/* * Copyright 2009-2010 Darren Long, darren.long@mac.com * Copyright 2006 Intel Corporation * * Licensed under the Apache License, Version 2.0 (the "License"); * you may not use this file except in compliance with the License. * You may obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. */ #ifndef _SEQPACKET_CONVERGENCE_LAYER_H_ #define _SEQPACKET_CONVERGENCE_LAYER_H_ #include "ConnectionConvergenceLayer.h" #include "CLConnection.h" namespace dtn { /** * Another shared-implementation convergence layer class for use with * reliable, in-order SEQ_PACKET protocols, i.e. Connected Mode AX.25. * The goal is to share as much functionality as * possible between protocols that have in-order, reliable, delivery * semantics, but require fixed sized payloads rather than conforming to * stream semantics. * * For the protocol, bundles are broken up into configurable-sized * segments that are sent sequentially. Only a single bundle is * inflight on the wire at one time (i.e. we don't interleave segments * from different bundles). When segment acknowledgements are enabled * (the default behavior), the receiving node sends an acknowledgement * for each segment of the bundle that was received. * * Keepalive messages are sent back and forth to ensure that the * connection remains open. In the case of on demand links, a * configurable idle timer is maintained to close the link when no * bundle traffic has been sent or received. Links that are expected * to be open but have broken due to underlying network conditions * (i.e. always on and on demand links) are reopened by a timer that * is managed by the contact manager. * * Flow control is managed through the poll callbacks given by the * base class CLConnection. In send_pending_data, we check if there * are any acks that need to be sent, then check if there are bundle * segments to be sent (i.e. acks are given priority). The only * exception to this is that the connection might be write blocked in * the middle of sending a data segment. In that case, we must first * finish transmitting the current segment before sending any other * acks (or the shutdown message), otherwise those messages will be * consumed as part of the payload. * * To make sure that we don't deadlock with the other side, we always * drain any data that is ready on the channel. All incoming messages * mark state in the appropriate data structures (i.e. InFlightList * and IncomingList), then rely on send_pending_data to send the * appropriate responses. * * The InflightBundle is used to record state about bundle * transmissions. To record the segments that have been sent, we fill * in the sent_data_ sparse bitmap with the range of bytes as we send * segments out. As acks arrive, we extend the ack_data_ field to * match. Once the whole bundle is acked, the entry is removed from * the InFlightList. * * The IncomingBundle is used to record state about bundle reception. * The rcvd_data_ bitmap is extended contiguously with the amount of * data that has been received, including partially received segments. * * To track segments that we have received but haven't yet acked, we * set a single bit for the offset of the end of the segment in the * ack_data_ bitmap. We also separately record the total range of acks * that have been previously sent in acked_length_. As we send acks * out, we clear away the bits in ack_data_ */ class SeqpacketConvergenceLayer : public ConnectionConvergenceLayer { public: /** * Constructor */ SeqpacketConvergenceLayer(const char* logpath, const char* cl_name, u_int8_t cl_version); protected: /** * Values for ContactHeader flags. */ typedef enum { SEGMENT_ACK_ENABLED = 1 << 0, ///< segment acks requested REACTIVE_FRAG_ENABLED = 1 << 1, ///< reactive fragmentation enabled NEGATIVE_ACK_ENABLED = 1 << 2, ///< refuse bundle enabled } contact_header_flags_t; /** * Contact initiation header. Sent at the beginning of a contact. */ struct ContactHeader { u_int32_t magic; ///< magic word (MAGIC: "dtn!") u_int8_t version; ///< cl protocol version u_int8_t flags; ///< connection flags (see above) u_int16_t keepalive_interval; ///< seconds between keepalive packets // SDNV local_eid_length local eid length // byte[] local_eid local eid data } __attribute__((packed)); /** * Valid type codes for the protocol messages, shifted into the * high-order four bits of the byte. The lower four bits are used * for per-message flags, defined below. */ typedef enum { DATA_SEGMENT = 0x1 << 4, ///< a segment of bundle data ///< (followed by a SDNV segment length) ACK_SEGMENT = 0x2 << 4, ///< acknowledgement of a segment ///< (followed by a SDNV ack length) REFUSE_BUNDLE = 0x3 << 4, ///< reject