p2p: extend inbound eviction protection by network to I2P peers

This commit extends our inbound eviction protection to I2P peers to
favorise the diversity of peer connections, as peers connected
through the I2P network are otherwise disadvantaged by our eviction
criteria for their higher latency (higher min ping times) relative
to IPv4 and IPv6 peers, as well as relative to Tor onion peers.

The `networks` array is order-dependent in the case of a tie in
candidate counts between networks (earlier array members receive
priority in the case of a tie).

Therefore, we place I2P candidates before localhost and onion ones
in terms of opportunity to recover unused remaining protected slots
from the previous iteration, guesstimating that most nodes allowing
both onion and I2P inbounds will have more onion peers, followed by
localhost, then I2P, as I2P support is only being added in the
upcoming v22.0 release.

1 files changed, 5 insertions, 5 deletions

diff --git a/src/test/net_peer_eviction_tests.cpp b/src/test/net_peer_eviction_tests.cpp
index ec4aa50173..bf56e1bea7 100644
--- a/src/test/net_peer_eviction_tests.cpp
+++ b/src/test/net_peer_eviction_tests.cpp
@@ -109,10 +109,10 @@ BOOST_AUTO_TEST_CASE(peer_protection_test)
         /* unprotected_peer_ids */ {0, 1, 2, 3, 4, 5},
         random_context));
 
-    // Test protection of onion and localhost peers...
+    // Test protection of onion, localhost, and I2P peers...
 
     // Expect 1/4 onion peers to be protected from eviction,
-    // if no localhost peers.
+    // if no localhost or I2P peers.
     BOOST_CHECK(IsProtected(
         num_peers, [](NodeEvictionCandidate& c) {
             c.m_is_local = false;
@@ -123,7 +123,7 @@ BOOST_AUTO_TEST_CASE(peer_protection_test)
         random_context));
 
     // Expect 1/4 onion peers and 1/4 of the other peers to be protected,
-    // sorted by longest uptime (lowest nTimeConnected), if no localhost peers.
+    // sorted by longest uptime (lowest nTimeConnected), if no localhost or I2P peers.
     BOOST_CHECK(IsProtected(
         num_peers, [](NodeEvictionCandidate& c) {
             c.nTimeConnected = c.id;
@@ -135,7 +135,7 @@ BOOST_AUTO_TEST_CASE(peer_protection_test)
         random_context));
 
     // Expect 1/4 localhost peers to be protected from eviction,
-    // if no onion peers.
+    // if no onion or I2P peers.
     BOOST_CHECK(IsProtected(
         num_peers, [](NodeEvictionCandidate& c) {
             c.m_is_local = (c.id == 1 || c.id == 9 || c.id == 11);
@@ -146,7 +146,7 @@ BOOST_AUTO_TEST_CASE(peer_protection_test)
         random_context));
 
     // Expect 1/4 localhost peers and 1/4 of the other peers to be protected,
-    // sorted by longest uptime (lowest nTimeConnected), if no onion peers.
+    // sorted by longest uptime (lowest nTimeConnected), if no onion or I2P peers.
     BOOST_CHECK(IsProtected(
         num_peers, [](NodeEvictionCandidate& c) {
             c.nTimeConnected = c.id;