[Xorp-hackers] XORT-NAT: Proposal for NAT interface XIF and a config file syntaks

Kristen Nielsen krn@krn.dk
Sun, 23 Apr 2006 16:26:23 +0200


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Hi Pavlin

Thank you for commenting on my nat suggestion.

I answer some of your questions below

Kristen.


Pavlin Radoslavov wrote:
> [Note: a follow-up of an old email that was postponed for discussion
>  after the 1.2 release].
> 
> 
>>After a long time of considerations and working on specifying a
>>configuratoin syntax and a XIF file for a NAT module, I am hereby
>>sending this proposal to the list for comments.
>>
>>(Re my mail from oct 16 2005 with subject: NAT support for XORP)
>>
>>
>>20060200-NAT-interface-descr.txt file contains the syntax and a few
>>samples of use of the configuration format.
>>
>>The nat.xif file has kdoc documentation documenting the various
>>functions and parameters.
>>
>>The idea is to provice a common interface for the NAT module, with a
>>defined syntax, and then use either the native (FreeBSD natd/or the
>>similar functionality in linux) daemon, or  a click module, with a rule
>>of thumb something like this:
>>
>>If the nat configuration is possible to implement with the native module
>>this can be used, else the user must switch to the click nat module to
>>achieve the wanted functionality.
> 
> 
> The caveat with the above rule is that the user must have Click.
> Currently, kernel-mode Click works only on Linux and some versions
> of FreeBSD, and those systems already have native NAT support.
> FYI, I believe user-mode Click works on a larger variety of systems
> (I have been able to compile and use it as-is on Mac OS X), but
> obviously you will get some performance penalty if you perform NAT
> in user space Click. The upside of user-space Click NAT of course
> would be that you don't have to modify your kernel and the
> performance hit may be acceptable in most cases (you may want to do
> some measurements here to prove this of course).

OK - I later realized that the kernel module was (almost) silently left
out when I compiled click on a FreeBSD Rel 6 machine.

I have been working some time trying to port it to FreeBSD 6, as this
gives me at reason to take a look at the FreeBSD networking system. For
now I will have to leave it for some weeks.


> 
> 
>>I have designed with the use of IP-realms (aka different ip domains)
>>which I am aware of is not possible to use in the standard ip stack of
>>Freebsd/Linux, but if one make configurations with non overlapping ip
>>ranges it will actually be possible to implement theese in the existing
>>kernel / ip stacks. The realm stuff is kept entirely in the nat config
>>area of the config file.
>>
>>I would apreaciate comments on this, as I would like to continue
>>planning and coding soon.
>>
>>I would also like to have ideas / comments about how to add more
>>datatypes to the idl generator scripts. (for the port type, and an
>>eventually ipv4-range type (which I here has made with 2 ipv4 ip-addresses.)
> 
> 
> Can you clarify what you mean by "idl generator scripts".

i mean the tgt-gen and clnt-gen in the xrl/scripts directory.

> 
> If you need ipv4-range type support, there is rtrmgr template type
> named "ipv4range" and "ipv6range" which has the syntax IPADDR..IPADDR.
> E.g. see the policy section inside etc/templates/bgp.tp.

I would also need some support for the "port" description language in
the scripts (as far as I understand) Is this doable?

