UDP RemoteAddr() returns always (wrong) IPv6

[darinkes]

Describe the bug
gnet.Conn.RemoteAddr() returns always IPv6 for UDP.
E.g. [::7f00:1]:52815 instead of 127.0.0.1:52815

To Reproduce

func (this *Server) React(c gnet.Conn) (out []byte, action gnet.Action) {
        data := c.Read()
        log.Debugf("DATA from %v to %v: %v", c.RemoteAddr(), c.LocalAddr(), data)
        c.ResetBuffer()
        return
}

func (this *Server) listen() error {                                                                                                                                                              
        listenAddr := fmt.Sprintf("udp://%s", this.cfg.Bind)                                                                                                                                      
        err := gnet.Serve(this, listenAddr, gnet.WithMulticore(true), gnet.WithReusePort(true))
        if err != nil {                                                                                                                                                                                   return fmt.Errorf("Failed to create listening udp socket: %v", err)
        }

        return nil
}   

Expected behavior
Correct RemoteAddr

System Info (please complete the following information):

• OS (e.g. Linux): Linux
• Go Version (e.g. Go 1.13): go1.12.10 linux/amd64
• gnet Version (e.g. v1.0.0-beta.3): gnet@v1.0.0-rc.3

Additional context

in eventloop.go SockaddrToUDPAddr gets always called with sa6 = unix.SockaddrInet6

func (lp *loop) loopUDPIn(fd int) error {
        c := &conn{
                fd:            fd,
                localAddr:     lp.svr.ln.lnaddr,
                remoteAddr:    netpoll.SockaddrToUDPAddr(&sa6),
                inboundBuffer: lp.svr.bytesPool.Get().(*ringbuffer.RingBuffer),
        }
}

in netpoll/socktoaddr.go

func SockaddrToUDPAddr(sa unix.Sockaddr) *net.UDPAddr {
        case *unix.SockaddrInet6:
                return &net.UDPAddr{IP: ip, Port: sa.Port, Zone: zone}
        }
}

So you always get an SockaddrInet converted to SockaddrInet6 for UDP.

[panjf2000]

Hi @darinkes
I believe that Go will give priority to the IPv6 when the server supports both IPv4 and IPv6, have you ever tried "udp4"？

[darinkes]

According to tcpdump its an IPv4 connection from 127.0.0.1 to 127.0.0.1.
E.g. listenAddr is "udp://127.0.0.1:5555"
Works fine with net.ListenUDP("udp", listenAddr), which also gives a correct RemoteAddr()

[::7f00:1] is the result of mangled data cause of the bug in eventloop.go

udp4 does not seem to exist:

listen udp4 127.0.0.1:5555: address 127.0.0.1:5555: unexpected address type

[panjf2000]

I've run a test with UDP on my linux server and printed some logs:

It seems that everything goes well, so could you make sure that the listenAddr := fmt.Sprintf("udp://%s", this.cfg.Bind) passes the right arguments to gnet？Maybe you print the whole string of it and check it out?

[panjf2000]

BTY, you could update to the latest code of gnet and try it again, let's see whether the issue still exists.

[darinkes]

func (this *Server) OnInitComplete(srv gnet.Server) (action gnet.Action) {
        log.Debugf("Server is listening on %s (multi-cores: %t, loops: %d)", srv.Addr.String(), srv.Multicore, srv.NumLoops)
        return
}

func (this *Server) React(c gnet.Conn) (out []byte, action gnet.Action) {
        log.Debugf("%v -> %v", c.RemoteAddr(), c.LocalAddr())
}

Results in

2019-11-11 15:25:15 [DEBUG] (udp/server): Server is listening on 127.0.0.1:5555 (multi-cores: true, loops: 24)
2019-11-11 15:25:16 [DEBUG] (udp/server): [::7f00:1]:55170 -> 127.0.0.1:5555

I saw you fixed it in master now: ec7bd36 👍
Thats nearly the same fix I also applied in my local gnet checkout and it works.

[darinkes]

checked out master and now it shows

2019-11-11 15:44:00 [DEBUG] (udp/server): 127.0.0.1:44772 -> 127.0.0.1:5555

Thanks for fixing this so quick