is "shared" by both layers. Interestingly, Reed further explains that the original intention was to have everything but the pseudo-header encrypted, and by encrypting the checksum that included this address information, man-in-the-middle attacks would be thwarted. This plan was blocked by both the NSA, and by "the terrorists who invented NAT". The pseudo-header isn't typically sent across the wire. The Reference states that: "[it's] conceptually prefixed to the UDP header", and Wikipedia stresses that: " "[it's] not the real IPv4 header used to send an IP packet, it is used only for the checksum calculation." (https://en.wikipedia.org/wiki/User_Datagram_Protocol#IPv4_pseudo_header). Since our implementation only deals with UDP, rather than implementing the IP protocol as well, we send the Pseudo-Header across the wire for destination resolving.

Constructor & Destructor Documentation

packet() [1/3]

udp::packet::packet ( const connection & dst, const std::string & data )

inline

Create a packet from a string.

Parameters

dst	The connection receiving the packet.
data	The data string to send.

Warning

This function will only take UINT16_MAX bytes from the data string.

packet() [2/3]

udp::packet::packet ( const std::string & in )

inline

Construct a packet from a string buffer.

Parameters

The	buffer, should be the value from udp::packet.buffer().

packet() [3/3]

template<typename T >

udp::packet::packet ( const connection & dst, const T & data, const size_t & size )

inline

Construct a packet from any variable data, and its size.

Parameters

dst	The destination.
data	The data to store.
size	The size of that data.

Member Function Documentation

buffer()

std::string udp::packet::buffer ( ) const

inline

Create a buffer of the packet that can be sent across the network.

Returns

The buffer.

cast()

template<typename T >

const T udp::packet::cast ( ) const

inline

Cast the content of the packet as a type.

Template Parameters

T	The type to cast

Returns

The casted value.

data()

std::string udp::packet::data ( ) const

inline

Return the data.

Returns

The data.

destination()

connection udp::packet::destination ( ) const

inline

Get the address and port of the destination.

Returns

The connection.

empty()

static packet udp::packet::empty ( const connection & dst )

inlinestatic

An empty packet.

Parameters

dst	The destination.

Returns

The empty packet.

Remarks

The Main Thread signals to the Network Thread that a destination should be closed by sending an empty packet. This packet doesn't actually get sent across the wire, just enqueued into the out thread. This is used when a WireGuard client stops the connection, and wants to close the FD associated with it. That way, the server can close the listening socket.

source()

connection udp::packet::source ( ) const

inline

Get the address and port of the source.

Returns

The connection.

str()

std::string udp::packet::str ( ) const

inline

Print the packet.

Returns

The string.

Remarks

Turn on –packet-print to see the packets like this.

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The documentation for this class was generated from the following file:

• src/udp.h