too many iterations panic

[renard]

Hello,

I am writing a A10 loadbalancer configuration parser which syntax is similar to cisco config files.

Here is a config block example:

slb virtual-server svc1.example.com 10.0.0.1
   port 80 http
      name svc1.example.com-http
      aflex HTTP_To_HTTPS
   port 443  https
      name svc1.example.com-https
      source-nat pool SNAT-10.10.0.240-254
      service-group svc1.example.com-https
      template http default-http
      template waf svc1.example.com
      template client-ssl wildcard.example.com
   port 4172  tcp
      name tcp1.example.com-tcp
      source-nat pool SNAT-10.10.0.240-254
      service-group tcp1.example.com-tcp
      template persist source-ip tpl-srcip

My go file looks like:

package main

import (
	"github.com/alecthomas/participle/v2"
	"github.com/alecthomas/participle/v2/lexer"
	"github.com/alecthomas/repr"
)

var (
	a10Lexer = lexer.MustSimple(
		[]lexer.Rule{
			{"whitespace", `\s+`, nil},
			{"eol", `[\n\r]+`, nil},
			{"Punct", `[ \t\n]`, nil},
			{"Int", `\d+`, nil},
			{"Ident", `[A-Za-z0-9._-][A-Za-z0-9._-]*`, nil},
		},
		lexer.MatchLongest(),
	)
)

// SlbVirtualServer holds virtual-server definition.
//
// virtual-server consists of a name, a bind IP address and a list of
// service definition.
//
// In A10 configuration file a virtual-server starts with:
//
//	!
//	slb virtual-server NAME IP
//	    ...
//	!
type SlbVirtualServer struct {
	Pos     lexer.Position
	Name    string                     `"slb" "virtual-server" @(Ident)`
	Ip      string                     `@(Ident)`
	Service []*SlbVirtualServerService `("port" @@)*`
}

// SlbVirtualServerService holds a virtual-server service definition.
// Each service definiton starts with:
//
//		port PORT PROTOCOL
//	        ...
//
// A service has several optional directives such as name, source-nat
// definition, service group definiton, list of templates to apply,
// etc...
type SlbVirtualServerService struct {
	// Port and Protocol appear on the same line
	Port     int    `@(Int)`
	Protocol string `@("http" | "https" | "tcp" | "udp" | "ssl-proxy")`
	// Other resources should be defined in any order.
	// However this definition generates an error:
	//
	//    panic: 10:1: too many iterations of (("name" <ident>) | ("source-nat" SlbVirtualServerServiceSourceNat) | ("service-group" <ident>) | ("template" "persist"? SlbVirtualServerServiceTemplate)* | ("aflex" <ident>)?)* (> 1000000)
	//
	Name         string                             `(  "name" @(Ident)`
	SourceNat    *SlbVirtualServerServiceSourceNat  ` | "source-nat" @@`
	ServiceGroup string                             ` | "service-group" @(Ident)`
	Templates    []*SlbVirtualServerServiceTemplate ` | ( "template" "persist"? @@ )*`
	Aflex        string                             ` | ("aflex" @(Ident))? )*`
}

// SlbVirtualServerServiceSourceNat host a service source-nat
// definiton such as:
//
//	source-nat TYPE SNAT_STRING
type SlbVirtualServerServiceSourceNat struct {
	Type string `@(Ident)`
	Name string `@(Ident)`
}

// SlbVirtualServerServiceTemplate holds a service template
// definiton such as:
//
//	      template TYPE NAME

type SlbVirtualServerServiceTemplate struct {
	Type string `@(Ident)`
	Name string `@(Ident)`
}

// newLtmVirtual parses data and creates a new SlbVirtualServer struct.
func newSlbVirtualServer(data string) (ret *SlbVirtualServer, err error) {
	ret = &SlbVirtualServer{}
	err = parseString("", data, ret)
	return
}

// parseString parses the data string into obj.
func parseString(name, data string, obj any) (err error) {
	parser := participle.MustBuild(
		obj,
		participle.Lexer(a10Lexer),
	)
	err = parser.ParseString(name, data, obj)
	return
}

func main() {
	data := `
slb virtual-server svc1.example.com 10.0.0.1
   port 80 http
      name svc1.example.com-http
      aflex HTTP_To_HTTPS
   port 443  https
      name svc1.example.com-https
      source-nat pool SNAT-10.10.0.240-254
      service-group svc1.example.com-https
      template http default-http
      template waf svc1.example.com
      template client-ssl wildcard.example.com
   port 4172  tcp
      name tcp1.example.com-tcp
      source-nat pool SNAT-10.10.0.240-254
      service-group tcp1.example.com-tcp
      template persist source-ip tpl-srcip
`
	newSlbVirtualServer, err := newSlbVirtualServer(data)
	if err != nil {
		panic(err)
	}
	repr.Println(newSlbVirtualServer)

}

However when I run it I panics:

The problem I see is that the service definition has no end delimiter. Hence I am not sure about the struct defintion:

	Port     int    `@(Int)`
	Protocol string `@("http" | "https" | "tcp" | "udp" | "ssl-proxy")`
	Name         string                             `(  "name" @(Ident)`
	SourceNat    *SlbVirtualServerServiceSourceNat  ` | "source-nat" @@`
	ServiceGroup string                             ` | "service-group" @(Ident)`
	Templates    []*SlbVirtualServerServiceTemplate ` | ( "template" "persist"? @@ )*`
	Aflex        string                             ` | ("aflex" @(Ident))? )*`

Did I missed something?

Thanks in advance.

[spatecon]

Hi!

I can't see the panic log in your issue. Could you please provide it?