gonet can write a empty data to a closed conn

[lysShub]

Description

package main_test

import (
	"context"
	"io"
	"net"
	"testing"

	// gvisor.dev/gvisor v0.0.0-20240216000150-e3cf008ab186
	"github.com/stretchr/testify/require"
	"gvisor.dev/gvisor/pkg/tcpip"
	"gvisor.dev/gvisor/pkg/tcpip/adapters/gonet"
	"gvisor.dev/gvisor/pkg/tcpip/header"
	"gvisor.dev/gvisor/pkg/tcpip/link/channel"
	"gvisor.dev/gvisor/pkg/tcpip/network/ipv4"
	"gvisor.dev/gvisor/pkg/tcpip/stack"
	"gvisor.dev/gvisor/pkg/tcpip/transport/tcp"
)

func Test_Closed_TCP_Write_Empty(t *testing.T) {
	t.Run("system", func(t *testing.T) {
		var addr = &net.TCPAddr{IP: []byte{127, 0, 0, 1}, Port: 8080}
		go func() {
			l, err := net.ListenTCP("tcp", addr)
			require.NoError(t, err)
			defer l.Close()
			conn, err := l.AcceptTCP()
			require.NoError(t, err)

			io.Copy(conn, conn)
		}()
		time.Sleep(time.Second)

		conn, err := net.DialTCP("tcp", nil, addr)
		require.NoError(t, err)
		err = conn.Close()
		require.NoError(t, err)

		n, err := conn.Write([]byte{})
		require.Error(t, err)
		require.Zero(t, n)
	})

	t.Run("gvisor", func(t *testing.T) {
		var addr = tcpip.AddrFromSlice([]byte{10, 0, 0, 1})
		var st = stack.New(stack.Options{
			NetworkProtocols:   []stack.NetworkProtocolFactory{ipv4.NewProtocol},
			TransportProtocols: []stack.TransportProtocolFactory{tcp.NewProtocol},
			HandleLocal:        true,
		})

		const nicid tcpip.NICID = 1234
		e := st.CreateNIC(nicid, channel.New(4, 1536, ""))
		require.Nil(t, e)
		st.AddProtocolAddress(nicid, tcpip.ProtocolAddress{
			Protocol:          header.IPv4ProtocolNumber,
			AddressWithPrefix: addr.WithPrefix(),
		}, stack.AddressProperties{})
		st.SetRouteTable([]tcpip.Route{{Destination: header.IPv4EmptySubnet, NIC: nicid}})

		go func() {
			l, err := gonet.ListenTCP(
				st,
				tcpip.FullAddress{Addr: addr, Port: 8080},
				header.IPv4ProtocolNumber,
			)
			require.NoError(t, err)
			defer l.Close()

			conn, err := l.Accept()
			require.NoError(t, err)
			io.Copy(conn, conn)
		}()
		time.Sleep(time.Second)

		conn, err := gonet.DialTCPWithBind(
			context.Background(), st,
			tcpip.FullAddress{Addr: addr, Port: 12345},
			tcpip.FullAddress{Addr: addr, Port: 8080},
			header.IPv4ProtocolNumber,
		)
		require.NoError(t, err)
		err = conn.Close()
		require.NoError(t, err)

		n, err := conn.Write([]byte{})
		require.Error(t, err)
		require.Zero(t, n)
	})
}

Steps to reproduce

No response

runsc version

No response

docker version (if using docker)

No response

uname

No response

kubectl (if using Kubernetes)

No response

repo state (if built from source)

No response

runsc debug logs (if available)

No response

[lysShub]

system test passed on windows and linux

[Kevin Krakauer]

Can you help describe the problem in more detail? Is this contradicted in a doc somewhere, or does this differ from other implementers of net.Conn?

[lysShub]

Can you help describe the problem in more detail? Is this contradicted in a doc somewhere, or does this differ from other implementers of net.Conn?

In most operating systems, writing to a closed TCP connection will return an error, including conn.Write([]byte{})，but gonet will return 0 and nil

[Kevin Krakauer]

We'd definitely accept a PR with this change!