> 
> Comments continuing below.
> 
> 
>>Sincerely
>>Mr. Kristen Nielsen
>>University of Copenhagen
>>Copenhagen
>>Denmark
>>kristen@diku.dk / krn@krn.dk
>>phone +4540466221 (gmt -1)
>>
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>>--------------040204020303010209060700
>>Content-Type: text/plain;
>> name="20060220-NAT-interface-descr.txt"
>>Content-Transfer-Encoding: 7bit
>>Content-Disposition: inline;
>> filename="20060220-NAT-interface-descr.txt"
>>
>>* Short description of the config file format for the xorp NAT module.
>>* Examples of configurations with alike FreeBSD natd commandline.
>>* Syntax of the port statement.
>>
>>protocols {
>>     nat {
>>	disable {disabled:bool}
>>
>>  	nat-realm <text:realm-name> <description: description:txt> {
> 
> 
> Currently, the rtrmgr template syntax doesn't support multi-value
> statements like the one above. You would have to break it into, say:
> 
>         nat-realm <text:realm-name>  {
>                 description: <description:txt>
> 
> 
> 
>>		interface <ifname> vif <vif-name>  { 
>>			description <description:txt>
>>			default-vif-address: <vif-hw-name:txt>
>>			ip-address: <ip:ipv4>
>>			tag: <tagid:txt>
>>
>>			interface-alias {
>>			description: <description:txt>
>>				alias-address: <ip:ipv4list> /* alt to more interface-alias clauses */
>>				tag: <tagid:txt>
>>			}
>>		}
> 
> 
> The interface/vif statements need to be specified separately:
>  		interface <ifname> {
>                         vif <vif-name>  {
>                                 ...
>                         }
>                         ...
>                 }
> 
> 
> Also, note that we don't support a list of addresses, hence you may
> want to specify all addresses with multi-value nodes like:
> 
>  		interface <ifname> {
>                         vif <vif-name>  {
>                                 address <ip:ipv4> {
>                                     description: <description:txt>
>                                     tag: <tagid:txt>
>                                 }
>                         }
>                         ...
>                 }
> 
> 
> 
>>		
>>		/* Address pool maps to the create/delete/get_nat_realm4 function) */
>>		address-pool {
>>			description: <description:txt>
>>			ip-address: <ip:ipv4>
>>			ip-range: <ipfrom:ipv4> - <ipto:ipv4>
>>			ipnet: <ipnet:ipv4net>
>>			tag:  <tag:txt>
>>		}
>>	}
>>
>>	static-nat {
>>		map {
>>			description: <description:txt>
>>			source { 
>>				realm: <srcrealm:txt>
>>				ip-address: <ip:ipv4>
>>				ip-range: <ipfrom:ipv4> - <ipto:ipv4>
>>				ipnet: <ipnet:ipv4net>
>>				tag:  <tag:txt>
>>				port: <ports:ipv4ports>
>>			}
>>			destination {
>>				realm: <destrealm:txt>
>>				ip-address: <ip:ipv4>
>>				ip-range: <ipfrom:ipv4> - <ipto:ipv4>
>>				ipnet: <ipnet:ipv4net>
>>				tag:  <tag:txt>
>>				port: <ports:ipv4ports>
>>			}
>>		}
>>	}
>>
>>	dynamic-nat {
>>		map {
>>			description: <description:txt>
>>			source { 
>>				realm: <srcrealm:txt>
>>				ip-address: <ip:ipv4>
>>				ip-range: <ipfrom:ipv4> - <ipto:ipv4>
>>				ipnet: <ipnet:ipv4net>
>>				tag:  <tag:txt>
>>				port: <ports:ipv4ports>
>>			}
>>			destination {
>>				realm: <destrealm:txt>
>>				ip-address: <ip:ipv4>
>>				ip-range: <ipfrom:ipv4> - <ipto:ipv4>
>>				ipnet: <ipnet:ipv4net>
>>				tag:  <tag:txt>
>>				port: <ports:ipv4ports>
>>				binding: <binding:txt>
>>
>>			}
>>		}
>>
>>	ls-nat {
>>		map {
>>			description: <description:txt>
>>			source { 
>>				realm: <srcrealm:txt>
>>				ip-address: <ip:ipv4>
>>				ip-range: <ipfrom:ipv4> - <ipto:ipv4>
>>				ipnet: <ipnet:ipv4net>
>>				tag:  <tag:txt>
>>				port: <ports:ipv4ports>
>>			}
>>			destination {
>>				realm: <destrealm:txt>
>>				ip-address: <ip:ipv4>
>>				ip-range: <ipfrom:ipv4> - <ipto:ipv4>
>>				ipnet: <ipnet:ipv4net>
>>				tag:  <tag:txt>
>>				port: <ports:ipv4ports>
>>			}
>>		}
>>	}
>>     }
>>}
>>
>>
>>The "port:" parameter is used to set the ports in use for an actual translation.
>>Syntax:
>>
>><ports-stmt> ::= ports: <port-def>
>><ports-def> ::= <protocol> <port-list>
>><port-list> ::=  <port-spec> [, <port-def>]...
>><port-spec> ::= <port-nr | service-name> | <port-range | service-name-range>
>><protocol> ::= tcp | udp
>><port-nr> ::=  <digits>
>>service-name ::= <letters><letters|digits>...
>>digits ::= <digit>...
>>digit ::= <0|1|2|3|4|5|6|7|8|9>
>>letters ::= <letter>...
>>letter ::=<a...z|A..Z>
>>
>>Example:
>>
>>ports: tcp 22,33,44-55, udp 22,33,66-77, 88
> 
> 
> 
> The above syntax seems to me as tcp/udp centric and assumes the
> particular protocol has the concept of a port.
> This is not true for protocols like ICMP and GRE.
> 
> 
OK See my comment later.

> 
>>Sample configurations with similar FreeBSD natd mappings.
>>
>>The FreeBSD 
>>
>>"natd -redirect_port tcp 172.17.16.15/telnet 6666" 
>>
>>command with the global ip address equal to 80.10.10.10 is expressed in XORP NAT configuration files as:
>>
>>protocols {
>>	NAT {
>>		realm "global" {
>>			ip: 80.10.1010
>>		}
>>		
>>		realm "local" {
>>			ip: 172.17.16.15	
>>		}
>>		static-map { <description> 
>>			source { ip-address: 80.10.10.10
>>				  ports: tcp 6666
>>			}
>>
>>			destination {
>>				ip-address: 172.17.16.15
>>				ports: tcp telnet
>>			}
>>		}
>>	}
>>}        
> 
> 
> 
> I would recommend to generalize the source and destination syntax by
> separating the concept of protocol and port. Of course, for
> protocols like tcp and udp you must have ports, so your syntax must
> incorporate that too :)
> 
I did this with NAT in my mind, but it seems naturally to come up with a
more generic dexcription for this which can be used more generally in xorp.

Do I understand you correct, that you would like a language that
supports all possible protocols in the IP packet not only TCP, UDP.

or do you also want the layer 2 protocols included in the language?

I will look into this again and come up with a new suggestion.

