libcurl extracted to the separate lib

git-svn-id: http://svn.miranda-ng.org/main/trunk@14683 1316c22d-e87f-b044-9b9b-93d7a3e3ba9c

1 files changed, 827 insertions, 0 deletions

diff --git a/libs/libcurl/src/hostip.c b/libs/libcurl/src/hostip.c
new file mode 100644
index 0000000000..f37b4925bb
--- /dev/null
+++ b/libs/libcurl/src/hostip.c
@@ -0,0 +1,827 @@
+/***************************************************************************
+ *                                  _   _ ____  _
+ *  Project                     ___| | | |  _ \| |
+ *                             / __| | | | |_) | |
+ *                            | (__| |_| |  _ <| |___
+ *                             \___|\___/|_| \_\_____|
+ *
+ * Copyright (C) 1998 - 2013, 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.
+ *
+ ***************************************************************************/
+
+#include "curl_setup.h"
+
+#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 __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 "share.h"
+#include "strerror.h"
+#include "url.h"
+#include "inet_ntop.h"
+#include "warnless.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"
+
+#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
+
+/*
+ * 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.
+ */
+
+/* These two symbols are for the global DNS cache */
+static struct curl_hash hostname_cache;
+static int host_cache_initialized;
+
+static void freednsentry(void *freethis);
+
+/*
+ * Curl_global_host_cache_init() initializes and sets up a global DNS cache.
+ * Global DNS cache is general badness. Do not use. This will be removed in
+ * a future version. Use the share interface instead!
+ *
+ * Returns a struct curl_hash pointer on success, NULL on failure.
+ */
+struct curl_hash *Curl_global_host_cache_init(void)
+{
+  int rc = 0;
+  if(!host_cache_initialized) {
+    rc = Curl_hash_init(&hostname_cache, 7, Curl_hash_str,
+                        Curl_str_key_compare, freednsentry);
+    if(!rc)
+      host_cache_initialized = 1;
+  }
+  return rc?NULL:&hostname_cache;
+}
+
+/*
+ * Destroy and cleanup the global DNS cache
+ */
+void Curl_global_host_cache_dtor(void)
+{
+  if(host_cache_initialized) {
+    /* first make sure that any custom "CURLOPT_RESOLVE" names are
+       cleared off */
+    Curl_hostcache_clean(NULL, &hostname_cache);
+    /* then free the remaining hash completely */
+    Curl_hash_clean(&hostname_cache);
+    host_cache_initialized = 0;
+  }
+}
+
+/*
+ * Return # of adresses in a Curl_addrinfo struct
+ */
+int Curl_num_addresses(const Curl_addrinfo *addr)
+{
+  int i = 0;
+  while(addr) {
+    addr = addr->ai_next;
+    i++;
+  }
+  return i;
+}
+
+/*
+ * Curl_printable_address() returns 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, it returns NULL.
+ */
+const char *
+Curl_printable_address(const Curl_addrinfo *ai, char *buf, size_t bufsize)
+{
+  const struct sockaddr_in *sa4;
+  const struct in_addr *ipaddr4;
+#ifdef ENABLE_IPV6
+  const struct sockaddr_in6 *sa6;
+  const struct in6_addr *ipaddr6;
+#endif
+
+  switch (ai->ai_family) {
+    case AF_INET:
+      sa4 = (const void *)ai->ai_addr;
+      ipaddr4 = &sa4->sin_addr;
+      return Curl_inet_ntop(ai->ai_family, (const void *)ipaddr4, buf,
+                            bufsize);
+#ifdef ENABLE_IPV6
+    case AF_INET6:
+      sa6 = (const void *)ai->ai_addr;
+      ipaddr6 = &sa6->sin6_addr;
+      return Curl_inet_ntop(ai->ai_family, (const void *)ipaddr6, buf,
+                            bufsize);
+#endif
+    default:
+      break;
+  }
+  return NULL;
+}
+
+/*
+ * Return a hostcache id string for the provided host + port, to be used by
+ * the DNS caching.
+ */
+static char *
+create_hostcache_id(const char *name, int port)
+{
+  /* create and return the new allocated entry */
+  char *id = aprintf("%s:%d", name, port);
+  char *ptr = id;
+  if(ptr) {
+    /* lower case the name part */
+    while(*ptr && (*ptr != ':')) {
+      *ptr = (char)TOLOWER(*ptr);
+      ptr++;
+    }
+  }
+  return id;
+}
+
+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 (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 SessionHandle *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);
+}
+
+/*
+ * Check if the entry should be pruned. Assumes a locked cache.
