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hostip.c
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/***************************************************************************
* _ _ ____ _
* Project ___| | | | _ \| |
* / __| | | | |_) | |
* | (__| |_| | _ <| |___
* \___|\___/|_| \_\_____|
*
* Copyright (C) 1998 - 2022, 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 https://curl.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.
*
* SPDX-License-Identifier: curl
*
***************************************************************************/
#include "curl_setup.h"
#ifdef HAVE_NETINET_IN_H
#include <netinet/in.h>
#endif
#ifdef HAVE_NETINET_IN6_H
#include <netinet/in6.h>
#endif
#ifdef HAVE_NETDB_H
#include <netdb.h>
#endif
#ifdef HAVE_ARPA_INET_H
#include <arpa/inet.h>
#endif
#ifdef __VMS
#include <in.h>
#include <inet.h>
#endif
#ifdef HAVE_SETJMP_H
#include <setjmp.h>
#endif
#ifdef HAVE_SIGNAL_H
#include <signal.h>
#endif
#ifdef HAVE_PROCESS_H
#include <process.h>
#endif
#include "urldata.h"
#include "sendf.h"
#include "hostip.h"
#include "hash.h"
#include "rand.h"
#include "share.h"
#include "url.h"
#include "inet_ntop.h"
#include "inet_pton.h"
#include "multiif.h"
#include "doh.h"
#include "warnless.h"
#include "strcase.h"
/* The last 3 #include files should be in this order */
#include "curl_printf.h"
#include "curl_memory.h"
#include "memdebug.h"
#if defined(ENABLE_IPV6) && defined(CURL_OSX_CALL_COPYPROXIES)
#include <SystemConfiguration/SCDynamicStoreCopySpecific.h>
#endif
#if defined(CURLRES_SYNCH) && \
defined(HAVE_ALARM) && defined(SIGALRM) && defined(HAVE_SIGSETJMP)
/* alarm-based timeouts can only be used with all the dependencies satisfied */
#define USE_ALARM_TIMEOUT
#endif
#define MAX_HOSTCACHE_LEN (255 + 7) /* max FQDN + colon + port number + zero */
/*
* hostip.c explained
* ==================
*
* The main COMPILE-TIME DEFINES to keep in mind when reading the host*.c
* source file are these:
*
* CURLRES_IPV6 - this host has getaddrinfo() and family, and thus we use
* that. The host may not be able to resolve IPv6, but we don't really have to
* take that into account. Hosts that aren't IPv6-enabled have CURLRES_IPV4
* defined.
*
* CURLRES_ARES - is defined if libcurl is built to use c-ares for
* asynchronous name resolves. This can be Windows or *nix.
*
* CURLRES_THREADED - is defined if libcurl is built to run under (native)
* Windows, and then the name resolve will be done in a new thread, and the
* supported API will be the same as for ares-builds.
*
* If any of the two previous are defined, CURLRES_ASYNCH is defined too. If
* libcurl is not built to use an asynchronous resolver, CURLRES_SYNCH is
* defined.
*
* The host*.c sources files are split up like this:
*
* hostip.c - method-independent resolver functions and utility functions
* hostasyn.c - functions for asynchronous name resolves
* hostsyn.c - functions for synchronous name resolves
* hostip4.c - IPv4 specific functions
* hostip6.c - IPv6 specific functions
*
* The two asynchronous name resolver backends are implemented in:
* asyn-ares.c - functions for ares-using name resolves
* asyn-thread.c - functions for threaded name resolves
* The hostip.h is the united header file for all this. It defines the
* CURLRES_* defines based on the config*.h and curl_setup.h defines.
*/
static void freednsentry(void *freethis);
/*
* Return # of addresses in a Curl_addrinfo struct
*/
int Curl_num_addresses(const struct Curl_addrinfo *addr)
{
int i = 0;
while(addr) {
addr = addr->ai_next;
i++;
}
return i;
}
/*
* Curl_printable_address() stores a printable version of the 1st address
* given in the 'ai' argument. The result will be stored in the buf that is
* bufsize bytes big.
*
* If the conversion fails, the target buffer is empty.
