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curl/ares/ares_process.c
Daniel Stenberg 3e3d10824f - Carlo Contavalli added support for the glibc "rotate" option, as documented 
in man resolv.conf:

  causes round robin selection of nameservers from among those listed.  This
  has the effect of spreading the query load among all listed servers, rather
  than having all clients try the first listed server first every time.

  You can enable it with ARES_OPT_ROTATE
2008-11-01 18:35:19 +00:00

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/* $Id$ */
/* Copyright 1998 by the Massachusetts Institute of Technology.
* Copyright (C) 2004-2008 by Daniel Stenberg
*
* 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 "setup.h"
#ifdef HAVE_SYS_SOCKET_H
# include <sys/socket.h>
#endif
#ifdef HAVE_SYS_UIO_H
# include <sys/uio.h>
#endif
#ifdef HAVE_NETINET_IN_H
# include <netinet/in.h>
#endif
#ifdef HAVE_NETINET_TCP_H
# include <netinet/tcp.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_SYS_TIME_H
# include <sys/time.h>
#endif
#ifdef HAVE_STRINGS_H
# include <strings.h>
#endif
#ifdef HAVE_UNISTD_H
# include <unistd.h>
#endif
#ifdef HAVE_SYS_IOCTL_H
# include <sys/ioctl.h>
#endif
#ifdef NETWARE
# include <sys/filio.h>
#endif
#include <assert.h>
#include <string.h>
#include <stdlib.h>
#include <fcntl.h>
#include <time.h>
#include <errno.h>
#include "ares.h"
#include "ares_dns.h"
#include "ares_private.h"
static int try_again(int errnum);
static void write_tcp_data(ares_channel channel, fd_set *write_fds,
ares_socket_t write_fd, struct timeval *now);
static void read_tcp_data(ares_channel channel, fd_set *read_fds,
ares_socket_t read_fd, struct timeval *now);
static void read_udp_packets(ares_channel channel, fd_set *read_fds,
ares_socket_t read_fd, struct timeval *now);
static void advance_tcp_send_queue(ares_channel channel, int whichserver,
ssize_t num_bytes);
static void process_timeouts(ares_channel channel, struct timeval *now);
static void process_broken_connections(ares_channel channel,
struct timeval *now);
static void process_answer(ares_channel channel, unsigned char *abuf,
int alen, int whichserver, int tcp,
struct timeval *now);
static void handle_error(ares_channel channel, int whichserver,
struct timeval *now);
static void skip_server(ares_channel channel, struct query *query,
int whichserver);
static void next_server(ares_channel channel, struct query *query,
struct timeval *now);
static int configure_socket(int s, ares_channel channel);
static int open_tcp_socket(ares_channel channel, struct server_state *server);
static int open_udp_socket(ares_channel channel, struct server_state *server);
static int same_questions(const unsigned char *qbuf, int qlen,
const unsigned char *abuf, int alen);
static void end_query(ares_channel channel, struct query *query, int status,
unsigned char *abuf, int alen);
/* return true if now is exactly check time or later */
int ares__timedout(struct timeval *now,
struct timeval *check)
{
int secs = (now->tv_sec - check->tv_sec);
if(secs > 0)
return 1; /* yes, timed out */
if(secs < 0)
return 0; /* nope, not timed out */
/* if the full seconds were identical, check the sub second parts */
return (now->tv_usec - check->tv_usec >= 0);
}
/* add the specific number of milliseconds to the time in the first argument */
int ares__timeadd(struct timeval *now,
int millisecs)
{
now->tv_sec += millisecs/1000;
now->tv_usec += (millisecs%1000)*1000;
if(now->tv_usec >= 1000000) {
++(now->tv_sec);
now->tv_usec -= 1000000;
}
return 0;
}
/* return time offset between now and (future) check, in milliseconds */
long ares__timeoffset(struct timeval *now,
struct timeval *check)
{
return (check->tv_sec - now->tv_sec)*1000 +
(check->tv_usec - now->tv_usec)/1000;
}
/* Something interesting happened on the wire, or there was a timeout.
* See what's up and respond accordingly.
