* Implement POOF aka "Passive Observation of Failure"

git-svn-id: file:///home/lennart/svn/public/avahi/trunk@632 941a03a8-eaeb-0310-b9a0-b1bbd8fe43fe

diff --git a/avahi-core/cache.c b/avahi-core/cache.c
index 6332b1258ae644da6c84be962df33ff7a4ecdc62..23e9036f48beda9256b43bcd3d39530ac3168fcb 100644 (file)
--- a/avahi-core/cache.c
+++ b/avahi-core/cache.c
@@ -165,41 +165,48 @@ static void next_expiry(AvahiCache *c, AvahiCacheEntry *e, unsigned percent);
 static void elapse_func(AvahiTimeEvent *t, void *userdata) {
     AvahiCacheEntry *e = userdata;
 /*     char *txt; */
+    unsigned percent = 0;
     
     assert(t);
     assert(e);
 
 /*     txt = avahi_record_to_string(e->record); */
 
-    if (e->state == AVAHI_CACHE_FINAL) {
-        remove_entry(e->cache, e);
+    switch (e->state) {
+
+        case AVAHI_CACHE_EXPIRY_FINAL:
+        case AVAHI_CACHE_POOF_FINAL:
+        case AVAHI_CACHE_GOODBYE_FINAL:
+        case AVAHI_CACHE_REPLACE_FINAL:
+
+            remove_entry(e->cache, e);
+            
+            e = NULL;
 /*         avahi_log_debug("Removing entry from cache due to expiration (%s)", txt); */
-    } else {
-        unsigned percent = 0;
-    
-        switch (e->state) {
-            case AVAHI_CACHE_VALID:
-                e->state = AVAHI_CACHE_EXPIRY1;
-                percent = 85;
-                break;
-                
-            case AVAHI_CACHE_EXPIRY1:
-                e->state = AVAHI_CACHE_EXPIRY2;
-                percent = 90;
-                break;
-            case AVAHI_CACHE_EXPIRY2:
-                e->state = AVAHI_CACHE_EXPIRY3;
-                percent = 95;
-                break;
+            break;
+            
+        case AVAHI_CACHE_VALID:
+        case AVAHI_CACHE_POOF:
+            e->state = AVAHI_CACHE_EXPIRY1;
+            percent = 85;
+            break;
                 
-            case AVAHI_CACHE_EXPIRY3:
-                e->state = AVAHI_CACHE_FINAL;
-                percent = 100;
-                break;
+        case AVAHI_CACHE_EXPIRY1:
+            e->state = AVAHI_CACHE_EXPIRY2;
+            percent = 90;
+            break;
+        case AVAHI_CACHE_EXPIRY2:
+            e->state = AVAHI_CACHE_EXPIRY3;
+            percent = 95;
+            break;
+            
+        case AVAHI_CACHE_EXPIRY3:
+            e->state = AVAHI_CACHE_EXPIRY_FINAL;
+            percent = 100;
+            break;
+    }
 
-            default:
-                ;
-        }
+    if (e) {
 
         assert(percent > 0);
 
@@ -208,9 +215,10 @@ static void elapse_func(AvahiTimeEvent *t, void *userdata) {
 /*             avahi_log_debug("Requesting cache entry update at %i%% for %s.", percent, txt);   */
             avahi_interface_post_query(e->cache->interface, e->record->key, 1);
         }
-
+        
         /* Check again later */
         next_expiry(e->cache, e, percent);
+        
     }
 
 /*     avahi_free(txt); */
@@ -248,11 +256,11 @@ static void next_expiry(AvahiCache *c, AvahiCacheEntry *e, unsigned percent) {
     update_time_event(c, e);
 }
 
-static void expire_in_one_second(AvahiCache *c, AvahiCacheEntry *e) {
+static void expire_in_one_second(AvahiCache *c, AvahiCacheEntry *e, AvahiCacheEntryState state) {
     assert(c);
     assert(e);
     
-    e->state = AVAHI_CACHE_FINAL;
+    e->state = state;
     gettimeofday(&e->expiry, NULL);
     avahi_timeval_add(&e->expiry, 1000000); /* 1s */
     update_time_event(c, e);
@@ -272,7 +280,7 @@ void avahi_cache_update(AvahiCache *c, AvahiRecord *r, int cache_flush, const Av
         AvahiCacheEntry *e;
 
         if ((e = avahi_cache_lookup_record(c, r)))
-            expire_in_one_second(c, e);
+            expire_in_one_second(c, e, AVAHI_CACHE_GOODBYE_FINAL);
 
     } else {
         AvahiCacheEntry *e = NULL, *first;
@@ -293,7 +301,7 @@ void avahi_cache_update(AvahiCache *c, AvahiRecord *r, int cache_flush, const Av
                     t = avahi_timeval_diff(&now, &e->timestamp);
 
                     if (t > 1000000)
-                        expire_in_one_second(c, e);
+                        expire_in_one_second(c, e, AVAHI_CACHE_REPLACE_FINAL);
                 }
             }
                 
