src: add SocketAddressLRU Utility

Adds a LRU cache for information associated with a SocketAddress.

PR-URL: #34618
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Rich Trott <rtrott@gmail.com>

src/node_sockaddr-inl.h

@@ -7,6 +7,7 @@
 #include "node_internals.h"
 #include "node_sockaddr.h"
 #include "util-inl.h"
+#include "memory_tracker-inl.h"
 
 #include <string>
 
@@ -164,6 +165,72 @@ bool SocketAddress::operator==(const SocketAddress& other) const {
 bool SocketAddress::operator!=(const SocketAddress& other) const {
   return !(*this == other);
 }
+
+template <typename T>
+SocketAddressLRU<T>::SocketAddressLRU(
+    size_t max_size)
+    : max_size_(max_size) {}
+
+template <typename T>
+typename T::Type* SocketAddressLRU<T>::Peek(
+    const SocketAddress& address) const {
+  auto it = map_.find(address);
+  return it == std::end(map_) ? nullptr : &it->second->second;
+}
+
+template <typename T>
+void SocketAddressLRU<T>::CheckExpired() {
+  auto it = list_.rbegin();
+  while (it != list_.rend()) {
+    if (T::CheckExpired(it->first, it->second)) {
+      map_.erase(it->first);
+      list_.pop_back();
+      it = list_.rbegin();
+      continue;
+    } else {
+      break;
+    }
+  }
+}
+
+template <typename T>
+void SocketAddressLRU<T>::MemoryInfo(MemoryTracker* tracker) const {
+  tracker->TrackFieldWithSize("list", size() * sizeof(Pair));
+}
+
+// If an item already exists for the given address, bump up it's
+// position in the LRU list and return it. If the item does not
+// exist, create it. If an item is created, check the size of the
+// cache and adjust if necessary. Whether the item exists or not,
+// purge expired items.
+template <typename T>
+typename T::Type* SocketAddressLRU<T>::Upsert(
+    const SocketAddress& address) {
+
+  auto on_exit = OnScopeLeave([&]() { CheckExpired(); });
+
+  auto it = map_.find(address);
+  if (it != std::end(map_)) {
+    list_.splice(list_.begin(), list_, it->second);
+    T::Touch(it->first, &it->second->second);
+    return &it->second->second;
+  }
+
+  list_.push_front(Pair(address, { }));
+  map_[address] = list_.begin();
+  T::Touch(list_.begin()->first, &list_.begin()->second);
+
+  // Drop the last item in the list if we are
+  // over the size limit...
+  if (map_.size() > max_size_) {
+    auto last = list_.end();
+    map_.erase((--last)->first);
+    list_.pop_back();
+  }
+
+  return &map_[address]->second;
+}
+
 }  // namespace node
 
 #endif  // NODE_WANT_INTERNALS

src/node_sockaddr.h

@@ -9,6 +9,7 @@
 #include "v8.h"
 
 #include <string>
+#include <list>
 #include <unordered_map>
 
 namespace node {
@@ -116,6 +117,41 @@ class SocketAddress : public MemoryRetainer {
   sockaddr_storage address_;
 };
 
+template <typename T>
+class SocketAddressLRU : public MemoryRetainer {
+ public:
+  using Type = typename T::Type;
+
+  inline explicit SocketAddressLRU(size_t max_size);
+
+  // If the item already exists, returns a reference to
+  // the existing item, adjusting items position in the
+  // LRU. If the item does not exist, emplaces the item
+  // and returns the new item.
+  Type* Upsert(const SocketAddress& address);
+
+  // Returns a reference to the item if it exists, or
+  // nullptr. The position in the LRU is not modified.
+  Type* Peek(const SocketAddress& address) const;
+
+  size_t size() const { return map_.size(); }
+  size_t max_size() const { return max_size_; }
+
+  void MemoryInfo(MemoryTracker* tracker) const override;
+  SET_MEMORY_INFO_NAME(SocketAddressLRU)
+  SET_SELF_SIZE(SocketAddressLRU)
+
+ private:
+  using Pair = std::pair<SocketAddress, Type>;
+  using Iterator = typename std::list<Pair>::iterator;
+
+  void CheckExpired();
+
+  std::list<Pair> list_;
+  SocketAddress::Map<Iterator> map_;
+  size_t max_size_;
+};
+
 }  // namespace node
 
