Commit 46574319 authored by Nick Mathewson's avatar Nick Mathewson 🏃
Browse files

r6959@Kushana: nickm | 2006-07-29 22:33:18 -0400

 start restructuring dns to use priority queues for expiring entries.


svn:r6954
parent 2fe537c5
......@@ -73,9 +73,11 @@ N . Improve memory usage on tight-memory machines.
- "bandwidth classes", for incoming vs initiated-here conns.
o Asynchronous DNS
. and test it
- Make it work on windows.
- make it the default on platforms where it works
. And test it
. Make it work on windows.
o Implement
- Test
- Make it the default on platforms where it works
- Security improvements
- Directory guards
......
......@@ -73,14 +73,12 @@ typedef struct cached_resolve_t {
#define CACHE_STATE_PENDING 0
#define CACHE_STATE_VALID 1
#define CACHE_STATE_FAILED 2
uint32_t expire; /**< Remove items from cache after this time. */
time_t expire; /**< Remove items from cache after this time. */
uint32_t ttl; /**< What TTL did the nameserver tell us? */
pending_connection_t *pending_connections;
struct cached_resolve_t *next;
} cached_resolve_t;
static void purge_expired_resolves(uint32_t now);
static void dns_purge_resolve(cached_resolve_t *resolve);
static void dns_found_answer(const char *address, uint32_t addr, char outcome,
uint32_t ttl);
static void send_resolved_cell(edge_connection_t *conn, uint8_t answer_type);
......@@ -202,6 +200,32 @@ _free_cached_resolve(cached_resolve_t *r)
tor_free(r);
}
/** DODDOC */
static int
_compare_cached_resolves_by_expiry(void *_a, void *_b)
{
cached_resolve_t *a = _a, *b = _b;
if (a->expire < b->expire)
return -1;
else if (a->expire == b->expire)
return 0;
else
return 1;
}
/** Linked list of resolved addresses, oldest to newest. DOCDOC*/
static smartlist_t *cached_resolve_pqueue = NULL;
static void
set_expiry(cached_resolve_t *resolve, time_t expires)
{
tor_assert(resolve && resolve->expire == 0);
resolve->expire = expires;
smartlist_pqueue_add(cached_resolve_pqueue,
_compare_cached_resolves_by_expiry,
resolve);
}
/** Free all storage held in the DNS cache */
void
dns_free_all(void)
......@@ -213,11 +237,11 @@ dns_free_all(void)
_free_cached_resolve(item);
}
HT_CLEAR(cache_map, &cache_root);
smartlist_free(cached_resolve_pqueue);
cached_resolve_pqueue = NULL;
}
/** Linked list of resolved addresses, oldest to newest. */
static cached_resolve_t *oldest_cached_resolve = NULL;
static cached_resolve_t *newest_cached_resolve = NULL;
/** Remove every cached_resolve whose <b>expire</b> time is before <b>now</b>
* from the cache. */
......@@ -229,11 +253,16 @@ purge_expired_resolves(uint32_t now)
edge_connection_t *pendconn;
assert_cache_ok();
/* this is fast because the linked list
* oldest_cached_resolve is ordered by when they came in.
*/
while (oldest_cached_resolve && (oldest_cached_resolve->expire < now)) {
resolve = oldest_cached_resolve;
if (!cached_resolve_pqueue)
return;
while (smartlist_len(cached_resolve_pqueue)) {
resolve = smartlist_get(cached_resolve_pqueue, 0);
if (resolve->expire > now)
break;
smartlist_pqueue_pop(cached_resolve_pqueue,
_compare_cached_resolves_by_expiry);
log_debug(LD_EXIT,
"Forgetting old cached resolve (address %s, expires %lu)",
escaped_safe_str(resolve->address),
......@@ -244,6 +273,7 @@ purge_expired_resolves(uint32_t now)
" Forgot to cull it?", escaped_safe_str(resolve->address));
tor_fragile_assert();
}
if (resolve->pending_connections) {
log_debug(LD_EXIT,
"Closing pending connections on expiring DNS resolve!");
......@@ -261,18 +291,19 @@ purge_expired_resolves(uint32_t now)
tor_free(pend);
}
}
oldest_cached_resolve = resolve->next;
if (!oldest_cached_resolve) /* if there are no more, */
newest_cached_resolve = NULL; /* then make sure the list's tail knows
* that too */
removed = HT_REMOVE(cache_map, &cache_root, resolve);
if (removed != resolve) {
log_notice(LD_EXIT, "Removed is %p, resolve is %p.", removed, resolve);
tor_assert(removed == resolve);
log_err(LD_BUG, "The expired resolve we purged didn't match any in"
" the cache. Tried to purge %s; instead got %s.",
resolve->address, removed ? removed->address : "NULL");
}
tor_assert(removed == resolve);
resolve->magic = 0xF0BBF0BB;
tor_free(resolve);
}
assert_cache_ok();
}
......@@ -316,22 +347,6 @@ send_resolved_cell(edge_connection_t *conn, uint8_t answer_type)
conn->cpath_layer);
}
/** Link <b>r</b> into the hash table of address-to-result mappings, and add it