+ */
+static int
+remove_entry_if_stale(struct SessionHandle *data, struct Curl_dns_entry *dns)
+{
+  struct hostcache_prune_data user;
+
+  if(!dns || (data->set.dns_cache_timeout == -1) || !data->dns.hostcache)
+    /* cache forever means never prune, and NULL hostcache means
+       we can't do it */
+    return 0;
+
+  time(&user.now);
+  user.cache_timeout = data->set.dns_cache_timeout;
+
+  if(!hostcache_timestamp_remove(&user,dns) )
+    return 0;
+
+  Curl_hash_clean_with_criterium(data->dns.hostcache,
+                                 (void *) &user,
+                                 hostcache_timestamp_remove);
+
+  return 1;
+}
+
+
+#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
+
+
+/*
+ * 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 SessionHandle *data,
+                Curl_addrinfo *addr,
+                const char *hostname,
+                int port)
+{
+  char *entry_id;
+  size_t entry_len;
+  struct Curl_dns_entry *dns;
+  struct Curl_dns_entry *dns2;
+
+  /* Create an entry id, based upon the hostname and port */
+  entry_id = create_hostcache_id(hostname, port);
+  /* If we can't create the entry id, fail */
+  if(!entry_id)
+    return NULL;
+  entry_len = strlen(entry_id);
+
+  /* Create a new cache entry */
+  dns = calloc(1, sizeof(struct Curl_dns_entry));
+  if(!dns) {
+    free(entry_id);
+    return NULL;
+  }
+
+  dns->inuse = 0;   /* init to not used */
+  dns->addr = addr; /* this is the address(es) */
+  time(&dns->timestamp);
+  if(dns->timestamp == 0)
+    dns->timestamp = 1;   /* zero indicates that entry isn't in hash table */
+
+  /* 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);
+    free(entry_id);
+    return NULL;
+  }
+
+  dns = dns2;
+  dns->inuse++;         /* mark entry as in-use */
+
+  /* free the allocated entry_id */
+  free(entry_id);
+
+  return dns;
+}
+
+/*
+ * 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.
+ *
+ * In debug mode, we specifically test for an interface name "LocalHost"
+ * and resolve "localhost" instead as a means to permit test cases
+ * to connect to a local test server with any host name.
+ *
+ * Return codes:
+ *
+ * CURLRESOLV_ERROR   (-1) = error, no pointer
+ * CURLRESOLV_RESOLVED (0) = OK, pointer provided
+ * CURLRESOLV_PENDING  (1) = waiting for response, no pointer
+ */
+
+int Curl_resolv(struct connectdata *conn,
+                const char *hostname,
+                int port,
+                struct Curl_dns_entry **entry)
+{
+  char *entry_id = NULL;
+  struct Curl_dns_entry *dns = NULL;
+  size_t entry_len;
+  struct SessionHandle *data = conn->data;
+  CURLcode result;
+  int rc = CURLRESOLV_ERROR; /* default to failure */
+
+  *entry = NULL;
+
+  /* Create an entry id, based upon the hostname and port */
+  entry_id = create_hostcache_id(hostname, port);
+  /* If we can't create the entry id, fail */
+  if(!entry_id)
+    return rc;
+
+  entry_len = strlen(entry_id);
+
+  if(data->share)
+    Curl_share_lock(data, CURL_LOCK_DATA_DNS, CURL_LOCK_ACCESS_SINGLE);
+
+  /* See if its already in our dns cache */
+  dns = Curl_hash_pick(data->dns.hostcache, entry_id, entry_len+1);
+
+  /* free the allocated entry_id again */
+  free(entry_id);
+
+  /* See whether the returned entry is stale. Done before we release lock */
+  if(remove_entry_if_stale(data, dns))
+    dns = NULL; /* the memory deallocation is being handled by the hash */
+
+  if(dns) {
+    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 */
+
+    Curl_addrinfo *addr;
+    int respwait;
+
+    /* Check what IP specifics the app has requested and if we can provide it.
+     * If not, bail out. */
+    if(!Curl_ipvalid(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(conn,
+#ifdef DEBUGBUILD
+                            (data->set.str[STRING_DEVICE]
+                             && !strcmp(data->set.str[STRING_DEVICE],
+                                        "LocalHost"))?"localhost":
+#endif
+                            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_resolver_is_resolved(conn, &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
+RETSIGTYPE alarmfunc(int sig)
+{
+  /* this is for "-ansi -Wall -pedantic" to stop complaining!   (rabe) */
+  (void)sig;
+  siglongjmp(curl_jmpenv, 1);
+  return;
+}
+#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
+ */
+
+int Curl_resolv_timeout(struct connectdata *conn,
+                        const char *hostname,
+                        int port,
+                        struct Curl_dns_entry **entry,
+                        long timeoutms)
+{
+#ifdef USE_ALARM_TIMEOUT
+#ifdef HAVE_SIGACTION
+  struct sigaction keep_sigact;   /* store the old struct here */
+  volatile bool keep_copysig = FALSE; /* wether 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;
+  struct SessionHandle *data = conn->data;
+#endif /* USE_ALARM_TIMEOUT */
+  int 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;
+
+  if(!timeout)
+    /* USE_ALARM_TIMEOUT defined, but no timeout actually requested */
+    return Curl_resolv(conn, hostname, port, 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. */
+    return CURLRESOLV_TIMEDOUT;
+
+  /*************************************************************
+   * 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 behaviour! */
+  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));
+
+  /* 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
+#ifndef CURLRES_ASYNCH
+  if(timeoutms)
+    infof(conn->data, "timeout on name lookup is not supported\n");
+#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(conn, hostname, port, 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 */
+    unsigned long elapsed_ms = Curl_tvdiff(Curl_tvnow(), conn->created);
+
+    /* the alarm period is counted in even number of seconds */
+    unsigned long alarm_set = prev_alarm - elapsed_ms/1000;
+
+    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
+ * made, the struct may be destroyed due to pruning. It is important that only
+ * one unlock is made for each Curl_resolv() call.
