From 1c31f95f7a1e4993ca0f1706002a975a0060dd88 Mon Sep 17 00:00:00 2001
From: Richard Moore <me@ricmoo.com>
Date: Mon, 30 Sep 2024 22:06:52 -0400
Subject: [PATCH] Allow CCIP-read to continue during low-level fetch failures
 (#4842).

---
 src.ts/_tests/test-providers-ccip.ts  | 17 +++++++++++++++-
 src.ts/providers/abstract-provider.ts | 29 ++++++++++++++++++---------
 2 files changed, 36 insertions(+), 10 deletions(-)

diff --git a/src.ts/_tests/test-providers-ccip.ts b/src.ts/_tests/test-providers-ccip.ts
index 49aba46f99..9a3e48628f 100644
--- a/src.ts/_tests/test-providers-ccip.ts
+++ b/src.ts/_tests/test-providers-ccip.ts
@@ -23,7 +23,7 @@ describe("Test CCIP execution", function() {
         assert.equal(result, keccak256(check), "response is equal");
     }
 
-    const address = "0xaeaa06a37e6421ac63120d6daddee0ffa04b43e8";
+    const address = "0xb66e9b20258712bfb9fd40acb13d7712ef149d6e";
     const networkName = "sepolia";
 
     const calldata = "0x1234";
@@ -176,6 +176,21 @@ describe("Test CCIP execution", function() {
         verify(address, calldata, result);
     });
 
+    it("testGetDeadHostFallback passes if any URL returns correctly", async function() {
+        this.timeout(60000);
+
+        const provider = connect(networkName);
+
+        // testGetDeadHostFallback(bytes callData = "0x1234")
+        const tx = {
+            to: address, enableCcipRead: true,
+            data: "0x0324be5a000000000000000000000000000000000000000000000000000000000000002000000000000000000000000000000000000000000000000000000000000000021234000000000000000000000000000000000000000000000000000000000000"
+        }
+
+        const result = await provider.call(tx);
+        verify(address, calldata, result);
+    });
+
     it("testPost passes under normal operation", async function() {
         this.timeout(60000);
 
diff --git a/src.ts/providers/abstract-provider.ts b/src.ts/providers/abstract-provider.ts
index 0a7448e249..0d75b435cc 100644
--- a/src.ts/providers/abstract-provider.ts
+++ b/src.ts/providers/abstract-provider.ts
@@ -42,7 +42,7 @@ import {
 
 import type { Addressable, AddressLike } from "../address/index.js";
 import type { BigNumberish, BytesLike } from "../utils/index.js";
-import type { Listener } from "../utils/index.js";
+import type { FetchResponse, Listener } from "../utils/index.js";
 
 import type { Networkish } from "./network.js";
 import type { FetchUrlFeeDataNetworkPlugin } from "./plugins-network.js";
@@ -604,15 +604,26 @@ export class AbstractProvider implements Provider {
 
             let errorMessage = "unknown error";
 
-            const resp = await request.send();
+            // Fetch the resource...
+            let resp: FetchResponse;
             try {
-                 const result = resp.bodyJson;
-                 if (result.data) {
-                     this.emit("debug", { action: "receiveCcipReadFetchResult", request, result });
-                     return result.data;
-                 }
-                 if (result.message) { errorMessage = result.message; }
-                 this.emit("debug", { action: "receiveCcipReadFetchError", request, result });
+                resp = await request.send();
+            } catch (error: any) {
+                // ...low-level fetch error (missing host, bad SSL, etc.),
+                // so try next URL
+                errorMessages.push(error.message);
+                this.emit("debug", { action: "receiveCcipReadFetchError", request, result: { error } });
+                continue;
+            }
+
+            try {
+                const result = resp.bodyJson;
+                if (result.data) {
+                    this.emit("debug", { action: "receiveCcipReadFetchResult", request, result });
+                    return result.data;
+                }
+                if (result.message) { errorMessage = result.message; }
+                this.emit("debug", { action: "receiveCcipReadFetchError", request, result });
             } catch (error) { }
 
             // 4xx indicates the result is not present; stop