Support RTM_SETLINK in gVisor.

RTM_NEWLINK is the preferred way to change a link's configs. RTM_SETLINK is
needed by setting up Docker in gVisor.

PiperOrigin-RevId: 649789500

pkg/sentry/socket/netlink/route/protocol.go

@@ -162,6 +162,7 @@ func (p *Protocol) getLink(ctx context.Context, s *netlink.Socket, msg *nlmsg.Me
 	return nil
 }
 
+// newLink handles RTM_NEWLINK reqeusts.
 func (p *Protocol) newLink(ctx context.Context, s *netlink.Socket, msg *nlmsg.Message, ms *nlmsg.MessageSet) *syserr.Error {
 	stack := s.Stack()
 	if stack == nil {
@@ -172,6 +173,21 @@ func (p *Protocol) newLink(ctx context.Context, s *netlink.Socket, msg *nlmsg.Me
 	return stack.SetInterface(ctx, msg)
 }
 
+// setLink handles RTM_SETLINK requests.
+func (p *Protocol) setLink(ctx context.Context, s *netlink.Socket, msg *nlmsg.Message, ms *nlmsg.MessageSet) *syserr.Error {
+	stack := s.Stack()
+	if stack == nil {
+		// No network stack.
+		return syserr.ErrProtocolNotSupported
+	}
+
+	if msg.Header().Flags&linux.NLM_F_CREATE == linux.NLM_F_CREATE {
+		return syserr.ErrInvalidArgument
+	}
+
+	return stack.SetInterface(ctx, msg)
+}
+
 // delLink handles RTM_DELLINK requests.
 func (p *Protocol) delLink(ctx context.Context, s *netlink.Socket, msg *nlmsg.Message, ms *nlmsg.MessageSet) *syserr.Error {
 	stack := s.Stack()
@@ -594,14 +610,15 @@ func (p *Protocol) ProcessMessage(ctx context.Context, s *netlink.Socket, msg *n
 			return p.getLink(ctx, s, msg, ms)
 		case linux.RTM_DELLINK:
 			return p.delLink(ctx, s, msg, ms)
+		case linux.RTM_SETLINK:
+			// RTM_NEWLINK is backward compatible to RTM_SETLINK.
+			return p.setLink(ctx, s, msg, ms)
 		case linux.RTM_GETROUTE:
 			return p.dumpRoutes(ctx, s, msg, ms)
 		case linux.RTM_NEWADDR:
 			return p.newAddr(ctx, s, msg, ms)
 		case linux.RTM_DELADDR:
 			return p.delAddr(ctx, s, msg, ms)
-		case linux.RTM_SETLINK:
-			return nil
 		default:
 			return syserr.ErrNotSupported
 		}

test/syscalls/linux/socket_netlink_route.cc

@@ -207,7 +207,14 @@ TEST(NetlinkRouteTest, GetLinkByIndex) {
   EXPECT_TRUE(found) << "Netlink response does not contain any links.";
 }
 
-TEST(NetlinkRouteTest, ChangeLinkName) {
+// NetlinkRouteTest with a single parameter that must be RTM_NEWLINK or
+// RTM_SETLINK.
+using NetlinkSetLinkTest = ::testing::TestWithParam<int>;
+
+INSTANTIATE_TEST_SUITE_P(_, NetlinkSetLinkTest,
+                         ::testing::Values(RTM_NEWLINK, RTM_SETLINK));
+
+TEST_P(NetlinkSetLinkTest, ChangeLinkName) {
   SKIP_IF(!ASSERT_NO_ERRNO_AND_VALUE(HaveCapability(CAP_NET_ADMIN)));
   SKIP_IF(IsRunningWithHostinet());
   // Hosts that run with old kernel allow renaming only when
@@ -231,7 +238,7 @@ TEST(NetlinkRouteTest, ChangeLinkName) {
   // Change the link name.
   struct request req = {};
   req.hdr.nlmsg_len = sizeof(req);
-  req.hdr.nlmsg_type = RTM_NEWLINK;
+  req.hdr.nlmsg_type = GetParam();
   req.hdr.nlmsg_flags = NLM_F_REQUEST | NLM_F_ACK;
   req.hdr.nlmsg_seq = kSeq;
   req.ifm.ifi_family = AF_UNSPEC;
@@ -265,7 +272,7 @@ TEST(NetlinkRouteTest, ChangeLinkName) {
   EXPECT_TRUE(found) << "Netlink response does not contain any links.";
 }
 
-TEST(NetlinkRouteTest, ChangeMTU) {
+TEST_P(NetlinkSetLinkTest, ChangeMTU) {
   SKIP_IF(!ASSERT_NO_ERRNO_AND_VALUE(HaveCapability(CAP_NET_ADMIN)));
   SKIP_IF(IsRunningWithHostinet());
   SKIP_IF(!IsRunningOnGvisor());
@@ -283,7 +290,7 @@ TEST(NetlinkRouteTest, ChangeMTU) {
 
   // Change the MTU.
   req.hdr.nlmsg_len = sizeof(req);
-  req.hdr.nlmsg_type = RTM_NEWLINK;
+  req.hdr.nlmsg_type = GetParam();
   req.hdr.nlmsg_flags = NLM_F_REQUEST | NLM_F_ACK;
   req.hdr.nlmsg_seq = kSeq;
   req.ifm.ifi_family = AF_UNSPEC;