/*-
 * SPDX-License-Identifier: BSD-3-Clause
 *
 * Copyright (C) 1995, 1996, 1997, and 1998 WIDE Project.
 * Copyright (c) 2018 Andrey V. Elsukov <ae@FreeBSD.org>
 * 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.
 * 3. Neither the name of the project nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE PROJECT 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 PROJECT 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.
 *
 *      $KAME: if_gif.c,v 1.87 2001/10/19 08:50:27 itojun Exp $
 */

#include <sys/cdefs.h>
#include "opt_inet.h"
#include "opt_inet6.h"

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/kernel.h>
#include <sys/lock.h>
#include <sys/malloc.h>
#include <sys/mbuf.h>
#include <sys/module.h>
#include <sys/rmlock.h>
#include <sys/socket.h>
#include <sys/sockio.h>
#include <sys/sx.h>
#include <sys/errno.h>
#include <sys/time.h>
#include <sys/sysctl.h>
#include <sys/syslog.h>
#include <sys/priv.h>
#include <sys/proc.h>
#include <sys/conf.h>
#include <machine/cpu.h>

#include <net/if.h>
#include <net/if_var.h>
#include <net/if_private.h>
#include <net/if_clone.h>
#include <net/if_types.h>
#include <net/netisr.h>
#include <net/route.h>
#include <net/bpf.h>
#include <net/vnet.h>

#include <netinet/in.h>
#include <netinet/in_systm.h>
#include <netinet/ip.h>
#include <netinet/ip_ecn.h>
#ifdef  INET
#include <netinet/in_var.h>
#include <netinet/ip_var.h>
#endif  /* INET */

#ifdef INET6
#ifndef INET
#include <netinet/in.h>
#endif
#include <netinet6/in6_var.h>
#include <netinet/ip6.h>
#include <netinet6/ip6_ecn.h>
#include <netinet6/ip6_var.h>
#endif /* INET6 */

#include <netinet/ip_encap.h>
#include <net/ethernet.h>
#include <net/if_bridgevar.h>
#include <net/if_gif.h>

#include <security/mac/mac_framework.h>

static const char gifname[] = "gif";

MALLOC_DEFINE(M_GIF, "gif", "Generic Tunnel Interface");
static struct sx gif_ioctl_sx;
SX_SYSINIT(gif_ioctl_sx, &gif_ioctl_sx, "gif_ioctl");

void    (*ng_gif_input_p)(struct ifnet *ifp, struct mbuf **mp, int af);
void    (*ng_gif_input_orphan_p)(struct ifnet *ifp, struct mbuf *m, int af);
void    (*ng_gif_attach_p)(struct ifnet *ifp);
void    (*ng_gif_detach_p)(struct ifnet *ifp);

#ifdef VIMAGE
static void     gif_reassign(struct ifnet *, struct vnet *, char *);
#endif
static void     gif_delete_tunnel(struct gif_softc *);
static int      gif_ioctl(struct ifnet *, u_long, caddr_t);
static int      gif_transmit(struct ifnet *, struct mbuf *);
static void     gif_qflush(struct ifnet *);
static int      gif_clone_create(struct if_clone *, int, caddr_t);
static void     gif_clone_destroy(struct ifnet *);
VNET_DEFINE_STATIC(struct if_clone *, gif_cloner);
#define V_gif_cloner    VNET(gif_cloner)

SYSCTL_DECL(_net_link);
static SYSCTL_NODE(_net_link, IFT_GIF, gif, CTLFLAG_RW | CTLFLAG_MPSAFE, 0,
    "Generic Tunnel Interface");
#ifndef MAX_GIF_NEST
/*
 * This macro controls the default upper limitation on nesting of gif tunnels.
 * Since, setting a large value to this macro with a careless configuration
 * may introduce system crash, we don't allow any nestings by default.
 * If you need to configure nested gif tunnels, you can define this macro
 * in your kernel configuration file.  However, if you do so, please be
 * careful to configure the tunnels so that it won't make a loop.
 */
#define MAX_GIF_NEST 1
#endif
VNET_DEFINE_STATIC(int, max_gif_nesting) = MAX_GIF_NEST;
#define V_max_gif_nesting       VNET(max_gif_nesting)
SYSCTL_INT(_net_link_gif, OID_AUTO, max_nesting, CTLFLAG_VNET | CTLFLAG_RW,
    &VNET_NAME(max_gif_nesting), 0, "Max nested tunnels");

static int
gif_clone_create(struct if_clone *ifc, int unit, caddr_t params)
{
        struct gif_softc *sc;

        sc = malloc(sizeof(struct gif_softc), M_GIF, M_WAITOK | M_ZERO);
        sc->gif_fibnum = curthread->td_proc->p_fibnum;
        GIF2IFP(sc) = if_alloc(IFT_GIF);
        GIF2IFP(sc)->if_softc = sc;
        if_initname(GIF2IFP(sc), gifname, unit);

