From b26f7503b545e106ea0934d2153aed54ee4374d3 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/tcpip/tcpip.go                  |  9 +++++++++
 pkg/tcpip/transport/tcp/endpoint.go | 33 +++++++++++++++++++++++++++++++++
 2 files changed, 42 insertions(+)

(limited to 'pkg/tcpip')

diff --git a/pkg/tcpip/tcpip.go b/pkg/tcpip/tcpip.go
index 07c85ce59..290c4e138 100644
--- a/pkg/tcpip/tcpip.go
+++ b/pkg/tcpip/tcpip.go
@@ -978,6 +978,15 @@ const (
 	TCPTimeWaitReuseLoopbackOnly
 )
 
+// LingerOption is used by SetSockOpt/GetSockOpt to set/get the
+// duration for which a socket lingers before returning from Close.
+//
+// +stateify savable
+type LingerOption struct {
+	Enabled bool
+	Timeout time.Duration
+}
+
 // IPPacketInfo is the message structure for IP_PKTINFO.
 //
 // +stateify savable
diff --git a/pkg/tcpip/transport/tcp/endpoint.go b/pkg/tcpip/transport/tcp/endpoint.go
index 9c0f4c9f4..ff9b8804d 100644
--- a/pkg/tcpip/transport/tcp/endpoint.go
+++ b/pkg/tcpip/transport/tcp/endpoint.go
@@ -654,6 +654,9 @@ type endpoint struct {
 
 	// owner is used to get uid and gid of the packet.
 	owner tcpip.PacketOwner
+
+	// linger is used for SO_LINGER socket option.
+	linger tcpip.LingerOption
 }
 
 // UniqueID implements stack.TransportEndpoint.UniqueID.
@@ -1007,6 +1010,26 @@ func (e *endpoint) Close() {
 		return
 	}
 
+	if e.linger.Enabled && e.linger.Timeout == 0 {
+		s := e.EndpointState()
+		isResetState := s == StateEstablished || s == StateCloseWait || s == StateFinWait1 || s == StateFinWait2 || s == StateSynRecv
+		if isResetState {
+			// Close the endpoint without doing full shutdown and
+			// send a RST.
+			e.resetConnectionLocked(tcpip.ErrConnectionAborted)
+			e.closeNoShutdownLocked()
+
+			// Wake up worker to close the endpoint.
+			switch s {
+			case StateSynRecv:
+				e.notifyProtocolGoroutine(notifyClose)
+			default:
+				e.notifyProtocolGoroutine(notifyTickleWorker)
+			}
+			return
+		}
+	}
+
 	// Issue a shutdown so that the peer knows we won't send any more data
 	// if we're connected, or stop accepting if we're listening.
 	e.shutdownLocked(tcpip.ShutdownWrite | tcpip.ShutdownRead)
@@ -1807,6 +1830,11 @@ func (e *endpoint) SetSockOpt(opt interface{}) *tcpip.Error {
 	case tcpip.SocketDetachFilterOption:
 		return nil
 
+	case tcpip.LingerOption:
+		e.LockUser()
+		e.linger = v
+		e.UnlockUser()
+
 	default:
 		return nil
 	}
@@ -2032,6 +2060,11 @@ func (e *endpoint) GetSockOpt(opt interface{}) *tcpip.Error {
 			Port: port,
 		}
 
+	case *tcpip.LingerOption:
+		e.LockUser()
+		*o = e.linger
+		e.UnlockUser()
+
 	default:
 		return tcpip.ErrUnknownProtocolOption
 	}
-- 
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