[Minor] DNS: Remove unused SERVFAIL cache

The fails_cache feature (introduced in e3057e5e4, Oct 2019) was undocumented,
disabled by default, never exercised in tests, and never adopted in
practice — including by the single deployment it was originally written for.

Negative DNS caching, if ever needed, belongs in librdns.

diff --git a/src/libserver/dns.c b/src/libserver/dns.c
index ad5cf8e759eaf1cbede52ef335aba942a6f0d674..92e7f6b156dace469537579f07ebbdbd48cde075 100644 (file)
--- a/src/libserver/dns.c
+++ b/src/libserver/dns.c
@@ -62,12 +62,6 @@ struct rspamd_dns_request_ud {
        struct rdns_reply *reply;
 };
 
-struct rspamd_dns_fail_cache_entry {
-       const char *name;
-       int32_t namelen;
-       enum rdns_request_type type;
-};
-
 static const int8_t ascii_dns_table[128] = {
        -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
        -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
@@ -83,30 +77,6 @@ static const int8_t ascii_dns_table[128] = {
        -1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
        1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, -1, -1, -1, -1, -1};
 
-static unsigned int
-rspamd_dns_fail_hash(gconstpointer ptr)
-{
-       struct rspamd_dns_fail_cache_entry *elt =
-               (struct rspamd_dns_fail_cache_entry *) ptr;
-
-       /* We don't care about type when doing hashing */
-       return rspamd_cryptobox_fast_hash(elt->name, elt->namelen,
-                                                                         rspamd_hash_seed());
-}
-
-static gboolean
-rspamd_dns_fail_equal(gconstpointer p1, gconstpointer p2)
-{
-       struct rspamd_dns_fail_cache_entry *e1 = (struct rspamd_dns_fail_cache_entry *) p1,
-                                                                          *e2 = (struct rspamd_dns_fail_cache_entry *) p2;
-
-       if (e1->type == e2->type && e1->namelen == e2->namelen) {
-               return memcmp(e1->name, e2->name, e1->namelen) == 0;
-       }
-
-       return FALSE;
-}
-
 static void
 rspamd_dns_fin_cb(gpointer arg)
 {
@@ -152,32 +122,6 @@ rspamd_dns_callback(struct rdns_reply *reply, gpointer ud)
 
 
        if (reqdata->session) {
-               if (reply->code == RDNS_RC_SERVFAIL &&
-                       reqdata->task &&
-                       reqdata->task->resolver->fails_cache) {
-
-                       /* Add to cache... */
-                       const char *name = reqdata->req->requested_names[0].name;
-                       char *target;
-                       gsize namelen;
-                       struct rspamd_dns_fail_cache_entry *nentry;
-
-                       /* Allocate in a single entry to allow further free in a single call */
-                       namelen = strlen(name);
-                       nentry = g_malloc(sizeof(nentry) + namelen + 1);
-                       target = ((char *) nentry) + sizeof(nentry);
-                       rspamd_strlcpy(target, name, namelen + 1);
-                       nentry->type = reqdata->req->requested_names[0].type;
-                       nentry->name = target;
-                       nentry->namelen = namelen;
-
-                       /* Rdns request is retained there */
-                       rspamd_lru_hash_insert(reqdata->task->resolver->fails_cache,
-                                                                  nentry, rdns_request_retain(reply->request),
-                                                                  reqdata->task->task_timestamp,
-                                                                  reqdata->task->resolver->fails_cache_time);
-               }
-
                /*
                 * Ref event to avoid double unref by
                 * event removing
@@ -292,31 +236,6 @@ rspamd_dns_resolver_request(struct rspamd_dns_resolver *resolver,
        return reqdata;
 }
 
-struct rspamd_dns_cached_delayed_cbdata {
-       struct rspamd_task *task;
-       dns_callback_type cb;
-       gpointer ud;
-       ev_timer tm;
-       struct rdns_request *req;
-};
-
-static void
-rspamd_fail_cache_cb(EV_P_ ev_timer *w, int revents)
-{
-       struct rspamd_dns_cached_delayed_cbdata *cbd =
-               (struct rspamd_dns_cached_delayed_cbdata *) w->data;
-       struct rdns_reply fake_reply;
-
-       ev_timer_stop(EV_A_ w);
-       memset(&fake_reply, 0, sizeof(fake_reply));
-       fake_reply.code = RDNS_RC_SERVFAIL;
-       fake_reply.request = cbd->req;
-       fake_reply.resolver = cbd->req->resolver;
-       fake_reply.requested_name = cbd->req->requested_names[0].name;
-       cbd->cb(&fake_reply, cbd->ud);
-       rdns_request_release(cbd->req);
-}
-
 static gboolean
 make_dns_request_task_common(struct rspamd_task *task,
                                                         dns_callback_type cb,
@@ -331,35 +250,6 @@ make_dns_request_task_common(struct rspamd_task *task,
                return FALSE;
        }
 
