| // Copyright (c) 2019 The Chromium 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 QUICHE_QUIC_QBONE_QBONE_PACKET_PROCESSOR_H_ |
| #define QUICHE_QUIC_QBONE_QBONE_PACKET_PROCESSOR_H_ |
| |
| #include <netinet/icmp6.h> |
| #include <netinet/ip6.h> |
| |
| #include "absl/strings/string_view.h" |
| #include "quic/core/quic_types.h" |
| #include "quic/platform/api/quic_ip_address.h" |
| |
| namespace quic { |
| |
| enum : size_t { |
| kIPv6HeaderSize = 40, |
| kICMPv6HeaderSize = sizeof(icmp6_hdr), |
| kTotalICMPv6HeaderSize = kIPv6HeaderSize + kICMPv6HeaderSize, |
| }; |
| |
| // QBONE packet processor accepts packets destined in either direction |
| // (client-to-network or network-to-client). It inspects them and makes |
| // decisions on whether they should be forwarded or dropped, replying with ICMP |
| // messages as appropriate. |
| class QbonePacketProcessor { |
| public: |
| enum class Direction { |
| // Packet is going from the QBONE client into the network behind the QBONE. |
| FROM_OFF_NETWORK = 0, |
| // Packet is going from the network begin QBONE to the client. |
| FROM_NETWORK = 1 |
| }; |
| |
| enum class ProcessingResult { |
| OK = 0, |
| SILENT_DROP = 1, |
| ICMP = 2, |
| // Equivalent to |SILENT_DROP| at the moment, but indicates that the |
| // downstream filter has buffered the packet and deferred its processing. |
| // The packet may be emitted at a later time. |
| DEFER = 3, |
| // In addition to sending an ICMP message, also send a TCP RST. This option |
| // requires the incoming packet to have been a valid TCP packet, as a TCP |
| // RST requires information from the current connection state to be |
| // well-formed. |
| ICMP_AND_TCP_RESET = 4, |
| // Send a TCP RST. |
| TCP_RESET = 5, |
| }; |
| |
| class OutputInterface { |
| public: |
| virtual ~OutputInterface(); |
| |
| virtual void SendPacketToClient(absl::string_view packet) = 0; |
| virtual void SendPacketToNetwork(absl::string_view packet) = 0; |
| }; |
| |
| class StatsInterface { |
| public: |
| virtual ~StatsInterface(); |
| |
| virtual void OnPacketForwarded(Direction direction) = 0; |
| virtual void OnPacketDroppedSilently(Direction direction) = 0; |
| virtual void OnPacketDroppedWithIcmp(Direction direction) = 0; |
| virtual void OnPacketDroppedWithTcpReset(Direction direction) = 0; |
| virtual void OnPacketDeferred(Direction direction) = 0; |
| }; |
| |
| // Allows to implement a custom packet filter on top of the filtering done by |
| // the packet processor itself. |
| class Filter { |
| public: |
| virtual ~Filter(); |
| // The main interface function. The following arguments are supplied: |
| // - |direction|, to indicate direction of the packet. |
| // - |full_packet|, which includes the IPv6 header and possibly the IPv6 |
| // options that were understood by the processor. |
| // - |payload|, the contents of the IPv6 packet, i.e. a TCP, a UDP or an |
| // ICMP packet. |
| // - |icmp_header|, an output argument which allows the filter to specify |
| // the ICMP message with which the packet is to be rejected. |
| // The method is called only on packets which were already verified as valid |
| // IPv6 packets. |
| // |
| // The implementer of this method has four options to return: |
| // - OK will cause the filter to pass the packet through |
| // - SILENT_DROP will cause the filter to drop the packet silently |
| // - ICMP will cause the filter to drop the packet and send an ICMP |
| // response. |
| // - DEFER will cause the packet to be not forwarded; the filter is |
| // responsible for sending (or not sending) it later using |output|. |
| // |
| // Note that |output| should not be used except in the DEFER case, as the |
| // processor will perform the necessary writes itself. |
| virtual ProcessingResult FilterPacket(Direction direction, |
| absl::string_view full_packet, |
