sdk/lib/zxio/dgram_cache.h

// Copyright 2022 The Fuchsia Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef LIB_ZXIO_DGRAM_CACHE_H_
#define LIB_ZXIO_DGRAM_CACHE_H_

#include <fidl/fuchsia.posix.socket/cpp/wire.h>
#include <lib/fit/result.h>
#include <lib/zx/eventpair.h>
#include <zircon/types.h>

#include <list>
#include <mutex>
#include <optional>
#include <unordered_map>

#include "socket_address.h"

using ErrOrOutCode = zx::result<int16_t>;

namespace std {
template <>
struct hash<SocketAddress> {
  size_t operator()(const SocketAddress& k) const { return k.hash(); }
};
}  // namespace std

class RequestedCmsgSet {
 public:
  explicit RequestedCmsgSet(
      const fuchsia_posix_socket::wire::DatagramSocketRecvMsgPostflightResponse& response);

  constexpr static RequestedCmsgSet AllRequestedCmsgSet() {
    RequestedCmsgSet cmsg_set;
    cmsg_set.requests_ |= fuchsia_posix_socket::wire::CmsgRequests::kMask;
    return cmsg_set;
  }

  std::optional<fuchsia_posix_socket::wire::TimestampOption> so_timestamp() const;

  bool ip_tos() const;
  bool ip_ttl() const;
  bool ipv6_tclass() const;
  bool ipv6_hoplimit() const;
  bool ipv6_pktinfo() const;

 private:
  RequestedCmsgSet() = default;
  fuchsia_posix_socket::wire::CmsgRequests requests_;
  std::optional<fuchsia_posix_socket::wire::TimestampOption> so_timestamp_filter_;
};

class RequestedCmsgCache {
 public:
  using Result = fit::result<ErrOrOutCode, std::optional<RequestedCmsgSet>>;
  Result Get(zx_wait_item_t err_wait_item, bool get_requested_cmsg_set,
             fidl::WireSyncClient<fuchsia_posix_socket::DatagramSocket>& client);

 private:
  struct Value {
    zx::eventpair validity;
    RequestedCmsgSet requested_cmsg_set;
  };
  std::optional<Value> cache_ __TA_GUARDED(lock_);
  std::mutex lock_;
};

class RouteCache {
 public:
  using Result = fit::result<ErrOrOutCode, uint32_t>;

  Result Get(std::optional<SocketAddress>& remote_addr,
             const std::optional<std::pair<uint64_t, fuchsia_net::wire::Ipv6Address>>&
                 local_iface_and_addr,
             const zx_wait_item_t& err_wait_item,
             fidl::WireSyncClient<fuchsia_posix_socket::DatagramSocket>& client);

  // Chosen to be arbitrarily large enough for the cache to be useful for most
  // clients, while preventing unbounded memory growth.
  static constexpr size_t kMaxEntries = 512;

 private:
  struct Key {
    SocketAddress remote_addr;
    std::optional<std::pair<uint64_t, fuchsia_net::wire::Ipv6Address>> local_iface_and_addr;

    bool operator==(const Key& o) const;
  };
  struct KeyHasher {
    size_t operator()(const Key& k) const;
  };
  struct Value {
    std::vector<zx::eventpair> eventpairs;
    uint32_t maximum_size;
    std::list<Key>::iterator lru;
  };

  std::list<Key>::iterator LruAddToFrontLocked(const Key& k) __TA_REQUIRES(lock_);

  std::unordered_map<Key, Value, KeyHasher> cache_ __TA_GUARDED(lock_);
  std::list<Key> lru_ __TA_GUARDED(lock_);
  std::optional<SocketAddress> connected_ __TA_GUARDED(lock_);
  std::mutex lock_;
};

std::optional<ErrOrOutCode> GetErrorWithClient(
    fidl::WireSyncClient<fuchsia_posix_socket::DatagramSocket>& client);

#endif  // LIB_ZXIO_DGRAM_CACHE_H_