*/
void Curl_printable_address(const struct Curl_addrinfo *ai, char *buf,
size_t bufsize)
{
DEBUGASSERT(bufsize);
buf[0] = 0;
switch(ai->ai_family) {
case AF_INET: {
const struct sockaddr_in *sa4 = (const void *)ai->ai_addr;
const struct in_addr *ipaddr4 = &sa4->sin_addr;
(void)Curl_inet_ntop(ai->ai_family, (const void *)ipaddr4, buf, bufsize);
break;
}
#ifdef ENABLE_IPV6
case AF_INET6: {
const struct sockaddr_in6 *sa6 = (const void *)ai->ai_addr;
const struct in6_addr *ipaddr6 = &sa6->sin6_addr;
(void)Curl_inet_ntop(ai->ai_family, (const void *)ipaddr6, buf, bufsize);
break;
}
#endif
default:
break;
}
}
/*
* Create a hostcache id string for the provided host + port, to be used by
* the DNS caching. Without alloc.
*/
static void
create_hostcache_id(const char *name, int port, char *ptr, size_t buflen)
{
size_t len = strlen(name);
if(len > (buflen - 7))
len = buflen - 7;
/* store and lower case the name */
while(len--)
*ptr++ = Curl_raw_tolower(*name++);
msnprintf(ptr, 7, ":%u", port);
}
struct hostcache_prune_data {
long cache_timeout;
time_t now;
};
/*
* This function is set as a callback to be called for every entry in the DNS
* cache when we want to prune old unused entries.
*
* Returning non-zero means remove the entry, return 0 to keep it in the
* cache.
*/
static int
hostcache_timestamp_remove(void *datap, void *hc)
{
struct hostcache_prune_data *data =
(struct hostcache_prune_data *) datap;
struct Curl_dns_entry *c = (struct Curl_dns_entry *) hc;
return (0 != c->timestamp)
&& (data->now - c->timestamp >= data->cache_timeout);
}
/*
* Prune the DNS cache. This assumes that a lock has already been taken.
*/
static void
hostcache_prune(struct Curl_hash *hostcache, long cache_timeout, time_t now)
{
struct hostcache_prune_data user;
user.cache_timeout = cache_timeout;
user.now = now;
Curl_hash_clean_with_criterium(hostcache,
(void *) &user,
hostcache_timestamp_remove);
}
/*
* Library-wide function for pruning the DNS cache. This function takes and
* returns the appropriate locks.
*/
void Curl_hostcache_prune(struct Curl_easy *data)
{
time_t now;
if((data->set.dns_cache_timeout == -1) || !data->dns.hostcache)
/* cache forever means never prune, and NULL hostcache means
we can't do it */
return;
if(data->share)
Curl_share_lock(data, CURL_LOCK_DATA_DNS, CURL_LOCK_ACCESS_SINGLE);
time(&now);
/* Remove outdated and unused entries from the hostcache */
hostcache_prune(data->dns.hostcache,
data->set.dns_cache_timeout,
now);
if(data->share)
Curl_share_unlock(data, CURL_LOCK_DATA_DNS);
}
#ifdef HAVE_SIGSETJMP
/* Beware this is a global and unique instance. This is used to store the
return address that we can jump back to from inside a signal handler. This
is not thread-safe stuff. */
sigjmp_buf curl_jmpenv;
#endif
/* lookup address, returns entry if found and not stale */
static struct Curl_dns_entry *fetch_addr(struct Curl_easy *data,
const char *hostname,
int port)
{
struct Curl_dns_entry *dns = NULL;
size_t entry_len;
char entry_id[MAX_HOSTCACHE_LEN];
/* Create an entry id, based upon the hostname and port */
create_hostcache_id(hostname, port, entry_id, sizeof(entry_id));
entry_len = strlen(entry_id);
/* See if its already in our dns cache */
dns = Curl_hash_pick(data->dns.hostcache, entry_id, entry_len + 1);
/* No entry found in cache, check if we might have a wildcard entry */
if(!dns && data->state.wildcard_resolve) {
create_hostcache_id("*", port, entry_id, sizeof(entry_id));
entry_len = strlen(entry_id);
/* See if it's already in our dns cache */
dns = Curl_hash_pick(data->dns.hostcache, entry_id, entry_len + 1);
}
if(dns && (data->set.dns_cache_timeout != -1)) {
