#include "syshead.h"
#include "common.h"
#include "buffer.h"
#include "error.h"
#include "integer.h"
#include "mtu.h"
#include "options.h"
#include "crypto.h"
#include "memdbg.h"

Include dependency graph for mtu.c:

Macros
#define	MTUDISC_NOT_SUPPORTED_MSG "--mtu-disc is not supported on this OS"

Functions
void	alloc_buf_sock_tun (struct buffer buf, const struct frame frame)

unsigned int	calc_packet_id_size_dc (const struct options options, const struct key_type kt)
	Return the size of the packet ID size that is currently in use by cipher and options for the data channel. More...

size_t	frame_calculate_protocol_header_size (const struct key_type kt, const struct options options, bool occ)
	Calculates the size of the OpenVPN protocol header. More...

size_t	frame_calculate_payload_overhead (size_t extra_tun, const struct options options, const struct key_type kt)
	Calculates the size of the payload overhead according to tun-mtu and tap overhead. More...

size_t	frame_calculate_payload_size (const struct frame frame, const struct options options, const struct key_type *kt)
	Calculates the size of the payload according to tun-mtu and tap overhead. More...

size_t	calc_options_string_link_mtu (const struct options o, const struct frame frame)
	Calculate the link-mtu to advertise to our peer. More...

void	frame_print (const struct frame frame, int level, const char prefix)

void	set_mtu_discover_type (socket_descriptor_t sd, int mtu_type, sa_family_t proto_af)

int	translate_mtu_discover_type_name (const char *name)

Macro Definition Documentation

◆ MTUDISC_NOT_SUPPORTED_MSG

#define MTUDISC_NOT_SUPPORTED_MSG "--mtu-disc is not supported on this OS"

Definition at line 222 of file mtu.c.

Function Documentation

◆ alloc_buf_sock_tun()

void alloc_buf_sock_tun	(	struct buffer *	buf,
		const struct frame *	frame
	)

Definition at line 42 of file mtu.c.

References alloc_buf(), ASSERT, frame::buf, buf_init, buf_safe(), BUF_SIZE, frame::headroom, buffer::len, and frame::payload_size.

Referenced by overlapped_io_init(), and socket_frame_init().

◆ calc_options_string_link_mtu()

size_t calc_options_string_link_mtu	(	const struct options *	options,
		const struct frame *	frame
	)

Calculate the link-mtu to advertise to our peer.

The actual value is not relevant, because we will possibly perform data channel cipher negotiation after this, but older clients will log warnings if we do not supply them the value they expect. This assumes that the traditional cipher/auth directives in the config match the config of the peer.

Definition at line 152 of file mtu.c.

References options::authname, options::ciphername, frame_calculate_payload_size(), frame_calculate_protocol_header_size(), init_key_type(), options::shared_secret_file, options::tls_client, and options::tls_server.

Referenced by options_string(), and test_occ_mtu_calculation().

◆ calc_packet_id_size_dc()

unsigned int calc_packet_id_size_dc	(	const struct options *	options,
		const struct key_type *	kt
	)

Return the size of the packet ID size that is currently in use by cipher and options for the data channel.

Definition at line 53 of file mtu.c.

References key_type::cipher, cipher_kt_mode_ofb_cfb(), packet_id_size(), options::tls_client, and options::tls_server.

Referenced by frame_calculate_fragment(), frame_calculate_payload_overhead(), and frame_calculate_protocol_header_size().

◆ frame_calculate_payload_overhead()

size_t frame_calculate_payload_overhead	(	size_t	extra_tun,
		const struct options *	options,
		const struct key_type *	kt
	)

Calculates the size of the payload overhead according to tun-mtu and tap overhead.

This all the overhead that is considered part of the payload itself. The compression and fragmentation header and extra header from tap are considered part of this overhead that increases the payload larger than tun-mtu.

In CBC mode, the IV is part of the payload instead of part of the OpenVPN protocol header and is included in the returned value.

In this context payload is identical to the size of the plaintext and this method can be also understand as number of bytes that are added to the plaintext before encryption.

[IP][UDP][OPENVPN PROTOCOL HEADER][ PAYLOAD incl compression header ]

Definition at line 101 of file mtu.c.

References compress_options::alg, calc_packet_id_size_dc(), options::ce, key_type::cipher, cipher_kt_mode_cbc(), options::comp, COMP_ALG_LZ4, COMP_ALG_LZO, COMP_ALG_STUB, and connection_entry::fragment.

Referenced by check_send_occ_msg_dowork(), frame_calculate_mssfix(), and frame_calculate_payload_size().

◆ frame_calculate_payload_size()

size_t frame_calculate_payload_size	(	const struct frame *	frame,
		const struct options *	options,
		const struct key_type *	kt
	)

Calculates the size of the payload according to tun-mtu and tap overhead.

In this context payload is identical to the size of the plaintext. This also includes compression, fragmentation overhead, and packet id in CBC mode if these options are used.

[IP][UDP][OPENVPN PROTOCOL HEADER][ PAYLOAD incl compression header ]

Definition at line 142 of file mtu.c.

References options::ce, frame::extra_tun, frame_calculate_payload_overhead(), and connection_entry::tun_mtu.

Referenced by calc_options_string_link_mtu(), and check_send_occ_load_test_dowork().

◆ frame_calculate_protocol_header_size()

size_t frame_calculate_protocol_header_size	(	const struct key_type *	kt,
		const struct options *	options,
		bool	occ
	)

Calculates the size of the OpenVPN protocol header.

This includes the crypto IV/tag/HMAC but does not include the IP encapsulation

This does NOT include the padding and rounding of CBC size as the users (mssfix/fragment) of this function need to adjust for this and add it themselves.

[IP][UDP][ OPENVPN PROTOCOL HEADER][PAYLOAD incl compression header]

Parameters