*/
void ares_process(ares_channel channel, fd_set *read_fds, fd_set *write_fds)
{
struct timeval now = ares__tvnow();
write_tcp_data(channel, write_fds, ARES_SOCKET_BAD, &now);
read_tcp_data(channel, read_fds, ARES_SOCKET_BAD, &now);
read_udp_packets(channel, read_fds, ARES_SOCKET_BAD, &now);
process_timeouts(channel, &now);
process_broken_connections(channel, &now);
}
/* Something interesting happened on the wire, or there was a timeout.
* See what's up and respond accordingly.
*/
void ares_process_fd(ares_channel channel,
ares_socket_t read_fd, /* use ARES_SOCKET_BAD or valid
file descriptors */
ares_socket_t write_fd)
{
struct timeval now = ares__tvnow();
write_tcp_data(channel, NULL, write_fd, &now);
read_tcp_data(channel, NULL, read_fd, &now);
read_udp_packets(channel, NULL, read_fd, &now);
process_timeouts(channel, &now);
}
/* Return 1 if the specified error number describes a readiness error, or 0
* otherwise. This is mostly for HP-UX, which could return EAGAIN or
* EWOULDBLOCK. See this man page
*
* http://devrsrc1.external.hp.com/STKS/cgi-bin/man2html?manpage=/usr/share/man/man2.Z/send.2
*/
static int try_again(int errnum)
{
#if !defined EWOULDBLOCK && !defined EAGAIN
#error "Neither EWOULDBLOCK nor EAGAIN defined"
#endif
switch (errnum)
{
#ifdef EWOULDBLOCK
case EWOULDBLOCK:
return 1;
#endif
#if defined EAGAIN && EAGAIN != EWOULDBLOCK
case EAGAIN:
return 1;
#endif
}
return 0;
}
/* If any TCP sockets select true for writing, write out queued data
* we have for them.
*/
static void write_tcp_data(ares_channel channel,
fd_set *write_fds,
ares_socket_t write_fd,
struct timeval *now)
{
struct server_state *server;
struct send_request *sendreq;
struct iovec *vec;
int i;
ssize_t scount;
ssize_t wcount;
size_t n;
if(!write_fds && (write_fd == ARES_SOCKET_BAD))
/* no possible action */
return;
for (i = 0; i < channel->nservers; i++)
{
/* Make sure server has data to send and is selected in write_fds or
write_fd. */
server = &channel->servers[i];
if (!server->qhead || server->tcp_socket == ARES_SOCKET_BAD ||
server->is_broken)
continue;
if(write_fds) {
if(!FD_ISSET(server->tcp_socket, write_fds))
continue;
}
else {
if(server->tcp_socket != write_fd)
continue;
}
if(write_fds)
/* If there's an error and we close this socket, then open
* another with the same fd to talk to another server, then we
* don't want to think that it was the new socket that was
* ready. This is not disastrous, but is likely to result in
* extra system calls and confusion. */
FD_CLR(server->tcp_socket, write_fds);
/* Count the number of send queue items. */
n = 0;
for (sendreq = server->qhead; sendreq; sendreq = sendreq->next)
n++;
/* Allocate iovecs so we can send all our data at once. */
vec = malloc(n * sizeof(struct iovec));
if (vec)
{
/* Fill in the iovecs and send. */
n = 0;
for (sendreq = server->qhead; sendreq; sendreq = sendreq->next)
{
vec[n].iov_base = (char *) sendreq->data;
vec[n].iov_len = sendreq->len;
n++;
}
wcount = (ssize_t)writev(server->tcp_socket, vec, (int)n);
free(vec);
if (wcount < 0)
{
if (!try_again(SOCKERRNO))
handle_error(channel, i, now);
continue;
}
/* Advance the send queue by as many bytes as we sent. */
advance_tcp_send_queue(channel, i, wcount);
}
else
{
/* Can't allocate iovecs; just send the first request. */
sendreq = server->qhead;
scount = swrite(server->tcp_socket, sendreq->data, sendreq->len);
if (scount < 0)
{
if (!try_again(SOCKERRNO))
handle_error(channel, i, now);
continue;
}
/* Advance the send queue by as many bytes as we sent. */
advance_tcp_send_queue(channel, i, scount);
}
}
}
/* Consume the given number of bytes from the head of the TCP send queue. */
static void advance_tcp_send_queue(ares_channel channel, int whichserver,
ssize_t num_bytes)
{
struct send_request *sendreq;
struct server_state *server = &channel->servers[whichserver];
while (num_bytes > 0)
{
sendreq = server->qhead;
if ((size_t)num_bytes >= sendreq->len)
{
num_bytes -= sendreq->len;
server->qhead = sendreq->next;
if (server->qhead == NULL)
{
SOCK_STATE_CALLBACK(channel, server->tcp_socket, 1, 0);
server->qtail = NULL;
}
if (sendreq->data_storage != NULL)
free(sendreq->data_storage);
free(sendreq);
}
else
{
sendreq->data += num_bytes;
sendreq->len -= num_bytes;
num_bytes = 0;
}
}
}
/* If any TCP socket selects true for reading, read some data,
* allocate a buffer if we finish reading the length word, and process
* a packet if we finish reading one.