> 
> 
>>The configline: 
>>"natd -interface em0"
>>Creation of a dynamic mapping from 172.17.16/24 to global address of em0 interface = ip 80.10.10.10 is expressed as:
>>
>>protocols {
>>	NAT{
>>		realm "global" {
>>			ip: 80.10.10.10
>>			tag "globalip"
>>		}
>>		
>>		realm "local" {
>>			ipnet: 172.17.16.0/24
>>			tag: "localnet"}	
>>
>>		dynamic-map { <description> 
>>			source {tag: "localnet"
>>			}
>>			destination {
>>				tag: "globalip"
>>			}
>>		}
>>	}
>>}        
>>Written by 
>>Kristen Nielsen
>>Computer Science dept
>>University of Copenhagen, Denmark
>>kristen@diku.dk / KrN@KrN.dk
>>
>>
>>
>>--------------040204020303010209060700
>>Content-Type: text/plain;
>> name="nat.xif"
>>Content-Transfer-Encoding: 7bit
>>Content-Disposition: inline;
>> filename="nat.xif"
>>
>>/* xorp/xrl/interfaces/nat.xif file by KrN@KrN.DK 20060220 */
>>/* Suggestion to a nat interface for xorp. */
>>
>>
>>/* The following interfaces exists for the xorp nat module */
>>
>>	/**
>>	 * Network address translation (NAT) interface.
>>	 * The NAT module consists of the following configuration elements:
>>	 *
>>	 * set_nat_disable and get_nat_disable:
>>	 * 	sets and returns the status of the nat module
>>	 *
>> 	 * nat_realm: 
>>	 *	Manages (creates/deletes/get) realms for use in nat mappings.
>>	 *	Before realms can be used in configurations, they must 
>>	 * 	be created.
>>	 *	
>>	 * nat_realm_vif4:
>>	 *	Manages (creates/delete/lists) vif addresses for nat use 
>>	 * 	in nat mappings.
>>	 *
>>	 * nat_realm_alias4:
>>	 *	Manages (creates/deletes/lists) alias ipv4 addresses for vif 
>>	 * 	interfaces for use in nat mappings.
>>	 *
>>	 * nat_realm4:
>>	 *	Defines ip4 addresses, ip4 networks and ip4 address ranges 
>>	 * 	for use in nat mappings. Addresses are not directly connected 
>>	 * 	to any vif on the xorp router. Addresses are reachable 
>>	 * 	via the realm / vif interface stated. (This will probably be
>>	 *	changed to be the interface pointed out by the next-hop entry
>>	 * 	in the rib.)
>>	 *
>>	 * nat_static_map4: 
>>	 *	Defines static NAT table mappings
>>	 *	From the realm and ip definitions in the nat_realm_* group
>>	 *	Tcp and/or udp port definitions can be defined here.
>>	 *
>>	 * nat_dynamic_map4: 
>>	 *	Defines dynamic NAT table mappings (triggers)
>>	 *	From the definitions in the nat_real_* group
>>	 *	Tcp and/or udp port definitions can be defined here.
>>	 *
>>	 * nat_lsnat_map4: 
>>	 *	Defines Load Sharing NAT mappings
>>	 *	From the definitions in the nat_real_* group
>>	 *	Tcp and/or udp port definitions can be defined here.
>>	 *
>>	 */
>>interface nat/0.1 {
>>
>>	/** 
>>	 * set nat disable (and enable) function
>>	 *
>>	 * @param disabled sets the status of the nat module true = disabled, 
>>	 * false = enabled
>>	 * @param disabledstatus returns the status of the module, 
>>	 * true = disabled, false = enabled
>>	 */
>>	set_nat_disable		? disabled:bool -> disabledstatus:bool
> 
> 
> What is the purpose of the returned disabledstatus?
> If "set_nat_disable" returned success, then the status must be same
> as the "disabled:bool" argument when the XRL was invoked.

I believe that the returned success was a "the communication went
through" kind of reply, and a no-success would indicate some kind of
fatal fault.
Did I misunderstand some of the docs?

> BTW, stylistically, we prefer that longer names are separated
> with, say, underscore: disabledstatus -> disabled_status :)
> 
OK - no problem. (I guess this is a leftover from Danish :-)

This is my last answer / comment in this mail.

Kristen.

