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curl/lib/hostares.c
Yang Tse 7e0b0763fc Revert Joshua Kwan's patch committed 11 Sep 2009. 
Some systems poll function sets POLLHUP in revents without setting
POLLIN, and sets POLLERR without setting POLLIN and POLLOUT. In some
libcurl code execution paths this could trigger busy wait loops with
high CPU usage until a timeout condition aborted the loop.

The reverted patch addressed the above issue for a very specific case,
when awaiting c-ares to resolve. A libcurl-wide fix superceeds this one.

http://cool.haxx.se/cvs.cgi/curl/lib/select.c.diff?r1=1.52&r2=1.53
2009-09-15 00:07:25 +00:00

364 lines
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/***************************************************************************
* _ _ ____ _
* Project ___| | | | _ \| |
* / __| | | | |_) | |
* | (__| |_| | _ <| |___
* \___|\___/|_| \_\_____|
*
* Copyright (C) 1998 - 2009, Daniel Stenberg, <daniel@haxx.se>, et al.
*
* This software is licensed as described in the file COPYING, which
* you should have received as part of this distribution. The terms
* are also available at http://curl.haxx.se/docs/copyright.html.
*
* You may opt to use, copy, modify, merge, publish, distribute and/or sell
* copies of the Software, and permit persons to whom the Software is
* furnished to do so, under the terms of the COPYING file.
*
* This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
* KIND, either express or implied.
*
* $Id$
***************************************************************************/
#include "setup.h"
#include <string.h>
#ifdef HAVE_LIMITS_H
#include <limits.h>
#endif
#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_INET_H
#include <arpa/inet.h>
#endif
#ifdef HAVE_STDLIB_H
#include <stdlib.h> /* required for free() prototypes */
#endif
#ifdef HAVE_UNISTD_H
#include <unistd.h> /* for the close() proto */
#endif
#ifdef VMS
#include <in.h>
#include <inet.h>
#include <stdlib.h>
#endif
#ifdef HAVE_PROCESS_H
#include <process.h>
#endif
#if (defined(NETWARE) && defined(__NOVELL_LIBC__))
#undef in_addr_t
#define in_addr_t unsigned long
#endif
#include "urldata.h"
#include "sendf.h"
#include "hostip.h"
#include "hash.h"
#include "share.h"
#include "strerror.h"
#include "url.h"
#include "multiif.h"
#include "inet_pton.h"
#include "connect.h"
#include "select.h"
#define _MPRINTF_REPLACE /* use our functions only */
#include <curl/mprintf.h>
#include "curl_memory.h"
/* The last #include file should be: */
#include "memdebug.h"
/***********************************************************************
* Only for ares-enabled builds
**********************************************************************/
#ifdef CURLRES_ARES
/*
* Curl_resolv_fdset() is called when someone from the outside world (using
* curl_multi_fdset()) wants to get our fd_set setup and we're talking with
* ares. The caller must make sure that this function is only called when we
* have a working ares channel.
*
* Returns: CURLE_OK always!
*/
int Curl_resolv_getsock(struct connectdata *conn,
curl_socket_t *socks,
int numsocks)
{
struct timeval maxtime;
struct timeval timebuf;
struct timeval *timeout;
int max = ares_getsock(conn->data->state.areschannel,
(int *)socks, numsocks);
maxtime.tv_sec = CURL_TIMEOUT_RESOLVE;
maxtime.tv_usec = 0;
timeout = ares_timeout(conn->data->state.areschannel, &maxtime, &timebuf);
Curl_expire(conn->data,
(timeout->tv_sec * 1000) + (timeout->tv_usec/1000));
return max;
}
/*
* ares_waitperform()
*
* 1) Ask ares what sockets it currently plays with, then
* 2) wait for the timeout period to check for action on ares' sockets.
* 3) tell ares to act on all the sockets marked as "with action"
*
* return number of sockets it worked on
*/
static int ares_waitperform(struct connectdata *conn, int timeout_ms)
{
struct SessionHandle *data = conn->data;
int nfds;
int bitmask;
int socks[ARES_GETSOCK_MAXNUM];
struct pollfd pfd[ARES_GETSOCK_MAXNUM];
int i;
int num = 0;
bitmask = ares_getsock(data->state.areschannel, socks, ARES_GETSOCK_MAXNUM);
for(i=0; i < ARES_GETSOCK_MAXNUM; i++) {
pfd[i].events = 0;
pfd[i].revents = 0;
if(ARES_GETSOCK_READABLE(bitmask, i)) {
pfd[i].fd = socks[i];
pfd[i].events |= POLLRDNORM|POLLIN;
}
if(ARES_GETSOCK_WRITABLE(bitmask, i)) {
pfd[i].fd = socks[i];
pfd[i].events |= POLLWRNORM|POLLOUT;
}
if(pfd[i].events != 0)
num++;
else
break;
}
if(num)
nfds = Curl_poll(pfd, num, timeout_ms);
else
nfds = 0;
if(!nfds)
/* Call ares_process() unconditonally here, even if we simply timed out
above, as otherwise the ares name resolve won't timeout! */
ares_process_fd(data->state.areschannel, ARES_SOCKET_BAD, ARES_SOCKET_BAD);
else {
/* move through the descriptors and ask for processing on them */
for(i=0; i < num; i++)
ares_process_fd(data->state.areschannel,
pfd[i].revents & (POLLRDNORM|POLLIN)?
pfd[i].fd:ARES_SOCKET_BAD,
pfd[i].revents & (POLLWRNORM|POLLOUT)?
pfd[i].fd:ARES_SOCKET_BAD);
}
