rpc:call from ergo to erlang node sometimes work failed

[xiaodoudou12]

my OTP version is Erlang/OTP 24 [erts-12.1.5] [source] [64-bit] [smp:4:4] [ds:4:4:10] [async-threads:1] [jit].
golang version is go1.18.ergo version is v1.999.211.
https://github.com/ergo-services/ergo/blob/v1.999.211/proto/dist/handshake.go:247

			case 'a':
				// 'a' + 16 (digest)
				if len(buffer) != 17 {
					return details, fmt.Errorf("malformed handshake ('a' length of digest)")
				}

				// 'a' + 16 (digest)
				digest := genDigest(dh.challenge, cookie)
				if bytes.Compare(buffer[1:17], digest) != 0 {
					return details, fmt.Errorf("malformed handshake ('a' digest)")
				}

				// handshaked
				return details, nil

sometime len(buffer) will more than 17
when like this, first receive 3 byte,then 45 byte,then 17 bytes, it work ok.

but like this,first recevie 3 byte, then 45 byte, then 122 bytes, it not work.

maybe handshake should think about TCP Stick Package.
maybe handshake should only need 17 bytes, the last bytes need take to distProto connection to read

[halturin]

Thanks for the report. May I ask you to try 2.2.0 version. This code was updated in the latest version.

[xiaodoudou12]

i try 2.2.0 version also.
and sometime is ok,sometimes get the same error. WARNING! Handshake error: malformed handshake ('a' length of digest)
i use like this

if v, e := process.CallRPC(m.node, m.mod, m.fun, m.args...); e != nil {

[halturin]

may I ask you to copy here the output you showed in the screenshot above? I need full hex data of the whole packet with 122 bytes

[xiaodoudou12]

this output when work failed

proto/dist/handshake.go:183<50> INFO! 1111111111222222222,3, []byte{0x73, 0x6f, 0x6b}
proto/dist/handshake.go:183<50> INFO! 1111111111222222222,45, []byte{0x4e, 0x0, 0x0, 0x0, 0xd, 0x3, 0xdf, 0x7f, 0xbd, 0xa1, 0x20, 0xdc, 0x2a, 0x63, 0x6c, 0xaf, 0xe5, 0x0, 0x1a, 0x70, 0x61, 0x74, 0x68, 0x69, 0x6e, 0x67, 0x5f, 0x70, 0x6f, 0x6f, 0x6c, 0x5f, 0x33, 0x39, 0x40, 0x31, 0x30, 0x2e, 0x32, 0x2e, 0x31, 0x38, 0x2e, 0x32, 0x32}
proto/dist/handshake.go:183<50> INFO! 1111111111222222222,122, []byte{0x61, 0xf0, 0xfb, 0x62, 0xca, 0xa7, 0x81, 0xa6, 0xf4, 0x5a, 0x19, 0x23, 0x83, 0xb7, 0x6e, 0x2b, 0x2d, 0x0, 0x0, 0x0, 0x65, 0x83, 0x44, 0x4, 0x8f, 0xe9, 0x0, 0xa2, 0x1a, 0x70, 0x61, 0x74, 0x68, 0x69, 0x6e, 0x67, 0x5f, 0x70, 0x6f, 0x6f, 0x6c, 0x5f, 0x33, 0x39, 0x40, 0x31, 0x30, 0x2e, 0x32, 0x2e, 0x31, 0x38, 0x2e, 0x32, 0x32, 0x5, 0x0, 0x2e, 0x3, 0x72, 0x65, 0x78, 0xfa, 0x10, 0x66, 0x65, 0x61, 0x74, 0x75, 0x72, 0x65, 0x73, 0x5f, 0x72, 0x65, 0x71, 0x75, 0x65, 0x73, 0x74, 0x68, 0x4, 0x61, 0x6, 0x58, 0x52, 0x0, 0x0, 0x0, 0x5, 0xee, 0x0, 0x0, 0x0, 0x0, 0x63, 0x6c, 0xaf, 0xe5, 0x52, 0x1, 0x52, 0x2, 0x68, 0x2, 0x58, 0x52, 0x0, 0x0, 0x0, 0x5, 0xee, 0x0, 0x0, 0x0, 0x0, 0x63, 0x6c, 0xaf, 0xe5, 0x52, 0x3}
node/network.go:1235<50> WARNING! Handshake error: malformed handshake ('a' length of digest)
/node/network.go:326<50> INFO! [[email protected]] CORE no route to node "[email protected]": malformed handshake ('a' length of digest)

