Skip to content

Commit

Permalink
Ingmar Runge provided a source snippet that caused a crash. The reaso…
Browse files Browse the repository at this point in the history 
…n for

the crash was that libcurl internally was a bit confused about who owned the
DNS cache at all times so if you created an easy handle that uses a shared
DNS cache and added that to a multi handle it would crash. Now we keep more
careful internal track of exactly what kind of DNS cache each easy handle
uses: None, Private (allocated for and used only by this single handle),
Shared (points to a cache held by a shared object), Global (points to the
global cache) or Multi (points to the cache within the multi handle that is
automatically shared between all easy handles that are added with private
caches).
  • Loading branch information
@bagder
bagder committed Jul 7, 2006
1 parent a09a816 commit ca319f6
Show file tree
Hide file tree
Showing 7 changed files with 84 additions and 43 deletions.
12 changes: 12 additions & 0 deletions CHANGES
View file
Original file line number Diff line number Diff line change
Expand Up @@ -6,6 +6,18 @@

Changelog

Daniel (8 July 2006)
- Ingmar Runge provided a source snippet that caused a crash. The reason for
the crash was that libcurl internally was a bit confused about who owned the
DNS cache at all times so if you created an easy handle that uses a shared
DNS cache and added that to a multi handle it would crash. Now we keep more
careful internal track of exactly what kind of DNS cache each easy handle
uses: None, Private (allocated for and used only by this single handle),
Shared (points to a cache held by a shared object), Global (points to the
global cache) or Multi (points to the cache within the multi handle that is
automatically shared between all easy handles that are added with private
caches).

Daniel (4 July 2006)
- Toshiyuki Maezawa fixed a problem where you couldn't override the
Proxy-Connection: header when using a proxy and not doing CONNECT.
Expand Down
4 changes: 3 additions & 1 deletion RELEASE-NOTES
View file
Original file line number Diff line number Diff line change
Expand Up @@ -18,6 +18,7 @@ This release includes the following changes:

This release includes the following bugfixes:

o an easy handle with shared DNS cache added to a multi handle caused a crash
o couldn't override the Proxy-Connection: header for non-CONNECT requests
o curl_multi_fdset() could wrongly return -1 as max_fd value

Expand All @@ -35,6 +36,7 @@ New curl mirrors:
This release would not have looked like this without help, code, reports and
advice from friends like these:

Dan Fandrich, Peter Silva, Arve Knudsen, Michael Wallner, Toshiyuki Maezawa
Dan Fandrich, Peter Silva, Arve Knudsen, Michael Wallner, Toshiyuki Maezawa,
Ingmar Runge

Thanks! (and sorry if I forgot to mention someone)
18 changes: 10 additions & 8 deletions lib/easy.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -5,7 +5,7 @@
* | (__| |_| | _ <| |___
* \___|\___/|_| \_\_____|
*
* Copyright (C) 1998 - 2005, Daniel Stenberg, <daniel@haxx.se>, et al.
* Copyright (C) 1998 - 2006, 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
Expand Down Expand Up @@ -436,16 +436,18 @@ CURLcode curl_easy_perform(CURL *curl)
if ( ! (data->share && data->share->hostcache) ) {

if (Curl_global_host_cache_use(data) &&
data->hostcache != Curl_global_host_cache_get()) {
if (data->hostcache)
Curl_hash_destroy(data->hostcache);
data->hostcache = Curl_global_host_cache_get();
(data->dns.hostcachetype != HCACHE_GLOBAL)) {
if (data->dns.hostcachetype == HCACHE_PRIVATE)
Curl_hash_destroy(data->dns.hostcache);
data->dns.hostcache = Curl_global_host_cache_get();
data->dns.hostcachetype = HCACHE_GLOBAL;
}

if (!data->hostcache) {
data->hostcache = Curl_mk_dnscache();
if (!data->dns.hostcache) {
data->dns.hostcachetype = HCACHE_PRIVATE;
data->dns.hostcache = Curl_mk_dnscache();

if(!data->hostcache)
if(!data->dns.hostcache)
/* While we possibly could survive and do good without a host cache,
the fact that creating it failed indicates that things are truly
screwed up and we should bail out! */
Expand Down
13 changes: 7 additions & 6 deletions lib/hostip.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -255,7 +255,7 @@ void Curl_hostcache_prune(struct SessionHandle *data)
{
time_t now;

if((data->set.dns_cache_timeout == -1) || !data->hostcache)
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;
Expand All @@ -266,7 +266,7 @@ void Curl_hostcache_prune(struct SessionHandle *data)
time(&now);