> This is my last comment. Without going into details, the rest of the
> XRLs seem reasonable. Though, if you change the NAT configuration
> syntax quite likely you would have to change some of the XRLs as
> well.
> 
> Pavlin
> 
> 
> 
>>	/** 
>>	 * get nat status function
>>	 *
>>	 * @param disabledstatus returns the status of the module, (as the 
>>	 * set_nat_disable function)  true = disabled, false = enabled
>>	 */
>>	get_nat_disable		-> disabledstatus:bool
>>
>>
>>	/** 
>>	 * create_nat_realm - creates a nat realm.
>>	 *
>>	 * @param realm holds the name of the realm to be created. The name 
>>	 * must not exist when the call is made.
>>	 * @param descr is the textual description of the realm.
>>	 */
>>	create_nat_realm	? realm:txt & descr:txt
>>	
>>	/** 
>>	 * delete_nat_realm - deletes a nat realm.
>>	 *
>>	 * @param realm holds the name of the realm to be deleted. The name 
>>	 * must exist when the call is made.
>>	 */
>>        delete_nat_realm 	? realm:txt
>>	
>>	/** 
>>	 * get_nat_realm - lists nat realms.
>>	 *
>>	 * @param realm holds the name of the realm to be deleted. 
>>	 * If the parameter is NULL, all existing realms is returned.
>>	 */
>>        get_nat_realm	 	? realm:txt -> realms:list 
>>
>>
>>	/** 
>>	 * create_nat_realm_vif4 - creates an entry for the base ipv4 address 
>>	 * of a virtual interface. 
>>	 * Any virtual interface can at most be a member of one realm. 
>>	 * Virtual interfaces must be in the same realm as the ip addresses
>>	 * passing the vif interface.
>>	 * 
>>	 * @param realm is an existing realm that the vif is mapped to.
>>	 * @param ifname is the name of the physical interface where the 
>>	 * vif is defined.
>>	 * @param vifname is the name of the virtual interface to be mapped.
>>	 * @param tag is a textlabel that the mapping is labeled with.
>>	 * @param description textual description of the mapping.
>>	 */
>>	create_nat_realm_vif4 	? realm:txt & ifname:txt & vifname:txt & \
>>				tag:txt & description:txt 
>>
>>	/** 
>>	 * delete_nat_realm_vif4 - removes an entry for a base ipv4 (vif) 
>>	 * address of virtual interface from a nat realm.
>>	 * The definitions matching all the supplied parameters is deleted.
>>	 * Wild card parameters must be set to NULL.
>>	 *
>>	 * @param realm all vif4 definitions to this realm is deleted.
>>	 * @param ifname all definitions with this ifname is deleted. 
>>	 * @param vifname all mappings to this vifname is deleted
>>	 * @param tag all mappings with this tag is deleted.
>>	 */
>>	delete_nat_realm_vif4	? realm:txt & ifname:txt & vifname:txt & \
>>				tag:txt
>>
>>	/**
>>	 * update_nat_realm_vif4 - updates an existing vif mapping with its
>>	 * new ipv4 address. 
>>	 * The vif4 mapping is updated when the vif get a new ipv4 address.
>>	 */
>>	update_nat_realm_vif4 	? ifname:txt & vifname:txt & ip:ipv4
>>	 
>>	/** 
>>	 * get_nat_realm_vif4 - lists nat_realm_vif4 definitions.
>>	 *
>>	 * get_nat_realm_vif4 returns a list of all nat_realm_vif4 
>>	 * interfaces in the router matching the realm supplied. 
>>	 * @param realm specifies the realm to return interfaces for. 
>>	 * If NULL then all defined nat_realm_vif4 interfaces are returned.
>>	 */
>>	get_nat_realm_vif4 	? realm:txt -> nat_realm_vif4s:list
>>
>>	
>>	/** 
>>	 * create_nat_realm_alias4 - creates a mapping to the nat_realm 
>>	 * definitions. Manipulates ipv4 address aliases of an interface 
>>	 * (vif) for in/out going nat gateways. Aliases are not the base 
>>	 * ipv4 address of the virtual interface, but ipv4 addresses in 
>>	 * the same subnet as the vif. (see nat_realm_vif)
>>	 *
>>	 * Any aliases, aliased to a vif must be in the same realm as the 
>>	 * vif itself.
>>	 *
>>	 * @param realm specifies the realm that the IP address belongs to.
>>	 * @param ifname is the physical interfaces for this interface
>>	 * @param vifname is the virtual interface name to add this alias to.
>>	 * @param tag is a label for grouping definitions.
>>	 * @param description is a textual description of this alias.
>>	 * @param ipaddr is the ipv4 alias address added to the vif.
>>	 */
>>	create_nat_realm_alias4	? realm:txt & ifname:txt & vifname:txt & \
>>				tag:txt & description:txt & ipaddr:ipv4
>>
>>
>>	/** 
>>	 * delete_realm_alias4 function
>>	 * Deletes ipv4 realm_alias4 address from the virtuel interface (vif). 
>>	 *
>>	 * The alias4 mappings matching the supplied parameters are deleted.
>>	 * Parameters that are not defined (=not matched against) must be NULL. 
>>	 *
>>	 * @param realm the alias4 mappings in the same realm is deleted.
>>	 * @param ifname all alias4 mappings defined for this interface is
>>	 * deleted.
>>	 * @param vifname all alias4 mappings defined under this vif is 
>>	 * deleted.
>>	 * @param tag all alias4 mappings with tag is deleted.
>>	 * @param ipaddr the alias4 mapping with this ipv4 address is deleted.
>>	 */
>>	delete_nat_realm_alias4	? realm:txt & ifname:txt & vifname:txt & \
>>				tag:txt & ipaddr:ipv4
>>
>>	/**
>>	 * get_nat_realm_alias4 returns a nat_realm_alias4 list with matching 
>>	 * alias4 elements. Wildcard parameters shuld be set to NULL.
>>	 *
>>	 * @param realm specifies the realm of the alias4 addresses to be 
>>	 * returned.
>>	 * @param ifname specifies the physical interfaces to match.
>>	 * @param vifname specifies the virtual interfaces to match.
>>	 * @param tag specifies the tag of the definitions to match.
>>	 * @param ipaddr specifies the ipv4 addr of the alias4 to match.
>>	 * @param nat_realm_alias4s is the list of the matching aliases 
>>	 * defined.
>>	 */
>>	get_nat_realm_alias4	? realm:txt & ifname:txt & vifname:txt & \
>>				tag:txt & ipaddr:ipv4 \
>>				-> nat_realm_alias4s:list
>>
>>	/** 
