Added bridge replacement

crates/lox-library/src/bridge_table.rs

@@ -224,8 +224,17 @@ pub struct BridgeTable {
     /// them.  When a new Migration credential is needed, a bucket is
     /// removed from this set and used for that purpose.
     pub spares: HashSet<u32>,
+    /// bucket ids of "recyclable" buckets.  These buckets have not been handed out
+    /// to users, nor do they have any Migration credentials pointing to
+    /// them. When a single bridge is needed and there are no more readily available bridges,
+    /// bridges are taken from a bucket of hot spares, making the unallocated spare bucket empty
+    /// but still useable as it has not been handed out previously.
+    pub recyclable: HashSet<u32>,
+    /// In some instances a single bridge may need to be added to a bucket
+    /// In some instances a single bridge may need to be added to a bucket
+    /// In that case, a spare bucket will be removed from the set of spare bridges. One
+    pub unallocated_bridges: Vec<BridgeLine>,
     /// The date the buckets were last encrypted to make the encbucket.
-    ///
     /// The encbucket must be rebuilt each day so that the Bucket
     /// Reachability credentials in the buckets can be refreshed.
     pub date_last_enc: u32,

crates/lox-library/src/lib.rs

@@ -366,11 +366,125 @@ impl BridgeAuth {
                 return res;
             }
         }
-        if !res {
-            // Assume the bridge is new and should be added to unallocated bridges or else a new bucket
+        // If this is returned, we assume that the bridge wasn't found in the bridge table
+        // and therefore should be treated as a "new bridge"
+        res
+    }
 
+    pub fn bridge_replace(
+        &mut self,
+        bridge: &BridgeLine,
+        available_bridge: Option<&BridgeLine>,
+        bdb: &mut BridgeDb,
+    ) -> bool {
+        let mut res: bool = false;
+        let reachable_bridges = &self.bridge_table.reachable.clone();
+        if let Some(positions) = reachable_bridges.get(bridge) {
+            for (bucketnum, offset) in positions.iter() {
+                // Remove the bridge from the bucket
+                assert!(self.bridge_table.buckets[*bucketnum as usize][*offset] == *bridge);
+                self.bridge_table.reachable.remove(bridge);
+                if available_bridge.is_some() {
+                    self.bridge_table.buckets[*bucketnum as usize][*offset] =
+                        *available_bridge.unwrap();
+                    // Remove the bridge from the reachable bridges and add new bridge
+                    self.bridge_table
+                        .reachable
+                        .insert(*available_bridge.unwrap(), positions.clone());
+                    res = true
+                } else if !self.bridge_table.unallocated_bridges.is_empty() {
+                    self.bridge_table.buckets[*bucketnum as usize][*offset] =
+                        self.bridge_table.unallocated_bridges.pop().unwrap();
+                    // Remove the bridge from the reachable bridges and add new bridge
+                    self.bridge_table.reachable.insert(
+                        self.bridge_table.unallocated_bridges.pop().unwrap(),
+                        positions.clone(),
+                    );
+                    res = true
+                } else if !self.bridge_table.spares.is_empty() {
+                    // Get the first spare and remove it from the spares
+                    // set.
+                    let spare = *self.bridge_table.spares.iter().next().unwrap();
+                    self.bridge_table.spares.remove(&spare);
+                    // Indicate the removed bucket as a recyclable bucket
+                    self.bridge_table.recyclable.insert(spare);
+                    // Get the actual bridges from the spare bucket
+                    let mut replacement: &BridgeLine = &BridgeLine::default();
+                    // Make the first spare the replacement bridge, add the others to the set of
+                    // unallocated_bridges
+                    let spare_bucket = self.bridge_table.buckets[spare as usize].clone();
+                    for spare_bridge in spare_bucket.iter() {
+                        if replacement.port > 0 {
+                            self.bridge_table.unallocated_bridges.push(*spare_bridge);
+                        } else {
+                            replacement = spare_bridge;
+                        }
+                    }
+                    self.bridge_table.buckets[*bucketnum as usize][*offset] = *replacement;
+                    self.bridge_table
+                        .reachable
+                        .insert(*replacement, positions.clone());
+                    res = true
+                }
+                // If there are no available bridges that can be assigned here, the only thing
+                // that can be done is return an indication that updating the gone bridge
+                // didn't work.
+
+                // Now we should check that the bucket hasn't become "blocked" due to having no available
+                // bridges
+                if !res {
+                    // Count how many bridges in this bucket are reachable
+                    let numreachable = self.bridge_table.buckets[*bucketnum as usize]
+                        .iter()
+                        .filter(|br| self.bridge_table.reachable.get(br).is_some())
+                        .count();
+
+                    // Is this bucket an open-invitation bucket?
+                    if bdb.openinv_buckets.contains(bucketnum) {
+                        bdb.openinv_buckets.remove(bucketnum);
+                        self.trustup_migration_table.table.remove(bucketnum);
+                        continue;
+                    }
+
+                    // Has the bucket fallen below the
+                    // threshold?
+                    if numreachable == MIN_BUCKET_REACHABILITY {
+                        // This bucket is now unreachable.  Get a spare bucket
+                        if self.bridge_table.spares.is_empty() {
+                            // Uh, oh.  No spares available.  Just delete any
+                            // migrations leading to this bucket.
+                            self.trustup_migration_table
+                                .table
+                                .retain(|_, &mut v| v != *bucketnum);
+                            self.blockage_migration_table
+                                .table
+                                .retain(|_, &mut v| v != *bucketnum);
+                        } else {
+                            // Get the first spare and remove it from the spares
+                            // set.
+                            let spare = *self.bridge_table.spares.iter().next().unwrap();
+                            self.bridge_table.spares.remove(&spare);
+                            // Add a blockage migration from this bucket to the spare
+                            self.blockage_migration_table
+                                .table
+                                .insert(*bucketnum, spare);
+                            // Remove any trust upgrade migrations to this
+                            // bucket
+                            self.trustup_migration_table
+                                .table
+                                .retain(|_, &mut v| v != *bucketnum);
+                            // Change any blockage migrations with this bucket
+                            // as the destination to the spare
+                            for (_, v) in self.blockage_migration_table.table.iter_mut() {
+                                if *v == *bucketnum {
+                                    *v = spare;
+                                }
+                            }
+                        }
+                    }
+                }
+            }
         }
-
         res
     }