/* Remove outdated and unused entries from the hostcache */
hostcache_prune(data->hostcache,
hostcache_prune(data->dns.hostcache,
data->set.dns_cache_timeout,
now);

Expand All @@ -279,7 +279,7 @@ 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->hostcache)
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;
Expand All @@ -296,7 +296,7 @@ remove_entry_if_stale(struct SessionHandle *data, struct Curl_dns_entry *dns)
if(data->share)
Curl_share_lock(data, CURL_LOCK_DATA_DNS, CURL_LOCK_ACCESS_SINGLE);

Curl_hash_clean_with_criterium(data->hostcache,
Curl_hash_clean_with_criterium(data->dns.hostcache,
(void *) &user,
hostcache_timestamp_remove);

Expand Down Expand Up @@ -356,7 +356,8 @@ Curl_cache_addr(struct SessionHandle *data,
/* Store the resolved data in our DNS cache. This function may return a
pointer to an existing struct already present in the hash, and it may
return the same argument we pass in. Make no assumptions. */
dns2 = Curl_hash_add(data->hostcache, entry_id, entry_len+1, (void *)dns);
dns2 = Curl_hash_add(data->dns.hostcache, entry_id, entry_len+1,
(void *)dns);
if(!dns2) {
/* Major badness, run away. */
free(dns);
Expand Down Expand Up @@ -428,7 +429,7 @@ int Curl_resolv(struct connectdata *conn,
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->hostcache, entry_id, entry_len+1);
dns = Curl_hash_pick(data->dns.hostcache, entry_id, entry_len+1);

if(data->share)
Curl_share_unlock(data, CURL_LOCK_DATA_DNS);
Expand Down
37 changes: 24 additions & 13 deletions lib/multi.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -317,13 +317,14 @@ CURLMcode curl_multi_add_handle(CURLM *multi_handle,
easy->easy_handle = easy_handle;
multistate(easy, CURLM_STATE_INIT);

/* for multi interface connections, we share DNS cache automaticly.
First kill the existing one if there is any. */
if (easy->easy_handle->hostcache &&
easy->easy_handle->hostcache != multi->hostcache)
Curl_hash_destroy(easy->easy_handle->hostcache);

easy->easy_handle->hostcache = multi->hostcache;
/* for multi interface connections, we share DNS cache automaticly if the
easy handle's one is currently private. */
if (easy->easy_handle->dns.hostcache &&
(easy->easy_handle->dns.hostcachetype == HCACHE_PRIVATE)) {
Curl_hash_destroy(easy->easy_handle->dns.hostcache);
easy->easy_handle->dns.hostcache = multi->hostcache;
easy->easy_handle->dns.hostcachetype = HCACHE_MULTI;
}

/* We add this new entry first in the list. We make our 'next' point to the
previous next and our 'prev' point back to the 'first' struct */
Expand Down Expand Up @@ -374,8 +375,12 @@ CURLMcode curl_multi_remove_handle(CURLM *multi_handle,
/* If the 'state' is not INIT or COMPLETED, we might need to do something
nice to put the easy_handle in a good known state when this returns. */

/* clear out the usage of the shared DNS cache */
easy->easy_handle->hostcache = NULL;
if(easy->easy_handle->dns.hostcachetype == HCACHE_MULTI) {
/* clear out the usage of the shared DNS cache */
easy->easy_handle->dns.hostcache = NULL;
easy->easy_handle->dns.hostcachetype = HCACHE_NONE;
}

Curl_easy_addmulti(easy->easy_handle, NULL); /* clear the association
to this multi handle */

Expand Down Expand Up @@ -893,8 +898,11 @@ static CURLMcode multi_runsingle(struct Curl_multi *multi,
} while (easy->easy_handle->change.url_changed);

if ((CURLM_STATE_COMPLETED == easy->state) && !easy->msg) {
/* clear out the usage of the shared DNS cache */
easy->easy_handle->hostcache = NULL;
if(easy->easy_handle->dns.hostcachetype == HCACHE_MULTI) {
/* clear out the usage of the shared DNS cache */
easy->easy_handle->dns.hostcache = NULL;
easy->easy_handle->dns.hostcachetype = HCACHE_NONE;
}