*/
static void read_tcp_data(ares_channel channel, fd_set *read_fds,
ares_socket_t read_fd, struct timeval *now)
{
struct server_state *server;
int i;
ssize_t count;
if(!read_fds && (read_fd == ARES_SOCKET_BAD))
/* no possible action */
return;
for (i = 0; i < channel->nservers; i++)
{
/* Make sure the server has a socket and is selected in read_fds. */
server = &channel->servers[i];
if (server->tcp_socket == ARES_SOCKET_BAD || server->is_broken)
continue;
if(read_fds) {
if(!FD_ISSET(server->tcp_socket, read_fds))
continue;
}
else {
if(server->tcp_socket != read_fd)
continue;
}
if(read_fds)
/* If there's an error and we close this socket, then open
* another with the same fd to talk to another server, then we
* don't want to think that it was the new socket that was
* ready. This is not disastrous, but is likely to result in
* extra system calls and confusion. */
FD_CLR(server->tcp_socket, read_fds);
if (server->tcp_lenbuf_pos != 2)
{
/* We haven't yet read a length word, so read that (or
* what's left to read of it).
*/
count = sread(server->tcp_socket,
server->tcp_lenbuf + server->tcp_lenbuf_pos,
2 - server->tcp_lenbuf_pos);
if (count <= 0)
{
if (!(count == -1 && try_again(SOCKERRNO)))
handle_error(channel, i, now);
continue;
}
server->tcp_lenbuf_pos += (int)count;
if (server->tcp_lenbuf_pos == 2)
{
/* We finished reading the length word. Decode the
* length and allocate a buffer for the data.
*/
server->tcp_length = server->tcp_lenbuf[0] << 8
| server->tcp_lenbuf[1];
server->tcp_buffer = malloc(server->tcp_length);
if (!server->tcp_buffer)
handle_error(channel, i, now);
server->tcp_buffer_pos = 0;
}
}
else
{
/* Read data into the allocated buffer. */
count = sread(server->tcp_socket,
server->tcp_buffer + server->tcp_buffer_pos,
server->tcp_length - server->tcp_buffer_pos);
if (count <= 0)
{
if (!(count == -1 && try_again(SOCKERRNO)))
handle_error(channel, i, now);
continue;
}
server->tcp_buffer_pos += (int)count;
if (server->tcp_buffer_pos == server->tcp_length)
{
/* We finished reading this answer; process it and
* prepare to read another length word.