 #endif  // NOE_WANT_INTERNALS

test/cctest/test_sockaddr.cc

@@ -2,6 +2,7 @@
 #include "gtest/gtest.h"
 
 using node::SocketAddress;
+using node::SocketAddressLRU;
 
 TEST(SocketAddress, SocketAddress) {
   CHECK(SocketAddress::is_numeric_host("123.123.123.123"));
@@ -55,3 +56,72 @@ TEST(SocketAddress, SocketAddressIPv6) {
   addr.set_flow_label(12345);
   CHECK_EQ(addr.flow_label(), 12345);
 }
+
+TEST(SocketAddressLRU, SocketAddressLRU) {
+  struct Foo {
+    int c;
+    bool expired;
+  };
+
+  struct FooLRUTraits {
+    using Type = Foo;
+
+    static bool CheckExpired(const SocketAddress& address, const Type& type) {
+      return type.expired;
+    }
+
+    static void Touch(const SocketAddress& address, Type* type) {
+      type->expired = false;
+    }
+  };
+
+  SocketAddressLRU<FooLRUTraits> lru(2);
+
+  sockaddr_storage storage[4];
+
+  SocketAddress::ToSockAddr(AF_INET, "123.123.123.123", 443, &storage[0]);
+  SocketAddress::ToSockAddr(AF_INET, "123.123.123.124", 443, &storage[1]);
+  SocketAddress::ToSockAddr(AF_INET, "123.123.123.125", 443, &storage[2]);
+  SocketAddress::ToSockAddr(AF_INET, "123.123.123.123", 443, &storage[3]);
+
+  SocketAddress addr1(reinterpret_cast<const sockaddr*>(&storage[0]));
+  SocketAddress addr2(reinterpret_cast<const sockaddr*>(&storage[1]));
+  SocketAddress addr3(reinterpret_cast<const sockaddr*>(&storage[2]));
+  SocketAddress addr4(reinterpret_cast<const sockaddr*>(&storage[3]));
+
+  Foo* foo = lru.Upsert(addr1);
+  CHECK_NOT_NULL(foo);
+  CHECK_EQ(foo->c, 0);
+  CHECK_EQ(foo->expired, false);
+
+  foo->c = 1;
+  foo->expired = true;
+
+  foo = lru.Upsert(addr1);
+  CHECK_NOT_NULL(lru.Peek(addr1));
+  CHECK_EQ(lru.Peek(addr1), lru.Peek(addr4));
+  CHECK_EQ(lru.Peek(addr1)->c, 1);
+  CHECK_EQ(lru.Peek(addr1)->expired, false);
+  CHECK_EQ(lru.size(), 1);
+
+  foo = lru.Upsert(addr2);
+  foo->c = 2;
+  foo->expired = true;
+  CHECK_NOT_NULL(lru.Peek(addr2));
+  CHECK_EQ(lru.Peek(addr2)->c, 2);
+  CHECK_EQ(lru.size(), 2);
+
+  foo->expired = true;
+
+  foo = lru.Upsert(addr3);
+  foo->c = 3;
+  foo->expired = false;
+  CHECK_NOT_NULL(lru.Peek(addr3));
+  CHECK_EQ(lru.Peek(addr3)->c, 3);
+  CHECK_EQ(lru.size(), 1);
+
+  // addr1 was removed because we exceeded size.
+  // addr2 was removed because it was expired.
+  CHECK_NULL(lru.Peek(addr1));
+  CHECK_NULL(lru.Peek(addr2));
+}