multithreaded supernode name resolution (#645)

configure.seed

@@ -81,6 +81,13 @@ if test x$cap != x; then
   AC_DEFINE([HAVE_LIBCAP],[1],[Support for linux capabilities])
 fi
 
+AC_CHECK_LIB([pthread], [pthread_mutex_trylock], pthread=true)
+if test x$pthread != x; then
+  LDFLAGS="${LDFLAGS} -pthread"
+  AC_DEFINE([HAVE_PTHREAD],[],[pthread is present])
+fi
+
+
 MACHINE=`uname -m`
 SYSTEM=`uname -s`
 

include/n2n_define.h

@@ -62,6 +62,9 @@
 
 #define SORT_COMMUNITIES_INTERVAL        90 /* sec. until supernode sorts communities' hash list again */
 
+#define N2N_RESOLVE_INTERVAL            300 /* seconds until edge and supernode try to resolve supernode names again */
+#define N2N_RESOLVE_CHECK_INTERVAL       30 /* seconds until main loop checking in on changes from resolver thread */
+
 #define ETH_FRAMESIZE 14
 #define IP4_SRCOFFSET 12
 #define IP4_DSTOFFSET 16

include/n2n_typedefs.h

@@ -586,6 +586,32 @@ typedef struct n2n_trans_op {
 
 /* *************************************************** */
 
+
+typedef struct n2n_resolve_ip_sock {
+    char          *org_ip;            /* pointer to original ip/named address string (used read only) */
+    n2n_sock_t    sock;               /* resolved socket */
+    n2n_sock_t    *org_sock;          /* pointer to original socket where 'sock' gets copied to from time to time */
+    int           error_code;         /* result of last resolution attempt */
+
+    UT_hash_handle hh;                /* makes this structure hashable */
+} n2n_resolve_ip_sock_t;
+
+
+// structure to hold resolver thread's parameters
+typedef struct n2n_resolve_parameter {
+    n2n_resolve_ip_sock_t   *list;        /* pointer to list of to be resolved nodes */
+    uint8_t                 changed;      /* indicates a change */
+#ifdef HAVE_PTHREAD
+    pthread_t               id;           /* thread id */
+    pthread_mutex_t         access;       /* mutex for shared access */
+#endif
+    time_t                  last_checked; /* last time the resolver completed */
+} n2n_resolve_parameter_t;
+
+
+/* *************************************************** */
+
+
 typedef struct n2n_edge_conf {
     struct peer_info         *supernodes;            /**< List of supernodes */
     n2n_route_t              *routes;                /**< Networks to route through n2n */
@@ -673,6 +699,8 @@ struct n2n_edge {
 
     struct n2n_edge_stats            stats;                              /**< Statistics */
 
+    n2n_resolve_parameter_t          *resolve_parameter;                 /**< Pointer to name resolver's parameter block */
+
     n2n_tuntap_priv_config_t         tuntap_priv_conf;                   /**< Tuntap config */
 
     network_traffic_filter_t         *network_traffic_filter;
@@ -773,6 +801,7 @@ typedef struct n2n_sn {
     struct sn_community                    *federation;
     n2n_private_public_key_t               private_key;       /* private federation key derived from federation name */
     n2n_auth_t                             auth;
+    n2n_resolve_parameter_t                *resolve_parameter;/*Pointer to name resolver's parameter block */
 } n2n_sn_t;
 
 

src/edge.c

@@ -50,6 +50,7 @@ int supernode_disconnect (n2n_edge_t *eee);
 int fetch_and_eventually_process_data (n2n_edge_t *eee, SOCKET sock,
                                        uint8_t *pktbuf, uint16_t *expected, uint16_t *position,
                                        time_t now);
+int resolve_create_thread (n2n_resolve_parameter_t **param, struct peer_info *sn_list);
 
 /* ***************************************************** */
 
@@ -1226,6 +1227,10 @@ int main (int argc, char* argv[]) {
         traceEvent(TRACE_WARNING, "Running as root is discouraged, check out the -u/-g options");
 #endif
 
