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) { ares_free(ptrname); return ARES_EBADRESP; } aptr += len + QFIXEDSZ; /* Examine each answer resource record (RR) in turn. */ hostname = NULL; aliases = ares_malloc(alias_alloc * sizeof(char *)); if (!aliases) { ares_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) { ares_free(rr_name); 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 (aptr + rr_len > abuf + alen) { ares_free(rr_name); status = ARES_EBADRESP; break; } 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) { ares_free(rr_name); break; } if (hostname) ares_free(hostname); hostname = rr_data; aliases[aliascnt] = ares_malloc((strlen(rr_data)+1) * sizeof(char)); if (!aliases[aliascnt]) { ares_free(rr_name); status = ARES_ENOMEM; break; } strncpy(aliases[aliascnt], rr_data, strlen(rr_data)+1); aliascnt++; if (aliascnt >= alias_alloc) { char **ptr; alias_alloc *= 2; ptr = ares_realloc(aliases, alias_alloc * sizeof(char *)); if(!ptr) { ares_free(rr_name); 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) { ares_free(rr_name); break; } ares_free(ptrname); ptrname = rr_data; } ares_free(rr_name); aptr += rr_len; if (aptr > abuf + alen) { /* LCOV_EXCL_START: already checked above */ status = ARES_EBADRESP; break; } /* LCOV_EXCL_STOP */ } if (status == ARES_SUCCESS && !hostname) status = ARES_ENODATA; if (status == ARES_SUCCESS) { /* We got our answer. Allocate memory to build the host entry. */ hostent = ares_malloc(sizeof(struct hostent)); if (hostent) { hostent->h_addr_list = ares_malloc(2 * sizeof(char *)); if (hostent->h_addr_list) { hostent->h_addr_list[0] = ares_malloc(addrlen); if (hostent->h_addr_list[0]) { hostent->h_aliases = ares_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 = aresx_sitoss(family); hostent->h_length = aresx_sitoss(addrlen); memcpy(hostent->h_addr_list[0], addr, addrlen); hostent->h_addr_list[1] = NULL; *host = hostent; ares_free(aliases); ares_free(ptrname); return ARES_SUCCESS; } ares_free(hostent->h_addr_list[0]); } ares_free(hostent->h_addr_list); } ares_free(hostent); } status = ARES_ENOMEM; } for (i=0 ; i<aliascnt ; i++) if (aliases[i]) ares_free(aliases[i]); ares_free(aliases); if (hostname) ares_free(hostname); ares_free(ptrname); return status; }
/* Handle an answer from a server. */ static void process_answer(ares_channel channel, unsigned char *abuf, int alen, int whichserver, int tcp, struct timeval *now) { int tc, rcode, packetsz; unsigned short id; struct query *query; struct list_node* list_head; struct list_node* list_node; /* If there's no room in the answer for a header, we can't do much * with it. */ if (alen < HFIXEDSZ) return; /* Grab the query ID, truncate bit, and response code from the packet. */ id = DNS_HEADER_QID(abuf); tc = DNS_HEADER_TC(abuf); rcode = DNS_HEADER_RCODE(abuf); /* Find the query corresponding to this packet. The queries are * hashed/bucketed by query id, so this lookup should be quick. Note that * both the query id and the questions must be the same; when the query id * wraps around we can have multiple outstanding queries with the same query * id, so we need to check both the id and question. */ query = NULL; list_head = &(channel->queries_by_qid[id % ARES_QID_TABLE_SIZE]); for (list_node = list_head->next; list_node != list_head; list_node = list_node->next) { struct query *q = list_node->data; if ((q->qid == id) && same_questions(q->qbuf, q->qlen, abuf, alen)) { query = q; break; } } if (!query) return; packetsz = PACKETSZ; /* If we use EDNS and server answers with one of these RCODES, the protocol * extension is not understood by the responder. We must retry the query * without EDNS enabled. */ if (channel->flags & ARES_FLAG_EDNS) { packetsz = channel->ednspsz; if (rcode == NOTIMP || rcode == FORMERR || rcode == SERVFAIL) { int qlen = (query->tcplen - 2) - EDNSFIXEDSZ; channel->flags ^= ARES_FLAG_EDNS; query->tcplen -= EDNSFIXEDSZ; query->qlen -= EDNSFIXEDSZ; query->tcpbuf[0] = (unsigned char)((qlen >> 8) & 0xff); query->tcpbuf[1] = (unsigned char)(qlen & 0xff); DNS_HEADER_SET_ARCOUNT(query->tcpbuf + 2, 0); query->tcpbuf = ares_realloc(query->tcpbuf, query->tcplen); query->qbuf = query->tcpbuf + 2; ares__send_query(channel, query, now); return; }