Merge bitcoin/bitcoin#24165: p2p: extend inbound eviction protection by network to CJDNS peers

b7be28cac50046b9f2ddfe63ecafccc80649a36c test: add combined CJDNS/I2P/localhost/onion eviction protection tests (Jon Atack)
0a1bb84770b403ab5cbd9d5474c76f91ce58e8f6 test: add tests for inbound eviction protection of CJDNS peers (Jon Atack)
0c00c0c981fc0b6cec101e68e8c1aeda1ccf33bb test: fix off-by-one logic in an eviction protection test (Jon Atack)
f7b8094d611531c6b41a94715dbc01f56257ccd2 p2p: extend inbound eviction protection by network to CJDNS peers (Jon Atack)

Pull request description:

  Extend inbound eviction protection for peers connected over CJDNS, as is the case for peers connected via onion, localhost, and I2P since #21261 and #20197.  CJDNS peers seem to have better min ping latency than onion and I2P peers but still higher than that of unencrypted IPv4/6 peers and can be disadvantaged under our eviction criteria. They are also very few in number, which is a further reason to protect them, as the goal of this logic is to favorise the diversity of our peer connections.  CJDNS support was added in #23077 for the upcoming v23 release.

ACKs for top commit:
  laanwj:
    Concept and code review ACK b7be28cac50046b9f2ddfe63ecafccc80649a36c
  w0xlt:
    tACK b7be28c

Tree-SHA512: 89ebdd217602e16ae14b9bd0d5a25fc09f9b2384c951f820bc0f5a6d8452bbc9042065db817d5d5296c0ad22988491a83fc5b9a611e660c40ebd4f03448c4061

1 files changed, 6 insertions, 6 deletions

diff --git a/src/net.cpp b/src/net.cpp
index 15616613d2..9bb264a38a 100644
--- a/src/net.cpp
+++ b/src/net.cpp
@@ -928,17 +928,17 @@ void ProtectEvictionCandidatesByRatio(std::vector<NodeEvictionCandidate>& evicti
     // Protect the half of the remaining nodes which have been connected the longest.
     // This replicates the non-eviction implicit behavior, and precludes attacks that start later.
     // To favorise the diversity of our peer connections, reserve up to half of these protected
-    // spots for Tor/onion, localhost and I2P peers, even if they're not longest uptime overall.
-    // This helps protect these higher-latency peers that tend to be otherwise
+    // spots for Tor/onion, localhost, I2P, and CJDNS peers, even if they're not longest uptime
+    // overall. This helps protect these higher-latency peers that tend to be otherwise
     // disadvantaged under our eviction criteria.
     const size_t initial_size = eviction_candidates.size();
     const size_t total_protect_size{initial_size / 2};
 
-    // Disadvantaged networks to protect: I2P, localhost, Tor/onion. In case of equal counts, earlier
-    // array members have first opportunity to recover unused slots from the previous iteration.
+    // Disadvantaged networks to protect. In the case of equal counts, earlier array members
+    // have the first opportunity to recover unused slots from the previous iteration.
     struct Net { bool is_local; Network id; size_t count; };
-    std::array<Net, 3> networks{
-        {{false, NET_I2P, 0}, {/* localhost */ true, NET_MAX, 0}, {false, NET_ONION, 0}}};
+    std::array<Net, 4> networks{
+        {{false, NET_CJDNS, 0}, {false, NET_I2P, 0}, {/*localhost=*/true, NET_MAX, 0}, {false, NET_ONION, 0}}};
 
     // Count and store the number of eviction candidates per network.
     for (Net& n : networks) {