+    if(resolve_create_thread(&(eee->resolve_parameter), eee->conf.supernodes) == 0) {
+         traceEvent(TRACE_NORMAL, "Successfully created resolver thread");
+    }
+
 #ifdef __linux__
     signal(SIGPIPE, SIG_IGN);
     signal(SIGTERM, term_handler);

src/edge_utils.c

@@ -26,6 +26,9 @@ static HEAP_ALLOC (wrkmem, LZO1X_1_MEM_COMPRESS);
 
 /* ************************************** */
 
+int resolve_check (n2n_resolve_parameter_t *param, time_t now);
+int resolve_cancel_thread (n2n_resolve_parameter_t *param);
+
 static const char * supernode_ip (const n2n_edge_t * eee);
 static void send_register (n2n_edge_t *eee, const n2n_sock_t *remote_peer, const n2n_mac_t peer_mac);
 
@@ -1458,12 +1461,16 @@ void update_supernode_reg (n2n_edge_t * eee, time_t now) {
         --(eee->sup_attempts);
     }
 
+#ifndef HAVE_PTHREAD
     if(supernode2sock(&(eee->curr_sn->sock), eee->curr_sn->ip_addr) == 0) {
+#endif
         traceEvent(TRACE_INFO, "Registering with supernode [%s][number of supernodes %d][attempts left %u]",
                    supernode_ip(eee), HASH_COUNT(eee->conf.supernodes), (unsigned int)eee->sup_attempts);
 
         send_register_super(eee);
+#ifndef HAVE_PTHREAD
     }
+#endif
 
     register_with_local_peers(eee);
 
@@ -2952,6 +2959,8 @@ int run_edge_loop (n2n_edge_t *eee, int *keep_running) {
 
         sort_supernodes(eee, now);
 
+        resolve_check(eee->resolve_parameter, now);
+
         if(eee->cb.main_loop_period)
             eee->cb.main_loop_period(eee, now);
 
@@ -2973,6 +2982,8 @@ int run_edge_loop (n2n_edge_t *eee, int *keep_running) {
 /** Deinitialise the edge and deallocate any owned memory. */
 void edge_term (n2n_edge_t * eee) {
 
+    resolve_cancel_thread(eee->resolve_parameter);
+
     if(eee->sock >= 0)
         closesocket(eee->sock);
 

src/n2n.c

@@ -256,8 +256,6 @@ char * macaddr_str (macstr_t buf,
 
 /** Resolve the supernode IP address.
  *
- *  REVISIT: This is a really bad idea. The edge will block completely while the
- *  hostname resolution is performed. This could take 15 seconds.
  */
 int supernode2sock (n2n_sock_t *sn, const n2n_sn_name_t addrIn) {
 
@@ -278,7 +276,7 @@ int supernode2sock (n2n_sock_t * sn, const n2n_sn_name_t addrIn) {
         if(supernode_port) {
             sn->port = atoi(supernode_port);
         } else {
-            traceEvent(TRACE_WARNING, "Bad supernode parameter (-l <host:port>) %s %s:%s",
+            traceEvent(TRACE_WARNING, "supernode2sock sees malformed supernode parameter (-l <host:port>) %s %s:%s",
                        addr, supernode_host, supernode_port);
         }
 
@@ -296,27 +294,141 @@ int supernode2sock (n2n_sock_t * sn, const n2n_sn_name_t addrIn) {
                 sn->family = AF_INET;
             } else {
                 /* Should only return IPv4 addresses due to aihints. */
-                traceEvent(TRACE_WARNING, "Failed to resolve supernode IPv4 address for %s", supernode_host);
+                traceEvent(TRACE_WARNING, "supernode2sock fails to resolve supernode IPv4 address for %s", supernode_host);
                 rv = -1;
             }
 
             freeaddrinfo(ainfo); /* free everything allocated by getaddrinfo(). */
             ainfo = NULL;
         } else {
-            traceEvent(TRACE_WARNING, "Failed to resolve supernode host %s, %d: %s", supernode_host, nameerr, gai_strerror(nameerr));
+            traceEvent(TRACE_WARNING, "supernode2sock fails to resolve supernode host %s, %d: %s", supernode_host, nameerr, gai_strerror(nameerr));
             rv = -2;
         }
 