/* See whether the returned entry is stale. Done before we release lock */
struct hostcache_prune_data user;
time(&user.now);
user.cache_timeout = data->set.dns_cache_timeout;
if(hostcache_timestamp_remove(&user, dns)) {
infof(data, "Hostname in DNS cache was stale, zapped");
dns = NULL; /* the memory deallocation is being handled by the hash */
Curl_hash_delete(data->dns.hostcache, entry_id, entry_len + 1);
}
}
/* See if the returned entry matches the required resolve mode */
if(dns && data->conn->ip_version != CURL_IPRESOLVE_WHATEVER) {
int pf = PF_INET;
bool found = false;
struct Curl_addrinfo *addr = dns->addr;
if(data->conn->ip_version == CURL_IPRESOLVE_V6)
pf = PF_INET6;
while(addr) {
if(addr->ai_family == pf) {
found = true;
break;
}
addr = addr->ai_next;
}
if(!found) {
infof(data, "Hostname in DNS cache doesn't have needed family, zapped");
dns = NULL; /* the memory deallocation is being handled by the hash */
Curl_hash_delete(data->dns.hostcache, entry_id, entry_len + 1);
}
}
return dns;
}
/*
* Curl_fetch_addr() fetches a 'Curl_dns_entry' already in the DNS cache.
*
* Curl_resolv() checks initially and multi_runsingle() checks each time
* it discovers the handle in the state WAITRESOLVE whether the hostname
* has already been resolved and the address has already been stored in
* the DNS cache. This short circuits waiting for a lot of pending
* lookups for the same hostname requested by different handles.
*
* Returns the Curl_dns_entry entry pointer or NULL if not in the cache.
*
* The returned data *MUST* be "unlocked" with Curl_resolv_unlock() after
* use, or we'll leak memory!
*/
struct Curl_dns_entry *
Curl_fetch_addr(struct Curl_easy *data,
const char *hostname,
int port)
{
struct Curl_dns_entry *dns = NULL;
if(data->share)
Curl_share_lock(data, CURL_LOCK_DATA_DNS, CURL_LOCK_ACCESS_SINGLE);
dns = fetch_addr(data, hostname, port);
if(dns)
dns->inuse++; /* we use it! */
if(data->share)
Curl_share_unlock(data, CURL_LOCK_DATA_DNS);
return dns;
}
#ifndef CURL_DISABLE_SHUFFLE_DNS
UNITTEST CURLcode Curl_shuffle_addr(struct Curl_easy *data,
struct Curl_addrinfo **addr);
/*
* Curl_shuffle_addr() shuffles the order of addresses in a 'Curl_addrinfo'
* struct by re-linking its linked list.
*
* The addr argument should be the address of a pointer to the head node of a
* `Curl_addrinfo` list and it will be modified to point to the new head after
* shuffling.
*
* Not declared static only to make it easy to use in a unit test!
*
* @unittest: 1608
*/
UNITTEST CURLcode Curl_shuffle_addr(struct Curl_easy *data,
struct Curl_addrinfo **addr)
{
CURLcode result = CURLE_OK;
const int num_addrs = Curl_num_addresses(*addr);
if(num_addrs > 1) {
struct Curl_addrinfo **nodes;
infof(data, "Shuffling %i addresses", num_addrs);
nodes = malloc(num_addrs*sizeof(*nodes));
if(nodes) {
int i;
unsigned int *rnd;
const size_t rnd_size = num_addrs * sizeof(*rnd);
/* build a plain array of Curl_addrinfo pointers */
nodes[0] = *addr;
for(i = 1; i < num_addrs; i++) {
nodes[i] = nodes[i-1]->ai_next;
}
rnd = malloc(rnd_size);
if(rnd) {
/* Fisher-Yates shuffle */
if(Curl_rand(data, (unsigned char *)rnd, rnd_size) == CURLE_OK) {
struct Curl_addrinfo *swap_tmp;
for(i = num_addrs - 1; i > 0; i--) {
swap_tmp = nodes[rnd[i] % (i + 1)];
nodes[rnd[i] % (i + 1)] = nodes[i];
nodes[i] = swap_tmp;
}
/* relink list in the new order */
for(i = 1; i < num_addrs; i++) {
nodes[i-1]->ai_next = nodes[i];
}
nodes[num_addrs-1]->ai_next = NULL;
*addr = nodes[0];
}
free(rnd);
}
else
result = CURLE_OUT_OF_MEMORY;
free(nodes);
}
else
result = CURLE_OUT_OF_MEMORY;
}
return result;
}
#endif
/*
* Curl_cache_addr() stores a 'Curl_addrinfo' struct in the DNS cache.