this output when work ok

proto/dist/handshake.go:183<5> INFO! 1111111111222222222,3, []byte{0x73, 0x6f, 0x6b}
proto/dist/handshake.go:183<5> INFO! 1111111111222222222,45, []byte{0x4e, 0x0, 0x0, 0x0, 0xd, 0x3, 0xdf, 0x7f, 0xbd, 0x25, 0x7a, 0x38, 0xd0, 0x63, 0x6c, 0xaf, 0xe5, 0x0, 0x1a, 0x70, 0x61, 0x74, 0x68, 0x69, 0x6e, 0x67, 0x5f, 0x70, 0x6f, 0x6f, 0x6c, 0x5f, 0x33, 0x39, 0x40, 0x31, 0x30, 0x2e, 0x32, 0x2e, 0x31, 0x38, 0x2e, 0x32, 0x32}
proto/dist/handshake.go:183<5> INFO! 1111111111222222222,17, []byte{0x61, 0xbd, 0x8f, 0xc7, 0xa9, 0x24, 0x33, 0x4b, 0x43, 0x60, 0x77, 0x8f, 0xe2, 0xaf, 0x8, 0x99, 0x72}
node/network.go:1294<5> INFO! [[email protected]] NETWORK registering peer "[email protected]"
node/core.go:838<5> INFO! [[email protected]] CORE route message by gen.ProcessID (remote) <ergo_msg_itf:[email protected]>

this my test code

package main

import (
        "flag"
        "fmt"
    
    "github.com/ergo-services/ergo/etf"
        "github.com/ergo-services/ergo"
        "github.com/ergo-services/ergo/gen"
        "github.com/ergo-services/ergo/node"
)
type testRPCGenServer struct {
    gen.Server
    res chan interface{}
}

type testRPCCase1 struct {
    node string
    mod  string
    fun  string
    args []etf.Term
}

func (trpc *testRPCGenServer) HandleCall(process *gen.ServerProcess, from gen.ServerFrom, message etf.Term) (etf.Term, gen.ServerStatus) {
    return message, gen.ServerStatusOK
}

func (trpc *testRPCGenServer) HandleInfo(process *gen.ServerProcess, message etf.Term) gen.ServerStatus {
    fmt.Printf("[%s] 88888888888888 HandleInfo: message:%v\n", process.Name(), message)
    to := gen.ProcessID{Name: "ergo_msg_itf", Node: "[email protected]"}
    args :=  []etf.Term{"ch", 1}
    //process.Send(to, args)
    process.Cast(to, args)
    return gen.ServerStatusStop
}

var (
        ServerName string
        NodeName   string
        Cookie     string
)

func init() {
        flag.StringVar(&ServerName, "server", "example", "server process name")
        flag.StringVar(&NodeName, "name", "[email protected]", "node name")
        flag.StringVar(&Cookie, "cookie", "wgame_dev_39", "cookie for interaction with erlang cluster")
}

func main() {
        flag.Parse()

        fmt.Println("")
        fmt.Println("to stop press Ctrl-C")
        fmt.Println("")

        node, err := ergo.StartNode(NodeName, Cookie, node.Options{})
        if err != nil {
                panic(err)
        }

    gs1 := &testRPCGenServer{
        res: make(chan interface{}, 2),
    }
    node1gs1, _ := node.Spawn("gs1", gen.ProcessOptions{}, gs1, nil)

        // Print how it can be used along with the Erlang node
        case1 := testRPCCase1{
                node: "[email protected]",
                mod:  "ergo_msg_itf",
                args: []etf.Term{"ch", 1},
        }
    
        fmt.Println("start call rpc 111111111:\n")
        if err := node1gs1.Send(node1gs1.Self(), case1); err != nil {
        }
        fmt.Println("finish call rpc 111111111:\n")
        node.Wait()
}

i don't find the better way to create a gen.ServerProcess, so i create a testRPCGenServer to send msg.
build the code and run it,the program start and send a msg to erlang node.handshake sometimes ok,sometimes failed.
i also try to sleep sometime between node.Spawn and node.Send,it same result.

[halturin]

yeah, this bug appears only if you connect from ergo to erlang. sometimes ergo receives handshake data along with the Erlang's dist packet (if it sends too fast). I'll fix it in the coming 2.2.1 release.

Thanks for the report. Nice catch 👍

[halturin]

created issue #117

[halturin]

Could you please check my fix in v221 branch?

[xiaodoudou12]

oh,well,no problem,i will check your fix when you commit

[xiaodoudou12]

i find the code.
proto/dist/handshake.go +259

if len(buffer) > 17 {
					details.Buffer = lib.TakeBuffer()
					details.Buffer.Set(buffer[18:])
				}

18 should equal 17,'a' + 16 (digest),so dist start from index 17.
i change it to 17 it work ok.

[halturin]

Oh, sorry for this misprint. It exactly must be 17.