*/
process_answer(channel, server->tcp_buffer, server->tcp_length,
i, 1, now);
if (server->tcp_buffer)
free(server->tcp_buffer);
server->tcp_buffer = NULL;
server->tcp_lenbuf_pos = 0;
server->tcp_buffer_pos = 0;
}
}
}
}
/* If any UDP sockets select true for reading, process them. */
static void read_udp_packets(ares_channel channel, fd_set *read_fds,
ares_socket_t read_fd, struct timeval *now)
{
struct server_state *server;
int i;
ssize_t count;
unsigned char buf[PACKETSZ + 1];
#ifdef HAVE_RECVFROM
struct sockaddr_in from;
socklen_t fromlen;
#endif
if(!read_fds && (read_fd == ARES_SOCKET_BAD))
/* no possible action */
return;
for (i = 0; i < channel->nservers; i++)
{
/* Make sure the server has a socket and is selected in read_fds. */
server = &channel->servers[i];
if (server->udp_socket == ARES_SOCKET_BAD || server->is_broken)
continue;
if(read_fds) {
if(!FD_ISSET(server->udp_socket, read_fds))
continue;
}
else {
if(server->udp_socket != read_fd)
continue;
}
if(read_fds)
/* If there's an error and we close this socket, then open
* another with the same fd to talk to another server, then we
* don't want to think that it was the new socket that was
* ready. This is not disastrous, but is likely to result in
* extra system calls and confusion. */
FD_CLR(server->udp_socket, read_fds);
/* To reduce event loop overhead, read and process as many
* packets as we can. */
do {
#ifdef HAVE_RECVFROM
fromlen = sizeof(from);
count = (ssize_t)recvfrom(server->udp_socket, (void *)buf, sizeof(buf),
0, (struct sockaddr *)&from, &fromlen);
#else
count = sread(server->udp_socket, buf, sizeof(buf));
#endif
if (count == -1 && try_again(SOCKERRNO))
continue;
else if (count <= 0)
handle_error(channel, i, now);
#ifdef HAVE_RECVFROM
else if (from.sin_addr.s_addr != server->addr.s_addr)
/* Address response came from did not match the address
* we sent the request to. Someone may be attempting
* to perform a cache poisoning attack */
break;
#endif
else
process_answer(channel, buf, (int)count, i, 0, now);
} while (count > 0);
}
}
/* If any queries have timed out, note the timeout and move them on. */
static void process_timeouts(ares_channel channel, struct timeval *now)
{
time_t t; /* the time of the timeouts we're processing */
struct query *query;
struct list_node* list_head;
struct list_node* list_node;
/* Process all the timeouts that have fired since the last time we
* processed timeouts. If things are going well, then we'll have
* hundreds/thousands of queries that fall into future buckets, and
* only a handful of requests that fall into the "now" bucket, so
* this should be quite quick.
*/
for (t = channel->last_timeout_processed; t <= now->tv_sec; t++)
{
list_head = &(channel->queries_by_timeout[t % ARES_TIMEOUT_TABLE_SIZE]);
for (list_node = list_head->next; list_node != list_head; )
{
query = list_node->data;
list_node = list_node->next; /* in case the query gets deleted */
if (query->timeout.tv_sec && ares__timedout(now, &query->timeout))
{
query->error_status = ARES_ETIMEOUT;
++query->timeouts;
next_server(channel, query, now);
}
}
}
channel->last_timeout_processed = now->tv_sec;
}
/* 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;
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;
/* If we got a truncated UDP packet and are not ignoring truncation,
* don't accept the packet, and switch the query to TCP if we hadn't
* done so already.
*/
if ((tc || alen > PACKETSZ) && !tcp && !(channel->flags & ARES_FLAG_IGNTC))
{
if (!query->using_tcp)
{
query->using_tcp = 1;
ares__send_query(channel, query, now);
}
return;
}
/* Limit alen to PACKETSZ if we aren't using TCP (only relevant if we
* are ignoring truncation.
*/
if (alen > PACKETSZ && !tcp)
alen = PACKETSZ;
/* If we aren't passing through all error packets, discard packets
* with SERVFAIL, NOTIMP, or REFUSED response codes.