*
* When calling Curl_resolv() has resulted in a response with a returned
* address, we call this function to store the information in the dns
* cache etc
*
* Returns the Curl_dns_entry entry pointer or NULL if the storage failed.
*/
struct Curl_dns_entry *
Curl_cache_addr(struct Curl_easy *data,
struct Curl_addrinfo *addr,
const char *hostname,
int port)
{
char entry_id[MAX_HOSTCACHE_LEN];
size_t entry_len;
struct Curl_dns_entry *dns;
struct Curl_dns_entry *dns2;
#ifndef CURL_DISABLE_SHUFFLE_DNS
/* shuffle addresses if requested */
if(data->set.dns_shuffle_addresses) {
CURLcode result = Curl_shuffle_addr(data, &addr);
if(result)
return NULL;
}
#endif
/* Create a new cache entry */
dns = calloc(1, sizeof(struct Curl_dns_entry));
if(!dns) {
return NULL;
}
/* Create an entry id, based upon the hostname and port */
create_hostcache_id(hostname, port, entry_id, sizeof(entry_id));
entry_len = strlen(entry_id);
dns->inuse = 1; /* the cache has the first reference */
dns->addr = addr; /* this is the address(es) */
time(&dns->timestamp);
if(dns->timestamp == 0)
dns->timestamp = 1; /* zero indicates permanent CURLOPT_RESOLVE entry */
/* Store the resolved data in our DNS cache. */
dns2 = Curl_hash_add(data->dns.hostcache, entry_id, entry_len + 1,
(void *)dns);
if(!dns2) {
free(dns);
return NULL;
}
dns = dns2;
dns->inuse++; /* mark entry as in-use */
return dns;
}
#ifdef ENABLE_IPV6
/* return a static IPv6 ::1 for the name */
static struct Curl_addrinfo *get_localhost6(int port, const char *name)
{
struct Curl_addrinfo *ca;
const size_t ss_size = sizeof(struct sockaddr_in6);
const size_t hostlen = strlen(name);
struct sockaddr_in6 sa6;
unsigned char ipv6[16];
unsigned short port16 = (unsigned short)(port & 0xffff);
ca = calloc(sizeof(struct Curl_addrinfo) + ss_size + hostlen + 1, 1);
if(!ca)
return NULL;
sa6.sin6_family = AF_INET6;
sa6.sin6_port = htons(port16);
sa6.sin6_flowinfo = 0;
sa6.sin6_scope_id = 0;
if(Curl_inet_pton(AF_INET6, "::1", ipv6) < 1)
return NULL;
memcpy(&sa6.sin6_addr, ipv6, sizeof(ipv6));
ca->ai_flags = 0;
ca->ai_family = AF_INET6;
ca->ai_socktype = SOCK_STREAM;
ca->ai_protocol = IPPROTO_TCP;
ca->ai_addrlen = (curl_socklen_t)ss_size;
ca->ai_next = NULL;
ca->ai_addr = (void *)((char *)ca + sizeof(struct Curl_addrinfo));
memcpy(ca->ai_addr, &sa6, ss_size);
ca->ai_canonname = (char *)ca->ai_addr + ss_size;
strcpy(ca->ai_canonname, name);
return ca;
}
#else
#define get_localhost6(x,y) NULL
#endif
/* return a static IPv4 127.0.0.1 for the given name */
static struct Curl_addrinfo *get_localhost(int port, const char *name)
{
struct Curl_addrinfo *ca;
const size_t ss_size = sizeof(struct sockaddr_in);
const size_t hostlen = strlen(name);
struct sockaddr_in sa;
unsigned int ipv4;
