Abstract packet handling class. More...

#include <pkt_filter.h>

Inheritance diagram for isc::dhcp::PktFilter:

Public Member Functions
virtual	~PktFilter ()
	Virtual Destructor.

virtual bool	isDirectResponseSupported () const =0
	Check if packet can be sent to the host without address directly.

virtual bool	isSocketReceivedTimeSupported () const =0
	Check if the socket received time is supported.

virtual SocketInfo	openSocket (Iface &iface, const isc::asiolink::IOAddress &addr, const uint16_t port, const bool receive_bcast, const bool send_bcast)=0
	Open primary and fallback socket.

virtual Pkt4Ptr	receive (Iface &iface, const SocketInfo &socket_info)=0
	Receive packet over specified socket.

virtual int	send (const Iface &iface, uint16_t sockfd, const Pkt4Ptr &pkt)=0
	Send packet over specified socket.

Protected Member Functions
virtual int	openFallbackSocket (const isc::asiolink::IOAddress &addr, const uint16_t port)
	Default implementation to open a fallback socket.

Detailed Description

Abstract packet handling class.

This class represents low level method to send and receive DHCP packet. Different methods, represented by classes derived from this class, use different socket families and socket types. Also, various packet filtering methods can be implemented by derived classes, e.g. Linux Packet Filtering (LPF) or Berkeley Packet Filtering (BPF).

Low-level code operating on sockets may require special privileges to execute. For example: opening raw socket or opening socket on low port number requires root privileges. This makes it impossible or very hard to unit test the IfaceMgr. In order to overcome this problem, it is recommended to create mock object derived from this class that mimics the behavior of the real packet handling class making IfaceMgr testable.

Definition at line 44 of file pkt_filter.h.

Constructor & Destructor Documentation

◆ ~PktFilter()

virtual isc::dhcp::PktFilter::~PktFilter ( )

inlinevirtual

Virtual Destructor.

Definition at line 48 of file pkt_filter.h.

Member Function Documentation

◆ isDirectResponseSupported()

virtual bool isc::dhcp::PktFilter::isDirectResponseSupported ( ) const

pure virtual

Check if packet can be sent to the host without address directly.

Checks if the Packet Filter class has capability to send a packet directly to the client having no address assigned. This capability is used by DHCPv4 servers which respond to the clients they assign addresses to. Not all classes derived from PktFilter support this because it requires injection of the destination host HW address to the link layer header of the packet.

Returns: true of the direct response is supported.

Implemented in isc::dhcp::PktFilterBPF, isc::dhcp::PktFilterInet, and isc::dhcp::PktFilterLPF.

◆ isSocketReceivedTimeSupported()

virtual bool isc::dhcp::PktFilter::isSocketReceivedTimeSupported ( ) const

pure virtual

Check if the socket received time is supported.

If true, then packets received through this filter will include a SOCKET_RECEIVED event in its event stack. Other than direct clients using BPF for which this is always true, this function is true provided SO_TIMESTAMP is defined.

Returns: True if it is supported.

Implemented in isc::dhcp::PktFilterBPF, isc::dhcp::PktFilterInet, and isc::dhcp::PktFilterLPF.

◆ openFallbackSocket()

int isc::dhcp::PktFilter::openFallbackSocket	(	const isc::asiolink::IOAddress &	addr,
		const uint16_t	port
	)

protectedvirtual

Default implementation to open a fallback socket.

This method provides a means to open a fallback socket and bind it to a given IPv4 address and UDP port. This function may be used by the derived classes to create a fallback socket. It can be overridden in the derived classes if it happens to be insufficient on some environments.

The fallback socket is meant to be opened together with the other socket (a.k.a. primary socket) used to receive and handle DHCPv4 traffic. The traffic received through the fallback should be dropped. The reasoning behind opening the fallback socket is explained in the documentation of isc::dhcp::SocketInfo structure.

Parameters

addr	An IPv4 address to bind the socket to.
port	A port number to bind socket to.

Returns: A fallback socket descriptor. This descriptor should be assigned to the fallbackfd_ field of the isc::dhcp::SocketInfo structure.

Exceptions

isc::dhcp::SocketConfigError if socket opening, binding or configuration fails.

Definition at line 18 of file pkt_filter.cc.

References isc_throw, and isc::asiolink::IOAddress::toUint32().

Referenced by isc::dhcp::PktFilterBPF::openSocket(), and isc::dhcp::PktFilterLPF::openSocket().

Here is the call graph for this function:

◆ openSocket()

virtual SocketInfo isc::dhcp::PktFilter::openSocket	(	Iface &	iface,
		const isc::asiolink::IOAddress &	addr,
		const uint16_t	port,
		const bool	receive_bcast,
		const bool	send_bcast
	)

pure virtual

Open primary and fallback socket.

A method implementation in the derived class may open one or two sockets:

a primary socket - used for communication with clients. DHCP messages received using this socket are processed and the same socket is used to send a response to the client.
a fallback socket which is optionally opened if there is a need for the presence of the socket which can be bound to a specific IP address and UDP port (e.g. raw primary socket can't be). For the details, see the documentation of isc::dhcp::SocketInfo.

Parameters

iface	Interface descriptor.
addr	Address on the interface to be used to send packets.
port	Port number.
receive_bcast	Configure socket to receive broadcast messages
send_bcast	configure socket to send broadcast messages.

Returns: A structure describing a primary and fallback socket.

Implemented in isc::dhcp::PktFilterBPF, isc::dhcp::PktFilterInet, and isc::dhcp::PktFilterLPF.

◆ receive()

virtual Pkt4Ptr isc::dhcp::PktFilter::receive	(	Iface &	iface,
		const SocketInfo &	socket_info
	)

pure virtual

Receive packet over specified socket.

Parameters

iface	interface
socket_info	structure holding socket information

Returns: Received packet

Implemented in isc::dhcp::PktFilterBPF, isc::dhcp::PktFilterInet, and isc::dhcp::PktFilterLPF.

◆ send()

virtual int isc::dhcp::PktFilter::send	(	const Iface &	iface,
		uint16_t	sockfd,
		const Pkt4Ptr &	pkt
	)

pure virtual

Send packet over specified socket.

Parameters

iface	interface to be used to send packet
sockfd	socket descriptor
pkt	packet to be sent

Returns: result of sending the packet. It is 0 if successful.

Implemented in isc::dhcp::PktFilterBPF, isc::dhcp::PktFilterInet, and isc::dhcp::PktFilterLPF.

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

Public Member Functions

Protected Member Functions

Detailed Description

Constructor & Destructor Documentation

◆ ~PktFilter()

Member Function Documentation

◆ isDirectResponseSupported()

◆ isSocketReceivedTimeSupported()

◆ openFallbackSocket()

◆ openSocket()

◆ receive()

◆ send()