From 19906c4262d8175602ac4ebb2c4e14ee8a9ce140 Mon Sep 17 00:00:00 2001
From: Michael FIG <michael+github@fig.org>
Date: Thu, 31 Oct 2019 13:32:14 -0700
Subject: [PATCH] fix(slot): prevent crosstalk by tracking inbound vs. outbound
 slots

---
 lib/captp.js      | 10 ++++++----
 test/crosstalk.js | 48 +++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 54 insertions(+), 4 deletions(-)
 create mode 100644 test/crosstalk.js

diff --git a/lib/captp.js b/lib/captp.js
index 161b03f93f1..0e185f963b5 100644
--- a/lib/captp.js
+++ b/lib/captp.js
@@ -34,7 +34,7 @@ export function makeCapTP(ourId, send, bootstrapObj = undefined) {
         if (Promise.resolve(val) === val) {
           lastPromiseID += 1;
           const promiseID = lastPromiseID;
-          slot = `p${promiseID}`;
+          slot = `p+${promiseID}`;
           val.then(
             res =>
               send({
@@ -52,7 +52,7 @@ export function makeCapTP(ourId, send, bootstrapObj = undefined) {
         } else {
           lastExportID += 1;
           const exportID = lastExportID;
-          slot = `o${exportID}`;
+          slot = `o+${exportID}`;
         }
         valToSlot.set(val, slot);
         slotToVal.set(slot, val);
@@ -114,8 +114,10 @@ export function makeCapTP(ourId, send, bootstrapObj = undefined) {
   }
 
   function unserializeSlot(data, slots) {
-    const slot = slots[Nat(data.index)];
+    const theirSlot = slots[Nat(data.index)];
     let val;
+    const otherDir = theirSlot[1] === '+' ? '-' : '+';
+    const slot = `${theirSlot[0]}${otherDir}${theirSlot.slice(2)}`;
     if (!slotToVal.has(slot)) {
       // Make a new handled promise for the slot.
       const pr = makeRemote(slot);
@@ -127,7 +129,7 @@ export function makeCapTP(ourId, send, bootstrapObj = undefined) {
         val = presence;
       } else {
         // A new promise
-        imports.set(Number(slot.slice(1)), pr);
+        imports.set(Number(slot.slice(2)), pr);
         val = pr.p;
       }
       slotToVal.set(slot, val);
diff --git a/test/crosstalk.js b/test/crosstalk.js
new file mode 100644
index 00000000000..1e692ab3f6a
--- /dev/null
+++ b/test/crosstalk.js
@@ -0,0 +1,48 @@
+import { test } from 'tape-promise/tape';
+import { harden, makeCapTP, E } from '../lib/captp';
+
+test('prevent crosstalk', async t => {
+  try {
+    const debug = false;
+    let rightDispatch;
+    const { dispatch: leftDispatch, getBootstrap: leftBootstrap } = makeCapTP(
+      'left',
+      obj => {
+        if (debug) {
+          console.log('toRight', obj);
+        }
+        rightDispatch(obj);
+      },
+    );
+    ({ dispatch: rightDispatch } = makeCapTP(
+      'right',
+      obj => {
+        if (debug) {
+          console.log('toLeft', obj);
+        }
+        leftDispatch(obj);
+      },
+      harden({
+        isSide(objP, side) {
+          return E(objP).side().then(s => t.equal(s, side, `obj.side() is ${side}`));
+        },
+        side() {
+          return 'right';
+        },
+      })
+    ));
+    const rightRef = leftBootstrap();
+
+    await E(rightRef).isSide(rightRef, 'right');
+    const leftRef = harden({
+      side() {
+        return 'left';
+      },
+    });
+    await E(rightRef).isSide(leftRef, 'left');
+  } catch (e) {
+    t.isNot(e, e, 'unexpected exception');
+  } finally {
+    t.end();
+  }
+});