unsigned short port16 = (unsigned short)(port & 0xffff);
/* memset to clear the sa.sin_zero field */
memset(&sa, 0, sizeof(sa));
sa.sin_family = AF_INET;
sa.sin_port = htons(port16);
if(Curl_inet_pton(AF_INET, "127.0.0.1", (char *)&ipv4) < 1)
return NULL;
memcpy(&sa.sin_addr, &ipv4, sizeof(ipv4));
ca = calloc(sizeof(struct Curl_addrinfo) + ss_size + hostlen + 1, 1);
if(!ca)
return NULL;
ca->ai_flags = 0;
ca->ai_family = AF_INET;
ca->ai_socktype = SOCK_STREAM;
ca->ai_protocol = IPPROTO_TCP;
ca->ai_addrlen = (curl_socklen_t)ss_size;
ca->ai_addr = (void *)((char *)ca + sizeof(struct Curl_addrinfo));
memcpy(ca->ai_addr, &sa, ss_size);
ca->ai_canonname = (char *)ca->ai_addr + ss_size;
strcpy(ca->ai_canonname, name);
ca->ai_next = get_localhost6(port, name);
return ca;
}
#ifdef ENABLE_IPV6
/*
* Curl_ipv6works() returns TRUE if IPv6 seems to work.
*/
bool Curl_ipv6works(struct Curl_easy *data)
{
if(data) {
/* the nature of most system is that IPv6 status doesn't come and go
during a program's lifetime so we only probe the first time and then we
have the info kept for fast re-use */
DEBUGASSERT(data);
DEBUGASSERT(data->multi);
if(data->multi->ipv6_up == IPV6_UNKNOWN) {
bool works = Curl_ipv6works(NULL);
data->multi->ipv6_up = works ? IPV6_WORKS : IPV6_DEAD;
}
return data->multi->ipv6_up == IPV6_WORKS;
}
else {
int ipv6_works = -1;
/* probe to see if we have a working IPv6 stack */
curl_socket_t s = socket(PF_INET6, SOCK_DGRAM, 0);
if(s == CURL_SOCKET_BAD)
/* an IPv6 address was requested but we can't get/use one */
ipv6_works = 0;
else {
ipv6_works = 1;
sclose(s);
}
return (ipv6_works>0)?TRUE:FALSE;
}
}
#endif /* ENABLE_IPV6 */
/*
* Curl_host_is_ipnum() returns TRUE if the given string is a numerical IPv4
* (or IPv6 if supported) address.
*/
bool Curl_host_is_ipnum(const char *hostname)
{
struct in_addr in;
#ifdef ENABLE_IPV6
struct in6_addr in6;
#endif
if(Curl_inet_pton(AF_INET, hostname, &in) > 0
#ifdef ENABLE_IPV6
|| Curl_inet_pton(AF_INET6, hostname, &in6) > 0
#endif
)
return TRUE;
return FALSE;
}
/* return TRUE if 'part' is a case insensitive tail of 'full' */
static bool tailmatch(const char *full, const char *part)
{
size_t plen = strlen(part);
size_t flen = strlen(full);
if(plen > flen)
return FALSE;
return strncasecompare(part, &full[flen - plen], plen);
}
/*
* Curl_resolv() is the main name resolve function within libcurl. It resolves
* a name and returns a pointer to the entry in the 'entry' argument (if one
* is provided). This function might return immediately if we're using asynch
* resolves. See the return codes.
*
* The cache entry we return will get its 'inuse' counter increased when this
* function is used. You MUST call Curl_resolv_unlock() later (when you're
* done using this struct) to decrease the counter again.
