/**
* "Called when the next hop link is available for transmission (i.e. either when it first arrives
* and the contact is brought up or when a bundle is completed and it's no longer busy).
*
* <p>Loops through the bundle list and calls fwd_to_matching on all bundles." [DTN2]
*/
protected void check_next_hop(Link next_hop) {
// "if the link isn't open, there's nothing to do now" [DTN2]
if (!next_hop.isopen()) {
Log.d(
TAG,
String.format(
"check_next_hop %s -> %s: link not open...", next_hop.name(), next_hop.nexthop()));
return;
}
// "if the link queue doesn't have space (based on the low water
// mark) don't do anything" [DTN2]
if (!next_hop.queue_has_space()) {
Log.d(
TAG,
String.format(
"check_next_hop %s -> %s: no space in queue...",
next_hop.name(), next_hop.nexthop()));
return;
}
Log.d(
TAG,
String.format(
"check_next_hop %s -> %s: checking deferred bundle list...",
next_hop.name(), next_hop.nexthop()));
// "because the loop below will remove the current bundle from
// the deferred list, invalidating any iterators pointing to its
// position, make sure to advance the iterator before processing
// the current bundle" [DTN2]
DeferredList deferred = deferred_list(next_hop);
deferred.list().get_lock().lock();
try {
Iterator<Bundle> iter = deferred.list().begin();
while (iter.hasNext()) {
if (next_hop.queue_is_full()) {
Log.d(
TAG,
String.format(
"check_next_hop %s: link queue is full, stopping loop", next_hop.name()));
break;
}
Bundle bundle = iter.next();
ForwardingInfo info = deferred.find(bundle);
assert info != null
: "TableBasedRouter: check_next_hop, ForwardingInfo regarding Bundle is null";
// "if should_fwd returns false, then the bundle was either
// already transmitted or is in flight on another node. since
// it's possible that one of the other transmissions will
// fail, we leave it on the deferred list for now, relying on
// the transmitted handlers to clean up the state" [DTN2]
if (!this.should_fwd(bundle, next_hop, info.action())) {
Log.d(TAG, String.format("check_next_hop: not forwarding to link %s", next_hop.name()));
continue;
}
// "if the link is available and not open, open it" [DTN2]
if (next_hop.isNotUnavailable() && (!next_hop.isopen()) && (!next_hop.isopening())) {
Log.d(
TAG,
String.format(
"check_next_hop: " + "opening %s because a message is intended for it",
next_hop.name()));
actions_.open_link(next_hop);
}
// "remove the bundle from the deferred list" [DTN2]
Log.d(
TAG,
String.format(
"check_next_hop: sending bundle %d to %s", bundle.bundleid(), next_hop.name()));
iter.remove();
actions_.queue_bundle(bundle, next_hop, info.action(), info.custody_spec());
}
} catch (BundleListLockNotHoldByCurrentThread e) {
Log.e(TAG, "Table Based Router " + e.toString());
} finally {
deferred.list().get_lock().unlock();
}
}
/** "Try to forward a bundle to a next hop route." [DTN2] */
protected boolean fwd_to_nexthop(Bundle bundle, RouteEntry route) {
Link link = route.link();
// "if the link is available and not open, open it" [DTN2]
if (link.isNotUnavailable() && (!link.isopen()) && (!link.isopening())) {
Log.d(TAG, String.format("opening %s because a message is intended for it", link.name()));
actions_.open_link(link);
}
// "if the link is open and has space in the queue, then queue the
// bundle for transmission there" [DTN2]
if (link.isopen() && !link.queue_is_full()) {
Log.d(TAG, String.format("queuing %d on %s", bundle.bundleid(), link.name()));
actions_.queue_bundle(bundle, link, route.action(), route.custody_spec());
return true;
}
// "otherwise we can't send the bundle now, so put it on the link's
// deferred list and log reason why we can't forward it" [DTN2]
DeferredList deferred = deferred_list(link);
if (!bundle.is_queued_on(deferred.list())) {
ForwardingInfo info =
new ForwardingInfo(
ForwardingInfo.state_t.NONE,
route.action(),
link.name_str(),
0xffffffff,
link.remote_eid(),
route.custody_spec());
deferred.add(bundle, info);
} else {
Log.w(
TAG,
String.format(
"bundle %d already exists on deferred list of link %s",
bundle.bundleid(), link.name()));
}
if (!link.isNotUnavailable()) {
Log.d(
TAG,
String.format(
"can't forward bundle %d to %s because link not available",
bundle.bundleid(), link.name()));
} else if (!link.isopen()) {
Log.d(
TAG,
String.format(
TAG,
"can't forward bundle %d to %s because link not open",
bundle.bundleid(),
link.name()));
} else if (link.queue_is_full()) {
Log.d(
TAG,
String.format(
TAG,
"can't forward bundle %d to %s because link queue is full",
bundle.bundleid(),
link.name()));
} else {
Log.d(TAG, String.format(TAG, "can't forward %d to %s", bundle.bundleid(), link.name()));
}
return false;
}