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/*
* ipsec_itf.c: IPSec dedicated interface type
*
* Copyright (c) 2020 Cisco and/or its affiliates.
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at:
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
#ifndef __IPSEC_ITF_H__
#define __IPSEC_ITF_H__
#include <vnet/tunnel/tunnel.h>
#include <vnet/ipsec/ipsec_sa.h>
/**
* @brief A dedicated IPSec interface type
*
* In order to support route based VPNs one needs 3 elements: an interface,
* for routing to resolve routes through, an SA from the peer to describe
* security, and encap, to describe how to reach the peer. There are two
* ways one could model this:
*
* interface + encap + SA = (interface + encap) + SA =
* ipip-interface + SA transport mode
*
* or
*
* interface + encap + SA = interface + (encap + SA) =
* IPSec-interface + SA tunnel mode
*
* It's a question of where you add the parenthesis, from the perspective
* of the external user the effect is identical.
*
* The IPsec interface serves as the encap-free interface to be used
* in conjunction with an encap-describing tunnel mode SA.
*
* VPP supports both models, which modelshould you pick?
* A route based VPN could impose 0, 1 or 2 encaps. the support matrix for
* these use cases is:
*
* | 0 | 1 | 2 |
* --------------------------
* ipip | N | Y | Y |
* ipsec | P | Y | P |
*
* Where P = potentially.
* ipsec could potnetially support 0 encap (i.e. transport mode) since neither
* the interface nor the SA *requires* encap. However, for a route beased VPN
* to use transport mode is probably wrong since one shouldn't use thransport
* mode for transit traffic, since without encap it is not guaranteed to return.
* ipsec could potnetially support 2 encaps, but that would require the SA to
* describe both, something it does not do at this time.
*
* ipsec currently does not support:
* - multipoint interfaces
* but this is only because it is not yet implemented, rather than it cannot
* be done.
*
* Internally the difference is that the midchain adjacency for the IPSec
* interface has no associated encap (whereas for an ipip tunnel it describes
* the peer). Consequently, features on the output arc see packets without
* any encap. Since the protecting SAs are in tunnel mode,
* they apply the encap. The midchain adj is stacked only once the proctecting
* SA is known, since only then is the peer known. Otherwise the VLIB graph
* nodes used are the same:
* (routing) --> ipX-michain --> espX-encrypt --> adj-midchain-tx --> (routing)
* where X = 4 or 6.
*
* Some benefits to the ipsec interface:
* - it is slightly more efficient since the encapsulating IP header has
* its checksum updated only once.
* - even when the interface is admin up traffic cannot be sent to a peer
* unless the SA is available (since it's the SA that determines the
* encap). With ipip interfaces a client must use the admin state to
* prevent sending until the SA is available.
*
* The best recommendations i can make are:
* - pick a model that supports your use case
* - make sure any other features you wish to use are supported by the model
* - choose the model that best fits your control plane's model.
*
*
* gun reloaded, fire away.
*/
typedef struct ipsec_itf_t_
{
tunnel_mode_t ii_mode;
int ii_user_instance;
u32 ii_sw_if_index;
} __clib_packed ipsec_itf_t;
extern int ipsec_itf_create (u32 user_instance,
tunnel_mode_t mode, u32 * sw_if_indexp);
extern int ipsec_itf_delete (u32 sw_if_index);
extern void ipsec_itf_adj_stack (adj_index_t ai, u32 sai);
extern void ipsec_itf_adj_unstack (adj_index_t ai);
/*
* fd.io coding-style-patch-verification: ON
*
* Local Variables:
* eval: (c-set-style "gnu")
* End:
*/
#endif
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