/*      $NetBSD: if_l2tp.h,v 1.10 2021/03/16 07:00:38 knakahara Exp $   */

/*
* Copyright (c) 2017 Internet Initiative Japan Inc.
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
*    notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
*    notice, this list of conditions and the following disclaimer in the
*    documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
* ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
* TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
* PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
* BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
* POSSIBILITY OF SUCH DAMAGE.
*/

/*
* L2TPv3 kernel interface
*/

#ifndef _NET_IF_L2TP_H_
#define _NET_IF_L2TP_H_

#include <sys/queue.h>
#include <sys/ioccom.h>
#ifdef _KERNEL
#include <sys/pserialize.h>
#include <sys/psref.h>
#include <sys/pslist.h>
#endif

#include <net/if_ether.h>
#include <netinet/in.h>

#define SIOCSL2TPSESSION        _IOW('i', 151, struct ifreq)
#define SIOCDL2TPSESSION        _IOW('i', 152, struct ifreq)
#define SIOCSL2TPCOOKIE         _IOW('i', 153, struct ifreq)
#define SIOCDL2TPCOOKIE         _IOW('i', 154, struct ifreq)
#define SIOCSL2TPSTATE          _IOW('i', 155, struct ifreq)
#define SIOCGL2TP               SIOCGIFGENERIC

struct l2tp_req {
       int state;
       u_int my_cookie_len;
       u_int peer_cookie_len;
       uint32_t my_sess_id;
       uint32_t peer_sess_id;
       uint64_t my_cookie;
       uint64_t peer_cookie;
};

#define L2TP_STATE_UP   1
#define L2TP_STATE_DOWN 0

#define L2TP_COOKIE_ON  1
#define L2TP_COOKIE_OFF 0

#ifdef _KERNEL
extern struct psref_class *lv_psref_class;

struct l2tp_variant {
       struct l2tp_softc *lv_softc;

       struct sockaddr *lv_psrc; /* Physical src addr */
       struct sockaddr *lv_pdst; /* Physical dst addr */
       const struct encaptab *lv_encap_cookie;

       /* L2TP session info */
       int lv_state;
       uint32_t lv_my_sess_id;         /* my session ID */
       uint32_t lv_peer_sess_id;       /* peer session ID */

       int lv_use_cookie;
       u_int lv_my_cookie_len;
       u_int lv_peer_cookie_len;
       uint64_t lv_my_cookie;          /* my cookie */
       uint64_t lv_peer_cookie;        /* peer cookie */

       struct psref_target lv_psref;
};

struct l2tp_softc {
       struct ethercom l2tp_ec;        /* common area - must be at the top */
                                       /* to use ether_input(), we must have this */
       percpu_t *l2tp_ro_percpu;       /* struct tunnel_ro */
       struct l2tp_variant *l2tp_var;  /*
                                       * reader must use l2tp_getref_variant()
                                       * instead of direct dereference.
                                       */
       kmutex_t l2tp_lock;             /* writer lock for l2tp_var */
       pserialize_t l2tp_psz;

       void *l2tp_si;
       percpu_t *l2tp_ifq_percpu;

       LIST_ENTRY(l2tp_softc) l2tp_list; /* list of all l2tps */
       struct pslist_entry l2tp_hash;  /* hashed list to lookup by session id */
};

#define L2TP_ROUTE_TTL  10

#define L2TP_MTU        (1280)  /* Default MTU */
#define L2TP_MTU_MIN    (1280)  /* Minimum MTU */
#define L2TP_MTU_MAX    (8192)  /* Maximum MTU */

/*
* Get l2tp_variant from l2tp_softc.
*
* l2tp_variant itself is protected not to be freed by lv_psref.
* In contrast, sc->sc_var can be changed to NULL even if reader critical
* section. see l2tp_variant_update().
* So, once a reader dereference sc->sc_var by this API, the reader must not
* re-dereference form sc->sc_var.
*/
static __inline struct l2tp_variant *
l2tp_getref_variant(struct l2tp_softc *sc, struct psref *psref)
{
       struct l2tp_variant *var;
       int s;

       s = pserialize_read_enter();
       var = atomic_load_consume(&sc->l2tp_var);
       if (var == NULL) {
               pserialize_read_exit(s);
               return NULL;
       }
       psref_acquire(psref, &var->lv_psref, lv_psref_class);
       pserialize_read_exit(s);

       return var;
}

static __inline void
l2tp_putref_variant(struct l2tp_variant *var, struct psref *psref)
{

       if (var == NULL)
               return;
       psref_release(psref, &var->lv_psref, lv_psref_class);
}

static __inline bool
l2tp_heldref_variant(struct l2tp_variant *var)
{

       return psref_held(&var->lv_psref, lv_psref_class);
}


/* Prototypes */
void l2tpattach(int);
int l2tpattach0(struct l2tp_softc *);
void l2tp_input(struct mbuf *, struct ifnet *);
int l2tp_ioctl(struct ifnet *, u_long, void *);

struct l2tp_variant *l2tp_lookup_session_ref(uint32_t, struct psref *);
int l2tp_check_nesting(struct ifnet *, struct mbuf *);

/* TODO IP_TCPMSS support */
#ifdef IP_TCPMSS
struct mbuf *l2tp_tcpmss_clamp(struct ifnet *, struct mbuf *);
#endif /* IP_TCPMSS */
#endif /* _KERNEL */

/*
* Locking notes:
* + l2tp_softc_list is protected by l2tp_list_lock (an adaptive mutex)
*       l2tp_softc_list is list of all l2tp_softcs, and it is used to avoid
*       unload while busy.
* + l2tp_hashed_list is protected by
*   - l2tp_hash_lock (an adaptive mutex) for writer
*   - pserialize for reader
*       l2tp_hashed_list is hashed list of all l2tp_softcs, and it is used by
*       input processing to find appropriate softc.
* + l2tp_softc->l2tp_var is protected by
*   - l2tp_softc->l2tp_lock (an adaptive mutex) for writer
*   - l2tp_var->lv_psref for reader
*       l2tp_softc->l2tp_var is used for variant values while the l2tp tunnel
*       exists.
* + struct l2tp_ro->lr_ro is protected by struct tunnel_ro->tr_lock.
*       This lock is required to exclude softnet/0 lwp(such as output
*       processing softint) and  processing lwp(such as DAD timer processing).
*
* Locking order:
*     - encap_lock => struct l2tp_softc->l2tp_lock
* Other mutexes must not hold simultaneously.
*
*   NOTICE
*   - l2tp_softc must not have a variant value while the l2tp tunnel exists.
*     Such variant values must be in l2tp_softc->l2tp_var.
*   - l2tp_softc->l2tp_var is modified like read-copy-update.
*     So, once we dereference l2tp_softc->l2tp_var, we must
*     keep the pointer during the same context. If we re-derefence
*     l2tp_softc->l2tp_var, the l2tp_var may be other one because of
*     concurrent writer processing.
*/
#endif /* _NET_IF_L2TP_H_ */

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