From 89bd71c942146f9a77aabab8bc832ec5c3912d6b Mon Sep 17 00:00:00 2001 From: Kevin Krakauer Date: Fri, 5 Jun 2020 11:22:44 -0700 Subject: iptables: don't NAT existing connections Fixes a NAT bug that manifested as: - A SYN was sent from gVisor to another host, unaffected by iptables. - The corresponding SYN/ACK was NATted by a PREROUTING REDIRECT rule despite being part of the existing connection. - The socket that sent the SYN never received the SYN/ACK and thus a connection could not be established. We handle this (as Linux does) by tracking all connections, inserting a no-op conntrack rule for new connections with no rules of their own. Needed for istio support (#170). --- test/iptables/iptables_test.go | 7 ++++++ test/iptables/nat.go | 52 ++++++++++++++++++++++++++++++++++++++++++ 2 files changed, 59 insertions(+) (limited to 'test/iptables') diff --git a/test/iptables/iptables_test.go b/test/iptables/iptables_test.go index f5ac79370..f303030aa 100644 --- a/test/iptables/iptables_test.go +++ b/test/iptables/iptables_test.go @@ -263,6 +263,13 @@ func TestNATPreRedirectTCPPort(t *testing.T) { singleTest(t, NATPreRedirectTCPPort{}) } +func TestNATPreRedirectTCPOutgoing(t *testing.T) { + singleTest(t, NATPreRedirectTCPOutgoing{}) +} + +func TestNATOutRedirectTCPIncoming(t *testing.T) { + singleTest(t, NATOutRedirectTCPIncoming{}) +} func TestNATOutRedirectUDPPort(t *testing.T) { singleTest(t, NATOutRedirectUDPPort{}) } diff --git a/test/iptables/nat.go b/test/iptables/nat.go index 8562b0820..149dec2bb 100644 --- a/test/iptables/nat.go +++ b/test/iptables/nat.go @@ -28,6 +28,8 @@ const ( func init() { RegisterTestCase(NATPreRedirectUDPPort{}) RegisterTestCase(NATPreRedirectTCPPort{}) + RegisterTestCase(NATPreRedirectTCPOutgoing{}) + RegisterTestCase(NATOutRedirectTCPIncoming{}) RegisterTestCase(NATOutRedirectUDPPort{}) RegisterTestCase(NATOutRedirectTCPPort{}) RegisterTestCase(NATDropUDP{}) @@ -91,6 +93,56 @@ func (NATPreRedirectTCPPort) LocalAction(ip net.IP) error { return connectTCP(ip, dropPort, sendloopDuration) } +// NATPreRedirectTCPOutgoing verifies that outgoing TCP connections aren't +// affected by PREROUTING connection tracking. +type NATPreRedirectTCPOutgoing struct{} + +// Name implements TestCase.Name. +func (NATPreRedirectTCPOutgoing) Name() string { + return "NATPreRedirectTCPOutgoing" +} + +// ContainerAction implements TestCase.ContainerAction. +func (NATPreRedirectTCPOutgoing) ContainerAction(ip net.IP) error { + // Redirect all incoming TCP traffic to a closed port. + if err := natTable("-A", "PREROUTING", "-p", "tcp", "-j", "REDIRECT", "--to-ports", fmt.Sprintf("%d", dropPort)); err != nil { + return err + } + + // Establish a connection to the host process. + return connectTCP(ip, acceptPort, sendloopDuration) +} + +// LocalAction implements TestCase.LocalAction. +func (NATPreRedirectTCPOutgoing) LocalAction(ip net.IP) error { + return listenTCP(acceptPort, sendloopDuration) +} + +// NATOutRedirectTCPIncoming verifies that incoming TCP connections aren't +// affected by OUTPUT connection tracking. +type NATOutRedirectTCPIncoming struct{} + +// Name implements TestCase.Name. +func (NATOutRedirectTCPIncoming) Name() string { + return "NATOutRedirectTCPIncoming" +} + +// ContainerAction implements TestCase.ContainerAction. +func (NATOutRedirectTCPIncoming) ContainerAction(ip net.IP) error { + // Redirect all outgoing TCP traffic to a closed port. + if err := natTable("-A", "OUTPUT", "-p", "tcp", "-j", "REDIRECT", "--to-ports", fmt.Sprintf("%d", dropPort)); err != nil { + return err + } + + // Establish a connection to the host process. + return listenTCP(acceptPort, sendloopDuration) +} + +// LocalAction implements TestCase.LocalAction. +func (NATOutRedirectTCPIncoming) LocalAction(ip net.IP) error { + return connectTCP(ip, acceptPort, sendloopDuration) +} + // NATOutRedirectUDPPort tests that packets are redirected to different port. type NATOutRedirectUDPPort struct{} -- cgit v1.2.3