lib/netutil: log only parsing errors for proxy-protocol (#3985)

* lib/netutil: log only parsing errors for proxy-protocol

Previosly every error was logged. With configured TCP health checks at load-balancer or kubernetes, vmauth spams a lot of false positive error message into logs

* Update docs/CHANGELOG.md

Co-authored-by: Roman Khavronenko <roman@victoriametrics.com>

* Update lib/netutil/tcplistener.go

Co-authored-by: Roman Khavronenko <roman@victoriametrics.com>

---------

Co-authored-by: Aliaksandr Valialkin <valyala@victoriametrics.com>
Co-authored-by: Roman Khavronenko <roman@victoriametrics.com>

docs/CHANGELOG.md

@@ -31,6 +31,7 @@ created by v1.90.0 or newer versions. The solution is to upgrade to v1.90.0 or n
 * FEATURE: [vmctl](https://docs.victoriametrics.com/vmctl.html): automatically disable progress bar when TTY isn't available. See [this issue](https://github.com/VictoriaMetrics/VictoriaMetrics/issues/3823).
 
 * BUGFIX: prevent from slow [snapshot creating](https://docs.victoriametrics.com/#how-to-work-with-snapshots) under high data ingestion rate. See [this issue](https://github.com/VictoriaMetrics/VictoriaMetrics/issues/3551).
+* BUGFIX: [vmauth](https://docs.victoriametrics.com/vmauth.html):  suppress [proxy protocol](https://www.haproxy.org/download/2.3/doc/proxy-protocol.txt) parsing errors in case of `EOF`. Usually, the error is caused by health checks and is not a sign of an actual error.
 
 ## [v1.89.1](https://github.com/VictoriaMetrics/VictoriaMetrics/releases/tag/v1.89.1)
 

lib/netutil/tcplistener.go

@@ -5,6 +5,7 @@ import (
 	"errors"
 	"flag"
 	"fmt"
+	"io"
 	"net"
 	"time"
 
@@ -98,7 +99,9 @@ func (ln *TCPListener) Accept() (net.Conn, error) {
 		if ln.useProxyProtocol {
 			pConn, err := newProxyProtocolConn(conn)
 			if err != nil {
+				if !errors.Is(err, io.EOF) {
 					proxyProtocolReadErrorLogger.Errorf("cannot read proxy proto conn for TCP addr %q: %s", ln.Addr(), err)
+				}
 				_ = conn.Close()
 				continue
 			}