From 3867774702c31c221caf797d97f715d26ae8067e Mon Sep 17 00:00:00 2001
From: Periyasamy Palanisamy <pepalani@redhat.com>
Date: Thu, 9 Nov 2023 12:28:09 +0530
Subject: [PATCH] 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 +++++++++++++++++++--
 client/options.go            |  1 +
 internal/syscall_linux.go    | 31 +++++++++++++++++++++++++++++++
 internal/syscall_nonlinux.go | 14 ++++++++++++++
 4 files changed, 65 insertions(+), 2 deletions(-)
 create mode 100644 internal/syscall_linux.go
 create mode 100644 internal/syscall_nonlinux.go

diff --git a/client/client.go b/client/client.go
index 53f368fc..5e92b8ff 100644
--- a/client/client.go
+++ b/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"
@@ -352,7 +353,10 @@ func (o *ovsdbClient) tryEndpoint(ctx context.Context, u *url.URL) (string, erro
 		return "", fmt.Errorf("failed to open connection: %w", err)
 	}
 
-	o.createRPC2Client(c)
+	err = o.createRPC2Client(c)
+	if err != nil {
+		return "", err
+	}
 
 	serverDBNames, err := o.listDbs(ctx)
 	if err != nil {
@@ -423,12 +427,24 @@ func (o *ovsdbClient) tryEndpoint(ctx context.Context, u *url.URL) (string, erro
 // createRPC2Client creates an rpcClient using the provided connection
 // It is also responsible for setting up go routines for client-side event handling
 // Should only be called when the mutex is held
-func (o *ovsdbClient) createRPC2Client(conn net.Conn) {
+func (o *ovsdbClient) createRPC2Client(conn net.Conn) error {
 	o.stopCh = make(chan struct{})
 	if o.options.inactivityTimeout > 0 {
 		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.
+	var userTimeout time.Duration
+	if o.options.timeout > 0 {
+		userTimeout = o.options.timeout * 3
+	} else {
+		userTimeout = defaultTimeout
+	}
+	err := syscall.SetTCPUserTimeout(conn, userTimeout)
+	if err != nil {
+		return err
+	}
 	o.rpcClient = rpc2.NewClientWithCodec(jsonrpc.NewJSONCodec(conn))
 	o.rpcClient.SetBlocking(true)
 	o.rpcClient.Handle("echo", func(_ *rpc2.Client, args []interface{}, reply *[]interface{}) error {
@@ -444,6 +460,7 @@ func (o *ovsdbClient) createRPC2Client(conn net.Conn) {
 		return o.update3(args, reply)
 	})
 	go o.rpcClient.Run()
+	return nil
 }
 
 // isEndpointLeader returns true if the currently connected endpoint is leader,
diff --git a/client/options.go b/client/options.go
index 6f9b7b17..66a60b5f 100644
--- a/client/options.go
+++ b/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 {
diff --git a/internal/syscall_linux.go b/internal/syscall_linux.go
new file mode 100644
index 00000000..5138f22d
--- /dev/null
+++ b/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
+}
diff --git a/internal/syscall_nonlinux.go b/internal/syscall_nonlinux.go
new file mode 100644
index 00000000..6e6a26d6
--- /dev/null
+++ b/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
+}