-       if (task->resolver->fails_cache) {
-               /* Search in failures cache */
-               struct rspamd_dns_fail_cache_entry search;
-               struct rdns_request *req;
-
-               search.name = name;
-               search.namelen = strlen(name);
-               search.type = type;
-
-               if ((req = rspamd_lru_hash_lookup(task->resolver->fails_cache,
-                                                                                 &search, task->task_timestamp)) != NULL) {
-                       /*
-                        * We need to reply with SERVFAIL again to the API, so add a special
-                        * timer, uh-oh, and fire it
-                        */
-                       struct rspamd_dns_cached_delayed_cbdata *cbd =
-                               rspamd_mempool_alloc0(task->task_pool, sizeof(*cbd));
-
-                       ev_timer_init(&cbd->tm, rspamd_fail_cache_cb, 0.0, 0.0);
-                       cbd->task = task;
-                       cbd->cb = cb;
-                       cbd->ud = ud;
-                       cbd->req = rdns_request_retain(req);
-                       cbd->tm.data = cbd;
-
-                       return TRUE;
-               }
-       }
-
        reqdata = rspamd_dns_resolver_request(
                task->resolver, task->s, task->task_pool, cb, ud,
                type, name);
@@ -809,9 +699,7 @@ rspamd_dns_resolver_config_ucl(struct rspamd_config *cfg,
                                                           struct rspamd_dns_resolver *dns_resolver,
                                                           const ucl_object_t *dns_section)
 {
-       const ucl_object_t *fake_replies, *fails_cache_size, *fails_cache_time,
-               *hosts;
-       static const ev_tstamp default_fails_cache_time = 10.0;
+       const ucl_object_t *fake_replies, *hosts;
 
        /* Process fake replies */
        fake_replies = ucl_object_lookup_any(dns_section, "fake_records",
@@ -854,22 +742,6 @@ rspamd_dns_resolver_config_ucl(struct rspamd_config *cfg,
                msg_err_config("invalid type for hosts parameter: %s",
                                           ucl_object_type_to_string(ucl_object_type(hosts)));
        }
-
-       fails_cache_size = ucl_object_lookup(dns_section, "fails_cache_size");
-       if (fails_cache_size && ucl_object_type(fails_cache_size) == UCL_INT) {
-
-               dns_resolver->fails_cache_time = default_fails_cache_time;
-               fails_cache_time = ucl_object_lookup(dns_section, "fails_cache_time");
-
-               if (fails_cache_time) {
-                       dns_resolver->fails_cache_time = ucl_object_todouble(fails_cache_time);
-               }
-
-               dns_resolver->fails_cache = rspamd_lru_hash_new_full(
-                       ucl_object_toint(fails_cache_size),
-                       g_free, (GDestroyNotify) rdns_request_release,
-                       rspamd_dns_fail_hash, rspamd_dns_fail_equal);
-       }
 }
 
 struct rspamd_dns_resolver *
@@ -988,10 +860,6 @@ void rspamd_dns_resolver_deinit(struct rspamd_dns_resolver *resolver)
                        rspamd_upstreams_destroy(resolver->ups);
                }
 
-               if (resolver->fails_cache) {
-                       rspamd_lru_hash_destroy(resolver->fails_cache);
-               }
-
                uidna_close(resolver->uidna);
 
                g_free(resolver);

diff --git a/src/libserver/dns.h b/src/libserver/dns.h
index 8485ee214c29eff208877d34e41d0beb33ad204a..0fa4f0e825777961422a8ea06ef2832c474d1870 100644 (file)
--- a/src/libserver/dns.h
+++ b/src/libserver/dns.h
@@ -36,9 +36,7 @@ struct event_loop;
 struct rspamd_dns_resolver {
        struct rdns_resolver *r;
        struct ev_loop *event_loop;
-       rspamd_lru_hash_t *fails_cache;
        void *uidna;
-       double fails_cache_time;
        struct upstream_list *ups;
        struct rspamd_config *cfg;
        double request_timeout;