*/
if (!(channel->flags & ARES_FLAG_NOCHECKRESP))
{
if (rcode == SERVFAIL || rcode == NOTIMP || rcode == REFUSED)
{
skip_server(channel, query, whichserver);
if (query->server == whichserver)
next_server(channel, query, now);
return;
}
}
end_query(channel, query, ARES_SUCCESS, abuf, alen);
}
/* Close all the connections that are no longer usable. */
static void process_broken_connections(ares_channel channel,
struct timeval *now)
{
int i;
for (i = 0; i < channel->nservers; i++)
{
struct server_state *server = &channel->servers[i];
if (server->is_broken)
{
handle_error(channel, i, now);
}
}
}
static void handle_error(ares_channel channel, int whichserver,
struct timeval *now)
{
struct server_state *server;
struct query *query;
struct list_node list_head;
struct list_node* list_node;
server = &channel->servers[whichserver];
/* Reset communications with this server. */
ares__close_sockets(channel, server);
/* Tell all queries talking to this server to move on and not try
* this server again. We steal the current list of queries that were
* in-flight to this server, since when we call next_server this can
* cause the queries to be re-sent to this server, which will
* re-insert these queries in that same server->queries_to_server
* list.
*/
ares__init_list_head(&list_head);
ares__swap_lists(&list_head, &(server->queries_to_server));
for (list_node = list_head.next; list_node != &list_head; )
{
query = list_node->data;
list_node = list_node->next; /* in case the query gets deleted */
assert(query->server == whichserver);
skip_server(channel, query, whichserver);
next_server(channel, query, now);
}
/* Each query should have removed itself from our temporary list as
* it re-sent itself or finished up...
*/
assert(ares__is_list_empty(&list_head));
}
static void skip_server(ares_channel channel, struct query *query,
int whichserver) {
/* The given server gave us problems with this query, so if we have
* the luxury of using other servers, then let's skip the
* potentially broken server and just use the others. If we only
* have one server and we need to retry then we should just go ahead
* and re-use that server, since it's our only hope; perhaps we
* just got unlucky, and retrying will work (eg, the server timed
* out our TCP connection just as we were sending another request).
*/
if (channel->nservers > 1)
{
query->server_info[whichserver].skip_server = 1;
}
}
static void next_server(ares_channel channel, struct query *query,
struct timeval *now)
{
/* We need to try each server channel->tries times. We have channel->nservers
* servers to try. In total, we need to do channel->nservers * channel->tries
* attempts. Use query->try to remember how many times we already attempted
* this query. Use modular arithmetic to find the next server to try. */
while (++(query->try) < (channel->nservers * channel->tries))
{
struct server_state *server;
/* Move on to the next server. */
query->server = (query->server + 1) % channel->nservers;
server = &channel->servers[query->server];
/* We don't want to use this server if (1) we decided this
* connection is broken, and thus about to be closed, (2)
* we've decided to skip this server because of earlier
* errors we encountered, or (3) we already sent this query
* over this exact connection.
*/
if (!server->is_broken &&
!query->server_info[query->server].skip_server &&
!(query->using_tcp &&
(query->server_info[query->server].tcp_connection_generation ==
server->tcp_connection_generation)))
{
ares__send_query(channel, query, now);
return;
}
/* You might think that with TCP we only need one try. However,
* even when using TCP, servers can time-out our connection just
* as we're sending a request, or close our connection because
* they die, or never send us a reply because they get wedged or
* tickle a bug that drops our request.
*/
}
/* If we are here, all attempts to perform query failed. */
end_query(channel, query, query->error_status, NULL, 0);
}
void ares__send_query(ares_channel channel, struct query *query,
struct timeval *now)
{
struct send_request *sendreq;
struct server_state *server;
server = &channel->servers[query->server];
if (query->using_tcp)
{
/* Make sure the TCP socket for this server is set up and queue
* a send request.
*/
if (server->tcp_socket == ARES_SOCKET_BAD)
{
if (open_tcp_socket(channel, server) == -1)
{
skip_server(channel, query, query->server);
next_server(channel, query, now);
return;
}
}
sendreq = calloc(sizeof(struct send_request), 1);
if (!sendreq)
{
end_query(channel, query, ARES_ENOMEM, NULL, 0);
return;
}
/* To make the common case fast, we avoid copies by using the
* query's tcpbuf for as long as the query is alive. In the rare
* case where the query ends while it's queued for transmission,
* then we give the sendreq its own copy of the request packet
* and put it in sendreq->data_storage.
