Set user timeout for tcp connection

This commit sets TCP_USER_TIMEOUT socket option for tcp connection
so that channel write doesn't block indefinitely on network disconnect.

Signed-off-by: Periyasamy Palanisamy <pepalani@redhat.com>

client/client.go

@@ -21,6 +21,7 @@ import (
 	"github.com/go-logr/logr"
 	"github.com/go-logr/stdr"
 	"github.com/ovn-org/libovsdb/cache"
+	syscall "github.com/ovn-org/libovsdb/internal"
 	"github.com/ovn-org/libovsdb/mapper"
 	"github.com/ovn-org/libovsdb/model"
 	"github.com/ovn-org/libovsdb/ovsdb"
@@ -429,6 +430,13 @@ func (o *ovsdbClient) createRPC2Client(conn net.Conn) {
 		o.trafficSeen = make(chan struct{})
 	}
 	o.conn = conn
+	// set TCP_USER_TIMEOUT socket option for connection so that
+	// channel write doesn't block indefinitely on network disconnect.
+	if o.options.timeout > 0 {
+		syscall.SetTCPUserTimeout(conn, o.options.timeout*3)
+	} else {
+		syscall.SetTCPUserTimeout(conn, defaultTimeOut)
+	}
 	o.rpcClient = rpc2.NewClientWithCodec(jsonrpc.NewJSONCodec(conn))
 	o.rpcClient.SetBlocking(true)
 	o.rpcClient.Handle("echo", func(_ *rpc2.Client, args []interface{}, reply *[]interface{}) error {

client/options.go

@@ -15,6 +15,7 @@ const (
 	defaultTCPEndpoint  = "tcp:127.0.0.1:6640"
 	defaultSSLEndpoint  = "ssl:127.0.0.1:6640"
 	defaultUnixEndpoint = "unix:/var/run/openvswitch/ovsdb.sock"
+	defaultTimeOut      = 60 * time.Second
 )
 
 type options struct {

internal/syscall_linux.go

@@ -0,0 +1,31 @@
+package internal
+
+import (
+	"fmt"
+	"net"
+	"syscall"
+	"time"
+
+	"golang.org/x/sys/unix"
+)
+
+// SetTCPUserTimeout sets the TCP user timeout on a connection's socket
+func SetTCPUserTimeout(conn net.Conn, timeout time.Duration) error {
+	tcpconn, ok := conn.(*net.TCPConn)
+	if !ok {
+		// not a TCP connection. exit early
+		return nil
+	}
+	rawConn, err := tcpconn.SyscallConn()
+	if err != nil {
+		return fmt.Errorf("error getting raw connection: %v", err)
+	}
+	err = rawConn.Control(func(fd uintptr) {
+		err = syscall.SetsockoptInt(int(fd), syscall.IPPROTO_TCP, unix.TCP_USER_TIMEOUT, int(timeout/time.Millisecond))
+	})
+	if err != nil {
+		return fmt.Errorf("error setting option on socket: %v", err)
+	}
+
+	return nil
+}

internal/syscall_nonlinux.go

@@ -0,0 +1,14 @@
+//go:build !linux
+// +build !linux
+
+package internal
+
+import (
+	"net"
+	"time"
+)
+
+// SetTCPUserTimeout is a no-op function under non-linux environments.
+func SetTCPUserTimeout(conn net.Conn, timeout time.Duration) error {
+	return nil
+}