     } else {
-        traceEvent(TRACE_WARNING, "Wrong supernode parameter (-l <host:port>)");
+        traceEvent(TRACE_WARNING, "supernode2sock sees wrong supernode parameter (-l <host:port>)");
         rv = -3;
     }
 
     return(rv);
 }
 
+
+void *resolve_thread (void *p) {
+
+#ifdef HAVE_PTHREAD
+    n2n_resolve_parameter_t *param = (n2n_resolve_parameter_t*)p;
+    n2n_resolve_ip_sock_t   *entry, *tmp_entry;
+
+    while(1) {
+        sleep(N2N_RESOLVE_INTERVAL);
+
+        // lock access
+        pthread_mutex_lock(&param->access);
+
+        HASH_ITER(hh, param->list, entry, tmp_entry) {
+            // resolve
+            entry->error_code = supernode2sock(&entry->sock, entry->org_ip);
+            // if socket changed and no error
+            if(!sock_equal(&entry->sock, entry->org_sock)
+              && (!entry->error_code)) {
+                // flag the change
+                param->changed = 1;
+            }
+        }
+
+        // unlock access
+        pthread_mutex_unlock(&param->access);
+    }
+#endif
+}
+
+
+int resolve_create_thread (n2n_resolve_parameter_t **param, struct peer_info *sn_list) {
+
+#ifdef HAVE_PTHREAD
+    struct peer_info        *sn, *tmp_sn;
+    n2n_resolve_ip_sock_t   *entry;
+    int                     ret;
+
+    // create parameter structure
+    *param = (n2n_resolve_parameter_t*)calloc(1, sizeof(n2n_resolve_parameter_t));
+    if(*param) {
+        HASH_ITER(hh, sn_list, sn, tmp_sn) {
+            // create entries for those peers that come with ip_addr string (from command-line)
+            if(sn->ip_addr) {
+                entry = (n2n_resolve_ip_sock_t*)calloc(1, sizeof(n2n_resolve_ip_sock_t));
+                if(entry) {
+                    entry->org_ip = sn->ip_addr;
+                    entry->org_sock = &(sn->sock);
+                    memcpy(&(entry->sock), &(sn->sock), sizeof(n2n_sock_t));
+                    HASH_ADD(hh, (*param)->list, org_ip, sizeof(char*), entry);
+                } else
+                    traceEvent(TRACE_WARNING, "resolve_create_thread was unable to add list entry for supernode '%s'", sn->ip_addr);
+            }
+        }
+    } else {
+        traceEvent(TRACE_WARNING, "resolve_create_thread was unable to create list of supernodes");
+        return -1;
+    }
+
+    // create thread
+    ret = pthread_create(&((*param)->id), NULL, resolve_thread, (void *)*param);
+    if(ret) {
+        traceEvent(TRACE_WARNING, "resolve_create_thread failed to create resolver thread with error number %d", ret);
+        return -1;
+    }
+
+    pthread_mutex_init(&((*param)->access), NULL);
+
+    return 0;
+#endif
+}
+
+
+void resolve_cancel_thread (n2n_resolve_parameter_t *param) {
+
+#ifdef HAVE_PTHREAD
+    pthread_cancel(param->id);
+    free(param);
+#endif
+}
+
+
+void resolve_check (n2n_resolve_parameter_t *param, time_t now) {
+
+#ifdef HAVE_PTHREAD
+    n2n_resolve_ip_sock_t   *entry, *tmp_entry;
+    n2n_sock_str_t sock_buf;
+
+    if(now - param->last_checked > N2N_RESOLVE_CHECK_INTERVAL) {
+        // try to lock access
+        if(pthread_mutex_trylock(&param->access) == 0) {
+            // any changes?
+            if(param->changed) {
+                // reset flag
+                param->changed = 0;
+                // unselectively copy all socks (even those with error code, that would be the old one because
+                // sockets do not get overwritten in case of error in resolve_thread) from list to supernode list
+                HASH_ITER(hh, param->list, entry, tmp_entry) {
+                    memcpy(entry->org_sock, &entry->sock, sizeof(n2n_sock_t));
+                    traceEvent(TRACE_DEBUG, "resolve_check renews ip address of supernode '%s' to %s",
+                                             entry->org_ip, sock_to_cstr(sock_buf, &(entry->sock)));
+                }
+            }
+            param->last_checked = now;
+
+            // unlock access
+            pthread_mutex_unlock(&param->access);
+        }
+    }
+#endif
+}
+
+
 /* ************************************** */
 