*/
sendreq->data_storage = NULL;
sendreq->data = query->tcpbuf;
sendreq->len = query->tcplen;
sendreq->owner_query = query;
sendreq->next = NULL;
if (server->qtail)
server->qtail->next = sendreq;
else
{
SOCK_STATE_CALLBACK(channel, server->tcp_socket, 1, 1);
server->qhead = sendreq;
}
server->qtail = sendreq;
query->server_info[query->server].tcp_connection_generation =
server->tcp_connection_generation;
}
else
{
if (server->udp_socket == ARES_SOCKET_BAD)
{
if (open_udp_socket(channel, server) == -1)
{
skip_server(channel, query, query->server);
next_server(channel, query, now);
return;
}
}
if (swrite(server->udp_socket, query->qbuf, query->qlen) == -1)
{
/* FIXME: Handle EAGAIN here since it likely can happen. */
skip_server(channel, query, query->server);
next_server(channel, query, now);
return;
}
}
query->timeout = *now;
ares__timeadd(&query->timeout,
channel->timeout << (query->try / channel->nservers));
/* Keep track of queries bucketed by timeout, so we can process
* timeout events quickly.
*/
ares__remove_from_list(&(query->queries_by_timeout));
ares__insert_in_list(
&(query->queries_by_timeout),
&(channel->queries_by_timeout[query->timeout.tv_sec %
ARES_TIMEOUT_TABLE_SIZE]));
/* Keep track of queries bucketed by server, so we can process server
* errors quickly.
*/
ares__remove_from_list(&(query->queries_to_server));
ares__insert_in_list(&(query->queries_to_server),
&(server->queries_to_server));
}
/*
* setsocknonblock sets the given socket to either blocking or non-blocking mode
* based on the 'nonblock' boolean argument. This function is highly portable.
*/
static int setsocknonblock(ares_socket_t sockfd, /* operate on this */
int nonblock /* TRUE or FALSE */)
{
#undef SETBLOCK
#define SETBLOCK 0
#ifdef HAVE_O_NONBLOCK
/* most recent unix versions */
int flags;
flags = fcntl(sockfd, F_GETFL, 0);
if (FALSE != nonblock)
return fcntl(sockfd, F_SETFL, flags | O_NONBLOCK);
else
return fcntl(sockfd, F_SETFL, flags & (~O_NONBLOCK));
#undef SETBLOCK
#define SETBLOCK 1
#endif
#if defined(HAVE_FIONBIO) && (SETBLOCK == 0)
/* older unix versions */
int flags;
flags = nonblock;
return ioctl(sockfd, FIONBIO, &flags);
#undef SETBLOCK
#define SETBLOCK 2
#endif
#if defined(HAVE_IOCTLSOCKET) && (SETBLOCK == 0)
#ifdef WATT32
char flags;
#else
/* Windows? */
unsigned long flags;
#endif
flags = nonblock;
return ioctlsocket(sockfd, FIONBIO, &flags);
#undef SETBLOCK
#define SETBLOCK 3
#endif
#if defined(HAVE_IOCTLSOCKET_CASE) && (SETBLOCK == 0)
/* presumably for Amiga */
return IoctlSocket(sockfd, FIONBIO, (long)nonblock);
#undef SETBLOCK
#define SETBLOCK 4
#endif
#if defined(HAVE_SO_NONBLOCK) && (SETBLOCK == 0)
/* BeOS */
long b = nonblock ? 1 : 0;
return setsockopt(sockfd, SOL_SOCKET, SO_NONBLOCK, &b, sizeof(b));
#undef SETBLOCK
#define SETBLOCK 5
#endif
#ifdef HAVE_DISABLED_NONBLOCKING
return 0; /* returns success */
#undef SETBLOCK
#define SETBLOCK 6
#endif
#if (SETBLOCK == 0)
#error "no non-blocking method was found/used/set"
#endif
}
static int configure_socket(int s, ares_channel channel)
{
setsocknonblock(s, TRUE);
#if defined(FD_CLOEXEC) && !defined(MSDOS)
/* Configure the socket fd as close-on-exec. */
if (fcntl(s, F_SETFD, FD_CLOEXEC) == -1)
return -1;
#endif
/* Set the socket's send and receive buffer sizes. */
if ((channel->socket_send_buffer_size > 0) &&
setsockopt(s, SOL_SOCKET, SO_SNDBUF,
(void *)&channel->socket_send_buffer_size,
sizeof(channel->socket_send_buffer_size)) == -1)
return -1;
if ((channel->socket_receive_buffer_size > 0) &&
setsockopt(s, SOL_SOCKET, SO_RCVBUF,
(void *)&channel->socket_receive_buffer_size,
sizeof(channel->socket_receive_buffer_size)) == -1)
return -1;
return 0;
}
static int open_tcp_socket(ares_channel channel, struct server_state *server)
{
ares_socket_t s;
int opt;
struct sockaddr_in sockin;
/* Acquire a socket. */
s = socket(AF_INET, SOCK_STREAM, 0);
if (s == ARES_SOCKET_BAD)
return -1;
/* Configure it. */
if (configure_socket(s, channel) < 0)
{
closesocket(s);
return -1;
}
/*
* Disable the Nagle algorithm (only relevant for TCP sockets, and thus not in
* configure_socket). In general, in DNS lookups we're pretty much interested
* in firing off a single request and then waiting for a reply, so batching
* isn't very interesting in general.