+ *
+ * May be called with 'data' == NULL for global cache.
+ */
+void Curl_resolv_unlock(struct SessionHandle *data, struct Curl_dns_entry *dns)
+{
+  DEBUGASSERT(dns && (dns->inuse>0));
+
+  if(data && data->share)
+    Curl_share_lock(data, CURL_LOCK_DATA_DNS, CURL_LOCK_ACCESS_SINGLE);
+
+  dns->inuse--;
+  /* only free if nobody is using AND it is not in hostcache (timestamp ==
+     0) */
+  if(dns->inuse == 0 && dns->timestamp == 0) {
+    Curl_freeaddrinfo(dns->addr);
+    free(dns);
+  }
+
+  if(data && data->share)
+    Curl_share_unlock(data, CURL_LOCK_DATA_DNS);
+}
+
+/*
+ * File-internal: free a cache dns entry.
+ */
+static void freednsentry(void *freethis)
+{
+  struct Curl_dns_entry *p = (struct Curl_dns_entry *) freethis;
+
+  /* mark the entry as not in hostcache */
+  p->timestamp = 0;
+  if(p->inuse == 0) {
+    Curl_freeaddrinfo(p->addr);
+    free(p);
+  }
+}
+
+/*
+ * Curl_mk_dnscache() creates a new DNS cache and returns the handle for it.
+ */
+struct curl_hash *Curl_mk_dnscache(void)
+{
+  return Curl_hash_alloc(7, Curl_hash_str, Curl_str_key_compare, freednsentry);
+}
+
+static int hostcache_inuse(void *data, void *hc)
+{
+  struct Curl_dns_entry *c = (struct Curl_dns_entry *) hc;
+
+  if(c->inuse == 1)
+    Curl_resolv_unlock(data, c);
+
+  return 1; /* free all entries */
+}
+
+/*
+ * Curl_hostcache_clean()
+ *
+ * This _can_ be called with 'data' == NULL but then of course no locking
+ * can be done!
+ */
+
+void Curl_hostcache_clean(struct SessionHandle *data,
+                          struct curl_hash *hash)
+{
+  /* Entries added to the hostcache with the CURLOPT_RESOLVE function are
+   * still present in the cache with the inuse counter set to 1. Detect them
+   * and cleanup!
+   */
+  Curl_hash_clean_with_criterium(hash, data, hostcache_inuse);
+}
+
+
+CURLcode Curl_loadhostpairs(struct SessionHandle *data)
+{
+  struct curl_slist *hostp;
+  char hostname[256];
+  char address[256];
+  int port;
+
+  for(hostp = data->change.resolve; hostp; hostp = hostp->next ) {
+    if(!hostp->data)
+      continue;
+    if(hostp->data[0] == '-') {
+      /* TODO: mark an entry for removal */
+    }
+    else if(3 == sscanf(hostp->data, "%255[^:]:%d:%255s", hostname, &port,
+                        address)) {
+      struct Curl_dns_entry *dns;
+      Curl_addrinfo *addr;
+      char *entry_id;
+      size_t entry_len;
+
+      addr = Curl_str2addr(address, port);
+      if(!addr) {
+        infof(data, "Resolve %s found illegal!\n", hostp->data);
+        continue;
+      }
+
+      /* Create an entry id, based upon the hostname and port */
+      entry_id = create_hostcache_id(hostname, port);
+      /* If we can't create the entry id, fail */
+      if(!entry_id) {
+        Curl_freeaddrinfo(addr);
+        return CURLE_OUT_OF_MEMORY;
+      }
+
+      entry_len = strlen(entry_id);
+
+      if(data->share)
+        Curl_share_lock(data, CURL_LOCK_DATA_DNS, CURL_LOCK_ACCESS_SINGLE);
+
+      /* See if its already in our dns cache */
+      dns = Curl_hash_pick(data->dns.hostcache, entry_id, entry_len+1);
+
+      /* free the allocated entry_id again */
+      free(entry_id);
+
+      if(!dns)
+        /* if not in the cache already, put this host in the cache */
+        dns = Curl_cache_addr(data, addr, hostname, port);
+      else
+        /* this is a duplicate, free it again */
+        Curl_freeaddrinfo(addr);
+
+      if(data->share)
+        Curl_share_unlock(data, CURL_LOCK_DATA_DNS);
+
+      if(!dns) {
+        Curl_freeaddrinfo(addr);
+        return CURLE_OUT_OF_MEMORY;
+      }
+      infof(data, "Added %s:%d:%s to DNS cache\n",
+            hostname, port, address);
+    }
+  }
+  data->change.resolve = NULL; /* dealt with now */
+
+  return CURLE_OK;
+}