From 09e8d5e730672813827dde19a4bf27f8629e7682 Mon Sep 17 00:00:00 2001
From: Logan oos Even <46396513+Logan007@users.noreply.github.com>
Date: Mon, 1 Feb 2021 18:31:36 +0545
Subject: [PATCH] limited number of concurrently pinged supernodes (#619)

---
 include/n2n_define.h   |  3 +++
 include/n2n_typedefs.h |  1 +
 src/edge.c             | 13 +++++++++----
 src/edge_utils.c       | 29 +++++++++++++++++++++++++++++
 4 files changed, 42 insertions(+), 4 deletions(-)

diff --git a/include/n2n_define.h b/include/n2n_define.h
index b71d748..252b873 100644
--- a/include/n2n_define.h
+++ b/include/n2n_define.h
@@ -48,6 +48,9 @@
 #define SWEEP_TIME                       30 /* sec, indicates the value after which we have to sort the hash list of supernodes in edges
                                              * and when we send out packets to query selection-relevant informations from supernodes. */
 
+#define NUMBER_SN_PINGS_INITIAL          15 /* number of supernodes to concurrently ping during bootstrap and immediately afterwards */
+#define NUMBER_SN_PINGS_REGULAR           5 /* number of supernodes to concurrently ping during regular edge operation */
+
 /* Timeouts used in re_register_and_purge_supernodes. LAST_SEEN_SN_ACTIVE and LAST_SEEN_SN_INACTIVE
  * values should be at least 3*SOCKET_TIMEOUT_INTERVAL_SECS apart. */
 #define LAST_SEEN_SN_ACTIVE              20 /* sec, indicates supernodes that are proven to be active */
diff --git a/include/n2n_typedefs.h b/include/n2n_typedefs.h
index 5b8fff2..2113e0f 100644
--- a/include/n2n_typedefs.h
+++ b/include/n2n_typedefs.h
@@ -601,6 +601,7 @@ typedef struct n2n_edge_conf {
     n2n_auth_t         auth;
     filter_rule_t      *network_traffic_filter_rules;
     int                metric;                /**< Network interface metric (Windows only). */
+    uint8_t            number_max_sn_pings;   /**< Number of maximum concurrently allowed supernode pings. */
 } n2n_edge_conf_t;
 
 
diff --git a/src/edge.c b/src/edge.c
index e61b88c..f52c5d3 100644
--- a/src/edge.c
+++ b/src/edge.c
@@ -962,6 +962,8 @@ int main (int argc, char* argv[]) {
         if(runlevel == 0) { /* PING to all known supernodes */
             last_action = now_time;
             eee->sn_pong = 0;
+            // (re-)initialize the number of max concurrent pings (decreases by calling send_query_peer)
+            eee->conf.number_max_sn_pings = NUMBER_SN_PINGS_INITIAL;
             send_query_peer(eee, null_mac);
             traceEvent(TRACE_NORMAL, "Send PING to supernodes.");
             runlevel++;
@@ -975,8 +977,7 @@ int main (int argc, char* argv[]) {
                 eee->curr_sn = eee->conf.supernodes;
                 traceEvent(TRACE_NORMAL, "Received first PONG from supernode [%s].", eee->curr_sn->ip_addr);
                 runlevel++;
-            }
-            if(last_action <= (now_time - BOOTSTRAP_TIMEOUT)) {
+            } else if(last_action <= (now_time - BOOTSTRAP_TIMEOUT)) {
                 // timeout
                 runlevel--;
                 // skip waiting for answer to direcly go to send PING again
@@ -1017,8 +1018,7 @@ int main (int argc, char* argv[]) {
                 runlevel++;
                 traceEvent(TRACE_NORMAL, "Received REGISTER_SUPER_ACK from supernode for IP address asignment.");
                 // it should be from curr_sn, but we can't determine definitely here, so no details to output
-            }
-            if(last_action <= (now_time - BOOTSTRAP_TIMEOUT)) {
+            } else if(last_action <= (now_time - BOOTSTRAP_TIMEOUT)) {
                 // timeout, so try next supernode
                 if(eee->curr_sn->hh.next)
                     eee->curr_sn = eee->curr_sn->hh.next;
@@ -1065,6 +1065,11 @@ int main (int argc, char* argv[]) {
         }
         seek_answer = 1;
     }
+    // allow a higher number of pings for first regular round of ping
+    // to quicker get an inital 'supernode selection criterion overview'
+    eee->conf.number_max_sn_pings = NUMBER_SN_PINGS_INITIAL;
+    // do not immediately ping again, allow some time
+    eee->last_sweep = now_time - SWEEP_TIME + 2 * BOOTSTRAP_TIMEOUT;
     eee->sn_wait = 1;
     eee->last_register_req = 0;
     eee->last_sup = 0; /* to allow gratuitous arp packet after regular REGISTER_SUPER_ACK */
diff --git a/src/edge_utils.c b/src/edge_utils.c
index 52b44ca..306e0f4 100644
--- a/src/edge_utils.c
+++ b/src/edge_utils.c
@@ -770,6 +770,10 @@ void send_query_peer (n2n_edge_t * eee,
     n2n_QUERY_PEER_t query = {{0}};
     struct peer_info *peer, *tmp;
     uint8_t tmp_pkt[N2N_PKT_BUF_SIZE];
+    int n_o_pings = 0;
+    int n_o_top_sn = 0;
+    int n_o_rest_sn = 0;
+    int n_o_skip_sn = 0;
 
     cmn.ttl = N2N_DEFAULT_TTL;
     cmn.pc = n2n_query_peer;
@@ -806,7 +810,32 @@ void send_query_peer (n2n_edge_t * eee,
                                   time_stamp ());
         }
 
+        n_o_pings = eee->conf.number_max_sn_pings;
+        eee->conf.number_max_sn_pings = NUMBER_SN_PINGS_REGULAR;
+
+        // ping the 'floor(n/2)' top supernodes and 'ceiling(n/2)' of the remaining
+        n_o_top_sn  = n_o_pings >> 1;
+        n_o_rest_sn = (n_o_pings + 1) >> 1;
+
+        // skip a random number of supernodes between top and remaining
+        n_o_skip_sn = HASH_COUNT(eee->conf.supernodes) - n_o_pings;
+        n_o_skip_sn = (n_o_skip_sn < 0) ? 0 : n2n_rand_sqr(n_o_skip_sn);
+
         HASH_ITER(hh, eee->conf.supernodes, peer, tmp) {
+            if(n_o_top_sn) {
+                n_o_top_sn--;
+                // fall through (send to top supernode)
+            } else if(n_o_skip_sn) {
+                n_o_skip_sn--;
+                // skip (do not send)
+                continue;
+            } else if(n_o_rest_sn) {
+                n_o_rest_sn--;
+                // fall through (send to remaining supernode)
+            } else {
+                // done with the remaining (do not send anymore)
+                break;
+            }
             sendto_sock(eee->udp_sock, pktbuf, idx, &(peer->sock));
         }
     }