mirror of https://github.com/c-ares/c-ares.git
Jérémy Lal
15 years ago
committed by
Daniel Stenberg
parent
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.\" |
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.\" Copyright 1998 by the Massachusetts Institute of Technology. |
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.\" |
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.\" Permission to use, copy, modify, and distribute this |
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.\" software and its documentation for any purpose and without |
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.\" fee is hereby granted, provided that the above copyright |
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.\" notice appear in all copies and that both that copyright |
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.\" notice and this permission notice appear in supporting |
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.\" documentation, and that the name of M.I.T. not be used in |
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.\" advertising or publicity pertaining to distribution of the |
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.\" software without specific, written prior permission. |
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.\" M.I.T. makes no representations about the suitability of |
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.\" this software for any purpose. It is provided "as is" |
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.\" without express or implied warranty. |
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.\" |
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.TH ARES_PARSE_MX_REPLY 3 "4 August 2009" |
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.SH NAME |
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ares_parse_mx_reply \- Parse a reply to a DNS query of type MX |
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.SH SYNOPSIS |
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.nf |
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.B #include <ares.h> |
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.PP |
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.B int ares_parse_mx_reply(const unsigned char* \fIabuf\fP, int \fIalen\fP, |
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.B struct ares_mx_reply** \fImx_out\fP); |
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.fi |
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.SH DESCRIPTION |
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The |
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.B ares_parse_mx_reply |
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function parses the response to a query of type MX into a |
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linked list of |
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.I struct ares_mx_reply |
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The parameters |
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.I abuf |
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and |
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.I alen |
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give the contents of the response. The result is stored in allocated |
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memory and a pointer to it stored into the variable pointed to by |
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.IR mx_out . |
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It is the caller's responsibility to free the resulting |
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.IR mx_out |
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structure when it is no longer needed using the function |
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.B ares_free_data |
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.PP |
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The structure |
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.I ares_mx_reply |
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contains the following fields: |
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.sp |
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.in +4n |
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.nf |
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struct ares_mx_reply { |
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struct ares_mx_reply *next; |
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char *host; |
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unsigned short priority; |
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}; |
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.fi |
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.in |
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.PP |
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.SH RETURN VALUES |
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.B ares_parse_mx_reply |
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can return any of the following values: |
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.TP 15 |
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.B ARES_SUCCESS |
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The response was successfully parsed. |
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.TP 15 |
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.B ARES_EBADRESP |
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The response was malformatted. |
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.TP 15 |
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.B ARES_ENODATA |
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The response did not contain an answer to the query. |
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.TP 15 |
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.B ARES_ENOMEM |
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Memory was exhausted. |
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.SH AVAILABILITY |
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This function was first introduced in c-ares version 1.7.2. |
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.SH SEE ALSO |
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.BR ares_query (3) |
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.BR ares_free_data (3) |
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.SH AUTHOR |
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Written by Jeremy Lal <kapouer@melix.org> |
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@ -0,0 +1,170 @@ |
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|
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/* Copyright 1998 by the Massachusetts Institute of Technology.
