// Copyright (c) 2012 The Chromium OS Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include "shill/connection.h"

#include <arpa/inet.h>
#include <linux/rtnetlink.h>

#include "shill/device_info.h"
#include "shill/resolver.h"
#include "shill/routing_table.h"
#include "shill/rtnl_handler.h"
#include "shill/scope_logger.h"

using std::string;

namespace shill {

// static
const uint32 Connection::kDefaultMetric = 1;
// static
const uint32 Connection::kNonDefaultMetricBase = 10;

Connection::Connection(int interface_index,
                       const std::string& interface_name,
                       Technology::Identifier technology,
                       const DeviceInfo *device_info)
    : is_default_(false),
      routing_request_count_(0),
      interface_index_(interface_index),
      interface_name_(interface_name),
      technology_(technology),
      device_info_(device_info),
      resolver_(Resolver::GetInstance()),
      routing_table_(RoutingTable::GetInstance()),
      rtnl_handler_(RTNLHandler::GetInstance()) {
  SLOG(Connection, 2) << __func__ << "(" << interface_index << ", "
                      << interface_name << ", "
                      << Technology::NameFromIdentifier(technology) << ")";
}

Connection::~Connection() {
  SLOG(Connection, 2) << __func__ << " " << interface_name_;

  DCHECK(!routing_request_count_);
  routing_table_->FlushRoutes(interface_index_);
  routing_table_->FlushRoutesWithTag(interface_index_);
  device_info_->FlushAddresses(interface_index_);
}

void Connection::UpdateFromIPConfig(const IPConfigRefPtr &config) {
  SLOG(Connection, 2) << __func__ << " " << interface_name_;

  const IPConfig::Properties &properties = config->properties();
  if (!properties.trusted_ip.empty() && !PinHostRoute(properties)) {
    LOG(ERROR) << "Unable to pin host route to " << properties.trusted_ip;
    return;
  }

  IPAddress local(properties.address_family);
  if (!local.SetAddressFromString(properties.address)) {
    LOG(ERROR) << "Local address " << properties.address << " is invalid";
    return;
  }
  local.set_prefix(properties.subnet_prefix);

  IPAddress broadcast(properties.address_family);
  if (!broadcast.SetAddressFromString(properties.broadcast_address) &&
      technology_ != Technology::kVPN) {
    LOG(ERROR) << "Broadcast address " << properties.broadcast_address
               << " is invalid";
    return;
  }

  IPAddress peer(properties.address_family);
  if (!properties.peer_address.empty() &&
      !peer.SetAddressFromString(properties.peer_address)) {
    LOG(ERROR) << "Peer address " << properties.peer_address
               << " is invalid";
    return;
  }

  IPAddress gateway_address(properties.address_family);
  if (!properties.gateway.empty() &&
      !gateway_address.SetAddressFromString(properties.gateway)) {
    LOG(ERROR) << "Gateway address " << properties.peer_address
               << " is invalid";
    return;
  }

  FixGatewayReachability(&local, gateway_address);

  rtnl_handler_->AddInterfaceAddress(interface_index_, local, broadcast, peer);

  if (gateway_address.IsValid()) {
    routing_table_->SetDefaultRoute(interface_index_, gateway_address,
                                    GetMetric(is_default_));
  } else if (!peer.IsValid()) {
    LOG(WARNING) << "No gateway or peer address was provided for this "
                 << "connection.  Expect limited network connectivity.";
  }

  // Install any explicitly configured routes at the default metric.
  routing_table_->ConfigureRoutes(interface_index_, config, kDefaultMetric);

