fix: interpret circuit relay expiry as seconds (#1636)

Spec update: libp2p/specs#531

Fixes #1635 which causes the circuit relay to repeatedly connect
to a discovered relay. If the relay returns connection expiration in
seconds, we get a negative ttl when calculating 
`expiration - new Date().getTime()`.

This caused the `addRelay` function to set the timeout at 0ms which
triggers instantly.

---------

Co-authored-by: achingbrain <alex@achingbrain.net>

src/circuit/transport/reservation-store.ts

@@ -8,7 +8,7 @@ import type { ConnectionManager } from '@libp2p/interface-connection-manager'
 import type { Connection } from '@libp2p/interface-connection'
 import type { Reservation } from '../pb/index.js'
 import { HopMessage, Status } from '../pb/index.js'
-import { getExpiration } from '../utils.js'
+import { getExpirationMilliseconds } from '../utils.js'
 import type { TransportManager } from '@libp2p/interface-transport'
 import type { Startable } from '@libp2p/interfaces/dist/src/startable.js'
 import { CustomEvent, EventEmitter } from '@libp2p/interfaces/events'
@@ -23,6 +23,9 @@ const REFRESH_WINDOW = (60 * 1000) * 10
 // try to refresh relay reservations 5 minutes before expiry
 const REFRESH_TIMEOUT = (60 * 1000) * 5
 
+// minimum duration before which a reservation must not be refreshed
+const REFRESH_TIMEOUT_MIN = 30 * 1000
+
 export interface RelayStoreComponents {
   peerId: PeerId
   connectionManager: ConnectionManager
@@ -131,7 +134,7 @@ export class ReservationStore extends EventEmitter<ReservationStoreEvents> imple
         const existingReservation = this.reservations.get(peerId)
 
         if (existingReservation != null) {
-          if (getExpiration(existingReservation.reservation.expire) > REFRESH_WINDOW) {
+          if (getExpirationMilliseconds(existingReservation.reservation.expire) > REFRESH_WINDOW) {
             log('already have reservation on relay peer %p and it expires in more than 10 minutes', peerId)
             return
           }
@@ -162,13 +165,16 @@ export class ReservationStore extends EventEmitter<ReservationStoreEvents> imple
 
         log('created reservation on relay peer %p', peerId)
 
-        const expiration = getExpiration(reservation.expire)
+        const expiration = getExpirationMilliseconds(reservation.expire)
+
+        // sets a lower bound on the timeout
+        const timeoutDuration = Math.max(expiration - REFRESH_TIMEOUT, REFRESH_TIMEOUT_MIN)
 
         const timeout = setTimeout(() => {
           this.addRelay(peerId, type).catch(err => {
             log.error('could not refresh reservation to relay %p', peerId, err)
           })
-        }, Math.max(expiration - REFRESH_TIMEOUT, 0))
+        }, timeoutDuration)
 
         this.reservations.set(peerId, {
           timeout,

src/circuit/utils.ts

@@ -115,6 +115,10 @@ export async function namespaceToCid (namespace: string): Promise<CID> {
 /**
  * returns number of ms between now and expiration time
  */
-export function getExpiration (expireTime: bigint): number {
-  return Number(expireTime) - new Date().getTime()
+export function getExpirationMilliseconds (expireTimeSeconds: bigint): number {
+  const expireTimeMillis = expireTimeSeconds * BigInt(1000)
+  const currentTime = new Date().getTime()
+
+  // downcast to number to use with setTimeout
+  return Number(expireTimeMillis - BigInt(currentTime))
 }

test/circuit/utils.spec.ts

@@ -2,7 +2,7 @@
 
 import { mockStream } from '@libp2p/interface-mocks'
 import { expect } from 'aegir/chai'
-import { createLimitedRelay, getExpiration, namespaceToCid } from '../../src/circuit/utils.js'
+import { createLimitedRelay, getExpirationMilliseconds, namespaceToCid } from '../../src/circuit/utils.js'
 import { fromString as uint8arrayFromString } from 'uint8arrays/from-string'
 import delay from 'delay'
 import drain from 'it-drain'
@@ -209,7 +209,7 @@ describe('circuit-relay utils', () => {
   it('should get expiration time', () => {
     const delta = 10
     const time = BigInt(Date.now() + delta)
-    const expiration = getExpiration(time)
+    const expiration = getExpirationMilliseconds(time)
 
     expect(expiration).to.be.above(delta / 2)
   })