return nfds;
}
/*
* Curl_is_resolved() is called repeatedly to check if a previous name resolve
* request has completed. It should also make sure to time-out if the
* operation seems to take too long.
*
* Returns normal CURLcode errors.
*/
CURLcode Curl_is_resolved(struct connectdata *conn,
struct Curl_dns_entry **dns)
{
struct SessionHandle *data = conn->data;
*dns = NULL;
ares_waitperform(conn, 0);
if(conn->async.done) {
/* we're done, kill the ares handle */
if(!conn->async.dns) {
failf(data, "Could not resolve host: %s (%s)", conn->host.dispname,
ares_strerror(conn->async.status));
return CURLE_COULDNT_RESOLVE_HOST;
}
*dns = conn->async.dns;
}
return CURLE_OK;
}
/*
* Curl_wait_for_resolv() waits for a resolve to finish. This function should
* be avoided since using this risk getting the multi interface to "hang".
*
* If 'entry' is non-NULL, make it point to the resolved dns entry
*
* Returns CURLE_COULDNT_RESOLVE_HOST if the host was not resolved, and
* CURLE_OPERATION_TIMEDOUT if a time-out occurred.
*/
CURLcode Curl_wait_for_resolv(struct connectdata *conn,
struct Curl_dns_entry **entry)
{
CURLcode rc=CURLE_OK;
struct SessionHandle *data = conn->data;
long timeout;
struct timeval now = Curl_tvnow();
/* now, see if there's a connect timeout or a regular timeout to
use instead of the default one */
if(conn->data->set.connecttimeout)
timeout = conn->data->set.connecttimeout;
else if(conn->data->set.timeout)
timeout = conn->data->set.timeout;
else
timeout = CURL_TIMEOUT_RESOLVE * 1000; /* default name resolve timeout */
/* Wait for the name resolve query to complete. */
while(1) {
struct timeval *tvp, tv, store;
long timediff;
int itimeout;
itimeout = (timeout > (long)INT_MAX) ? INT_MAX : (int)timeout;
store.tv_sec = itimeout/1000;
store.tv_usec = (itimeout%1000)*1000;
tvp = ares_timeout(data->state.areschannel, &store, &tv);
/* use the timeout period ares returned to us above */
ares_waitperform(conn, (int)(tvp->tv_sec * 1000 + tvp->tv_usec/1000));
if(conn->async.done)
break;
timediff = Curl_tvdiff(Curl_tvnow(), now); /* spent time */
timeout -= timediff?timediff:1; /* always deduct at least 1 */
if(timeout < 0) {
/* our timeout, so we cancel the ares operation */
ares_cancel(data->state.areschannel);
break;
}
}
/* Operation complete, if the lookup was successful we now have the entry
in the cache. */
if(entry)
*entry = conn->async.dns;
if(!conn->async.dns) {
/* a name was not resolved */
if((timeout < 0) || (conn->async.status == ARES_ETIMEOUT)) {
failf(data, "Resolving host timed out: %s", conn->host.dispname);
rc = CURLE_COULDNT_RESOLVE_HOST;
}
else if(conn->async.done) {
failf(data, "Could not resolve host: %s (%s)", conn->host.dispname,
ares_strerror(conn->async.status));
rc = CURLE_COULDNT_RESOLVE_HOST;
}
else
rc = CURLE_OPERATION_TIMEDOUT;
/* close the connection, since we can't return failure here without
cleaning up this connection properly */
conn->bits.close = TRUE;
}
return rc;
}
/*
* Curl_getaddrinfo() - when using ares
*
* Returns name information about the given hostname and port number. If
* successful, the 'hostent' is returned and the forth argument will point to
* memory we need to free after use. That memory *MUST* be freed with
* Curl_freeaddrinfo(), nothing else.
*/
Curl_addrinfo *Curl_getaddrinfo(struct connectdata *conn,
const char *hostname,
int port,
int *waitp)
{
char *bufp;
struct SessionHandle *data = conn->data;
struct in_addr in;
int family = PF_INET;
#ifdef ENABLE_IPV6 /* CURLRES_IPV6 */
struct in6_addr in6;
#endif /* CURLRES_IPV6 */
*waitp = FALSE;
/* First check if this is an IPv4 address string */
if(Curl_inet_pton(AF_INET, hostname, &in) > 0) {
/* This is a dotted IP address 123.123.123.123-style */
return Curl_ip2addr(AF_INET, &in, hostname, port);
}
#ifdef ENABLE_IPV6 /* CURLRES_IPV6 */
/* Otherwise, check if this is an IPv6 address string */
if (Curl_inet_pton (AF_INET6, hostname, &in6) > 0) {
/* This must be an IPv6 address literal. */
return Curl_ip2addr(AF_INET6, &in6, hostname, port);
}
switch(data->set.ip_version) {
default:
#if ARES_VERSION >= 0x010601
family = PF_UNSPEC; /* supported by c-ares since 1.6.1, so for older
c-ares versions this just falls through and defaults
to PF_INET */
break;
#endif
case CURL_IPRESOLVE_V4:
family = PF_INET;
break;
case CURL_IPRESOLVE_V6:
family = PF_INET6;
break;
}
#endif /* CURLRES_IPV6 */
bufp = strdup(hostname);
if(bufp) {
Curl_safefree(conn->async.hostname);
conn->async.hostname = bufp;
conn->async.port = port;
conn->async.done = FALSE; /* not done */
conn->async.status = 0; /* clear */
conn->async.dns = NULL; /* clear */
/* areschannel is already setup in the Curl_open() function */
ares_gethostbyname(data->state.areschannel, hostname, family,
(ares_host_callback)Curl_addrinfo4_callback, conn);
*waitp = TRUE; /* please wait for the response */
}
return NULL; /* no struct yet */
}
#endif /* CURLRES_ARES */
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