Implement SO_NO_CHECK socket option.

SO_NO_CHECK is used to skip the UDP checksum generation on a TX socket
(UDP checksum is optional on IPv4).

Test:
 - TestNoChecksum
 - SoNoCheckOffByDefault (UdpSocketTest)
 - SoNoCheck (UdpSocketTest)

Fixes #3055

PiperOrigin-RevId: 318575215

2 files changed, 19 insertions, 1 deletions

diff --git a/pkg/sentry/socket/netstack/netstack.go b/pkg/sentry/socket/netstack/netstack.go
index c0b63a803..e7d2c83d7 100644
--- a/pkg/sentry/socket/netstack/netstack.go
+++ b/pkg/sentry/socket/netstack/netstack.go
@@ -1169,6 +1169,17 @@ func getSockOptSocket(t *kernel.Task, s socket.SocketOps, ep commonEndpoint, fam
 
 		return int32(v), nil
 
+	case linux.SO_NO_CHECK:
+		if outLen < sizeOfInt32 {
+			return nil, syserr.ErrInvalidArgument
+		}
+
+		v, err := ep.GetSockOptBool(tcpip.NoChecksumOption)
+		if err != nil {
+			return nil, syserr.TranslateNetstackError(err)
+		}
+		return boolToInt32(v), nil
+
 	default:
 		socket.GetSockOptEmitUnimplementedEvent(t, name)
 	}
@@ -1720,6 +1731,14 @@ func setSockOptSocket(t *kernel.Task, s socket.SocketOps, ep commonEndpoint, nam
 
 		return syserr.TranslateNetstackError(ep.SetSockOpt(tcpip.OutOfBandInlineOption(v)))
 
+	case linux.SO_NO_CHECK:
+		if len(optVal) < sizeOfInt32 {
+			return syserr.ErrInvalidArgument
+		}
+
+		v := usermem.ByteOrder.Uint32(optVal)
+		return syserr.TranslateNetstackError(ep.SetSockOptBool(tcpip.NoChecksumOption, v != 0))
+
 	case linux.SO_LINGER:
 		if len(optVal) < linux.SizeOfLinger {
 			return syserr.ErrInvalidArgument
diff --git a/pkg/sentry/socket/socket.go b/pkg/sentry/socket/socket.go
index 6580bd6e9..fcd7f9d7f 100644
--- a/pkg/sentry/socket/socket.go
+++ b/pkg/sentry/socket/socket.go
@@ -407,7 +407,6 @@ func emitUnimplementedEvent(t *kernel.Task, name int) {
 		linux.SO_MARK,
 		linux.SO_MAX_PACING_RATE,
 		linux.SO_NOFCS,
-		linux.SO_NO_CHECK,
 		linux.SO_OOBINLINE,
 		linux.SO_PASSCRED,
 		linux.SO_PASSSEC,