Add listener side proxy protocol support and enable it in traefik (#5332)

Co-authored-by: mlsmaycon <mlsmaycon@gmail.com>

proxy/proxyprotocol_test.go

@@ -0,0 +1,106 @@
+package proxy
+
+import (
+	"net"
+	"net/netip"
+	"testing"
+	"time"
+
+	proxyproto "github.com/pires/go-proxyproto"
+	log "github.com/sirupsen/logrus"
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+func TestWrapProxyProtocol_OverridesRemoteAddr(t *testing.T) {
+	srv := &Server{
+		Logger:         log.StandardLogger(),
+		TrustedProxies: []netip.Prefix{netip.MustParsePrefix("127.0.0.1/32")},
+		ProxyProtocol:  true,
+	}
+
+	raw, err := net.Listen("tcp", "127.0.0.1:0")
+	require.NoError(t, err)
+	defer raw.Close()
+
+	ln := srv.wrapProxyProtocol(raw)
+
+	realClientIP := "203.0.113.50"
+	realClientPort := uint16(54321)
+
+	accepted := make(chan net.Conn, 1)
+	go func() {
+		conn, err := ln.Accept()
+		if err != nil {
+			return
+		}
+		accepted <- conn
+	}()
+
+	// Connect and send a PROXY v2 header.
+	conn, err := net.Dial("tcp", ln.Addr().String())
+	require.NoError(t, err)
+	defer conn.Close()
+
+	header := &proxyproto.Header{
+		Version:           2,
+		Command:           proxyproto.PROXY,
+		TransportProtocol: proxyproto.TCPv4,
+		SourceAddr:        &net.TCPAddr{IP: net.ParseIP(realClientIP), Port: int(realClientPort)},
+		DestinationAddr:   &net.TCPAddr{IP: net.ParseIP("10.0.0.1"), Port: 443},
+	}
+	_, err = header.WriteTo(conn)
+	require.NoError(t, err)
+
+	select {
+	case accepted := <-accepted:
+		defer accepted.Close()
+		host, _, err := net.SplitHostPort(accepted.RemoteAddr().String())
+		require.NoError(t, err)
+		assert.Equal(t, realClientIP, host, "RemoteAddr should reflect the PROXY header source IP")
+	case <-time.After(2 * time.Second):
+		t.Fatal("timed out waiting for connection")
+	}
+}
+
+func TestProxyProtocolPolicy_TrustedRequires(t *testing.T) {
+	srv := &Server{
+		Logger:         log.StandardLogger(),
+		TrustedProxies: []netip.Prefix{netip.MustParsePrefix("10.0.0.0/8")},
+	}
+
+	opts := proxyproto.ConnPolicyOptions{
+		Upstream: &net.TCPAddr{IP: net.ParseIP("10.0.0.1"), Port: 1234},
+	}
+	policy, err := srv.proxyProtocolPolicy(opts)
+	require.NoError(t, err)
+	assert.Equal(t, proxyproto.REQUIRE, policy, "trusted source should require PROXY header")
+}
+
+func TestProxyProtocolPolicy_UntrustedIgnores(t *testing.T) {
+	srv := &Server{
+		Logger:         log.StandardLogger(),
+		TrustedProxies: []netip.Prefix{netip.MustParsePrefix("10.0.0.0/8")},
+	}
+
+	opts := proxyproto.ConnPolicyOptions{
+		Upstream: &net.TCPAddr{IP: net.ParseIP("203.0.113.50"), Port: 1234},
+	}
+	policy, err := srv.proxyProtocolPolicy(opts)
+	require.NoError(t, err)
+	assert.Equal(t, proxyproto.IGNORE, policy, "untrusted source should have PROXY header ignored")
+}
+
+func TestProxyProtocolPolicy_InvalidIPRejects(t *testing.T) {
+	srv := &Server{
+		Logger:         log.StandardLogger(),
+		TrustedProxies: []netip.Prefix{netip.MustParsePrefix("10.0.0.0/8")},
+	}
+
+	opts := proxyproto.ConnPolicyOptions{
+		Upstream: &net.UnixAddr{Name: "/tmp/test.sock", Net: "unix"},
+	}
+	policy, err := srv.proxyProtocolPolicy(opts)
+	require.NoError(t, err)
+	assert.Equal(t, proxyproto.REJECT, policy, "unparsable address should be rejected")
+}