Rename subnet for clarity, pick subnet on client

server/lib/exitNodes/getUniqueSubnetForExitNode.ts

@@ -0,0 +1,41 @@
+import { db, ExitNode, Transaction, sites, clients } from "@server/db";
+import { eq } from "drizzle-orm";
+import config from "@server/lib/config";
+import { findNextAvailableCidr } from "@server/lib/ip";
+import { lockManager } from "#dynamic/lib/lock";
+
+export async function getUniqueSubnetForExitNode(
+    exitNode: ExitNode,
+    trx: Transaction | typeof db = db
+): Promise<string | null> {
+    const lockKey = `subnet-allocation:${exitNode.exitNodeId}`;
+
+    return await lockManager.withLock(
+        lockKey,
+        async () => {
+            const [sitesQuery, clientsQuery] = await Promise.all([
+                trx
+                    .select({ subnet: sites.exitNodeSubnet })
+                    .from(sites)
+                    .where(eq(sites.exitNodeId, exitNode.exitNodeId)),
+                trx
+                    .select({ subnet: clients.exitNodeSubnet })
+                    .from(clients)
+                    .where(eq(clients.exitNodeId, exitNode.exitNodeId))
+            ]);
+
+            const blockSize = config.getRawConfig().gerbil.site_block_size;
+            const subnets = [...sitesQuery, ...clientsQuery]
+                .map((row) => row.subnet)
+                .filter(
+                    (subnet): subnet is string =>
+                        !!subnet &&
+                        /^(\d{1,3}\.){3}\d{1,3}\/\d{1,2}$/.test(subnet)
+                );
+            subnets.push(exitNode.address.replace(/\/\d+$/, `/${blockSize}`));
+
+            return findNextAvailableCidr(subnets, blockSize, exitNode.address);
+        },
+        5000 // 5 second lock TTL - subnet allocation should be quick
+    );
+}

server/lib/exitNodes/index.ts

@@ -3,3 +3,4 @@ export * from "./exitNodeComms";
 export * from "./subnet";
 export * from "./getCurrentExitNodeId";
 export * from "./calculateExitNodeWeight";
+export * from "./getUniqueSubnetForExitNode";