From 51de0f831bf4b1bdcb84101f95009fde83d35a27 Mon Sep 17 00:00:00 2001
From: Xargin <buaa.cch@gmail.com>
Date: Wed, 8 Sep 2021 00:22:00 +0800
Subject: [PATCH] crypto/tls: shrink tls Conn's rawInput buffer when Read
 timeout

This will reduce the rawInput buffer memory cost for large number of idle tls connections
---
 src/crypto/tls/conn.go | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/src/crypto/tls/conn.go b/src/crypto/tls/conn.go
index 969f357834c..6d37600a38b 100644
--- a/src/crypto/tls/conn.go
+++ b/src/crypto/tls/conn.go
@@ -797,6 +797,14 @@ func (c *Conn) readFromUntil(r io.Reader, n int) error {
 	// "predict" closeNotify alerts.
 	c.rawInput.Grow(needs + bytes.MinRead)
 	_, err := c.rawInput.ReadFrom(&atLeastReader{r, int64(needs)})
+
+	// Read timeout, and we do not get any data, connection is idle,
+	// we should replace rawInput buffer with a small one
+	if e, ok := err.(net.Error); ok && e.Timeout() &&
+		c.rawInput.Len() == 0 && c.rawInput.Cap() > 4*bytes.MinRead {
+		c.rawInput = *bytes.NewBuffer(make([]byte, 0, bytes.MinRead))
+	}
+
 	return err
 }