|
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* Copyright (C) 2010 Jeremy Lal <kapouer@melix.org> |
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* |
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* Permission to use, copy, modify, and distribute this |
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* software and its documentation for any purpose and without |
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* fee is hereby granted, provided that the above copyright |
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* notice appear in all copies and that both that copyright |
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* notice and this permission notice appear in supporting |
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* documentation, and that the name of M.I.T. not be used in |
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* advertising or publicity pertaining to distribution of the |
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* software without specific, written prior permission. |
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* M.I.T. makes no representations about the suitability of |
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* this software for any purpose. It is provided "as is" |
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* without express or implied warranty. |
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*/ |
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|
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#include "ares_setup.h" |
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|
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#ifdef HAVE_SYS_SOCKET_H |
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# include <sys/socket.h> |
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#endif |
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#ifdef HAVE_NETINET_IN_H |
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# include <netinet/in.h> |
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#endif |
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#ifdef HAVE_NETDB_H |
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# include <netdb.h> |
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#endif |
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#ifdef HAVE_ARPA_INET_H |
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# include <arpa/inet.h> |
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#endif |
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#ifdef HAVE_ARPA_NAMESER_H |
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# include <arpa/nameser.h> |
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#else |
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# include "nameser.h" |
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#endif |
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#ifdef HAVE_ARPA_NAMESER_COMPAT_H |
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# include <arpa/nameser_compat.h> |
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#endif |
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|
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#include <stdlib.h> |
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#include <string.h> |
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#include "ares.h" |
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#include "ares_dns.h" |
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#include "ares_data.h" |
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#include "ares_private.h" |
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|
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int |
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ares_parse_mx_reply (const unsigned char *abuf, int alen, |
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struct ares_mx_reply **mx_out) |
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{ |
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unsigned int qdcount, ancount, i; |
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const unsigned char *aptr, *vptr; |
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int status, rr_type, rr_class, rr_len; |
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long len; |
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char *hostname = NULL, *rr_name = NULL; |
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struct ares_mx_reply *mx_head = NULL; |
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struct ares_mx_reply *mx_last = NULL; |
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struct ares_mx_reply *mx_curr; |
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|
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/* Set *mx_out to NULL for all failure cases. */ |
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*mx_out = NULL; |
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|
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/* Give up if abuf doesn't have room for a header. */ |
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if (alen < HFIXEDSZ) |
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return ARES_EBADRESP; |
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|
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/* Fetch the question and answer count from the header. */ |
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qdcount = DNS_HEADER_QDCOUNT (abuf); |
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ancount = DNS_HEADER_ANCOUNT (abuf); |
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if (qdcount != 1) |
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return ARES_EBADRESP; |
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if (ancount == 0) |
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return ARES_ENODATA; |
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|
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/* Expand the name from the question, and skip past the question. */ |
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aptr = abuf + HFIXEDSZ; |
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status = ares_expand_name (aptr, abuf, alen, &hostname, &len); |
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if (status != ARES_SUCCESS) |
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return status; |
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|
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if (aptr + len + QFIXEDSZ > abuf + alen) |
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{ |
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free (hostname); |
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return ARES_EBADRESP; |
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} |
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aptr += len + QFIXEDSZ; |
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|
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/* Examine each answer resource record (RR) in turn. */ |
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for (i = 0; i < ancount; i++) |
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{ |
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/* Decode the RR up to the data field. */ |
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status = ares_expand_name (aptr, abuf, alen, &rr_name, &len); |
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if (status != ARES_SUCCESS) |
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{ |
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break; |
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} |
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aptr += len; |
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if (aptr + RRFIXEDSZ > abuf + alen) |
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{ |
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status = ARES_EBADRESP; |
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break; |
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} |
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rr_type = DNS_RR_TYPE (aptr); |
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rr_class = DNS_RR_CLASS (aptr); |
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rr_len = DNS_RR_LEN (aptr); |
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aptr += RRFIXEDSZ; |
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|
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/* Check if we are really looking at a MX record */ |
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if (rr_class == C_IN && rr_type == T_MX) |
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{ |
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/* parse the MX record itself */ |
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if (rr_len < 2) |
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{ |
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status = ARES_EBADRESP; |
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break; |
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} |
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|
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/* Allocate storage for this MX answer appending it to the list */ |
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mx_curr = ares_malloc_data(ARES_DATATYPE_MX_REPLY); |
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if (!mx_curr) |
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{ |
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status = ARES_ENOMEM; |
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break; |
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} |
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if (mx_last) |
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{ |
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mx_last->next = mx_curr; |
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} |
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else |
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{ |
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mx_head = mx_curr; |
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} |
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mx_last = mx_curr; |
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vptr = aptr; |
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mx_curr->priority = ntohs (*((unsigned short *)vptr)); |
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vptr += sizeof(unsigned short); |
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status = ares_expand_name (vptr, abuf, alen, &mx_curr->host, &len); |
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if (status != ARES_SUCCESS) |
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break; |
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} |
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|
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/* Don't lose memory in the next iteration */ |
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free (rr_name); |
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rr_name = NULL; |
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|
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/* Move on to the next record */ |
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aptr += rr_len; |
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} |
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if (hostname) |
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free (hostname); |
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if (rr_name) |
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free (rr_name); |
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|
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/* clean up on error */ |
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if (status != ARES_SUCCESS) |
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{ |
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if (mx_head) |
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ares_free_data (mx_head); |
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return status; |
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} |
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/* everything looks fine, return the data */ |
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*mx_out = mx_head; |
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return ARES_SUCCESS; |
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} |
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