/* $Id: ares_parse_ptr_reply.c,v 1.21 2009-11-02 11:55:53 yangtse Exp $ */ /* Copyright 1998 by the Massachusetts Institute of Technology. * * Permission to use, copy, modify, and distribute this * software and its documentation for any purpose and without * fee is hereby granted, provided that the above copyright * notice appear in all copies and that both that copyright * notice and this permission notice appear in supporting * documentation, and that the name of M.I.T. not be used in * advertising or publicity pertaining to distribution of the * software without specific, written prior permission. * M.I.T. makes no representations about the suitability of * this software for any purpose. It is provided "as is" * without express or implied warranty. */ #include "ares_setup.h" #ifdef HAVE_SYS_SOCKET_H # include <sys/socket.h> #endif #ifdef HAVE_NETINET_IN_H # include <netinet/in.h> #endif #ifdef HAVE_NETDB_H # include <netdb.h> #endif #ifdef HAVE_ARPA_NAMESER_H # include <arpa/nameser.h> #else # include "nameser.h" #endif #ifdef HAVE_ARPA_NAMESER_COMPAT_H # include <arpa/nameser_compat.h> #endif #ifdef HAVE_STRINGS_H # include <strings.h> #endif #include <stdlib.h> #include <string.h> #include "ares.h" #include "ares_dns.h" #include "ares_private.h" int ares_parse_ptr_reply(const unsigned char *abuf, int alen, const void *addr, int addrlen, int family, struct hostent **host) { unsigned int qdcount, ancount; int status, i, rr_type, rr_class, rr_len; long len; const unsigned char *aptr; char *ptrname, *hostname, *rr_name, *rr_data; struct hostent *hostent; int aliascnt = 0; int alias_alloc = 8; char ** aliases; /* Set *host to NULL for all failure cases. */ *host = NULL; /* Give up if abuf doesn't have room for a header. */ if (alen < HFIXEDSZ) return ARES_EBADRESP; /* Fetch the question and answer count from the header. */ qdcount = DNS_HEADER_QDCOUNT(abuf); ancount = DNS_HEADER_ANCOUNT(abuf); if (qdcount != 1) return ARES_EBADRESP; /* Expand the name from the question, and skip past the question. */ aptr = abuf + HFIXEDSZ; status = ares__expand_name_for_response(aptr, abuf, alen, &ptrname, &len); if (status != ARES_SUCCESS) return status; if (aptr + len + QFIXEDSZ > abuf + alen) { free(ptrname); return ARES_EBADRESP; } aptr += len + QFIXEDSZ; /* Examine each answer resource record (RR) in turn. */ hostname = NULL; aliases = malloc(alias_alloc * sizeof(char *)); if (!aliases) { free(ptrname); return ARES_ENOMEM; } for (i = 0; i < (int)ancount; i++) { /* Decode the RR up to the data field. */ status = ares__expand_name_for_response(aptr, abuf, alen, &rr_name, &len); if (status != ARES_SUCCESS) break; aptr += len; if (aptr + RRFIXEDSZ > abuf + alen) { status = ARES_EBADRESP; break; } rr_type = DNS_RR_TYPE(aptr); rr_class = DNS_RR_CLASS(aptr); rr_len = DNS_RR_LEN(aptr); aptr += RRFIXEDSZ; if (rr_class == C_IN && rr_type == T_PTR && strcasecmp(rr_name, ptrname) == 0) { /* Decode the RR data and set hostname to it. */ status = ares__expand_name_for_response(aptr, abuf, alen, &rr_data, &len); if (status != ARES_SUCCESS) break; if (hostname) free(hostname); hostname = rr_data; aliases[aliascnt] = malloc((strlen(rr_data)+1) * sizeof(char *)); if (!aliases[aliascnt]) { status = ARES_ENOMEM; break; } strncpy(aliases[aliascnt], rr_data, strlen(rr_data)+1); aliascnt++; if (aliascnt >= alias_alloc) { char **ptr; alias_alloc *= 2; ptr = realloc(aliases, alias_alloc * sizeof(char *)); if(!ptr) { status = ARES_ENOMEM; break; } aliases = ptr; } } if (rr_class == C_IN && rr_type == T_CNAME) { /* Decode the RR data and replace ptrname with it. */ status = ares__expand_name_for_response(aptr, abuf, alen, &rr_data, &len); if (status != ARES_SUCCESS) break; free(ptrname); ptrname = rr_data; } free(rr_name); aptr += rr_len; if (aptr > abuf + alen) { status = ARES_EBADRESP; break; } } if (status == ARES_SUCCESS && !hostname) status = ARES_ENODATA; if (status == ARES_SUCCESS) { /* We got our answer. Allocate memory to build the host entry. */ hostent = malloc(sizeof(struct hostent)); if (hostent) { hostent->h_addr_list = malloc(2 * sizeof(char *)); if (hostent->h_addr_list) { hostent->h_addr_list[0] = malloc(addrlen); if (hostent->h_addr_list[0]) { hostent->h_aliases = malloc((aliascnt+1) * sizeof (char *)); if (hostent->h_aliases) { /* Fill in the hostent and return successfully. */ hostent->h_name = hostname; for (i=0 ; i<aliascnt ; i++) hostent->h_aliases[i] = aliases[i]; hostent->h_aliases[aliascnt] = NULL; hostent->h_addrtype = family; hostent->h_length = addrlen; memcpy(hostent->h_addr_list[0], addr, addrlen); hostent->h_addr_list[1] = NULL; *host = hostent; free(aliases); free(ptrname); return ARES_SUCCESS; } free(hostent->h_addr_list[0]); } free(hostent->h_addr_list); } free(hostent); } status = ARES_ENOMEM; } for (i=0 ; i<aliascnt ; i++) if (aliases[i]) free(aliases[i]); free(aliases); if (hostname) free(hostname); free(ptrname); return status; }