*/
opt = 1;
if (setsockopt(s, IPPROTO_TCP, TCP_NODELAY,
(void *)&opt, sizeof(opt)) == -1)
{
closesocket(s);
return -1;
}
/* Connect to the server. */
memset(&sockin, 0, sizeof(sockin));
sockin.sin_family = AF_INET;
sockin.sin_addr = server->addr;
sockin.sin_port = (unsigned short)(channel->tcp_port & 0xffff);
if (connect(s, (struct sockaddr *) &sockin, sizeof(sockin)) == -1)
{
int err = SOCKERRNO;
if (err != EINPROGRESS && err != EWOULDBLOCK)
{
closesocket(s);
return -1;
}
}
SOCK_STATE_CALLBACK(channel, s, 1, 0);
server->tcp_buffer_pos = 0;
server->tcp_socket = s;
server->tcp_connection_generation = ++channel->tcp_connection_generation;
return 0;
}
static int open_udp_socket(ares_channel channel, struct server_state *server)
{
ares_socket_t s;
struct sockaddr_in sockin;
/* Acquire a socket. */
s = socket(AF_INET, SOCK_DGRAM, 0);
if (s == ARES_SOCKET_BAD)
return -1;
/* Set the socket non-blocking. */
if (configure_socket(s, channel) < 0)
{
closesocket(s);
return -1;
}
/* Connect to the server. */
memset(&sockin, 0, sizeof(sockin));
sockin.sin_family = AF_INET;
sockin.sin_addr = server->addr;
sockin.sin_port = (unsigned short)(channel->udp_port & 0xffff);
if (connect(s, (struct sockaddr *) &sockin, sizeof(sockin)) == -1)
{
int err = SOCKERRNO;
if (err != EINPROGRESS && err != EWOULDBLOCK)
{
closesocket(s);
return -1;
}
}
SOCK_STATE_CALLBACK(channel, s, 1, 0);
server->udp_socket = s;
return 0;
}
static int same_questions(const unsigned char *qbuf, int qlen,
const unsigned char *abuf, int alen)
{
struct {
const unsigned char *p;
int qdcount;
char *name;
long namelen;
int type;
int dnsclass;
} q, a;
int i, j;
if (qlen < HFIXEDSZ || alen < HFIXEDSZ)
return 0;
/* Extract qdcount from the request and reply buffers and compare them. */
q.qdcount = DNS_HEADER_QDCOUNT(qbuf);
a.qdcount = DNS_HEADER_QDCOUNT(abuf);
if (q.qdcount != a.qdcount)
return 0;
/* For each question in qbuf, find it in abuf. */
q.p = qbuf + HFIXEDSZ;
for (i = 0; i < q.qdcount; i++)
{
/* Decode the question in the query. */
if (ares_expand_name(q.p, qbuf, qlen, &q.name, &q.namelen)
!= ARES_SUCCESS)
return 0;
q.p += q.namelen;
if (q.p + QFIXEDSZ > qbuf + qlen)
{
free(q.name);
return 0;
}
q.type = DNS_QUESTION_TYPE(q.p);
q.dnsclass = DNS_QUESTION_CLASS(q.p);
q.p += QFIXEDSZ;
/* Search for this question in the answer. */
a.p = abuf + HFIXEDSZ;
for (j = 0; j < a.qdcount; j++)
{
/* Decode the question in the answer. */
if (ares_expand_name(a.p, abuf, alen, &a.name, &a.namelen)
!= ARES_SUCCESS)
{
free(q.name);
return 0;
}
a.p += a.namelen;
if (a.p + QFIXEDSZ > abuf + alen)
{
free(q.name);
free(a.name);
return 0;
}
a.type = DNS_QUESTION_TYPE(a.p);
a.dnsclass = DNS_QUESTION_CLASS(a.p);
a.p += QFIXEDSZ;
/* Compare the decoded questions. */
if (strcasecmp(q.name, a.name) == 0 && q.type == a.type
&& q.dnsclass == a.dnsclass)
{
free(a.name);
break;
}
free(a.name);
}
free(q.name);
if (j == a.qdcount)
return 0;
}
return 1;
}
