net/http: also log TLS errors which look like HTTP sent to an HTTPS port

We log TLS handshake errors in general, but currently do not log errors
when the first TLS record looks like an attempt to send HTTP to an HTTPS
port. There doesn't seem to be any principled reason to log the one and
not the other, so just log all TLS handshake errors.

Fixes #66501

Change-Id: I5d78a754d054c220be935513448515721fa387a6
Reviewed-on: https://go-review.googlesource.com/c/go/+/573979
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Jonathan Amsterdam <jba@google.com>
Reviewed-by: Emmanuel Odeke <emmanuel@orijtech.com>
Auto-Submit: Emmanuel Odeke <emmanuel@orijtech.com>
Run-TryBot: Emmanuel Odeke <emmanuel@orijtech.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>

src/net/http/server.go

@@ -1922,12 +1922,15 @@ func (c *conn) serve(ctx context.Context) {
 			// If the handshake failed due to the client not speaking
 			// TLS, assume they're speaking plaintext HTTP and write a
 			// 400 response on the TLS conn's underlying net.Conn.
+			var reason string
 			if re, ok := err.(tls.RecordHeaderError); ok && re.Conn != nil && tlsRecordHeaderLooksLikeHTTP(re.RecordHeader) {
 				io.WriteString(re.Conn, "HTTP/1.0 400 Bad Request\r\n\r\nClient sent an HTTP request to an HTTPS server.\n")
 				re.Conn.Close()
-				return
+				reason = "client sent an HTTP requset to an HTTPS server"
+			} else {
+				reason = err.Error()
 			}
-			c.server.logf("http: TLS handshake error from %s: %v", c.rwc.RemoteAddr(), err)
+			c.server.logf("http: TLS handshake error from %s: %v", c.rwc.RemoteAddr(), reason)
 			return
 		}
 		// Restore Conn-level deadlines.