tcp: change the limit of TCP_LINGER2

It was changed in the Linux kernel:

commit f0628c524fd188c3f9418e12478dfdfadacba815
Date:   Fri Apr 24 16:06:16 2020 +0800
net: Replace the limit of TCP_LINGER2 with TCP_FIN_TIMEOUT_MAX
PiperOrigin-RevId: 325493859

pkg/tcpip/transport/tcp/endpoint.go

@@ -1777,15 +1777,8 @@ func (e *endpoint) SetSockOpt(opt interface{}) *tcpip.Error {
 			// Same as effectively disabling TCPLinger timeout.
 			v = 0
 		}
-		var stkTCPLingerTimeout tcpip.TCPLingerTimeoutOption
-		if err := e.stack.TransportProtocolOption(header.TCPProtocolNumber, &stkTCPLingerTimeout); err != nil {
-			// We were unable to retrieve a stack config, just use
-			// the DefaultTCPLingerTimeout.
-			if v > tcpip.TCPLingerTimeoutOption(DefaultTCPLingerTimeout) {
-				stkTCPLingerTimeout = tcpip.TCPLingerTimeoutOption(DefaultTCPLingerTimeout)
-			}
-		}
-		// Cap it to the stack wide TCPLinger timeout.
+		// Cap it to MaxTCPLingerTimeout.
+		stkTCPLingerTimeout := tcpip.TCPLingerTimeoutOption(MaxTCPLingerTimeout)
 		if v > stkTCPLingerTimeout {
 			v = stkTCPLingerTimeout
 		}

pkg/tcpip/transport/tcp/protocol.go

@@ -62,6 +62,10 @@ const (
 	// FIN_WAIT_2 state before being marked closed.
 	DefaultTCPLingerTimeout = 60 * time.Second
 
+	// MaxTCPLingerTimeout is the maximum amount of time that sockets
+	// linger in FIN_WAIT_2 state before being marked closed.
+	MaxTCPLingerTimeout = 120 * time.Second
+
 	// DefaultTCPTimeWaitTimeout is the amount of time that sockets linger
 	// in TIME_WAIT state before being marked closed.
 	DefaultTCPTimeWaitTimeout = 60 * time.Second

pkg/tcpip/transport/tcp/tcp_test.go

@@ -6112,7 +6112,7 @@ func TestTCPLingerTimeout(t *testing.T) {
 		{"InRangeLingerTimeout", 10 * time.Second, 10 * time.Second},
 		// Values > stack's TCPLingerTimeout are capped to the stack's
 		// value. Defaults to tcp.DefaultTCPLingerTimeout(60 seconds)
-		{"AboveMaxLingerTimeout", 65 * time.Second, 60 * time.Second},
+		{"AboveMaxLingerTimeout", 125 * time.Second, 120 * time.Second},
 	}
 	for _, tc := range testCases {
 		t.Run(tc.name, func(t *testing.T) {

test/syscalls/linux/socket_ip_tcp_generic.cc

@@ -34,6 +34,9 @@
 namespace gvisor {
 namespace testing {
 
+using ::testing::AnyOf;
+using ::testing::Eq;
+
 TEST_P(TCPSocketPairTest, TcpInfoSucceeds) {
   auto sockets = ASSERT_NO_ERRNO_AND_VALUE(NewSocketPair());
 
@@ -800,6 +803,9 @@ TEST_P(TCPSocketPairTest, SetCongestionControlFailsForUnsupported) {
 
 // Linux and Netstack both default to a 60s TCP_LINGER2 timeout.
 constexpr int kDefaultTCPLingerTimeout = 60;
+// On Linux, the maximum linger2 timeout was changed from 60sec to 120sec.
+constexpr int kMaxTCPLingerTimeout = 120;
+constexpr int kOldMaxTCPLingerTimeout = 60;
 
 TEST_P(TCPSocketPairTest, TCPLingerTimeoutDefault) {
   auto sockets = ASSERT_NO_ERRNO_AND_VALUE(NewSocketPair());
@@ -827,12 +833,12 @@ TEST_P(TCPSocketPairTest, SetTCPLingerTimeoutZeroOrLess) {
               SyscallSucceedsWithValue(0));
 }
 
-TEST_P(TCPSocketPairTest, SetTCPLingerTimeoutAboveDefault) {
+TEST_P(TCPSocketPairTest, SetTCPLingerTimeoutAboveMax) {
   auto sockets = ASSERT_NO_ERRNO_AND_VALUE(NewSocketPair());
 
   // Values above the net.ipv4.tcp_fin_timeout are capped to tcp_fin_timeout
   // on linux (defaults to 60 seconds on linux).
-  constexpr int kAboveDefault = kDefaultTCPLingerTimeout + 1;
+  constexpr int kAboveDefault = kMaxTCPLingerTimeout + 1;
   EXPECT_THAT(setsockopt(sockets->first_fd(), IPPROTO_TCP, TCP_LINGER2,
                          &kAboveDefault, sizeof(kAboveDefault)),
               SyscallSucceedsWithValue(0));
@@ -843,7 +849,12 @@ TEST_P(TCPSocketPairTest, SetTCPLingerTimeoutAboveDefault) {
       getsockopt(sockets->first_fd(), IPPROTO_TCP, TCP_LINGER2, &get, &get_len),
       SyscallSucceedsWithValue(0));
   EXPECT_EQ(get_len, sizeof(get));
-  EXPECT_EQ(get, kDefaultTCPLingerTimeout);
+  if (IsRunningOnGvisor()) {
+    EXPECT_EQ(get, kMaxTCPLingerTimeout);
+  } else {
+    EXPECT_THAT(get,
+                AnyOf(Eq(kMaxTCPLingerTimeout), Eq(kOldMaxTCPLingerTimeout)));
+  }
 }
 
 TEST_P(TCPSocketPairTest, SetTCPLingerTimeout) {