>>	 * create_nat_realm - create definitions of ipv4 addresses/ipv4/
>>	 * networks/ipv4 ip ranges to the nat_realm list.
>>	 *
>>	 * The ipv4 addresses / ipv4 networks / ipv4 address ranges / tagged
>>	 * list of definitions, are all ip-addresses not directly attached
>>	 * to any physical/virtual interface on the xorp router.
>>	 * 
>>	 * The function have the following way of interpreting the address 
>>	 * arguments:
>>	 * All function calls must have theese parameters defined: 
>>	 * <realm> <ifname> <vifname>, where realm specifies the actural realm.
>>	 * ifname and vifname the interfaces to route these addresses through.
>>	 * (If the ifname and vifname is possible to acquire via the routing
>>	 * info, these parameters might disappear during implementation) 
>>	 *
>>	 * To specify a tag for the definition, supply the <tag> parameter.
>>	 *
>>	 * To specify an single ipv4 address supply ONLY the <ip> parameter. 
>>	 *
>>	 * To specify an ipv4 network supply ONLY the <ipnet> parameter. 
>>	 *
>>	 * To specify an ipv4 range supply ONLY the <ip> and <ipto> parameters. 
>>	 * <ip> is the lowest ip address and ipto is the highest ip address
>>	 * in the range.
>>	 * 
>>	 * The 3 types of definitions above can not be mixed in a single call
>>	 * to the function. Grouping is done with defining more of the 3
>>	 * first classes with the same tag.
>>	 * 
>>	 * create_nat_realm4 create an ipv4 address/ipv4network/ipv4-range/tag
>>	 * at the nat map list.
>>	 *
>>	 * @param realm specifies the realm to which the mapping belong.
>>	 * @param tag maps the definition with this tag.
>>	 * @param description a textual description of this alias.
>>	 * @param ip is the ip address or the lowest bound of an ip range.
>>	 * @param ipto is the highest bound of a range.
>>	 * @param ipnet specifies an ipv4 network (ip address + subnetmask)
>>	 */
>>	create_nat_realm4	 	? realm:txt & \
>>					tag:txt & description:txt & \
>>					ip:ipv4 & ipto:ipv4 & \
>>					ipnet:ipv4net
>>
>>	/**
>>	 * delete_nat_realm4 deletes all nat_realm4 mappings, matching
>>	 * all supplied parameters. Wild card parameters must be set to NULL.
>>	 * (For further doc see add_nat_realm4)
>>	 *
>>	 * @param realm all nat_realm4 with this realm is deleted.
>>	 * @param tag all nat_realm4 definitions with this tag is deleted.
>>	 * @param ip the ipv4 address mapping is deleted. (see ipto param too)
>>	 * @param ipto the range defined together with the ip parameter is 
>>	 * deleted.
>>	 * @param ipnet the ipv4network defined is deleted.
>>	 * 
>>	 * If more parameters are defined, only the definitions that match 
>>	 * ALL the supplied parameters is deleted. 
>>	 */
>>	delete_nat_realm4 		? realm:txt & \
>>					tag:txt & \
>>					ip:ipv4 & ipto:ipv4 & \
>>					ipnet:ipv4net
>>
>>	/**
>>	 * get_nat_realm4 function - returns the list of defined elements 
>>	 * that matches the supplied parameters.
>>	 * (For further doc on the use see add_nat_realm4 the doc.)
>>	 * Wildcard parameters must be set to NULL.
>>	 *
>>	 * @param realm returns the list of realm4 definitions for this realm.
>>	 * @param tag returns the list of definitions tagged with this tag.
>>	 * @param ip returns the list of definitions with this ipv4 address.
>>	 * @param ipto returns the list of definitions with this ipv4 range. 
>>	 * @param ipnet returns the list of ipv4 networks defined.
>>	 * @param nat_realm4s is a list of the matched definitions.
>>	 */
>>	get_nat_realm4 			? realm:txt & \
>>					tag:txt & description:txt & \
>>					ip:ipv4 & ipto:ipv4 & \
>>					ipnet:ipv4net -> nat_realm4s:list
>>
>>	/**
>>	 * create_nat_static_map4
>>	 *
>>	 * create_nat_static_map4 - defines static NAT table entries from the 
>>	 * ip definitions from the nat_realm* functions.
>>	 *
>>	 * The nat_static_map functions defines static nat mappings between 
>>	 * ip addresses at the source side realm and the ip addresses of 
>>	 * the destination side realm.
>>	 * If the ip sizes of the ranges on either side of the mapping is not 
>>	 * equal, then the mappings must go from the source side realm 
>>	 * (aka local realm) to the destination side realm (aka global realm).
>>	 * ip addresses that is used for TCP/UDP port mapping 
>>	 * (port overloading) must always be defined at the destination side.
>>	 *
>>	 * The nat_static_map function has more sub functions dependent of 
>>	 * the supplied parameters. The parameters can define either a single
>>	 * ip address, a contiguous range of ip addresses or a sub net, or a
>>	 * tagged set of definitions. The ip addresses and realm used in a map 
>>	 * statement must be defined in a nat_realm* clause.
>>	 * The source and destination side of a mapping can take all 4 forms
>>	 * from the following definitions.
>>	 *  
>>	 * To specify a single ip address the ip parameter is used. The 
>>	 * ipto paramter must be NULL.
>>	 * 
>>	 * To specify a contiguous range of IP addresses, the ip and ipto 
>>	 * parameters are used. The ipnet parameter must be NULL.
>>	 * 
>>	 * To specify an ipnetwork, the ipnet parameters must be specified. 
>>	 * The ipnet takes a subnet-address and a submet-mask. The ip and ipto
>>	 * parameters must be NULL.
>>	 * 
>>	 * To use a tag from the nat_realm definitions, specify the tag at 
>>	 * the tag parameter. The ip, ipto and ipnet parameters must be NULL.
>>	 *
>>	 * @param srcrealm specifies the realm for the source side of the map.
>>	 *
>>	 * @param destrealm specifies the realm for the destination side 
>>	 * of the map.
>>	 *
>>	 * @param srcip is the ipv4 source ip address of a mapping.
>>	 *
>>	 * @param srcipto is the source ipv4 address that forms the upper 
>>	 * bound of an ip range.
>>	 *
