bp(3) Bundle Protocol communications library


#include "bp.h"
[see description for available functions]


The bp library provides functions enabling application software to use Bundle Protocol to send and receive information over a delay-tolerant network. It conforms to the Bundle Protocol specification as documented in Internet RFC 5050.
int bp_attach( )
Attaches the application to BP functionality on the local computer. Returns 0 on success, -1 on any error.

Note that all ION libraries and applications draw memory dynamically, as needed, from a shared pool of ION working memory. The size of the pool is established when ION node functionality is initialized by ionadmin(1). This is a precondition for initializing BP functionality by running bpadmin(1), which in turn is required in order for bp_attach() to succeed.

Sdr bp_get_sdr( )
Returns handle for the SDR data store used for BP, to enable creation and interrogation of bundle payloads (application data units).
void bp_detach( )
Terminates all access to BP functionality on the local computer.
int bp_open(char *eid, BpSAP *ionsapPtr)
Opens the application's access to the BP endpoint identified by eid, so that the application can take delivery of bundles destined for the indicated endpoint and can send bundles whose source is the indicated endpoint. On success, places a value in *ionsapPtr that can be supplied to future bp function invocations and returns 0. Returns -1 on any error.
int bp_send(BpSAP sap, char *destEid, char *reportToEid, int lifespan, int classOfService, BpCustodySwitch custodySwitch, unsigned char srrFlags, int ackRequested, BpExtendedCOS *extendedCOS, Object adu, Object *newBundle)
Sends a bundle to the endpoint identified by destEid, from the source endpoint as provided to the bp_open() call that returned sap. When sap is NULL, the transmitted bundle is anonymous, i.e., the source of the bundle is not identified. This is legal, but anonymous bundles cannot be uniquely identified; custody transfer and status reporting therefore cannot be requested for an anonymous bundle.

reportToEid identifies the endpoint to which any status reports pertaining to this bundle will be sent; if NULL, defaults to the source endpoint.

lifespan is the maximum number of seconds that the bundle can remain in-transit (undelivered) in the network prior to automatic deletion.

classOfService is simply priority for now: BP_BULK_PRIORITY, BP_STD_PRIORITY, or BP_EXPEDITED_PRIORITY. If class-of-service flags are defined in a future version of Bundle Protocol, those flags would be OR'd with priority.

custodySwitch indicates whether or not custody transfer is requested for this bundle and, if so, whether or not the source node itself is required to be the initial custodian. The valid values are SourceCustodyRequired, SourceCustodyOptional, NoCustodyRequired. Note that custody transfer is possible only for bundles that are uniquely identified, so it cannot be requested for bundles for which BP_MINIMUM_LATENCY is requested, since BP_MINIMUM_LATENCY may result in the production of multiple identical copies of the same bundle. Similarly, custody transfer should never be requested for a ``loopback'' bundle, i.e., one whose destination node is the same as the source node: the received bundle will be identical to the source bundle, both residing in the same node, so no custody acceptance signal can be applied to the source bundle and the source bundle will remain in storage until its TTL expires.

srrFlags, if non-zero, is the logical OR of the status reporting behaviors requested for this bundle: BP_RECEIVED_RPT, BP_CUSTODY_RPT, BP_FORWARDED_RPT, BP_DELIVERED_RPT, BP_DELETED_RPT.

ackRequested is a Boolean parameter indicating whether or not the recipient application should be notified that the source application requests some sort of application-specific end-to-end acknowledgment upon receipt of the bundle.

extendedCOS, if not NULL, is used to populate the Extended Class Of Service block for this bundle. The block's ordinal value is used to provide fine-grained ordering within ``expedited'' traffic: ordinal values from 0 (the default) to 254 (used to designate the most urgent traffic) are valid, with 255 reserved for custody signals. The value of the block's flags is the logical OR of the applicable extended class-of-service flags:

BP_MINIMUM_LATENCY designates the bundle as ``critical'' for the purposes of Contact Graph Routing.

BP_BEST_EFFORT signifies that non-reliable convergence-layer protocols, as available, may be used to transmit the bundle. Notably, the bundle may be sent as ``green'' data rather than ``red'' data when issued via LTP.

BP_FLOW_LABEL_PRESENT signifies whether or not the value of flowLabel in extendedCOS must be encoded into the ECOS block when the bundle is transmitted.

adu is the ``application data unit'' that will be conveyed as the payload of the new bundle. adu must be a ``zero-copy object'' (ZCO). ZCOs are normally created by invoking ionCreateZco(), which will block so long as insufficient ZCO storage space is available for creation of the requested ZCO (admission control); if non-blocking behavior is preferred, ZCOs may instead be created by zco_create(), which fails immediately if insufficient ZCO storage space is available.