static void end_query (ares_channel channel, struct query *query, int status,
unsigned char *abuf, int alen)
{
int i;
/* First we check to see if this query ended while one of our send
* queues still has pointers to it.
*/
for (i = 0; i < channel->nservers; i++)
{
struct server_state *server = &channel->servers[i];
struct send_request *sendreq;
for (sendreq = server->qhead; sendreq; sendreq = sendreq->next)
if (sendreq->owner_query == query)
{
sendreq->owner_query = NULL;
assert(sendreq->data_storage == NULL);
if (status == ARES_SUCCESS)
{
/* We got a reply for this query, but this queued
* sendreq points into this soon-to-be-gone query's
* tcpbuf. Probably this means we timed out and queued
* the query for retransmission, then received a
* response before actually retransmitting. This is
* perfectly fine, so we want to keep the connection
* running smoothly if we can. But in the worst case
* we may have sent only some prefix of the query,
* with some suffix of the query left to send. Also,
* the buffer may be queued on multiple queues. To
* prevent dangling pointers to the query's tcpbuf and
* handle these cases, we just give such sendreqs
* their own copy of the query packet.
*/
sendreq->data_storage = malloc(sendreq->len);
if (sendreq->data_storage != NULL)
{
memcpy(sendreq->data_storage, sendreq->data, sendreq->len);
sendreq->data = sendreq->data_storage;
}
}
if ((status != ARES_SUCCESS) || (sendreq->data_storage == NULL))
{
/* We encountered an error (probably a timeout,
* suggesting the DNS server we're talking to is
* probably unreachable, wedged, or severely
* overloaded) or we couldn't copy the request, so
* mark the connection as broken. When we get to
* process_broken_connections() we'll close the
* connection and try to re-send requests to another
* server.
*/
server->is_broken = 1;
/* Just to be paranoid, zero out this sendreq... */
sendreq->data = NULL;
sendreq->len = 0;
}
}
}
/* Invoke the callback */
query->callback(query->arg, status, query->timeouts, abuf, alen);
ares__free_query(query);
/* Simple cleanup policy: if no queries are remaining, close all
* network sockets unless STAYOPEN is set.
*/
if (!(channel->flags & ARES_FLAG_STAYOPEN) &&
ares__is_list_empty(&(channel->all_queries)))
{
for (i = 0; i < channel->nservers; i++)
ares__close_sockets(channel, &channel->servers[i]);
}
}
void ares__free_query(struct query *query)
{
/* Remove the query from all the lists in which it is linked */
ares__remove_from_list(&(query->queries_by_qid));
ares__remove_from_list(&(query->queries_by_timeout));
ares__remove_from_list(&(query->queries_to_server));
ares__remove_from_list(&(query->all_queries));
/* Zero out some important stuff, to help catch bugs */
query->callback = NULL;
query->arg = NULL;
/* Deallocate the memory associated with the query */
free(query->tcpbuf);
free(query->server_info);
free(query);
}
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