>>	 * @param srcipnet is the ipv4 network which forms the source mapping.
>>	 * bound of an ip range.
>>	 *
>>	 * @param srctag maps all nat_realm definitions with the same tag as
>>	 * the source definition.
>>	 *
>>	 * @param srcport is the range of ports used to this mapping.
>>	 *
>>	 * @param destip is the ipv4 destination address of the mapping
>>	 *
>>	 * @param destipto is the ipv4 address that forms the upper bound of 
>>	 * the destination ip range. 
>>	 *
>>	 * @param destipnet is the ipv4 network that is the destination ip 
>>	 * addresses for the mapping.
>>	 *
>>	 * @param desttag maps all nat_realm definitions with the same tag as
>>	 * the destination definition.
>> 	 *
>>	 * @param destport is a list of tcp and/or udp ports used at the
>>	 * destination addresses.
>>	 *
>>	 */
>>	create_nat_static_map4		? description:txt & \
>>					srcrealm:txt & \
>>					srcip:ipv4 & srcipto:ipv4 & \
>>					srcipnet:ipv4net & \
>>					srctag:txt & \
>>					srcport:ipv4ports & \
>>					destrealm:txt & \
>>					destip:ipv4 & destipto:ipv4 & \
>>					destipnet:ipv4net & \
>>					desttag:txt & \
>>					destport:ipv4ports
>>
>>	/**
>>	 * delete_nat_static_map4
>>	 *
>>	 * delete_nat_static_map4 - delete static nat table entries from the 
>>	 * ip definitions from the nat_static_map4 functions.
>>	 *
>>	 * The function deletes the nat_static_map4 entries that matches
>>	 * all the supplied parameters.  (for more information about the 
>>	 * interfaces see create_nat_static_map4 documentation)
>>	 *
>>	 * The selected ranges must be fully matching sets from the
>>	 * create_nat_static_map4 definition. No internal ranges can be deleted.
>>	 *
>>	 * @param srcrealm specifies the source realm to be deleted. All 
>>	 * nat_static_map4 definitions with the same realm is selected.
>>	 *
>>	 * @param destrealm specifies the realm for the destination side 
>>	 * to be deleted. All nat_static_map4 definitions with the same realm 
>>	 * is selected.
>>	 *
>>	 * @param srcip is the ipv4 source ip address to be deleted.
>>	 *
>>	 * @param srcipto is together with the srcip parameter defines the
>>	 * source ip range to be deleted. 
>>	 *
>>	 * @param srcipnet is the ipv4 network source mapping to be deleted.
>>	 *
>>	 * @param srctag maps selects the source tags to be deleted.
>>	 * 
>>	 * @param srcport is the range of tcp and/or udp ports to be deleted.
>>	 *
>>	 * @param destip is the ipv4 destination address to be deleted.
>>	 *
>>	 * @param destipto is together with the destip parameter defines 
>>	 * the destination ip range to be deleted.
>>	 *
>>	 * @param destipnet is the ipv4 network to be deleted.
>>	 *
>>	 * @param desttag maps defines the destination tags to be deleted.
>>	 *
>>	 * @param destport is a list of tcp and/or udp ports to be deleted.
>>	 */
>>	delete_nat_static_map4		? srcrealm:txt & \
>>					srcip:ipv4 & srcipto:ipv4 & \
>>					srcipnet:ipv4net & \
>>					srctag:txt & \
>>					srcport:ipv4ports & \
>>					destrealm:txt & \
>>					destip:ipv4 & destipto:ipv4 & \
>>					destipnet:ipv4net & \
>>					desttag:txt & \
>>					destport:ipv4ports
>>
>>	/**
>>	 * get_nat_static_map4 - lists nat_static_map4 entries.
>>	 *
>>	 * get_nat_static_map4 - lists static NAT table entries that matches 
>>	 * the supplied parameters.
>>	 *
>>	 * The function deletes the nat_static_map4 entries that is matches
>>	 * all the supplied parameters.
>>	 * (for more information about the interfaces see 
>>	 * create_nat_static_map4 documentation)
>>	 *
>>	 * @param srcrealm specifies the source realm to be listed.
>>	 *
>>	 * @param destrealm specifies the realm for the destination side 
>>	 * to be listed.
>>	 *
>>	 * @param srcip is the ipv4 source ip address to be listed.
>>	 *
>>	 * @param srcipto is together with the srcip parameter defines the
>>	 * source ip range to be listed. 
>>	 *
>>	 * @param srcipnet is the ipv4 network source to be listed.
>>	 *
>>	 * @param srctag maps selects the srctags to be listed.
>>	 *
>>	 * @param srcport is the range of tcp and/or udp ports to be delted.
>>	 *
>>	 * @param destip is the ipv4 destination address to be listed.
>>	 *
>>	 * @param destipto is together with the destip parameter defines 
>>	 * the destination ip range to be listed.
>>	 *
>>	 * @param destipnet is the ipv4 network to be listed.
>>	 *
>>	 * @param desttag maps defines the destination tags to be listed.
>>	 *
>>	 * @param nat_static_map4s contains the list of matched elements.
>>	 *
>>	 * @param destport is a list of tcp and/or udp ports to be matched.
>>	 */
>>	get_nat_static_map4	? description:txt & \
>>				srcrealm:txt & \
>>				srcip:ipv4 & srcipto:ipv4 & \
>>				srcipnet:ipv4net & \
>>				srctag:txt & \
>>				srcport:ipv4ports & \
>>				destrealm:txt & \
>>				destip:ipv4 & destipto:ipv4 & \
>>				destipnet:ipv4net & \
>>				destport:ipv4ports & \
>>				desttag:txt -> nat_static_map4s:list
>>
>>
>>	/** 
>>	 * create_nat_dynamic map definitions.
>>	 *
>>	 * The nat_static_map functions defines static mappings between 
>>	 * IP addresses at the source side realm and the IP addresses of 
>>	 * the destination side realm.
>>	 * If the IP sizes of the ranges on either side is not equal, 
>>	 * then the mappings must go from the source side realm 
>>	 * (aka local realm) and the destination side realm (aka global realm).
>>	 * IP addresses that is used for TCP/UDP port mapping 
>>	 * (port overloading) must be defined on the destination side.
>>	 *
>>	 * @param srcrealm specify the network realm for the source part
>>	 * of the mapping.
>>	 *
>>	 * @param srctag maps the nat_realm* definitions with this tag as
>>	 * the source side of the mapping. The tagged definitions must belong
>>	 * to the same realm as stated in srcrealm. If the special meaning
