From 98e652f6f1d8f3d0bbc4600b1ef2ce471d8e6406 Mon Sep 17 00:00:00 2001
From: Nayana Bidari <nybidari@google.com>
Date: Tue, 25 Aug 2020 09:59:42 -0700
Subject: Support SO_LINGER socket option.

When SO_LINGER option is enabled, the close will not return until all the
queued messages are sent and acknowledged for the socket or linger timeout is
reached. If the option is not set, close will return immediately. This option
is mainly supported for connection oriented protocols such as TCP.

PiperOrigin-RevId: 328350576
---
 pkg/sentry/socket/netstack/netstack.go   | 45 +++++++++++++++++++++++++++++---
 pkg/sentry/socket/unix/transport/unix.go |  2 +-
 2 files changed, 43 insertions(+), 4 deletions(-)

(limited to 'pkg/sentry/socket')

diff --git a/pkg/sentry/socket/netstack/netstack.go b/pkg/sentry/socket/netstack/netstack.go
index 921464f5d..626195be2 100644
--- a/pkg/sentry/socket/netstack/netstack.go
+++ b/pkg/sentry/socket/netstack/netstack.go
@@ -479,8 +479,35 @@ func (s *socketOpsCommon) fetchReadView() *syserr.Error {
 }
 
 // Release implements fs.FileOperations.Release.
-func (s *socketOpsCommon) Release(context.Context) {
+func (s *socketOpsCommon) Release(ctx context.Context) {
+	e, ch := waiter.NewChannelEntry(nil)
+	s.EventRegister(&e, waiter.EventHUp|waiter.EventErr)
+	defer s.EventUnregister(&e)
+
 	s.Endpoint.Close()
+
+	// SO_LINGER option is valid only for TCP. For other socket types
+	// return after endpoint close.
+	if family, skType, _ := s.Type(); skType != linux.SOCK_STREAM || (family != linux.AF_INET && family != linux.AF_INET6) {
+		return
+	}
+
+	var v tcpip.LingerOption
+	if err := s.Endpoint.GetSockOpt(&v); err != nil {
+		return
+	}
+
+	// The case for zero timeout is handled in tcp endpoint close function.
+	// Close is blocked until either:
+	// 1. The endpoint state is not in any of the states: FIN-WAIT1,
+	// CLOSING and LAST_ACK.
+	// 2. Timeout is reached.
+	if v.Enabled && v.Timeout != 0 {
+		t := kernel.TaskFromContext(ctx)
+		start := t.Kernel().MonotonicClock().Now()
+		deadline := start.Add(v.Timeout)
+		t.BlockWithDeadline(ch, true, deadline)
+	}
 }
 
 // Read implements fs.FileOperations.Read.
@@ -1195,7 +1222,16 @@ func getSockOptSocket(t *kernel.Task, s socket.SocketOps, ep commonEndpoint, fam
 			return nil, syserr.ErrInvalidArgument
 		}
 
-		linger := linux.Linger{}
+		var v tcpip.LingerOption
+		var linger linux.Linger
+		if err := ep.GetSockOpt(&v); err != nil {
+			return &linger, nil
+		}
+
+		if v.Enabled {
+			linger.OnOff = 1
+		}
+		linger.Linger = int32(v.Timeout.Seconds())
 		return &linger, nil
 
 	case linux.SO_SNDTIMEO:
@@ -1865,7 +1901,10 @@ func setSockOptSocket(t *kernel.Task, s socket.SocketOps, ep commonEndpoint, nam
 			socket.SetSockOptEmitUnimplementedEvent(t, name)
 		}
 
-		return nil
+		return syserr.TranslateNetstackError(
+			ep.SetSockOpt(tcpip.LingerOption{
+				Enabled: v.OnOff != 0,
+				Timeout: time.Second * time.Duration(v.Linger)}))
 
 	case linux.SO_DETACH_FILTER:
 		// optval is ignored.
diff --git a/pkg/sentry/socket/unix/transport/unix.go b/pkg/sentry/socket/unix/transport/unix.go
index 475d7177e..ab7bab5cd 100644
--- a/pkg/sentry/socket/unix/transport/unix.go
+++ b/pkg/sentry/socket/unix/transport/unix.go
@@ -942,7 +942,7 @@ func (e *baseEndpoint) GetSockOptInt(opt tcpip.SockOptInt) (int, *tcpip.Error) {
 // GetSockOpt implements tcpip.Endpoint.GetSockOpt.
 func (e *baseEndpoint) GetSockOpt(opt interface{}) *tcpip.Error {
 	switch opt.(type) {
-	case tcpip.ErrorOption:
+	case tcpip.ErrorOption, *tcpip.LingerOption:
 		return nil
 
 	default:
-- 
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