| absl::string_view payload, |
| icmp6_hdr* icmp_header, |
| OutputInterface* output); |
| |
| protected: |
| // Helper methods that allow to easily extract information that is required |
| // for filtering from the |ipv6_header| argument. All of those assume that |
| // the header is of valid size, which is true for everything passed into |
| // FilterPacket(). |
| uint8_t TransportProtocolFromHeader(absl::string_view ipv6_header) { |
| return ipv6_header[6]; |
| } |
| QuicIpAddress SourceIpFromHeader(absl::string_view ipv6_header) { |
| QuicIpAddress address; |
| address.FromPackedString(&ipv6_header[8], |
| QuicIpAddress::kIPv6AddressSize); |
| return address; |
| } |
| QuicIpAddress DestinationIpFromHeader(absl::string_view ipv6_header) { |
| QuicIpAddress address; |
| address.FromPackedString(&ipv6_header[24], |
| QuicIpAddress::kIPv6AddressSize); |
| return address; |
| } |
| }; |
| |
| // |self_ip| is the IP address from which the processor will originate ICMP |
| // messages. |client_ip| is the expected IP address of the client, used for |
| // packet validation. |
| // |
| // |output| and |stats| are the visitor interfaces used by the processor. |
| // |output| gets notified whenever the processor decides to send a packet, and |
| // |stats| gets notified about any decisions that processor makes, without a |
| // reference to which packet that decision was made about. |
| QbonePacketProcessor(QuicIpAddress self_ip, |
| QuicIpAddress client_ip, |
| size_t client_ip_subnet_length, |
| OutputInterface* output, |
| StatsInterface* stats); |
| QbonePacketProcessor(const QbonePacketProcessor&) = delete; |
| QbonePacketProcessor& operator=(const QbonePacketProcessor&) = delete; |
| |
| // Accepts an IPv6 packet and handles it accordingly by either forwarding it, |
| // replying with an ICMP packet or silently dropping it. |packet| will be |
| // modified in the process, by having the TTL field decreased. |
| void ProcessPacket(std::string* packet, Direction direction); |
| |
| void set_filter(std::unique_ptr<Filter> filter) { |
| filter_ = std::move(filter); |
| } |
| |
| void set_client_ip(QuicIpAddress client_ip) { client_ip_ = client_ip; } |
| void set_client_ip_subnet_length(size_t client_ip_subnet_length) { |
| client_ip_subnet_length_ = client_ip_subnet_length; |
| } |
| |
| static const QuicIpAddress kInvalidIpAddress; |
| |
| protected: |
| // Processes the header and returns what should be done with the packet. |
| // After that, calls an external packet filter if registered. TTL of the |
| // packet may be decreased in the process. |
| ProcessingResult ProcessIPv6HeaderAndFilter(std::string* packet, |
| Direction direction, |
| uint8_t* transport_protocol, |
| char** transport_data, |
| icmp6_hdr* icmp_header); |
| |
| void SendIcmpResponse(icmp6_hdr* icmp_header, |
| absl::string_view original_packet, |
| Direction original_direction); |
| |
| void SendTcpReset(absl::string_view original_packet, |
| Direction original_direction); |
| |
| bool IsValid() const { return client_ip_ != kInvalidIpAddress; } |
| |
| // IP address of the server. Used to send ICMP messages. |
| in6_addr self_ip_; |
| // IP address range of the VPN client. |
| QuicIpAddress client_ip_; |
| size_t client_ip_subnet_length_; |
| |
| OutputInterface* output_; |
| StatsInterface* stats_; |
| std::unique_ptr<Filter> filter_; |
| |
| private: |
| // Performs basic sanity and permission checks on the packet, and decreases |
| // the TTL. |
| ProcessingResult ProcessIPv6Header(std::string* packet, |
| Direction direction, |
| uint8_t* transport_protocol, |
| char** transport_data, |
| icmp6_hdr* icmp_header); |
| |
| void SendResponse(Direction original_direction, absl::string_view packet); |
| }; |
| |
| } // namespace quic |
| #endif // QUICHE_QUIC_QBONE_QBONE_PACKET_PROCESSOR_H_ |