>>	 * tag "all" is given then all the definitions in the nat_realm 
>>	 * with the same realm as stated in srcrealm is matched.
>>	 *
>>	 * Src or dest definitions defults to "all" which is all addresses 
>>	 * in the matching (src/dest) realm as defined in nat_realm_* group.
>>	 *
>>	 * @param srcip is the ipv4 source ip address of a mapping.
>>	 *
>>	 * @param srcipnet is the ipv4 network which forms the source mapping.
>>	 *
>>	 * @param scrip is the source ipv4 address that forms the lower bound 
>>	 * of an ip range.
>>	 *
>>	 * @param srcipto is the source ipv4 address that forms the upper 
>>	 * bound of an ip range.
>>	 *
>>	 * @param srcport is the range of tcp and/or udp ports to be used in
>>	 * the mapping.
>>	 *
>>	 * @param destip is the ipv4 destination address of the mapping
>>	 *
>>	 * @param destipnet is the ipv4 network that is the destination ip 
>>	 * addresses for the mapping.
>>	 *
>>	 * @param destip is the ipv4 address that forms the lower bound of the 
>>	 * destination ip range.
>>	 *
>>	 * @param destipto is the ipv4 address that forms the upper bound of 
>>	 * the destination ip range. 
>>	 *
>>	 * @param desttag maps the nat_realm* definitions with this tag as
>>	 * the destination side of the mapping. The tagged definitions must 
>>	 * belong to the same realm as stated in srcrealm. If the special 
>>	 * meaning tag "all" is given then all the definitions in the nat_realm 
>>	 * with the same realm as stated in srcrealm is matched.
>>	 * 
>>	 * @param destport is a list of tcp and/or udp ports to use for the
>>	 * dynamic mapping.
>>	 *
>>	 * @param binding This argument can be "dynamic" (default) or "fixed"
>>	 * Dynamic can be a new mapping each time the mapping is used for a 
>>	 * new connection (from src side). "fixed" is using the same source 
>>	 * and destination mapping each time the src ip/port is connecting.
>>	 */
>>	create_nat_dynamic_map4	? description:txt & \
>>				srcrealm:txt & \
>>				srcip:ipv4 & srcipto:ipv4 & \
>>				srcipnet:ipv4net & \
>>				srctag:txt & \
>>				srcport:ipv4ports & \
>>				destrealm:txt & \
>>				destip:ipv4 & destipto:ipv4 & \
>>				destipnet:ipv4net & \
>>				desttag:txt & \
>>				destport:ipv4ports & \
>>				binding:txt
>>
>>	/** 
>>	 * delete_nat_dynamic_map4
>>	 * 
>>	 * The delete_nat_dynamic_map4 function deletes the elements from the
>>	 * nat_dynamic_map4 table that matches the supplied parameters.
>>	 *
>>	 * @param srcrealm matches source realm parameter of mappings.
>>	 *
>>	 * @param srctag matches the source tag paramter of the mappings to 
>>	 * be deleted.
>>	 * If the special meaning tag "all" is given then all the definitions 
>>	 * with this tag on the source side is matched. With the same realm 
>>	 * as stated in srcrealm is matched.
>>	 *
>>	 * @param srcip matches the ipv4 source ip, or the lower bound of an
>>	 * ipv4 ip-range to be deleted.
>>	 *
>>	 * @param srcipto matches the source ipv4 address that forms the upper 
>>	 * bound of an ip range to be deleted.
>>	 *
>>	 * @param srcipnet matches the source ipv4 network to be deleted.
>>	 * 
>>	 * @param srcport is the tcp and/or udp port range to be deleted.
>>	 *
>>	 * @param destip matches the ipv4 destination address of the mapping
>>	 * or the ipv4 address that forms the lower bound of the destination
>>	 * ip range.
>>	 *
>>	 * @param destipto matches the destination ipv4 address to be deleted.
>>	 *
>>	 * @param destipnet matches the destination ipv4 network.
>>	 *
>>	 * @param desttag maps the mappings with this tag as the destination 
>>	 * side of the mapping. The tagged definitions must belong to the
>>	 * same realm as stated in srcrealm. If the special 
>>	 * meaning tag "all" is given then all the definitions in the 
>>	 * nat_dynamic_realm with the same source realm as stated in srcrealm 
>>	 * is matched.
>>	 * 
>>	 * @param destport is a list of tcp and/or udp ports to be deleted.
>>	 *
>>	 * @param binding This argument can be "dynamic" (default) or "fixed"
>>	 * Dynamic can be a new mapping each time the mapping is used for a 
>>	 * new connection (from src side). "fixed" is using the same source 
>>	 * and destination mapping each time the src ip/port is connecting.
>>	 */
>>	delete_nat_dynamic_map4	? srcrealm:txt & \
>>				srcip:ipv4 & srcipto:ipv4 & \
>>				srcipnet:ipv4net & \
>>				srctag:txt & \
>>				srcport:ipv4ports & \
>>				destrealm:txt & \
>>				destip:ipv4 & destipto:ipv4 & \
>>				destipnet:ipv4net & \
>>				desttag:txt & \
>>				destport:ipv4ports & \
>>				binding:txt
>>
>>	/** 
>>	 * get_nat_dynamic_map4
>>	 * 
>>	 * The get_nat_dynamic_map4 function returns the elements from the
>>	 * nat_dynamic_map4 table that matches all the supplied parameters.
>>	 *
>>	 * @param srcrealm matches source realm parameter of the mappings.
>>	 *
>>	 * @param srctag matches the source tag parameter of the mappings.
>>	 * If the special meaning tag "all" is given then all the definitions 
>>	 * with this tag on the source side is matched. With the same realm 
>>	 * as stated in srcrealm is matched.
>>	 *
>>	 * @param srcip matches the ipv4 source ip, or the lower bound of an
>>	 * ipv4 ip-range.
>>	 *
>>	 * @param srcipto matches the source ipv4 address that forms the upper 
>>	 * bound of an ip range.
>>	 *
>>	 * @param srcipnet matches the source ipv4 network.
>>	 * 
>>	 * @param srcport is the tcp and/or udp range to be returned.
>>	 *
>>	 * @param destip matches the ipv4 destination address of the mapping
>>	 * or the ipv4 address that forms the lower bound of the destination
>>	 * ip range.
>>	 *
>>	 * @param destipto matches the destination ipv4 address.
>>	 *
>>	 * @param destipnet matches the destination ipv4 network.
