dns.h File Reference

Functions to manipulate DNS labels. More...

Go to the source code of this file.

Data Structures
struct	fr_dns_block_t
struct	fr_dns_labels_t

Functions
ssize_t	fr_dns_label_from_value_box (size_t *need, uint8_t *buf, size_t buflen, uint8_t *where, bool compression, fr_value_box_t const *value, fr_dns_labels_t *lb)
	Encode a single value box of type string, serializing its contents to a dns label. More...
ssize_t	fr_dns_label_from_value_box_dbuff (fr_dbuff_t *dbuff, bool compression, fr_value_box_t const *value, fr_dns_labels_t *lb)
	Encode a single value box of type string, serializing its contents to a dns label in a dbuff. More...
ssize_t	fr_dns_label_to_value_box (TALLOC_CTX *ctx, fr_value_box_t *dst, uint8_t const *src, size_t len, uint8_t const *label, bool tainted, fr_dns_labels_t *lb)
	Decode a fr_value_box_t from one DNS label. More...
ssize_t	fr_dns_label_uncompressed_length (uint8_t const *packet, uint8_t const *buf, size_t buf_len, uint8_t const **p_label, fr_dns_labels_t *lb)
	Get the uncompressed length of a DNS label in a network buffer. More...
ssize_t	fr_dns_labels_network_verify (uint8_t const *packet, uint8_t const *buf, size_t buf_len, uint8_t const *start, fr_dns_labels_t *lb))
	Verify that a network buffer contains valid DNS labels. More...

Detailed Description

Functions to manipulate DNS labels.

Copyright

2019 Network RADIUS SAS (legal.nosp@m.@net.nosp@m.workr.nosp@m.adiu.nosp@m.s.com)

Definition in file dns.h.

---

Data Structure Documentation

fr_dns_block_t

struct fr_dns_block_t

Definition at line 30 of file dns.h.

Data Fields
uint16_t	end
uint16_t	start

fr_dns_labels_t

struct fr_dns_labels_t

Definition at line 35 of file dns.h.

Collaboration diagram for fr_dns_labels_t:

Data Fields
fr_dns_block_t *	blocks	maximum number of labels array holding "max" labels
uint8_t const *	end	end of the packet
uint8_t *	mark	markup buffer used for decoding.
int	max
int	num	number of used labels
uint8_t const *	start	start of packet

Function Documentation

fr_dns_label_from_value_box()

ssize_t fr_dns_label_from_value_box	(	size_t *	need,
		uint8_t *	buf,
		size_t	buf_len,
		uint8_t *	where,
		bool	compression,
		fr_value_box_t const *	value,
		fr_dns_labels_t *	lb
	)

Encode a single value box of type string, serializing its contents to a dns label.

This functions takes a large buffer and encodes the label in part of the buffer. This API is necessary in order to allow DNS label compression.

Parameters

[out]	need	if not NULL, how long "buf_len" should be to serialize the rest of the data. Note: Only variable length types will be partially encoded. Fixed length types will not be partially encoded.
[out]	buf	Buffer where labels are stored
[in]	buf_len	The length of the output buffer
[out]	where	Where to write this label
[in]	compression	Whether or not to do DNS label compression.
[in]	value	to encode.
[in]	lb	label tracking data structure

Returns

• 0 no bytes were written, see need value to determine
• >0 the number of bytes written to "where", NOT "buf + where + outlen"
• <0 on error.

Definition at line 639 of file dns.c.

Here is the call graph for this function:

Here is the caller graph for this function:

fr_dns_label_from_value_box_dbuff()

ssize_t fr_dns_label_from_value_box_dbuff	(	fr_dbuff_t *	dbuff,
		bool	compression,
		fr_value_box_t const *	value,
		fr_dns_labels_t *	lb
	)

Encode a single value box of type string, serializing its contents to a dns label in a dbuff.

Parameters

[in]	dbuff	Buffer where labels are written
[in]	compression	Whether or not to do DNS label compression.
[in]	value	to encode.
[in]	lb	label tracking data structure.

Returns

• >0 the number of bytes written to the dbuff
• 0 could not encode anything, an error has occurred.
• <0 the number of bytes the dbuff should have had, instead of "remaining".

Definition at line 604 of file dns.c.

Here is the call graph for this function:

Here is the caller graph for this function:

fr_dns_label_to_value_box()

ssize_t fr_dns_label_to_value_box	(	TALLOC_CTX *	ctx,
		fr_value_box_t *	dst,
		uint8_t const *	src,
		size_t	len,
		uint8_t const *	label,
		bool	tainted,
		fr_dns_labels_t *	lb
	)

Decode a fr_value_box_t from one DNS label.

The output type is always FR_TYPE_STRING

Note that the caller MUST call fr_dns_labels_network_verify(src, len, start) before calling this function. Otherwise bad things will happen.

Parameters

[in]	ctx	Where to allocate any talloc buffers required.
[out]	dst	value_box to write the result to.
[in]	src	Start of the buffer containing DNS labels
[in]	len	Length of the buffer to decode
[in]	label	This particular label
[in]	tainted	Whether the value came from a trusted source.
[in]	lb	label tracking data structure

Returns

• >= 0 The number of network bytes consumed.
• <0 on error.

Definition at line 1225 of file dns.c.

Here is the call graph for this function:

Here is the caller graph for this function:

fr_dns_label_uncompressed_length()

ssize_t fr_dns_label_uncompressed_length	(	uint8_t const *	packet,
		uint8_t const *	buf,
		size_t	buf_len,
		uint8_t const **	next,
		fr_dns_labels_t *	lb
	)

Get the uncompressed length of a DNS label in a network buffer.

i.e. how bytes are required to store the uncompressed version of the label.

Note that a bare 0x00 byte has length 1, to account for '.'

Parameters

[in]	packet	where the packet starts
[in]	buf	buffer holding one or more DNS labels
[in]	buf_len	total length of the buffer
[in,out]	next	the DNS label to check, updated to point to the next label
[in]	lb	label tracking data structure

Returns

• <=0 on error, offset from buf where the invalid label is located.
• > 0 decoded size of this particular DNS label

Definition at line 884 of file dns.c.

Here is the call graph for this function:

Here is the caller graph for this function:

fr_dns_labels_network_verify()

ssize_t fr_dns_labels_network_verify	(	uint8_t const *	packet,
		uint8_t const *	buf,
		size_t	buf_len,
		uint8_t const *	start,
		fr_dns_labels_t *	lb
	)

Verify that a network buffer contains valid DNS labels.

Parameters

[in]	packet	where the packet starts
[in]	buf	buffer holding one or more DNS labels
[in]	buf_len	total length of the buffer
[in]	start	where to start looking
[in]	lb	label tracking data structure

Returns

• <=0 on error, where in the buffer the invalid label is located.
• > 0 total size of the encoded label(s). Will be <= buf_len

Definition at line 1137 of file dns.c.

Here is the call graph for this function:

Here is the caller graph for this function: