Detailed Description

Structure for holding an IPv4 Header, including options.

For creating new headers, see ip::Dispatch::next_header(...)

Definition at line 180 of file ip_core.h.

#include <ip_core.h>

Public Member Functions
	Header (const Header &t)=default

Header &	operator= (const Header &t)=default

constexpr unsigned	ver () const
	< Header version (i.e., "4")

constexpr unsigned	ihl () const
	< Header length (4-byte words)

constexpr unsigned	len_total () const
	< Total bytes including header

constexpr u16	id () const
	< Identifier / sequence number

constexpr u16	frg () const
	< Fragment offset

constexpr unsigned	len_inner () const
	< Inner bytes excluding header

constexpr u8	ttl () const
	< Time to Live (TTL)

constexpr u8	proto () const
	< Inner protocol (UDP/TCP/etc.)

constexpr u16	chk () const
	< Checksum (incoming only)

constexpr satcat5::ip::Addr	src () const
	< Source address

constexpr satcat5::ip::Addr	dst () const
	< Destination address

void	chk_incr16 (u16 prev, u16 next)
	Incremental update to checksum when replacing a given field. More...

void	chk_incr32 (u32 prev, u32 next)

void	option_alert ()
	} More...

void	write_to (satcat5::io::Writeable *wr) const
	Write IPv4 header to the designated stream. More...

bool	read_core (satcat5::io::Readable *rd)
	Read a partial IPv4 header from the designated stream. More...

bool	read_from (satcat5::io::Readable *rd)
	Read an entire IPv4 header from the designated stream. More...

Public Attributes
u16	data [HDR_MAX_SHORTS]
	Raw access to the underlying header contents.

Member Function Documentation

◆ chk_incr16()

void Header::chk_incr16	(	u16	prev,
		u16	next
	)

Incremental update to checksum when replacing a given field.

Given a before/after change to any field in this IPv4 header, update the header checksum by applying the method of IETF RFC1624 Section 3, i.e., "HC' = ~(~HC + ~m + m')". Variants are provided for changing 16-bit and 32-bit fields. {

Definition at line 94 of file ip_core.cc.

◆ option_alert()

void Header::option_alert ( )

}

Append the "router alert" option (RFC-2113)

Definition at line 106 of file ip_core.cc.

◆ read_core()

bool Header::read_core ( satcat5::io::Readable * rd )

Read a partial IPv4 header from the designated stream.

This method reads the first 20 bytes of an IPv4 header, which contains basic header fields but not variable-length options (i.e., IHL > 5). This is used in cases where the full header is unavailable or unnecessary (e.g., due to "peek" limits). To read options and validate the header checksum,

See also: read_from.

Returns: True if the partial header is valid, false otherwise.

Definition at line 115 of file ip_core.cc.

◆ read_from()

bool Header::read_from ( satcat5::io::Readable * rd )

Read an entire IPv4 header from the designated stream.

This method calls read_core, then reads variable-length header options and validates the IPv4 header checksum.

Returns: True if header and checksum are valid, false otherwise.

Definition at line 127 of file ip_core.cc.

◆ write_to()

void Header::write_to ( satcat5::io::Writeable * wr ) const

Write IPv4 header to the designated stream.

If the checksum has not already been calculated, update in-place.

Definition at line 82 of file ip_core.cc.

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