dns_txt.c File Reference

DNS TXT Record Parsing API. More...

#include "asterisk.h"
#include <netinet/in.h>
#include <resolv.h>
#include "asterisk/dns_core.h"
#include "asterisk/dns_txt.h"
#include "asterisk/dns_internal.h"
#include "asterisk/utils.h"

Include dependency graph for dns_txt.c:

Go to the source code of this file.

Functions
void	ast_dns_txt_free_strings (struct ast_vector_string *strings)
	Free strings returned by ast_dns_txt_get_strings. More...
size_t	ast_dns_txt_get_count (const struct ast_dns_record *record)
	Get the number of character strings in a TXT record. More...
struct ast_vector_string *	ast_dns_txt_get_strings (const struct ast_dns_record *record)
	Get the character strings from this TXT record. More...
struct ast_dns_record *	dns_txt_alloc (struct ast_dns_query *query, const char *data, const size_t size)
	Allocate and parse a DNS TXT record. More...

Detailed Description

DNS TXT Record Parsing API.

Author

Sean Bright sean..nosp@m.brig.nosp@m.ht@gm.nosp@m.ail..nosp@m.com

Definition in file dns_txt.c.

Function Documentation

ast_dns_txt_free_strings()

void ast_dns_txt_free_strings

(

struct ast_vector_string *

strings

)

Free strings returned by ast_dns_txt_get_strings.

Since

16.10.0, 17.4.0

Parameters

strings

The vector to free

Definition at line 123 of file dns_txt.c.

{
    AST_VECTOR_CALLBACK_VOID(strings, ast_free);
    AST_VECTOR_PTR_FREE(strings);
}

References ast_free, AST_VECTOR_CALLBACK_VOID, and AST_VECTOR_PTR_FREE.

Referenced by ast_dns_txt_get_strings().

ast_dns_txt_get_count()

size_t ast_dns_txt_get_count

(

const struct ast_dns_record *

record

)

Get the number of character strings in a TXT record.

Since

16.10.0, 17.4.0

Parameters

record

The DNS record

Returns

the number of character strings in this TXT record

Definition at line 68 of file dns_txt.c.

{
    struct ast_dns_txt_record *txt = (struct ast_dns_txt_record *) record;
    ast_assert(ast_dns_record_get_rr_type(record) == T_TXT);
    return txt->count;
}

References ast_assert, ast_dns_record_get_rr_type(), and ast_dns_txt_record::count.

Referenced by ast_dns_txt_get_strings().

ast_dns_txt_get_strings()

struct ast_vector_string * ast_dns_txt_get_strings

(

const struct ast_dns_record *

record

)

Get the character strings from this TXT record.

Since

16.10.0, 17.4.0

Parameters

record

The DNS record

Return values

NULL	Unable to allocate memory

Returns

Vector of strings. Free with ast_dns_txt_free_strings

Definition at line 75 of file dns_txt.c.

{
    struct ast_vector_string *strings;
 
    const size_t size = ast_dns_record_get_data_size(record);
    const char *data = ast_dns_record_get_data(record);
    const char *end_of_record = data + size;
 
    ast_assert(ast_dns_record_get_rr_type(record) == T_TXT);
 
    strings = ast_malloc(sizeof(struct ast_vector_const_string));
    if (!strings) {
        return NULL;
    }
 
    if (AST_VECTOR_INIT(strings, ast_dns_txt_get_count(record))) {
        ast_free(strings);
        return NULL;
    }
 
    while (data < end_of_record) {
        char *s;
        uint8_t bytes = (uint8_t) *data;
 
        s = ast_malloc(bytes + 1);
        if (!s) {
            ast_dns_txt_free_strings(strings);
            return NULL;
        }
 
        memcpy(s, &data[1], bytes);
        s[bytes] = 0;
 
        /* We know the size in advance so this can't fail */
        AST_VECTOR_APPEND(strings, s);
 
        data += bytes + 1;
    }
 
    /* Sanity check */
    if (data != end_of_record) {
        ast_dns_txt_free_strings(strings);
        return NULL;
    }
 
    return strings;
}

References ast_assert, ast_dns_record_get_data(), ast_dns_record_get_data_size(), ast_dns_record_get_rr_type(), ast_dns_txt_free_strings(), ast_dns_txt_get_count(), ast_free, ast_malloc, AST_VECTOR_APPEND, AST_VECTOR_INIT, and NULL.

dns_txt_alloc()

struct ast_dns_record * dns_txt_alloc	(	struct ast_dns_query *	query,
		const char *	data,
		const size_t	size
	)

Allocate and parse a DNS TXT record.

Since

16.10.0, 17.4.0

Parameters

query	The DNS query
data	This specific TXT record
size	The size of the TXT record

Return values

non-NULL	success
NULL	failure

Definition at line 38 of file dns_txt.c.

{
    struct ast_dns_txt_record *txt;
    const char *end_of_record = data + size;
    size_t count = 0;
 
    /* Because we can't allocate additional memory, the best we can do here is just
     * validate that this conforms to a TXT record. */
    while (data < end_of_record) {
        uint8_t byte_count = (uint8_t) *data;
        count++;
        data += byte_count + 1;
    }
 
    if (data != end_of_record) {
        /* This is not a valid TXT record, so we can bail out */
        return NULL;
    }
 
    txt = ast_calloc(1, sizeof(*txt) + size);
    if (!txt) {
        return NULL;
    }
 
    txt->count = count;
    txt->generic.data_ptr = txt->data;
 
    return (struct ast_dns_record *) txt;
}

References ast_calloc, ast_dns_txt_record::count, ast_dns_txt_record::data, ast_dns_record::data_ptr, ast_dns_txt_record::generic, and NULL.