From aea752b62dde0f02195b9c2143bdfcdfe65fb6fb Mon Sep 17 00:00:00 2001
From: Azat Khuzhin <azat@libevent.org>
Date: Tue, 23 Mar 2021 09:00:24 +0300
Subject: [PATCH 1/2] bufferevent: introduce bufferevent_replacefd() (like
 setfd() but also close fd)

---
 bufferevent.c                | 28 ++++++++++++++++++++++++++++
 include/event2/bufferevent.h | 12 ++++++++++++
 2 files changed, 40 insertions(+)

diff --git a/bufferevent.c b/bufferevent.c
index 27f2a9ba..53d3a995 100644
--- a/bufferevent.c
+++ b/bufferevent.c
@@ -881,6 +881,34 @@ bufferevent_setfd(struct bufferevent *bev, evutil_socket_t fd)
 	return res;
 }
 
+int
+bufferevent_replacefd(struct bufferevent *bev, evutil_socket_t fd)
+{
+	union bufferevent_ctrl_data d;
+	int err = -1;
+	evutil_socket_t old_fd = EVUTIL_INVALID_SOCKET;
+
+	BEV_LOCK(bev);
+	if (bev->be_ops->ctrl) {
+		err = bev->be_ops->ctrl(bev, BEV_CTRL_GET_FD, &d);
+		if (!err) {
+			old_fd = d.fd;
+			if (old_fd != EVUTIL_INVALID_SOCKET) {
+				err = evutil_closesocket(old_fd);
+			}
+		}
+		if (!err) {
+			d.fd = fd;
+			err = bev->be_ops->ctrl(bev, BEV_CTRL_SET_FD, &d);
+		}
+	}
+	if (err)
+		event_debug(("%s: cannot replace fd for %p from "EV_SOCK_FMT" to "EV_SOCK_FMT, __func__, bev, old_fd, fd));
+	BEV_UNLOCK(bev);
+
+	return err;
+}
+
 evutil_socket_t
 bufferevent_getfd(struct bufferevent *bev)
 {
diff --git a/include/event2/bufferevent.h b/include/event2/bufferevent.h
index 58baf831..a50944f7 100644
--- a/include/event2/bufferevent.h
+++ b/include/event2/bufferevent.h
@@ -377,6 +377,18 @@ void bufferevent_getcb(struct bufferevent *bufev,
 EVENT2_EXPORT_SYMBOL
 int bufferevent_setfd(struct bufferevent *bufev, evutil_socket_t fd);
 
+/**
+  Replaces the file descriptor on which the bufferevent operates.
+  Not supported for all bufferevent types.
+
+  Unlike bufferevent_setfd() it will close previous file descriptor (if any).
+
+  @param bufev the bufferevent object for which to change the file descriptor
+  @param fd the file descriptor to operate on
+*/
+EVENT2_EXPORT_SYMBOL
+int bufferevent_replacefd(struct bufferevent *bufev, evutil_socket_t fd);
+
 /**
    Returns the file descriptor associated with a bufferevent, or -1 if
    no file descriptor is associated with the bufferevent.

From 2385638edf9cb833ebc2759cdb6d6d45dc51a0da Mon Sep 17 00:00:00 2001
From: Azat Khuzhin <azat@libevent.org>
Date: Tue, 23 Mar 2021 09:02:39 +0300
Subject: [PATCH 2/2] http: fix fd leak on fd reset (by using
 bufferevent_replacefd())

Fixes: afa66ea4 ("http: eliminate redundant bev fd manipulating and caching [WIP]")
---
 http.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/http.c b/http.c
index 9dcb1696..28b59b88 100644
--- a/http.c
+++ b/http.c
@@ -1420,7 +1420,7 @@ evhttp_connection_reset_hard_(struct evhttp_connection *evcon)
 	int err;
 
 	/* XXXX This is not actually an optimal fix.  Instead we ought to have
-	   an API for "stop connecting", or use bufferevent_setfd to turn off
+	   an API for "stop connecting", or use bufferevent_replacefd to turn off
 	   connecting.  But for Libevent 2.0, this seems like a minimal change
 	   least likely to disrupt the rest of the bufferevent and http code.
 
@@ -1437,7 +1437,7 @@ evhttp_connection_reset_hard_(struct evhttp_connection *evcon)
 		(*evcon->closecb)(evcon, evcon->closecb_arg);
 
 	/** FIXME: manipulating with fd is unwanted */
-	err = bufferevent_setfd(evcon->bufev, -1);
+	err = bufferevent_replacefd(evcon->bufev, -1);
 	EVUTIL_ASSERT(!err && "setfd");
 
 	/* we need to clean up any buffered data */
@@ -2766,7 +2766,7 @@ evhttp_connection_connect_(struct evhttp_connection *evcon)
 			return (-1);
 		}
 
-		if (bufferevent_setfd(evcon->bufev, fd))
+		if (bufferevent_replacefd(evcon->bufev, fd))
 			return (-1);
 	}
 
@@ -4495,7 +4495,7 @@ evhttp_get_request_connection(
 	evcon->flags |= EVHTTP_CON_INCOMING;
 	evcon->state = EVCON_READING_FIRSTLINE;
 
-	if (bufferevent_setfd(evcon->bufev, fd))
+	if (bufferevent_replacefd(evcon->bufev, fd))
 		goto err;
 	if (bufferevent_enable(evcon->bufev, EV_READ))
 		goto err;