*
* Return codes:
*
* CURLRESOLV_ERROR (-1) = error, no pointer
* CURLRESOLV_RESOLVED (0) = OK, pointer provided
* CURLRESOLV_PENDING (1) = waiting for response, no pointer
*/
enum resolve_t Curl_resolv(struct Curl_easy *data,
const char *hostname,
int port,
bool allowDOH,
struct Curl_dns_entry **entry)
{
struct Curl_dns_entry *dns = NULL;
CURLcode result;
enum resolve_t rc = CURLRESOLV_ERROR; /* default to failure */
struct connectdata *conn = data->conn;
*entry = NULL;
#ifndef CURL_DISABLE_DOH
conn->bits.doh = FALSE; /* default is not */
#else
(void)allowDOH;
#endif
if(data->share)
Curl_share_lock(data, CURL_LOCK_DATA_DNS, CURL_LOCK_ACCESS_SINGLE);
dns = fetch_addr(data, hostname, port);
if(dns) {
infof(data, "Hostname %s was found in DNS cache", hostname);
dns->inuse++; /* we use it! */
rc = CURLRESOLV_RESOLVED;
}
if(data->share)
Curl_share_unlock(data, CURL_LOCK_DATA_DNS);
if(!dns) {
/* The entry was not in the cache. Resolve it to IP address */
struct Curl_addrinfo *addr = NULL;
int respwait = 0;
#if !defined(CURL_DISABLE_DOH) || !defined(USE_RESOLVE_ON_IPS)
struct in_addr in;
#endif
#ifndef CURL_DISABLE_DOH
#ifndef USE_RESOLVE_ON_IPS
const
#endif
bool ipnum = FALSE;
#endif
/* notify the resolver start callback */
if(data->set.resolver_start) {
int st;
Curl_set_in_callback(data, true);
st = data->set.resolver_start(
#ifdef USE_CURL_ASYNC
data->state.async.resolver,
#else
NULL,
#endif
NULL,
data->set.resolver_start_client);
Curl_set_in_callback(data, false);
if(st)
return CURLRESOLV_ERROR;
}
#if defined(ENABLE_IPV6) && defined(CURL_OSX_CALL_COPYPROXIES)
{
/*
* The automagic conversion from IPv4 literals to IPv6 literals only
* works if the SCDynamicStoreCopyProxies system function gets called
* first. As Curl currently doesn't support system-wide HTTP proxies, we
* therefore don't use any value this function might return.
*
* This function is only available on a macOS and is not needed for
* IPv4-only builds, hence the conditions above.
*/
CFDictionaryRef dict = SCDynamicStoreCopyProxies(NULL);
if(dict)
CFRelease(dict);
}
#endif
#ifndef USE_RESOLVE_ON_IPS
/* 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 */
addr = Curl_ip2addr(AF_INET, &in, hostname, port);
#ifdef ENABLE_IPV6
if(!addr) {
struct in6_addr in6;
/* check if this is an IPv6 address string */
if(Curl_inet_pton(AF_INET6, hostname, &in6) > 0)
/* This is an IPv6 address literal */
addr = Curl_ip2addr(AF_INET6, &in6, hostname, port);
}
#endif /* ENABLE_IPV6 */
#else /* if USE_RESOLVE_ON_IPS */
#ifndef CURL_DISABLE_DOH
/* 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 */
ipnum = TRUE;
#ifdef ENABLE_IPV6
else {
struct in6_addr in6;
/* check if this is an IPv6 address string */
if(Curl_inet_pton(AF_INET6, hostname, &in6) > 0)
/* This is an IPv6 address literal */
ipnum = TRUE;
}
#endif /* ENABLE_IPV6 */
#endif /* CURL_DISABLE_DOH */
#endif /* !USE_RESOLVE_ON_IPS */
if(!addr) {
if(conn->ip_version == CURL_IPRESOLVE_V6 && !Curl_ipv6works(data))
return CURLRESOLV_ERROR;
if(strcasecompare(hostname, "localhost") ||
tailmatch(hostname, ".localhost"))
addr = get_localhost(port, hostname);
#ifndef CURL_DISABLE_DOH
else if(allowDOH && data->set.doh && !ipnum)
addr = Curl_doh(data, hostname, port, &respwait);
#endif
else {
/* Check what IP specifics the app has requested and if we can provide
* it. If not, bail out. */
if(!Curl_ipvalid(data, conn))
return CURLRESOLV_ERROR;
/* If Curl_getaddrinfo() returns NULL, 'respwait' might be set to a
non-zero value indicating that we need to wait for the response to
the resolve call */