>>	 *
>>	 * @param desttag maps the mappings with this tag as the destination 
>>	 * side of the mapping. The tagged definitions must belong to the
>>	 * same realm as stated in srcrealm. If the special 
>>	 * mening tag "all" is given then all the definitions in the 
>>	 * nat_dynamic_realm with the same source realm as stated in srcrealm 
>>	 * is matched.
>>	 *
>>	 * @param destport is a list of tcp and/or udp ports to be returned.
>>	 *
>>	 * @param binding This argument can be "dynamic" (default) or "fixed"
>>	 * Dynamic can be a new mapping each time the mapping is used for a 
>>	 * new connection (from src side). "fixed" is using the same source 
>>	 * and destination mapping each time the src ip/port is connecting.
>>	 */
>>	get_nat_dynamic_map4	? description:txt & \
>>				srcrealm:txt & \
>>				srcip:ipv4 & srcipto:ipv4 & \
>>				srcipnet:ipv4net & \
>>				srctag:txt & \
>>				srcport:ipv4ports & \
>>				destrealm:txt & \
>>				destip:ipv4 & destipto:ipv4 & \
>>				destipnet:ipv4net & \
>>				desttag:txt & \
>>				destport:ipv4ports & \
>>				binding:txt -> nat_dynamic_map4s:list
>>
>>
>>
>>	/** 
>>	 * lsnat_map functions - define Load Sharing NAT (LSNAT) functionality.
>>	 *  
>>	 * lsnat_map defines hosts at the destination side which is to be
>>	 * loadshared when accesses via a common global address and port, 
>>	 * defined at the source side.
>>	 *
>>	 * The lsnat_map function has a range of ways to define ipv4 addresses,
>>	 * ipv4 networks and ipv4 ip address ranges.
>>	 * The parameters can define either a single ip address, a contigous 
>>	 * range of IP addresses or a subnet, or a tag.
>>	 * The source and destination side of a mapping can each take all 
>>	 * 4 forms.
>>	 *  
>>	 * To specify an single ip address the ip parameter is used. The 
>>	 * ipto paramter must be NULL.
>>	 * 
>>	 * To specify a contiguous range of IP addresses, the ip and ipto 
>>	 * parameters are used. The ipnet parameter must be NULL.
>>	 * 
>>	 * To specify an ipnetwork, the ipnet parameters must be specified. 
>>	 * The ipnet takes a sub net-address and a sub net-mask. The ip and ipto
>>	 * parameters must be NULL.
>>	 * 
>>	 * To use a named tag from the nat_realm definitions, specify the tag 
>>	 * at the tag parameter. The ip, ipto and ipnet parameters must be 
>>	 * NULL. Tags with the special value "all" matches all defined 
>>	 * addresses in the same realm as the tag.
>>	 *
>>	 * @param srcrealm defines which realm the source addresses belongs 
>>	 * to. The common ip addresses to access the load shared services must
>>	 * be load shared must be connected to the source side of the map. 
>>	 *
>>	 * @param destrealm defines which realm the destination addresses  
>>	 * belongs to (host network realm). The ip addresses of the hosts
>>	 * with the services to be load shared is on this realm.
>>	 *
>>	 * @param srcip is the ipv4 source ip address of a mapping.
>>	 *
>>	 * @param srcipto is the source ipv4 address that forms the upper 
>>	 * bound of an ip range.
>>	 *
>>	 * @param srcipnet is the ipv4 network which forms the source mapping.
>>	 * bound of an ip range.
>>	 *
>>	 * @param srctag maps all nat_realm definitions with the same tag as
>>	 * the source definition. The special tag value "all" matches all 
>>	 * definitions from the nat_realm with the same realm.
>>	 *
>>	 * @param srcport is the list of tcp and/or udp ports to created.
>>	 *
>>	 * @param destip is the ipv4 destination address of the mapping
>>	 *
>>	 * @param destipto is the ipv4 address that forms the upper bound of 
>>	 * the destination ip range. 
>>	 *
>>	 * @param destipnet is the ipv4 network that is the destination ip 
>>	 * addresses for the mapping.
>>	 *
>>	 * @param desttag maps all nat_realm definitions with the same tag as
>>	 * the destination definition. The special tag value "all" matches all 
>>	 * definitions from the nat_realm with the same realm.
>>	 *
>>	 * @param destport is the tcp and/or udp port to load share.
>>	 *
>>	 * @param lsalgorithm defines the load sharing algorithm, and takes 
>>	 * the values: round-robin, random, (more ?), ...
>>	 *
>>	 */
>>
>>	/**
>>	 * create_lsnat_map4 function -
>>	 * Creates a lsnat_map4 table entry to the nat mappings.
>>	 */
>>	create_lsnat_map4	? description:txt & \
>>				srcrealm:txt & \
>>				srcip:ipv4 & srcipto:ipv4 & \
>>				srcipnet:ipv4net & \
>>				srctag:txt & \
>>				srcport:ipv4ports & \
>>				destrealm:txt & \
>>				destip:ipv4 & destipto:ipv4 & \
>>				destipnet:ipv4net & \
>>				desttag:txt & \
>>				destport:ipv4ports & \
>>				lsalgorithm:txt
>>
>>	/**
>>	 * delete_lsnat_map4 function -
>>	 * Deletes the lsnat_map4 tableentries from the nat mappings that
>>	 * matches all the defined parameters.
>>	 */
>>	delete_lsnat_map4	? srcrealm:txt & \
>>				srcip:ipv4 & srcipto:ipv4 & \
>>				srcipnet:ipv4net & \
>>				srctag:txt & \
>>				srcport:ipv4ports & \
>>				destrealm:txt & \
>>				destip:ipv4 & destipto:ipv4 & \
>>				destipnet:ipv4net & \
>>				desttag:txt & \
>>				destport:ipv4ports & \
>>
>>	/**
>>	 * get_lsnat_map4 function -
>>	 * Lists lsnat_map4 table entries that matches all the defined the
>>	 * parameters. 
>>	 */
>>	get_lsnat_map4		? description:txt & \
>>				srcrealm:txt & \
>>				srcip:ipv4 & srcipto:ipv4 & \
>>				srcipnet:ipv4net & \
>>				srctag:txt & \
>>				srcport:ipv4ports & \
>>				destrealm:txt & \
>>				destip:ipv4 & destipto:ipv4 & \
>>				destipnet:ipv4net & \
>>				desttag:txt & \
>>				destport:ipv4ports & \
>>				lsalgorithm:txt -> lsnat_map4s:list
>>}
>>
>>
>>
>>--------------040204020303010209060700--
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> 
> 
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