From 0287837241e45bcc1e4de6157e8ebf42c17842b8 Mon Sep 17 00:00:00 2001
From: Logan oos Even <46396513+Logan007@users.noreply.github.com>
Date: Tue, 16 Mar 2021 23:24:39 +0545
Subject: [PATCH] skewed supernode selection for the benefit of current
 supernode in no-pong case (#663)

---
 include/sn_selection.h |  1 +
 src/edge.c             | 10 ++++++++++
 src/edge_utils.c       | 14 ++++++++++----
 src/sn_selection.c     | 10 +++++++++-
 4 files changed, 30 insertions(+), 5 deletions(-)

diff --git a/include/sn_selection.h b/include/sn_selection.h
index 333e969..82ff869 100644
--- a/include/sn_selection.h
+++ b/include/sn_selection.h
@@ -27,6 +27,7 @@ typedef char selection_criterion_str_t[SN_SELECTION_CRITERION_BUF_SIZE];
 int sn_selection_criterion_init (peer_info_t *peer);
 int sn_selection_criterion_default (SN_SELECTION_CRITERION_DATA_TYPE *selection_criterion);
 int sn_selection_criterion_bad (SN_SELECTION_CRITERION_DATA_TYPE *selection_criterion);
+int sn_selection_criterion_good (SN_SELECTION_CRITERION_DATA_TYPE *selection_criterion);
 int sn_selection_criterion_calculate (n2n_edge_t *eee, peer_info_t *peer, SN_SELECTION_CRITERION_DATA_TYPE *data);
 
 /* common data's functions */
diff --git a/src/edge.c b/src/edge.c
index 68cb9f1..141161a 100644
--- a/src/edge.c
+++ b/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);
+
 /* ***************************************************** */
 
 /** Find the address and IP mode for the tuntap device.
@@ -852,6 +853,7 @@ int main (int argc, char* argv[]) {
     macstr_t mac_buf;             /*            output mac address */
     fd_set socket_mask;           /*            for supernode answer */
     struct timeval wait_time;     /*            timeout for sn answer */
+    peer_info_t *scan, *scan_tmp; /*            supernode iteration */
 
     uint16_t expected = sizeof(uint16_t);
     uint16_t position = 0;
@@ -1095,6 +1097,14 @@ int main (int argc, char* argv[]) {
     // 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;
+    // shape supernode list; make current one the first on the list
+    HASH_ITER(hh, eee->conf.supernodes, scan, scan_tmp) {
+        if(scan == eee->curr_sn)
+            sn_selection_criterion_good(&(scan->selection_criterion));
+        else
+            sn_selection_criterion_default(&(scan->selection_criterion));
+    }
+    sn_selection_sort(&(eee->conf.supernodes));
     // do not immediately ping again, allow some time
     eee->last_sweep = now - SWEEP_TIME + 2 * BOOTSTRAP_TIMEOUT;
     eee->sn_wait = 1;
diff --git a/src/edge_utils.c b/src/edge_utils.c
index d025334..0ed98fc 100644
--- a/src/edge_utils.c
+++ b/src/edge_utils.c
@@ -502,6 +502,7 @@ static void register_with_local_peers (n2n_edge_t * eee) {
 }
 
 /* ************************************** */
+
 static struct peer_info* find_peer_by_sock (const n2n_sock_t *sock, struct peer_info *peer_list) {
 
     struct peer_info *scan, *tmp, *ret = NULL;
@@ -1146,7 +1147,10 @@ static int sort_supernodes (n2n_edge_t *eee, time_t now) {
         }
 
         HASH_ITER(hh, eee->conf.supernodes, scan, tmp) {
-            sn_selection_criterion_default(&(scan->selection_criterion));
+            if(scan == eee->curr_sn)
+                sn_selection_criterion_good(&(scan->selection_criterion));
+            else
+                sn_selection_criterion_default(&(scan->selection_criterion));
         }
         sn_selection_criterion_common_data_default(eee);
 
@@ -2383,9 +2387,11 @@ void process_udp (n2n_edge_t *eee, const struct sockaddr_in *sender_sock, const
 
                         handle_remote_auth(eee, sn, &(ra.auth));
 
-                        HASH_DEL(eee->conf.supernodes, eee->curr_sn);
-                        memcpy(&eee->curr_sn->mac_addr, ra.srcMac, N2N_MAC_SIZE);
-                        HASH_ADD_PEER(eee->conf.supernodes, eee->curr_sn);
+                        if(is_null_mac(eee->curr_sn->mac_addr)) {
+                            HASH_DEL(eee->conf.supernodes, eee->curr_sn);
+                            memcpy(&eee->curr_sn->mac_addr, ra.srcMac, N2N_MAC_SIZE);
+                            HASH_ADD_PEER(eee->conf.supernodes, eee->curr_sn);
+                        }
 
                         payload = (n2n_REGISTER_SUPER_ACK_payload_t*)tmpbuf;
 
diff --git a/src/sn_selection.c b/src/sn_selection.c
index 2efc176..061cf8c 100644
--- a/src/sn_selection.c
+++ b/src/sn_selection.c
@@ -47,7 +47,15 @@ int sn_selection_criterion_default (SN_SELECTION_CRITERION_DATA_TYPE *selection_
 /* Set selection_criterion field to 'bad' value (worse than default) according to selected strategy. */
 int sn_selection_criterion_bad (SN_SELECTION_CRITERION_DATA_TYPE *selection_criterion) {
 
-    *selection_criterion = (SN_SELECTION_CRITERION_DATA_TYPE) UINT32_MAX >> 1;
+    *selection_criterion = (SN_SELECTION_CRITERION_DATA_TYPE) (UINT32_MAX >> 1);
+
+    return 0; /* OK */
+}
+
+/* Set selection_criterion field to 'good' value (better than default) according to selected strategy. */
+int sn_selection_criterion_good (SN_SELECTION_CRITERION_DATA_TYPE *selection_criterion) {
+
+    *selection_criterion = (SN_SELECTION_CRITERION_DATA_TYPE) (UINT32_MAX >> 1) - 2;
 
     return 0; /* OK */
 }