/* now add a node to the Curl_message linked list with this info */
msg = (struct Curl_message *)malloc(sizeof(struct Curl_message));
Expand Down Expand Up @@ -975,8 +983,11 @@ CURLMcode curl_multi_cleanup(CURLM *multi_handle)
easy = multi->easy.next;
while(easy) {
nexteasy=easy->next;
/* clear out the usage of the shared DNS cache */
easy->easy_handle->hostcache = NULL;
if(easy->easy_handle->dns.hostcachetype == HCACHE_MULTI) {
/* clear out the usage of the shared DNS cache */
easy->easy_handle->dns.hostcache = NULL;
easy->easy_handle->dns.hostcachetype = HCACHE_NONE;
}
Curl_easy_addmulti(easy->easy_handle, NULL); /* clear the association */

if (easy->msg)
Expand Down
17 changes: 10 additions & 7 deletions lib/url.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -205,7 +205,7 @@ CURLcode Curl_close(struct SessionHandle *data)

if ( ! (data->share && data->share->hostcache) ) {
if ( !Curl_global_host_cache_use(data)) {
Curl_hash_destroy(data->hostcache);
Curl_hash_destroy(data->dns.hostcache);
}
}

Expand Down Expand Up @@ -1392,8 +1392,10 @@ CURLcode Curl_setopt(struct SessionHandle *data, CURLoption option,
if(data->share) {
Curl_share_lock(data, CURL_LOCK_DATA_SHARE, CURL_LOCK_ACCESS_SINGLE);

if(data->share->hostcache == data->hostcache)
data->hostcache = NULL;
if(data->dns.hostcachetype == HCACHE_SHARED) {
data->dns.hostcache = NULL;
data->dns.hostcachetype = HCACHE_NONE;
}

if(data->share->cookies == data->cookies)
data->cookies = NULL;
Expand All @@ -1413,11 +1415,12 @@ CURLcode Curl_setopt(struct SessionHandle *data, CURLoption option,
data->share->dirty++;

if(data->share->hostcache) {
/* use shared host cache, first free own one if any */
if(data->hostcache)
Curl_hash_destroy(data->hostcache);
/* use shared host cache, first free the private one if any */
if(data->dns.hostcachetype == HCACHE_PRIVATE)
Curl_hash_destroy(data->dns.hostcache);

data->hostcache = data->share->hostcache;
data->dns.hostcache = data->share->hostcache;
data->dns.hostcachetype = HCACHE_SHARED;
}
#if !defined(CURL_DISABLE_HTTP) && !defined(CURL_DISABLE_COOKIES)
if(data->share->cookies) {
Expand Down
26 changes: 18 additions & 8 deletions lib/urldata.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -1145,19 +1145,29 @@ struct UserDefined {
bool connect_only; /* make connection, let application use the socket */
};

struct Names {
struct curl_hash *hostcache;
enum {
HCACHE_NONE, /* not pointing to anything */
HCACHE_PRIVATE, /* points to our own */
HCACHE_GLOBAL, /* points to the (shrug) global one */
HCACHE_MULTI, /* points to a shared one in the multi handle */
HCACHE_SHARED /* points to a shared one in a shared object */
} hostcachetype;
};

/*
* In August 2001, this struct was redesigned and is since stricter than
* before. The 'connectdata' struct MUST have all the connection oriented
* stuff as we may now have several simultaneous connections and connection
* structs in memory.
* The 'connectdata' struct MUST have all the connection oriented stuff as we
* may have several simultaneous connections and connection structs in memory.
*
* From now on, the 'SessionHandle' must only contain data that is set once to
* go for many (perhaps) independent connections. Values that are generated or
* The 'struct UserDefined' must only contain data that is set once to go for
* many (perhaps) independent connections. Values that are generated or
* calculated internally for the "session handle" must be defined within the
* 'struct UrlState' instead. */
* 'struct UrlState' instead.
*/

struct SessionHandle {
struct curl_hash *hostcache;
struct Names dns;
struct Curl_multi *multi; /* if non-NULL, points to the multi handle
struct of which this "belongs" */
struct Curl_share *share; /* Share, handles global variable mutexing */
Expand Down

0 comments on commit ca319f6

Please sign in to comment.