Add support for custom socket options and setting the experiment IP option.

PiperOrigin-RevId: 700011458

pkg/sentry/socket/netstack/BUILD

@@ -12,6 +12,7 @@ go_library(
         "netstack_state.go",
         "provider.go",
         "save_restore.go",
+        "socketopt_custom.go",
         "stack.go",
         "tun.go",
     ],

pkg/sentry/socket/netstack/netstack.go

@@ -1107,6 +1107,10 @@ func getSockOptSocket(t *kernel.Task, s socket.Socket, ep commonEndpoint, family
 
 		v := primitive.Int32(ep.SocketOptions().GetRcvlowat())
 		return &v, nil
+	default:
+		if v, err, handled := getSockOptSocketCustom(t, s, ep, name, outLen); handled {
+			return v, err
+		}
 	}
 	return nil, syserr.ErrProtocolNotAvailable
 }
@@ -2028,6 +2032,10 @@ func setSockOptSocket(t *kernel.Task, s socket.Socket, ep commonEndpoint, name i
 		v := hostarch.ByteOrder.Uint32(optVal)
 		ep.SocketOptions().SetRcvlowat(int32(v))
 		return nil
+	default:
+		if err, handled := setSockOptSocketCustom(t, s, ep, name, optVal); handled {
+			return err
+		}
 	}
 
 	return nil

pkg/sentry/socket/netstack/socketopt_custom.go

@@ -0,0 +1,39 @@
+// Copyright 2024 The gVisor Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+//go:build !false
+// +build !false
+
+package netstack
+
+import (
+	"gvisor.dev/gvisor/pkg/marshal"
+	"gvisor.dev/gvisor/pkg/sentry/kernel"
+	"gvisor.dev/gvisor/pkg/sentry/socket"
+	"gvisor.dev/gvisor/pkg/syserr"
+)
+
+// setSockOptSocketCustom handles SetSockOpt options not handled by setSockOptSocket.
+// It returns a bool indicating whether the option was handled in addition to
+// return values from setSockOptSocket.
+func setSockOptSocketCustom(t *kernel.Task, s socket.Socket, ep commonEndpoint, name int, optVal []byte) (*syserr.Error, bool) {
+	return nil, false
+}
+
+// getSockOptSocketCustom handles GetSockOpt options not handled by getSockOptSocket.
+// It returns a bool indicating whether the option was handled in addition to
+// return values from getSockOptSocket.
+func getSockOptSocketCustom(t *kernel.Task, s socket.Socket, ep commonEndpoint, name int, outLen int) (marshal.Marshallable, *syserr.Error, bool) {
+	return nil, nil, false
+}