Add /proc/sys/net/ipv4/ip_forward

2 files changed, 33 insertions, 0 deletions

diff --git a/pkg/sentry/socket/hostinet/BUILD b/pkg/sentry/socket/hostinet/BUILD
index 4d174dda4..c1b20eaf8 100644
--- a/pkg/sentry/socket/hostinet/BUILD
+++ b/pkg/sentry/socket/hostinet/BUILD
@@ -32,6 +32,9 @@ go_library(
         "//pkg/sentry/usermem",
         "//pkg/syserr",
         "//pkg/syserror",
+        "//pkg/tcpip",
+        "//pkg/tcpip/network/ipv4",
+        "//pkg/tcpip/network/ipv6",
         "//pkg/waiter",
     ],
 )
diff --git a/pkg/sentry/socket/hostinet/stack.go b/pkg/sentry/socket/hostinet/stack.go
index d4387f5d4..4b460d30e 100644
--- a/pkg/sentry/socket/hostinet/stack.go
+++ b/pkg/sentry/socket/hostinet/stack.go
@@ -31,6 +31,9 @@ import (
 	"gvisor.dev/gvisor/pkg/sentry/usermem"
 	"gvisor.dev/gvisor/pkg/syserr"
 	"gvisor.dev/gvisor/pkg/syserror"
+	"gvisor.dev/gvisor/pkg/tcpip"
+	"gvisor.dev/gvisor/pkg/tcpip/network/ipv4"
+	"gvisor.dev/gvisor/pkg/tcpip/network/ipv6"
 )
 
 var defaultRecvBufSize = inet.TCPBufferSize{
@@ -57,6 +60,8 @@ type Stack struct {
 	tcpSACKEnabled bool
 	netDevFile     *os.File
 	netSNMPFile    *os.File
+	ipv4Forwarding bool
+	ipv6Forwarding bool
 }
 
 // NewStack returns an empty Stack containing no configuration.
@@ -116,6 +121,13 @@ func (s *Stack) Configure() error {
 		s.netSNMPFile = f
 	}
 
+	s.ipv4Forwarding = false
+	if ipForwarding, err := ioutil.ReadFile("/proc/sys/net/ipv4/ip_forward"); err == nil {
+		s.ipv4Forwarding = strings.TrimSpace(string(ipForwarding)) != "0"
+	} else {
+		log.Warningf("Failed to read if IPv4 forwarding is enabled, setting to false")
+	}
+
 	return nil
 }
 
@@ -442,3 +454,21 @@ func (s *Stack) RouteTable() []inet.Route {
 
 // Resume implements inet.Stack.Resume.
 func (s *Stack) Resume() {}
+
+// Forwarding implements inet.Stack.Forwarding.
+func (s *Stack) Forwarding(protocol tcpip.NetworkProtocolNumber) bool {
+	switch protocol {
+	case ipv4.ProtocolNumber:
+		return s.ipv4Forwarding
+	case ipv6.ProtocolNumber:
+		return s.ipv6Forwarding
+	default:
+		log.Warningf("Forwarding(%v) failed: unsupported protocol", protocol)
+		return false
+	}
+}
+
+// SetForwarding implements inet.Stack.SetForwarding.
+func (s *Stack) SetForwarding(protocol tcpip.NetworkProtocolNumber, enable bool) error {
+	return syserror.EACCES
+}