* to the linked list of resolves-by-age. */
static void
insert_resolve(cached_resolve_t *r)
{
/* add us to the linked list of resolves */
if (!oldest_cached_resolve) {
oldest_cached_resolve = r;
} else {
newest_cached_resolve->next = r;
}
newest_cached_resolve = r;
HT_INSERT(cache_map, &cache_root, r);
}
/** See if we have a cache entry for <b>exitconn</b>-\>address. if so,
* if resolve valid, put it into <b>exitconn</b>-\>addr and return 1.
* If resolve failed, unlink exitconn if needed, free it, and return -1.
......@@ -418,7 +433,6 @@ dns_resolve(edge_connection_t *exitconn)
resolve = tor_malloc_zero(sizeof(cached_resolve_t));
resolve->magic = CACHED_RESOLVE_MAGIC;
resolve->state = CACHE_STATE_PENDING;
resolve->expire = now + DEFAULT_DNS_TTL; /* this will get replaced. */
strlcpy(resolve->address, exitconn->_base.address, sizeof(resolve->address));
/* add us to the pending list */
......@@ -427,7 +441,10 @@ dns_resolve(edge_connection_t *exitconn)
resolve->pending_connections = pending_connection;
exitconn->_base.state = EXIT_CONN_STATE_RESOLVING;
insert_resolve(resolve);
/* Add this resolve to the cache. It has no expiry yet, so it doesn't
* go into the priority queue. */
HT_INSERT(cache_map, &cache_root, resolve);
log_debug(LD_EXIT,"Assigning question %s to dnsworker.",
escaped_safe_str(exitconn->_base.address));
assert_cache_ok();
......@@ -528,7 +545,7 @@ dns_cancel_pending_resolve(char *address)
{
pending_connection_t *pend;
cached_resolve_t search;
cached_resolve_t *resolve;
cached_resolve_t *resolve, *tmp;
edge_connection_t *pendconn;
circuit_t *circ;
......@@ -550,6 +567,7 @@ dns_cancel_pending_resolve(char *address)
return;
}
tor_assert(resolve->pending_connections);
tor_assert(! resolve->expire);
/* mark all pending connections to fail */
log_debug(LD_EXIT,
......@@ -573,37 +591,9 @@ dns_cancel_pending_resolve(char *address)
tor_free(pend);
}
dns_purge_resolve(resolve);
}
/** Remove <b>resolve</b> from the cache.
*/
static void
dns_purge_resolve(cached_resolve_t *resolve)
{
cached_resolve_t *tmp;
/* remove resolve from the linked list */
if (resolve == oldest_cached_resolve) {
oldest_cached_resolve = resolve->next;
if (oldest_cached_resolve == NULL)
newest_cached_resolve = NULL;
} else {
/* FFFF make it a doubly linked list if this becomes too slow */
for (tmp=oldest_cached_resolve; tmp && tmp->next != resolve; tmp=tmp->next)
;
tor_assert(tmp); /* it's got to be in the list, or we screwed up somewhere
* else */
tmp->next = resolve->next; /* unlink it */
if (newest_cached_resolve == resolve)
newest_cached_resolve = tmp;
}
/* remove resolve from the map */
tmp = HT_REMOVE(cache_map, &cache_root, resolve);
tor_assert(tmp == resolve);
resolve->magic = 0xAAAAAAAA;
resolve->magic = 0xABABABAB;
tor_free(resolve);
}
......@@ -638,10 +628,10 @@ dns_found_answer(const char *address, uint32_t addr, char outcome,
CACHE_STATE_VALID : CACHE_STATE_FAILED;
strlcpy(resolve->address, address, sizeof(resolve->address));
resolve->addr = addr;
resolve->expire = time(NULL) + dns_get_expiry_ttl(ttl);
resolve->ttl = ttl;
assert_resolve_ok(resolve);
insert_resolve(resolve);
HT_INSERT(cache_map, &cache_root, resolve);
set_expiry(resolve, time(NULL) + dns_get_expiry_ttl(ttl));
return;
}
assert_resolve_ok(resolve);
......@@ -661,7 +651,6 @@ dns_found_answer(const char *address, uint32_t addr, char outcome,
/* tor_assert(resolve->state == CACHE_STATE_PENDING); */
resolve->addr = addr;
resolve->expire = time(NULL) + dns_get_expiry_ttl(ttl);
resolve->ttl = ttl;
if (outcome == DNS_RESOLVE_SUCCEEDED)
resolve->state = CACHE_STATE_VALID;
......@@ -724,7 +713,12 @@ dns_found_answer(const char *address, uint32_t addr, char outcome,
assert_cache_ok();
if (outcome == DNS_RESOLVE_FAILED_TRANSIENT) { /* remove from cache */
dns_purge_resolve(resolve);
cached_resolve_t *tmp = HT_REMOVE(cache_map, &cache_root, resolve);
tor_assert(tmp == resolve);
resolve->magic = 0xAAAAAAAA;
tor_free(resolve);
} else {
set_expiry(resolve, time(NULL) + dns_get_expiry_ttl(ttl));
}
assert_cache_ok();
......@@ -1216,7 +1210,6 @@ assert_resolve_ok(cached_resolve_t *resolve)
tor_assert(resolve);
tor_assert(resolve->magic == CACHED_RESOLVE_MAGIC);
tor_assert(strlen(resolve->address) < MAX_ADDRESSLEN);
tor_assert(! resolve->next || resolve->next->magic == CACHED_RESOLVE_MAGIC);
}
static void
......
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