VPP/NATLast updated 4 years ago

VPP NAT implementation

Introduction

The VPP SNAT is an implementation of NAT44. It is a plugin and is meant to replace the VCGN component. The target use case is a general IPv4 CPE NAT, a CGN and to act as a NAT44 in a Openstack deployment.

It is intended to be pluggable, in the sense that it should be possible to plug the NAT44 function together with the MAP-E IPv4 to IPv6 translator to create a MAP-E CE, likewise one can plug the NAT44 together with MAP-T to create a MAP-T CE or 464XLAT.

Features are tracked as they are developed in the following VPP-441.

Until code is upstreamed it is developed on gitub.

Requirements

• Scale to millions of bindings
• Performance goal of 10Mpps/core.
• Configurable address and port selection algorithm.
• User quotas for sessions.
• Thread safe
• Efficient port utilisation. Endpoint independent for applications requiring it, address and port filtering otherwise
• No ALGs
• Configurable IP address pooling behavour
• Plugable with MAP-E/T to create MAP-E/T CE, 464XLAT
• Stateful NAT64
• Support for NAT on a stick (single inside / outside interface)

Work list

Task	Owner	Priority	Status	Description
1:1 NAT	Matus	0	Committed	VPP-339
1:1 NAT with ports	Matus	0	Committed	VPP-339
1:1 NAT with disabled dynamic translation	Matus	0	Committed	VPP-339 add "static mapping only [connection tracking]" to snat startup config.
VRF awareness	Matus	0	Committed	VPP-339 One tenant == One VRF. One VRF == multiple interfaces / multiple subnets, add vrf to static mapping API/CLI.
1:1 NAT delete and dump API	Matus	0	Committed	VPP-339
Multiple inside interface - Multiple subnets		0		VPP-447 Multiple inside interfaces for the same "tenant" with non-overlapping address space.
Inside overlapping interfaces		0		VPP-446 Tenants on separate interfaces, separate VRFs with overlapping address space.
Thread safe		0		VPP-443
Hairpinning		1		VPP-444 Hosts communicating behind the same NAT using the external representation of their address.
Logging		1		VPP-445	Netflow - IPFix
API (Java and Python)
Input ACL support before NAT
Multiple outside interfaces
ICMP error packet translation
DS-lite
NAT64

API

add/del 1:1 NAT:

define snat_add_static_mapping {
 u32 client_index;
 u32 context;
 u8 is_add;
 u8 is_ip4;
 u8 addr_only;
 u8 local_ip_address[16];
 u8 external_ip_address[16];
 u16 local_port;
 u16 external_port;
 u32 vrf_id;
};

dump 1:1 NAT:

define snat_static_mapping_dump {
 u32 client_index;
 u32 context;
};

define snat_static_mapping_details {
 u32 context;
 u8 is_ip4;
 u8 addr_only;
 u8 local_ip_address[16];
 u8 external_ip_address[16];
 u16 local_port;
 u16 external_port;
 u32 vrf_id;
};

dump S-NAT plugin config:

define snat_show_config {
 u32 client_index;
 u32 context;
};

define snat_show_config_reply {
 u32 context;
 i32 retval;
 u8 static_mapping_only;
 u8 static_mapping_connection_tracking;
 u32 translation_buckets;
 u32 translation_memory_size;
 u32 user_buckets;
 u32 user_memory_size;
 u32 max_translations_per_user;
 u32 outside_vrf_id;
 u32 inside_vrf_id;
};

CLI

snat add static mapping local <ip4-addr> [<port>] external <ip4-addr> [<port>] [vrf <table-id>] [del]

Startup config

translation hash buckets <n> - default 1024 translation hash memory <n> - default 128<<20 user hash buckets <n> - default 128 user hash memory <n> - default 64<<20 max translations per user <n> - default 100 outside VRF id <table-id> - default 0 inside VRF id <table-id> - default 0 static mapping only [connection tracking] - default dynamic traslations enabled

References

• RFC2663 - NAT terminology and considerations
• RFC4787 - NAT requirements for UDP
• RFC5382 - NAT requirements for TCP
• RFC5508 - NAT requirements for ICMP
• RFC6888 - CGN requirements - qualify and plan dev sequence:
• RFC7422 - Deterministic address mapping
• draft-ietf-behave-ipfix-nat-logging - IPFIX Information Elements for logging NAT Events