mirror of https://github.com/c-ares/c-ares.git
Daniel Stenberg
16 years ago
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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_SRV_REPLY 3 "4 August 2009" |
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.SH NAME |
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ares_parse_srv_reply \- Parse a reply to a DNS query of type SRV into a |
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struct srv_reply |
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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_srv_reply(const unsigned char* \fIabuf\fP, int \fIalen\fP, |
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.B struct srv_reply** \fIsrv_out\fP, int *\fInsrvreply\fP); |
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.fi |
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.SH DESCRIPTION |
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The |
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.B ares_parse_srv_reply |
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function parses the response to a query of type SRV into a |
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.I struct srv_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 srv_out . |
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The number of responses is stored into the variable pointed to by |
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.IR nsrvreply . |
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It is the caller's responsibility to free the resulting |
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.IR srv_out |
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structure when it is no longer needed. |
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.PP |
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The structure |
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.I srv_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 srv_reply { |
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u_int16_t weight; |
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u_int16_t priority; |
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u_int16_t port; |
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char *host; |
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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_srv_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 SEE ALSO |
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.BR ares_query (3) |
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.SH AUTHOR |
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Written by Jakub Hrozek <jhrozek@redhat.com>, on behalf of Red Hat, Inc http://www.redhat.com |
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@ -0,0 +1,159 @@ |
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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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|
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/*
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* ares_parse_srv_reply created by Jakub Hrozek <jhrozek@redhat.com> |
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* on behalf of Red Hat - http://www.redhat.com
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*/ |
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|
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#include "setup.h" |
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#if defined(WIN32) && !defined(WATT32) |
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#include "nameser.h" |
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#else |
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#include <sys/socket.h> |
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#include <netinet/in.h> |
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#include <arpa/inet.h> |
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#include <netdb.h> |
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#include <arpa/nameser.h> |
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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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#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_private.h" |
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|
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int |
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ares_parse_srv_reply (const unsigned char *abuf, int alen, |
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struct srv_reply **srv_out, int *nsrvreply) |
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{ |
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unsigned int qdcount, ancount; |
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const unsigned char *aptr; |
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int status, i, 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 srv_reply *srv = NULL; |
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/* Set *srv_out to NULL for all failure cases. */ |
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if (srv_out) |
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*srv_out = NULL; |
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/* Same with *nsrvreply. */ |
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if (nsrvreply) |
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*nsrvreply = 0; |
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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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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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/* Allocate srv_reply array; ancount gives an upper bound */ |
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srv = malloc ((ancount) * sizeof (struct srv_reply)); |
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if (!srv) |
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{ |
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free (hostname); |
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return ARES_ENOMEM; |
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} |
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|
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/* Examine each answer resource record (RR) in turn. */ |
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for (i = 0; i < (int) 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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/* Check if we are really looking at a SRV record */ |
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if (rr_class == C_IN && rr_type == T_SRV) |
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{ |
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/* parse the SRV record itself */ |
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if (rr_len < 6) |
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{ |
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status = ARES_EBADRESP; |
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break; |
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} |
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srv[i].priority = ntohs (*((uint16_t *)aptr)); |
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aptr += sizeof(uint16_t); |
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srv[i].weight = ntohs (*((uint16_t *)aptr)); |
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aptr += sizeof(uint16_t); |
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srv[i].port = ntohs (*((uint16_t *)aptr)); |
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aptr += sizeof(uint16_t); |
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status = ares_expand_name (aptr, abuf, alen, &srv[i].host, &len); |
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if (status != ARES_SUCCESS) |
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break; |
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/* Move on to the next record */ |
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aptr += len; |
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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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} |
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/* clean up on error */ |
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if (status != ARES_SUCCESS) |
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{ |
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free (srv); |
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free (hostname); |
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free (rr_name); |
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return status; |
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} |
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/* everything looks fine, return the data */ |
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*srv_out = srv; |
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*nsrvreply = ancount; |
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free (hostname); |
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free (rr_name); |
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return status; |
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} |
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