The function returns 1 on success, 0 on user error, -1 on any system error. If 0 is returned, then an invalid argument value was passed to bp_send(); a message to this effect will have been written to the log file. If 1 is returned, then either the destination of the bundle was ``dtn:none'' (the bit bucket) or the ADU has been accepted and queued for transmission in a bundle; in the latter case (and only in this case) the address of the newly created bundle within the ION database is placed in newBundle, in case the bundle needs to be canceled in the future.

int bp_track(Object bundle, Object trackingElt)
Adds trackingElt to the list of ``tracking'' references in bundle. trackingElt must be the address of an SDR list element --- whose data is the address of this same bundle --- within some list of bundles that is privately managed by the application. Upon destruction of the bundle this list element will automatically be deleted, thus removing the bundle from the application's privately managed list of bundles. This enables the application to keep track of bundles that it is operating on without risk of inadvertently de-referencing the address of a nonexistent bundle.
void bp_untrack(Object bundle, Object trackingElt)
Removes trackingElt from the list of ``tracking'' references in bundle, if it is in that list. Does not delete trackingElt itself.
int bp_suspend(Object bundle)
Suspends transmission of bundle. Has no effect if bundle is ``critical'' (i.e., has got extended class of service BP_MINIMUM_LATENCY flag set) or if the bundle is already suspended. Otherwise, reverses the enqueuing of the bundle to its selected transmission outduct and places it in the ``limbo'' queue until the suspension is lifted by calling bp_resume. Returns 0 on success, -1 on any error.
int bp_resume(Object bundle)
Terminates suspension of transmission of bundle. Has no effect if bundle is ``critical'' (i.e., has got extended class of service BP_MINIMUM_LATENCY flag set) or is not suspended. Otherwise, removes the bundle from the ``limbo'' queue and queues it for route re-computation and re-queuing. Returns 0 on success, -1 on any error.
int bp_cancel(Object bundle)
Cancels transmission of bundle. If the indicated bundle is currently queued for forwarding, transmission, or retransmission, it is removed from the relevant queue and destroyed exactly as if its Time To Live had expired. Returns 0 on success, -1 on any error.
int bp_receive(BpSAP sap, BpDelivery *dlvBuffer, int timeoutSeconds)
Receives a bundle, or reports on some failure of bundle reception activity.

The ``result'' field of the dlvBuffer structure will be used to indicate the outcome of the data reception activity.

If at least one bundle destined for the endpoint for which this SAP is opened has not yet been delivered to the SAP, then the payload of the oldest such bundle will be returned in dlvBuffer->adu and dlvBuffer->result will be set to BpPayloadPresent. If there is no such bundle, bp_receive() blocks for up to timeoutSeconds while waiting for one to arrive.

If timeoutSeconds is BP_POLL (i.e., zero) and no bundle is awaiting delivery, or if timeoutSeconds is greater than zero but no bundle arrives before timeoutSeconds have elapsed, then dlvBuffer->result will be set to BpReceptionTimedOut. If timeoutSeconds is BP_BLOCKING (i.e., -1) then bp_receive() blocks until either a bundle arrives or the function is interrupted by an invocation of bp_interrupt().

dlvBuffer->result will be set to BpReceptionInterrupted in the event that the calling process received and handled some signal other than SIGALRM while waiting for a bundle.

dlvBuffer->result will be set to BpEndpointStopped in the event that the operation of the indicated endpoint has been terminated.

The application data unit delivered in the data delivery structure, if any, will be a ``zero-copy object'' reference. Use zco reception functions (see zco(3)) to read the content of the application data unit.

Be sure to call bp_release_delivery() after every successful invocation of bp_receive().

The function returns 0 on success, -1 on any error.

void bp_interrupt(BpSAP sap)
Interrupts a bp_receive() invocation that is currently blocked. This function is designed to be called from a signal handler; for this purpose, sap may need to be obtained from a static variable.
void bp_release_delivery(BpDelivery *dlvBuffer, int releaseAdu)
Releases resources allocated to the indicated delivery. releaseAdu is a Boolean parameter: if non-zero, the ADU ZCO reference in dlvBuffer (if any) is destroyed, causing the ZCO itself to be destroyed if no other references to it remain.
void bp_close(BpSAP sap)
Terminates the application's access to the BP endpoint identified by the eid cited by the indicated service access point. The application relinquishes its ability to take delivery of bundles destined for the indicated endpoint and to send bundles whose source is the indicated endpoint.