addr = Curl_getaddrinfo(data, hostname, port, &respwait);
}
}
if(!addr) {
if(respwait) {
/* the response to our resolve call will come asynchronously at
a later time, good or bad */
/* First, check that we haven't received the info by now */
result = Curl_resolv_check(data, &dns);
if(result) /* error detected */
return CURLRESOLV_ERROR;
if(dns)
rc = CURLRESOLV_RESOLVED; /* pointer provided */
else
rc = CURLRESOLV_PENDING; /* no info yet */
}
}
else {
if(data->share)
Curl_share_lock(data, CURL_LOCK_DATA_DNS, CURL_LOCK_ACCESS_SINGLE);
/* we got a response, store it in the cache */
dns = Curl_cache_addr(data, addr, hostname, port);
if(data->share)
Curl_share_unlock(data, CURL_LOCK_DATA_DNS);
if(!dns)
/* returned failure, bail out nicely */
Curl_freeaddrinfo(addr);
else
rc = CURLRESOLV_RESOLVED;
}
}
*entry = dns;
return rc;
}
#ifdef USE_ALARM_TIMEOUT
/*
* This signal handler jumps back into the main libcurl code and continues
* execution. This effectively causes the remainder of the application to run
* within a signal handler which is nonportable and could lead to problems.
*/
static
void alarmfunc(int sig)
{
/* this is for "-ansi -Wall -pedantic" to stop complaining! (rabe) */
(void)sig;
siglongjmp(curl_jmpenv, 1);
}
#endif /* USE_ALARM_TIMEOUT */
/*
* Curl_resolv_timeout() is the same as Curl_resolv() but specifies a
* timeout. This function might return immediately if we're using asynch
* resolves. See the return codes.
*
* The cache entry we return will get its 'inuse' counter increased when this
* function is used. You MUST call Curl_resolv_unlock() later (when you're
* done using this struct) to decrease the counter again.
*
* If built with a synchronous resolver and use of signals is not
* disabled by the application, then a nonzero timeout will cause a
* timeout after the specified number of milliseconds. Otherwise, timeout
* is ignored.
*
* Return codes:
*
* CURLRESOLV_TIMEDOUT(-2) = warning, time too short or previous alarm expired
* CURLRESOLV_ERROR (-1) = error, no pointer
* CURLRESOLV_RESOLVED (0) = OK, pointer provided
* CURLRESOLV_PENDING (1) = waiting for response, no pointer
*/
enum resolve_t Curl_resolv_timeout(struct Curl_easy *data,
const char *hostname,
int port,
struct Curl_dns_entry **entry,
timediff_t timeoutms)
{
#ifdef USE_ALARM_TIMEOUT
#ifdef HAVE_SIGACTION
struct sigaction keep_sigact; /* store the old struct here */
volatile bool keep_copysig = FALSE; /* whether old sigact has been saved */
struct sigaction sigact;
#else
#ifdef HAVE_SIGNAL
void (*keep_sigact)(int); /* store the old handler here */
#endif /* HAVE_SIGNAL */
#endif /* HAVE_SIGACTION */
volatile long timeout;
volatile unsigned int prev_alarm = 0;
#endif /* USE_ALARM_TIMEOUT */
enum resolve_t rc;
*entry = NULL;
if(timeoutms < 0)
/* got an already expired timeout */
return CURLRESOLV_TIMEDOUT;
#ifdef USE_ALARM_TIMEOUT
if(data->set.no_signal)
/* Ignore the timeout when signals are disabled */
timeout = 0;
else
timeout = (timeoutms > LONG_MAX) ? LONG_MAX : (long)timeoutms;
if(!timeout)
/* USE_ALARM_TIMEOUT defined, but no timeout actually requested */
return Curl_resolv(data, hostname, port, TRUE, entry);
if(timeout < 1000) {
/* The alarm() function only provides integer second resolution, so if
we want to wait less than one second we must bail out already now. */
failf(data,
"remaining timeout of %ld too small to resolve via SIGALRM method",
timeout);
return CURLRESOLV_TIMEDOUT;
}
/* This allows us to time-out from the name resolver, as the timeout
will generate a signal and we will siglongjmp() from that here.