@@ -421,3 +429,70 @@ void avahi_cache_flush(AvahiCache *c) {
     while (c->entries)
         remove_entry(c, c->entries);
 }
+
+/*** Passive observation of failure ***/
+
+static void* start_poof_callback(AvahiCache *c, AvahiKey *pattern, AvahiCacheEntry *e, void *userdata) {
+    AvahiAddress *a = userdata;
+
+    assert(c);
+    assert(pattern);
+    assert(e);
+    assert(a);
+    
+    switch (e->state) {
+        case AVAHI_CACHE_VALID:
+
+            /* The entry was perfectly valid till, now, so let's enter
+             * POOF mode */
+
+            e->state = AVAHI_CACHE_POOF;
+            e->poof_address = *a;
+            
+            break;
+
+        case AVAHI_CACHE_POOF:
+
+            /* This is the second time we got no response, so let's
+             * fucking remove this entry. */
+            
+            expire_in_one_second(c, e, AVAHI_CACHE_POOF_FINAL);
+            break;
+
+        default:
+            ;
+    }
+    
+    return NULL;
+}
+
+void avahi_cache_start_poof(AvahiCache *c, AvahiKey *key, const AvahiAddress *a) {
+    assert(c);
+    assert(key);
+
+    avahi_cache_walk(c, key, start_poof_callback, a);
+}
+
+void avahi_cache_stop_poof(AvahiCache *c, AvahiRecord *record, const AvahiAddress *a) {
+    AvahiCacheEntry *e;
+
+    assert(c);
+    assert(record);
+    assert(a);
+
+    if (!(e = avahi_cache_lookup_record(c, record)))
+        return;
+
+    /* This function is called for each response suppression
+       record. If the matching cache entry is in POOF state and the
+       query address is the same, we put it back into valid mode */
+
+    if (e->state == AVAHI_CACHE_POOF || e->state == AVAHI_CACHE_POOF_FINAL)
+        if (avahi_address_cmp(a, &e->poof_address) == 0) {
+            e->state = AVAHI_CACHE_VALID;
+            next_expiry(c, e, 80);
+        }
+}
+
+
+

diff --git a/avahi-core/cache.h b/avahi-core/cache.h
index fa723e9d68125c1d165c0a978bac03fce91a75a8..bd1cd6c5258ac5dcba0e690a71ec8ca2c5cd0112 100644 (file)
--- a/avahi-core/cache.h
+++ b/avahi-core/cache.h
@@ -35,7 +35,11 @@ typedef enum {
     AVAHI_CACHE_EXPIRY1,
     AVAHI_CACHE_EXPIRY2,
     AVAHI_CACHE_EXPIRY3,
-    AVAHI_CACHE_FINAL
+    AVAHI_CACHE_EXPIRY_FINAL,
+    AVAHI_CACHE_POOF,       /* Passive observation of failure */
+    AVAHI_CACHE_POOF_FINAL,
+    AVAHI_CACHE_GOODBYE_FINAL,
+    AVAHI_CACHE_REPLACE_FINAL
 } AvahiCacheEntryState;
 
 typedef struct AvahiCacheEntry AvahiCacheEntry;
@@ -52,6 +56,8 @@ struct AvahiCacheEntry {
     AvahiCacheEntryState state;
     AvahiTimeEvent *time_event;
 
+    AvahiAddress poof_address;
+
     AVAHI_LLIST_FIELDS(AvahiCacheEntry, by_key);
     AVAHI_LLIST_FIELDS(AvahiCacheEntry, entry);
 };
@@ -83,6 +89,13 @@ void* avahi_cache_walk(AvahiCache *c, AvahiKey *pattern, AvahiCacheWalkCallback
 
 int avahi_cache_entry_half_ttl(AvahiCache *c, AvahiCacheEntry *e);
 
+/** Start the "Passive observation of Failure" algorithm for all
+ * records of the specified key. The specified address is  */
+void avahi_cache_start_poof(AvahiCache *c, AvahiKey *key, const AvahiAddress *a);
+
+/* Stop a previously started POOF algorithm for a record. (Used for response suppresions records */    
+void avahi_cache_stop_poof(AvahiCache *c, AvahiRecord *record, const AvahiAddress *a);
+
 void avahi_cache_flush(AvahiCache *c);
 
 #endif

diff --git a/avahi-core/server.c b/avahi-core/server.c
index 27142982f7273b2b7fb13b8b5194c04f312b5530..dc63c67da75d1dc0eb569dcf62686ed492dabe69 100644 (file)
--- a/avahi-core/server.c
+++ b/avahi-core/server.c
@@ -613,8 +613,10 @@ static void handle_query_packet(AvahiServer *s, AvahiDnsPacket *p, AvahiInterfac
             goto fail;
         }
 
-        if (!legacy_unicast && !from_local_iface)
+        if (!legacy_unicast && !from_local_iface) {
             reflect_query(s, i, key);
+            avahi_cache_start_poof(i->cache, key, a);
+        }
 
         if (avahi_dns_packet_get_field(p, AVAHI_DNS_FIELD_ANCOUNT) == 0 &&
             !(avahi_dns_packet_get_field(p, AVAHI_DNS_FIELD_FLAGS) & AVAHI_DNS_FLAG_TC))
@@ -641,6 +643,7 @@ static void handle_query_packet(AvahiServer *s, AvahiDnsPacket *p, AvahiInterfac
             if (handle_conflict(s, i, record, unique, a)) {
                 avahi_response_scheduler_suppress(i->response_scheduler, record, a);
                 avahi_record_list_drop(s->record_list, record);
+                avahi_cache_stop_poof(i->cache, record, a);
             }
             
             avahi_record_unref(record);