[or-cvs] r6954: start restructuring dns to use priority queues for expiring (in tor/trunk: . doc src/or)
nickm at seul.org
nickm at seul.org
Mon Jul 31 18:00:19 UTC 2006
Author: nickm
Date: 2006-07-31 14:00:18 -0400 (Mon, 31 Jul 2006)
New Revision: 6954
Modified:
tor/trunk/
tor/trunk/doc/TODO
tor/trunk/src/or/dns.c
Log:
r6959 at Kushana: nickm | 2006-07-29 22:33:18 -0400
start restructuring dns to use priority queues for expiring entries.
Property changes on: tor/trunk
___________________________________________________________________
Name: svk:merge
- c95137ef-5f19-0410-b913-86e773d04f59:/tor/branches/eventdns:6958
c95137ef-5f19-0410-b913-86e773d04f59:/tor/branches/oo-connections:6950
+ c95137ef-5f19-0410-b913-86e773d04f59:/tor/branches/eventdns:6959
c95137ef-5f19-0410-b913-86e773d04f59:/tor/branches/oo-connections:6950
Modified: tor/trunk/doc/TODO
===================================================================
--- tor/trunk/doc/TODO 2006-07-31 17:59:37 UTC (rev 6953)
+++ tor/trunk/doc/TODO 2006-07-31 18:00:18 UTC (rev 6954)
@@ -73,9 +73,11 @@
- "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
Modified: tor/trunk/src/or/dns.c
===================================================================
--- tor/trunk/src/or/dns.c 2006-07-31 17:59:37 UTC (rev 6953)
+++ tor/trunk/src/or/dns.c 2006-07-31 18:00:18 UTC (rev 6954)
@@ -73,14 +73,12 @@
#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 @@
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)
@@ -213,12 +237,12 @@
_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. */
static void
@@ -229,11 +253,16 @@
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 @@
" 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 @@
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 @@
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 @@
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 @@
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 @@
{
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 @@
return;
}
tor_assert(resolve->pending_connections);
+ tor_assert(! resolve->expire);
/* mark all pending connections to fail */
log_debug(LD_EXIT,
@@ -573,37 +591,9 @@
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 @@
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 @@
/* 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 @@
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 @@
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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