feat: memory based connection limits

Implements memory-based connection limits where the user can specify an absolute or a relative limit of the process' memory usage in relation to the available system memory.

Related: #4252.

Pull-Request: #4281.

misc/memory-connection-limits/tests/max_bytes.rs

@@ -0,0 +1,89 @@
+// Copyright 2023 Protocol Labs.
+//
+// Permission is hereby granted, free of charge, to any person obtaining a
+// copy of this software and associated documentation files (the "Software"),
+// to deal in the Software without restriction, including without limitation
+// the rights to use, copy, modify, merge, publish, distribute, sublicense,
+// and/or sell copies of the Software, and to permit persons to whom the
+// Software is furnished to do so, subject to the following conditions:
+//
+// The above copyright notice and this permission notice shall be included in
+// all copies or substantial portions of the Software.
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
+// OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+// FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+// DEALINGS IN THE SOFTWARE.
+
+mod util;
+
+use libp2p_core::Multiaddr;
+use libp2p_identity::PeerId;
+use libp2p_memory_connection_limits::*;
+use std::time::Duration;
+use util::*;
+
+use libp2p_swarm::{dial_opts::DialOpts, DialError, Swarm};
+use libp2p_swarm_test::SwarmExt;
+
+#[test]
+fn max_bytes() {
+    const CONNECTION_LIMIT: usize = 20;
+    let max_allowed_bytes = CONNECTION_LIMIT * 1024 * 1024;
+
+    let mut network = Swarm::new_ephemeral(|_| TestBehaviour {
+        connection_limits: Behaviour::with_max_bytes(max_allowed_bytes),
+        mem_consumer: ConsumeMemoryBehaviour1MBPending0Established::default(),
+    });
+
+    let addr: Multiaddr = "/memory/1234".parse().unwrap();
+    let target = PeerId::random();
+
+    // Exercise `dial` function to get more stable memory stats later
+    network
+        .dial(
+            DialOpts::peer_id(target)
+                .addresses(vec![addr.clone()])
+                .build(),
+        )
+        .expect("Unexpected connection limit.");
+
+    // Adds current mem usage to the limit and update
+    let max_allowed_bytes_plus_base_usage =
+        max_allowed_bytes + memory_stats::memory_stats().unwrap().physical_mem;
+    network.behaviour_mut().connection_limits =
+        Behaviour::with_max_bytes(max_allowed_bytes_plus_base_usage);
+
+    for _ in 0..CONNECTION_LIMIT {
+        network
+            .dial(
+                DialOpts::peer_id(target)
+                    .addresses(vec![addr.clone()])
+                    .build(),
+            )
+            .expect("Unexpected connection limit.");
+    }
+
+    std::thread::sleep(Duration::from_millis(100)); // Memory stats are only updated every 100ms internally, ensure they are up-to-date when we try to exceed it.
+
+    match network
+        .dial(DialOpts::peer_id(target).addresses(vec![addr]).build())
+        .expect_err("Unexpected dialing success.")
+    {
+        DialError::Denied { cause } => {
+            let exceeded = cause
+                .downcast::<MemoryUsageLimitExceeded>()
+                .expect("connection denied because of limit");
+
+            assert_eq!(
+                exceeded.max_allowed_bytes(),
+                max_allowed_bytes_plus_base_usage
+            );
+            assert!(exceeded.process_physical_memory_bytes() >= exceeded.max_allowed_bytes());
+        }
+        e => panic!("Unexpected error: {e:?}"),
+    }
+}