From 22e251ac35b54b81732566378fc8d336c6dac0bb Mon Sep 17 00:00:00 2001
From: Justin Karneges <jkarneges@fastly.com>
Date: Fri, 6 Sep 2024 14:07:04 -0700
Subject: [PATCH] add support for gone links

---
 src/handler/httpsession.cpp | 51 ++++++++++++++++++++++++++++++++++++-
 src/handler/instruct.cpp    |  6 +++++
 src/handler/instruct.h      |  1 +
 src/proxy/proxyutil.cpp     |  2 +-
 4 files changed, 58 insertions(+), 2 deletions(-)

diff --git a/src/handler/httpsession.cpp b/src/handler/httpsession.cpp
index 84b3cf2b..d96d2f91 100644
--- a/src/handler/httpsession.cpp
+++ b/src/handler/httpsession.cpp
@@ -115,7 +115,8 @@ class HttpSession::Private : public QObject
 		Proxying,
 		SendingQueue,
 		Holding,
-		Closing
+		Closing,
+		SendingGone,
 	};
 
 	enum Priority
@@ -165,6 +166,7 @@ class HttpSession::Private : public QObject
 	QString errorMessage;
 	QUrl currentUri;
 	QUrl nextUri;
+	QUrl goneUri;
 	bool needUpdate;
 	Priority needUpdatePriority;
 	UpdateAction *pendingAction;
@@ -231,6 +233,12 @@ class HttpSession::Private : public QObject
 
 		if(!instruct.nextLink.isEmpty())
 			nextUri = currentUri.resolved(instruct.nextLink);
+
+		// only work with a gone link provided at initialization time. this
+		// way each request can have a unique gone link, and still share
+		// instructions from next link fetches
+		if(!instruct.goneLink.isEmpty())
+			goneUri = currentUri.resolved(instruct.goneLink);
 	}
 
 	~Private()
@@ -1168,6 +1176,23 @@ class HttpSession::Private : public QObject
 			stats->removeConnection(cid, false);
 		}
 
+		if(!goneUri.isEmpty())
+		{
+			state = SendingGone;
+			prepareOutReq(goneUri);
+			outReq->start("POST", goneUri, HttpHeaders());
+			outReq->endBody();
+			return;
+		}
+
+		finished();
+	}
+
+	void finished()
+	{
+		ZhttpRequest::Rid rid = req->rid();
+		QByteArray cid = rid.first + ':' + rid.second;
+
 		log_debug("httpsession: cleaning up %s", cid.data());
 		cleanup();
 
@@ -1361,6 +1386,25 @@ class HttpSession::Private : public QObject
 					}
 				}
 			}
+			else if(state == SendingGone)
+			{
+				// response should be empty
+				if(outReq->bytesAvailable() > 0)
+				{
+					outReq_error();
+					return;
+				}
+
+				if(outReq->isFinished())
+				{
+					logRequest(outReq->requestMethod(), outReq->requestUri(), outReq->requestHeaders(), outReq->responseCode(), 0);
+
+					cleanupOutReq();
+
+					finished();
+					return;
+				}
+			}
 			else
 			{
 				// unexpected state
@@ -1558,6 +1602,11 @@ private slots:
 				doError();
 			}
 		}
+		else if(state == SendingGone)
+		{
+			log_debug("httpsession: failed to request gone link");
+			finished();
+		}
 		else
 		{
 			// unexpected state
diff --git a/src/handler/instruct.cpp b/src/handler/instruct.cpp
index adeee4ba..5b2c5c0d 100644
--- a/src/handler/instruct.cpp
+++ b/src/handler/instruct.cpp
@@ -287,6 +287,7 @@ Instruct Instruct::fromResponse(const HttpResponseData &response, bool *ok, QStr
 
 	QUrl nextLink;
 	int nextLinkTimeout = -1;
+	QUrl goneLink;
 	foreach(const HttpHeaderParameters &params, response.headers.getAllAsParameters("Grip-Link"))
 	{
 		if(params.count() < 2)
@@ -332,6 +333,10 @@ Instruct Instruct::fromResponse(const HttpResponseData &response, bool *ok, QStr
 				nextLinkTimeout = DEFAULT_NEXTLINK_TIMEOUT;
 			}
 		}
+		else if(rel == "gone")
+		{
+			goneLink = link;
+		}
 	}
 
 	newResponse.headers.clear();
@@ -806,6 +811,7 @@ Instruct Instruct::fromResponse(const HttpResponseData &response, bool *ok, QStr
 	i.response = newResponse;
 	i.nextLink = nextLink;
 	i.nextLinkTimeout = nextLinkTimeout;
+	i.goneLink = goneLink;
 
 	if(ok)
 		*ok = true;
diff --git a/src/handler/instruct.h b/src/handler/instruct.h
index 71bac159..b6b5730a 100644
--- a/src/handler/instruct.h
+++ b/src/handler/instruct.h
@@ -67,6 +67,7 @@ class Instruct
 	HttpResponseData response;
 	QUrl nextLink;
 	int nextLinkTimeout;
+	QUrl goneLink;
 
 	Instruct() :
 		holdMode(NoHold),
diff --git a/src/proxy/proxyutil.cpp b/src/proxy/proxyutil.cpp
index 9191e7d3..ec39ee2a 100644
--- a/src/proxy/proxyutil.cpp
+++ b/src/proxy/proxyutil.cpp
@@ -177,7 +177,7 @@ void manipulateRequestHeaders(const char *logprefix, void *object, HttpRequestDa
 
 		requestData->headers.removeAll("Grip-Feature");
 		requestData->headers += HttpHeader("Grip-Feature",
-			"status, session, link:next, filter:skip-self, filter:skip-users, filter:require-sub, filter:build-id, filter:var-subst");
+			"status, session, link:next, link:gone, filter:skip-self, filter:skip-users, filter:require-sub, filter:build-id, filter:var-subst");
 
 		if(!idata.sid.isEmpty())
 		{