  // Save a copy of the last non-null DNS config
  if (!config->properties().dns_servers.empty()) {
    dns_servers_ = config->properties().dns_servers;
    dns_domain_search_ = config->properties().domain_search;
  }

  ipconfig_rpc_identifier_ = config->GetRpcIdentifier();

  if (is_default_) {
    resolver_->SetDNSFromIPConfig(config);
  }
}

void Connection::SetIsDefault(bool is_default) {
  SLOG(Connection, 2) << __func__ << " " << interface_name_
                      << " (index " << interface_index_ << ") "
                      << is_default_ << " -> " << is_default;
  if (is_default == is_default_) {
    return;
  }

  routing_table_->SetDefaultMetric(interface_index_, GetMetric(is_default));

  is_default_ = is_default;

  if (is_default) {
    resolver_->SetDNSFromLists(dns_servers_, dns_domain_search_);
    DeviceRefPtr device = device_info_->GetDevice(interface_index_);
    if (device) {
      device->RequestPortalDetection();
    }
  }
}

void Connection::RequestRouting() {
  if (routing_request_count_++ == 0) {
    DeviceRefPtr device = device_info_->GetDevice(interface_index_);
    DCHECK(device.get());
    if (!device.get()) {
      LOG(ERROR) << "Device is NULL!";
      return;
    }
    device->DisableReversePathFilter();
  }
}

void Connection::ReleaseRouting() {
  DCHECK(routing_request_count_ > 0);
  if (--routing_request_count_ == 0) {
    DeviceRefPtr device = device_info_->GetDevice(interface_index_);
    DCHECK(device.get());
    if (!device.get()) {
      LOG(ERROR) << "Device is NULL!";
      return;
    }
    device->EnableReversePathFilter();

    // Clear any cached routes that might have accumulated while reverse-path
    // filtering was disabled.
    routing_table_->FlushCache();
  }
}

bool Connection::RequestHostRoute(const IPAddress &address) {
  // Set the prefix to be the entire address size.
  IPAddress address_prefix(address);
  address_prefix.set_prefix(address_prefix.GetLength() * 8);

  // Do not set interface_index_ since this may not be the
  // default route through which this destination can be found.
  // However, we should tag the created route with our interface
  // index so we can clean this route up when this connection closes.
  if (!routing_table_->RequestRouteToHost(address_prefix, -1,
                                          interface_index_)) {
    LOG(ERROR) << "Could not request route to " << address.ToString();
    return false;
  }

  return true;
}

// static
void Connection::FixGatewayReachability(IPAddress *local,
                                        const IPAddress &gateway) {
  if (!gateway.IsValid() || local->CanReachAddress(gateway)) {
    return;
  }

  LOG(WARNING) << "Gateway "
               << gateway.ToString()
               << " is unreachable from local address/prefix "
               << local->ToString() << "/" << local->prefix();

  size_t original_prefix = local->prefix();
  size_t prefix = original_prefix - 1;
  for (; prefix >= local->GetMinPrefixLength(); --prefix) {
    local->set_prefix(prefix);
    if (local->CanReachAddress(gateway)) {
      break;
    }
  }

  if (prefix < local->GetMinPrefixLength()) {
    // Restore the original prefix since we cannot find a better one.
    local->set_prefix(original_prefix);
    LOG(WARNING) << "Expect limited network connectivity.";
  } else {
    LOG(WARNING) << "Mitigating this by setting local prefix to " << prefix;
  }
}

uint32 Connection::GetMetric(bool is_default) {
  // If this is not the default route, assign a metric based on the interface
  // index.  This way all non-default routes (even to the same gateway IP) end
  // up with unique metrics so they do not collide.
  return is_default ? kDefaultMetric : kNonDefaultMetricBase + interface_index_;
}

bool Connection::PinHostRoute(const IPConfig::Properties &properties) {
  SLOG(Connection, 2) << __func__;
  if (properties.gateway.empty() || properties.trusted_ip.empty()) {
    return false;
  }

  IPAddress trusted_ip(properties.address_family);
  if (!trusted_ip.SetAddressFromString(properties.trusted_ip)) {
    LOG(ERROR) << "Failed to parse trusted_ip "
               << properties.trusted_ip << "; ignored.";
    return false;
  }

  return RequestHostRoute(trusted_ip);
}

}  // namespace shill