+
 struct peer_info* add_sn_to_list_by_mac_or_sock (struct peer_info **sn_list, n2n_sock_t *sock, const n2n_mac_t mac, int *skip_add) {
 
     struct peer_info *scan, *tmp, *peer = NULL;
@@ -608,6 +720,7 @@ int sock_equal (const n2n_sock_t * a,
     return(1);
 }
 
+
 /* *********************************************** */
 
 // fills a specified memory area with random numbers

src/sn.c

@@ -25,6 +25,8 @@
 
 static n2n_sn_t sss_node;
 
+int resolve_create_thread (n2n_resolve_parameter_t **param, struct peer_info *sn_list);
+
 /** Load the list of allowed communities. Existing/previous ones will be removed
  *
  */
@@ -858,6 +860,10 @@ int main (int argc, char * const argv[]) {
     }
 #endif
 
+    if(resolve_create_thread(&(sss_node.resolve_parameter), sss_node.federation->edges) == 0) {
+         traceEvent(TRACE_NORMAL, "Successfully created resolver thread");
+    }
+
     traceEvent(TRACE_NORMAL, "supernode started");
 
 #ifdef __linux__

src/sn_utils.c

@@ -20,6 +20,8 @@
 
 #define HASH_FIND_COMMUNITY(head, name, out) HASH_FIND_STR(head, name, out)
 
+int resolve_check (n2n_resolve_parameter_t *param, time_t now);
+int resolve_cancel_thread (n2n_resolve_parameter_t *param);
 
 static ssize_t sendto_peer (n2n_sn_t *sss,
                             const struct peer_info *peer,
@@ -430,6 +432,8 @@ void sn_term (n2n_sn_t *sss) {
     n2n_tcp_connection_t *conn, *tmp_conn;
     node_supernode_association_t *assoc, *tmp_assoc;
 
+    resolve_cancel_thread(sss->resolve_parameter);
+
     if(sss->sock >= 0) {
         closesocket(sss->sock);
     }
@@ -2358,6 +2362,7 @@ int run_sn_loop (n2n_sn_t *sss, int *keep_running) {
         re_register_and_purge_supernodes(sss, sss->federation, &last_re_reg_and_purge, now);
         purge_expired_communities(sss, &last_purge_edges, now);
         sort_communities(sss, &last_sort_communities, now);
+        resolve_check(sss->resolve_parameter, now);
     } /* while */
 
     sn_term(sss);

win32/n2n_win32.h

@@ -65,6 +65,7 @@ struct ip {
 
 /* ************************************* */
 
+
 typedef struct tuntap_dev {
 	HANDLE          device_handle;
 	char            *device_name;
@@ -77,7 +78,44 @@ typedef struct tuntap_dev {
 	unsigned int    metric;
 } tuntap_dev;
 
+
+/* ************************************* */
+
+
 #define index(a, b) strchr(a, b)
 #define sleep(x) Sleep(x * 1000)
 
+
+/* ************************************* */
+
+
+#define HAVE_PTHREAD
+#define pthread_t       HANDLE
+#define pthread_mutex_t HANDLE
+
+#define pthread_create(p_thread_handle, attr, thread_func, p_param)                         \
+    (*p_thread_handle = CreateThread(0 /* default security flags */, 0 /*default stack*/,   \
+                 thread_func, p_param, 0 /* default creation flags */,                      \
+                 NULL) == 0)
+
+#define pthread_cancel(p_thread_handle) \
+    TerminateThread(p_thread_handle, 0)
+
+#define pthread_mutex_init(p_mutex_handle, attr)                      \
+     *p_mutex_handle = CreateMutex(NULL /*default security flags */,  \
+     FALSE /* initially not owned */, NULL /* unnamed */)
+
+#define pthread_mutex_lock(mutex)         \
+    WaitForSingleObject(*mutex, INFINITE)
+
+#define pthread_mutex_trylock(mutex)  \
+    WaitForSingleObject(*mutex, NULL)
+
+#define pthread_mutex_unlock(mutex) \
+    ReleaseMutex(*mutex)
+
+
+/* ************************************* */
+
+
 #endif