/* $Id: ares_send.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_ARPA_NAMESER_H # include <arpa/nameser.h> #else # include "nameser.h" #endif #ifdef HAVE_ARPA_NAMESER_COMPAT_H # include <arpa/nameser_compat.h> #endif #include <stdlib.h> #include <string.h> #include <time.h> #include "ares.h" #include "ares_dns.h" #include "ares_private.h" void ares_send(ares_channel channel, const unsigned char *qbuf, int qlen, ares_callback callback, void *arg) { struct query *query; int i; struct timeval now; /* Verify that the query is at least long enough to hold the header. */ if (qlen < HFIXEDSZ || qlen >= (1 << 16)) { callback(arg, ARES_EBADQUERY, 0, NULL, 0); return; } /* Allocate space for query and allocated fields. */ query = malloc(sizeof(struct query)); if (!query) { callback(arg, ARES_ENOMEM, 0, NULL, 0); return; } query->tcpbuf = malloc(qlen + 2); if (!query->tcpbuf) { free(query); callback(arg, ARES_ENOMEM, 0, NULL, 0); return; } query->server_info = malloc(channel->nservers * sizeof(query->server_info[0])); if (!query->server_info) { free(query->tcpbuf); free(query); callback(arg, ARES_ENOMEM, 0, NULL, 0); return; } /* Compute the query ID. Start with no timeout. */ query->qid = (unsigned short)DNS_HEADER_QID(qbuf); query->timeout.tv_sec = 0; query->timeout.tv_usec = 0; /* Form the TCP query buffer by prepending qlen (as two * network-order bytes) to qbuf. */ query->tcpbuf[0] = (unsigned char)((qlen >> 8) & 0xff); query->tcpbuf[1] = (unsigned char)(qlen & 0xff); memcpy(query->tcpbuf + 2, qbuf, qlen); query->tcplen = qlen + 2; /* Fill in query arguments. */ query->qbuf = query->tcpbuf + 2; query->qlen = qlen; query->callback = callback; query->arg = arg; /* Initialize query status. */ query->try = 0; /* Choose the server to send the query to. If rotation is enabled, keep track * of the next server we want to use. */ query->server = channel->last_server; if (channel->rotate == 1) channel->last_server = (channel->last_server + 1) % channel->nservers; for (i = 0; i < channel->nservers; i++) { query->server_info[i].skip_server = 0; query->server_info[i].tcp_connection_generation = 0; } query->using_tcp = (channel->flags & ARES_FLAG_USEVC) || qlen > PACKETSZ; query->error_status = ARES_ECONNREFUSED; query->timeouts = 0; /* Initialize our list nodes. */ ares__init_list_node(&(query->queries_by_qid), query); ares__init_list_node(&(query->queries_by_timeout), query); ares__init_list_node(&(query->queries_to_server), query); ares__init_list_node(&(query->all_queries), query); /* Chain the query into the list of all queries. */ ares__insert_in_list(&(query->all_queries), &(channel->all_queries)); /* Keep track of queries bucketed by qid, so we can process DNS * responses quickly. */ ares__insert_in_list( &(query->queries_by_qid), &(channel->queries_by_qid[query->qid % ARES_QID_TABLE_SIZE])); /* Perform the first query action. */ now = ares__tvnow(); ares__send_query(channel, query, &now); }