This technique has problems (see alarmfunc).
This should be the last thing we do before calling Curl_resolv(),
as otherwise we'd have to worry about variables that get modified
before we invoke Curl_resolv() (and thus use "volatile"). */
if(sigsetjmp(curl_jmpenv, 1)) {
/* this is coming from a siglongjmp() after an alarm signal */
failf(data, "name lookup timed out");
rc = CURLRESOLV_ERROR;
goto clean_up;
}
else {
/*************************************************************
* Set signal handler to catch SIGALRM
* Store the old value to be able to set it back later!
*************************************************************/
#ifdef HAVE_SIGACTION
sigaction(SIGALRM, NULL, &sigact);
keep_sigact = sigact;
keep_copysig = TRUE; /* yes, we have a copy */
sigact.sa_handler = alarmfunc;
#ifdef SA_RESTART
/* HPUX doesn't have SA_RESTART but defaults to that behavior! */
sigact.sa_flags &= ~SA_RESTART;
#endif
/* now set the new struct */
sigaction(SIGALRM, &sigact, NULL);
#else /* HAVE_SIGACTION */
/* no sigaction(), revert to the much lamer signal() */
#ifdef HAVE_SIGNAL
keep_sigact = signal(SIGALRM, alarmfunc);
#endif
#endif /* HAVE_SIGACTION */
/* alarm() makes a signal get sent when the timeout fires off, and that
will abort system calls */
prev_alarm = alarm(curlx_sltoui(timeout/1000L));
}
#else
#ifndef CURLRES_ASYNCH
if(timeoutms)
infof(data, "timeout on name lookup is not supported");
#else
(void)timeoutms; /* timeoutms not used with an async resolver */
#endif
#endif /* USE_ALARM_TIMEOUT */
/* Perform the actual name resolution. This might be interrupted by an
* alarm if it takes too long.
*/
rc = Curl_resolv(data, hostname, port, TRUE, entry);
#ifdef USE_ALARM_TIMEOUT
clean_up:
if(!prev_alarm)
/* deactivate a possibly active alarm before uninstalling the handler */
alarm(0);
#ifdef HAVE_SIGACTION
if(keep_copysig) {
/* we got a struct as it looked before, now put that one back nice
and clean */
sigaction(SIGALRM, &keep_sigact, NULL); /* put it back */
}
#else
#ifdef HAVE_SIGNAL
/* restore the previous SIGALRM handler */
signal(SIGALRM, keep_sigact);
#endif
#endif /* HAVE_SIGACTION */
/* switch back the alarm() to either zero or to what it was before minus
the time we spent until now! */
if(prev_alarm) {
/* there was an alarm() set before us, now put it back */
timediff_t elapsed_secs = Curl_timediff(Curl_now(),
data->conn->created) / 1000;
/* the alarm period is counted in even number of seconds */
unsigned long alarm_set = (unsigned long)(prev_alarm - elapsed_secs);
if(!alarm_set ||
((alarm_set >= 0x80000000) && (prev_alarm < 0x80000000)) ) {
/* if the alarm time-left reached zero or turned "negative" (counted
with unsigned values), we should fire off a SIGALRM here, but we
won't, and zero would be to switch it off so we never set it to
less than 1! */
alarm(1);
rc = CURLRESOLV_TIMEDOUT;
failf(data, "Previous alarm fired off");
}
else
alarm((unsigned int)alarm_set);
}
#endif /* USE_ALARM_TIMEOUT */
return rc;
}
/*
* Curl_resolv_unlock() unlocks the given cached DNS entry. When this has been