Name

ares_parse_txt_reply - Parse a reply to a DNS query of type TXT

Synopsis

#include <ares.h>
 
int ares_parse_txt_reply(const unsigned char* abuf, int alen,
                         struct ares_txt_reply **txt_out);
 
int ares_parse_txt_reply_ext(const unsigned char* abuf, int alen,
                             struct ares_txt_ext **txt_out);

Description

The ares_parse_txt_reply and ares_parse_txt_reply_ext(3) functions parse the response to a query of type TXT into a linked list (one element per sub-string) of struct ares_txt_reply (struct ares_txt_ext) The parameters abuf and alen give the contents of the response. The result is stored in allocated memory and a pointer to it stored into the variable pointed to by txt_out. It is the caller's responsibility to free the resulting txt_out structure when it is no longer needed using the function ares_free_data.

The structure ares_txt_reply contains the following fields: 

struct ares_txt_reply {
  struct ares_txt_reply  *next;
  unsigned int  length;
  unsigned char *txt;
};

The structure ares_txt_ext contains the following fields: 

struct ares_txt_ext {
  struct ares_txt_ext  *next;
  unsigned int  length;
  unsigned char *txt;
  unsigned char record_start;
};

The record_start field in struct ares_txt_ext is 1 if this structure is a start of a TXT record, and 0 if the structure is a continuation of a previous record. The linked list of the struct ares_txt_ext will have at least one item with record_start equal to 1, and may have some items with record_start equal to 0 between them.

These sequences of struct ares_txt_ext (starting from the item with record_start equal to 1, and ending right before the record start item) may be treated as either components of a single TXT record or as a multi-parted TXT record, depending on particular use case.

Return values

ares_parse_txt_reply (ares_parse_txt_reply_ext) can return any of the following values:

ARES_SUCCESS The response was successfully parsed.

ARES_EBADRESP The response was malformatted.

ARES_ENODATA The response did not contain an answer to the query.

ARES_ENOMEM Memory was exhausted.

Availability

This function was first introduced in c-ares version 1.7.0.

See also

ares_query(3) ares_free_data(3)

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