reception of current bundle KEEPALIVE = 0x4 << 4, ///< keepalive packet SHUTDOWN = 0x5 << 4, ///< about to shutdown } msg_type_t; /** * Valid flags for the DATA_SEGMENT message. */ typedef enum { BUNDLE_START = 0x1 << 1, ///< First segment of a bundle BUNDLE_END = 0x1 << 0, ///< Last segment of a bundle } data_segment_flags_t; /** * Valid flags for the SHUTDOWN message. */ typedef enum { SHUTDOWN_HAS_REASON = 0x1 << 1, ///< Has reason code SHUTDOWN_HAS_DELAY = 0x1 << 0, ///< Has reconnect delay } shutdown_flags_t; /** * Values for the SHUTDOWN reason codes */ typedef enum { SHUTDOWN_NO_REASON = 0xff, ///< no reason code (never sent) SHUTDOWN_IDLE_TIMEOUT = 0x0, ///< idle connection SHUTDOWN_VERSION_MISMATCH = 0x1, ///< version mismatch SHUTDOWN_BUSY = 0x2, ///< node is busy } shutdown_reason_t; /** * Convert a reason code to a string. */ static const char* shutdown_reason_to_str(shutdown_reason_t reason) { switch (reason) { case SHUTDOWN_NO_REASON: return "no reason"; case SHUTDOWN_IDLE_TIMEOUT: return "idle connection"; case SHUTDOWN_VERSION_MISMATCH: return "version mismatch"; case SHUTDOWN_BUSY: return "node is busy"; } NOTREACHED; } /** * Link parameters shared among all Seqpacket based convergence layers. */ class SeqpacketLinkParams : public ConnectionConvergenceLayer::LinkParams { public: bool segment_ack_enabled_; ///< Use per-segment acks bool negative_ack_enabled_;///< Enable negative acks u_int keepalive_interval_; ///< Seconds between keepalive packets u_int segment_length_; ///< Maximum size of transmitted segments u_int ack_window_; ///< Number of segments before acking protected: // See comment in LinkParams for why this should be protected SeqpacketLinkParams(bool init_defaults); }; /** * Version of the actual CL protocol. */ u_int8_t cl_version_; /** * Seqpacket connection class. */ class Connection : public CLConnection { public: /** * Constructor. */ Connection(const char* classname, const char* logpath, SeqpacketConvergenceLayer* cl, SeqpacketLinkParams* params, bool active_connector); /// @{ virtual from CLConnection bool send_pending_data(); void handle_bundles_queued(); void handle_cancel_bundle(Bundle* bundle); void handle_poll_timeout(); void break_contact(ContactEvent::reason_t reason); /// @} protected: /** * Hook used to tell the derived CL class to drain data out of * the send buffer. */ virtual void send_data() = 0; /// @{ utility functions used by derived classes void initiate_contact(); void process_data(); void check_keepalive(); /// @} private: /// @{ utility functions used internally in this class void note_data_rcvd(); void note_data_sent(); bool send_pending_acks(); bool start_next_bundle(); bool send_next_segment(InFlightBundle* inflight); bool send_data_todo(InFlightBundle* inflight); bool finish_bundle(InFlightBundle* inflight); void check_completed(InFlightBundle* inflight); void send_keepalive(); void handle_contact_initiation(); bool handle_data_segment(u_int8_t flags); bool handle_data_todo(); bool handle_ack_segment(u_int8_t flags); bool handle_refuse_bundle(u_int8_t flags); bool handle_keepalive(u_int8_t flags); bool handle_shutdown(u_int8_t flags); void check_completed(IncomingBundle* incoming); /// @} /** * Utility function to downcast the params_ pointer that's * stored in the CLConnection parent class. */ SeqpacketLinkParams* seqpacket_lparams() { SeqpacketLinkParams* ret = dynamic_cast(params_); ASSERT(ret != NULL); return ret; } protected: InFlightBundle* current_inflight_; ///< Current bundle that's in flight size_t send_segment_todo_; ///< Bytes left to send of current segment std::queue sendbuf_sequence_delimiters_; ///< sendbuf_ may hold many segments size_t recv_segment_todo_; ///< Bytes left to recv of current segment struct timeval data_rcvd_; ///< Timestamp for idle/keepalive timer struct timeval data_sent_; ///< Timestamp for idle timer struct timeval keepalive_sent_; ///< Timestamp for keepalive timer bool breaking_contact_; ///< Bit to catch multiple calls to ///< break_contact bool contact_initiated_; ///< bit to prevent certain actions before ///< contact is initiated u_int ack_window_todo_; ///< number of segments left in ack_window }; /// For some gcc variants, this typedef seems to be needed typedef ConnectionConvergenceLayer::LinkParams LinkParams; /// @{ Virtual from ConvergenceLayer void dump_link(const LinkRef& link, oasys::StringBuffer* buf); /// @} /// @{ Virtual from ConnectionConvergenceLayer bool parse_link_params(LinkParams* params, int argc, const char** argv, const char** invalidp); bool finish_init_link(const LinkRef& link, LinkParams* params); /// @} }; } // namespace dtn #endif /* _STREAM_CONVERGENCE_LAYER_H_ */