        GIF2IFP(sc)->if_addrlen = 0;
        GIF2IFP(sc)->if_mtu    = GIF_MTU;
        GIF2IFP(sc)->if_flags  = IFF_POINTOPOINT | IFF_MULTICAST;
        GIF2IFP(sc)->if_ioctl  = gif_ioctl;
        GIF2IFP(sc)->if_transmit = gif_transmit;
        GIF2IFP(sc)->if_qflush = gif_qflush;
        GIF2IFP(sc)->if_output = gif_output;
#ifdef VIMAGE
        GIF2IFP(sc)->if_reassign = gif_reassign;
#endif
        GIF2IFP(sc)->if_capabilities |= IFCAP_LINKSTATE;
        GIF2IFP(sc)->if_capenable |= IFCAP_LINKSTATE;
        if_attach(GIF2IFP(sc));
        bpfattach(GIF2IFP(sc), DLT_NULL, sizeof(u_int32_t));
        if (ng_gif_attach_p != NULL)
                (*ng_gif_attach_p)(GIF2IFP(sc));

        return (0);
}

#ifdef VIMAGE
static void
gif_reassign(struct ifnet *ifp, struct vnet *new_vnet __unused,
    char *unused __unused)
{
        struct gif_softc *sc;

        sx_xlock(&gif_ioctl_sx);
        sc = ifp->if_softc;
        if (sc != NULL)
                gif_delete_tunnel(sc);
        sx_xunlock(&gif_ioctl_sx);
}
#endif /* VIMAGE */

static void
gif_clone_destroy(struct ifnet *ifp)
{
        struct gif_softc *sc;

        sx_xlock(&gif_ioctl_sx);
        sc = ifp->if_softc;
        gif_delete_tunnel(sc);
        if (ng_gif_detach_p != NULL)
                (*ng_gif_detach_p)(ifp);
        bpfdetach(ifp);
        if_detach(ifp);
        ifp->if_softc = NULL;
        sx_xunlock(&gif_ioctl_sx);

        GIF_WAIT();
        if_free(ifp);
        free(sc, M_GIF);
}

static void
vnet_gif_init(const void *unused __unused)
{

        V_gif_cloner = if_clone_simple(gifname, gif_clone_create,
            gif_clone_destroy, 0);
#ifdef INET
        in_gif_init();
#endif
#ifdef INET6
        in6_gif_init();
#endif
}
VNET_SYSINIT(vnet_gif_init, SI_SUB_PSEUDO, SI_ORDER_ANY,
    vnet_gif_init, NULL);

static void
vnet_gif_uninit(const void *unused __unused)
{

        if_clone_detach(V_gif_cloner);
#ifdef INET
        in_gif_uninit();
#endif
#ifdef INET6
        in6_gif_uninit();
#endif
}
VNET_SYSUNINIT(vnet_gif_uninit, SI_SUB_PSEUDO, SI_ORDER_ANY,
    vnet_gif_uninit, NULL);

static int
gifmodevent(module_t mod, int type, void *data)
{

        switch (type) {
        case MOD_LOAD:
        case MOD_UNLOAD:
                break;
        default:
                return (EOPNOTSUPP);
        }
        return (0);
}

static moduledata_t gif_mod = {
        "if_gif",
        gifmodevent,
        0
};

DECLARE_MODULE(if_gif, gif_mod, SI_SUB_PSEUDO, SI_ORDER_ANY);
MODULE_VERSION(if_gif, 1);

struct gif_list *
gif_hashinit(void)
{
        struct gif_list *hash;
        int i;

        hash = malloc(sizeof(struct gif_list) * GIF_HASH_SIZE,
            M_GIF, M_WAITOK);
        for (i = 0; i < GIF_HASH_SIZE; i++)
                CK_LIST_INIT(&hash[i]);

        return (hash);
}

void
gif_hashdestroy(struct gif_list *hash)
{

        free(hash, M_GIF);
}

#define MTAG_GIF        1080679712
static int
gif_transmit(struct ifnet *ifp, struct mbuf *m)
{
        struct gif_softc *sc;
        struct etherip_header *eth;
#ifdef INET
        struct ip *ip;
#endif
#ifdef INET6
        struct ip6_hdr *ip6;
        uint32_t t;
#endif
        uint32_t af;
        uint8_t proto, ecn;
        int error;

        NET_EPOCH_ASSERT();
#ifdef MAC
        error = mac_ifnet_check_transmit(ifp, m);
        if (error) {
                m_freem(m);
                goto err;
        }
#endif
        error = ENETDOWN;
        sc = ifp->if_softc;
        if ((ifp->if_flags & IFF_MONITOR) != 0 ||
            (ifp->if_flags & IFF_UP) == 0 ||
            (ifp->if_drv_flags & IFF_DRV_RUNNING) == 0 ||
            sc->gif_family == 0 ||
            (error = if_tunnel_check_nesting(ifp, m, MTAG_GIF,
                V_max_gif_nesting)) != 0) {
                m_freem(m);
                goto err;
        }
        /* Now pull back the af that we stashed in the csum_data. */
        af = m->m_pkthdr.csum_data;
        m->m_flags &= ~(M_BCAST|M_MCAST);
        M_SETFIB(m, sc->gif_fibnum);
        BPF_MTAP2(ifp, &af, sizeof(af), m);
        if_inc_counter(ifp, IFCOUNTER_OPACKETS, 1);
        if_inc_counter(ifp, IFCOUNTER_OBYTES, m->m_pkthdr.len);
        /* inner AF-specific encapsulation */
        ecn = 0;
        switch (af) {
#ifdef INET
        case AF_INET:
                proto = IPPROTO_IPV4;
                if (m->m_len < sizeof(struct ip))
                        m = m_pullup(m, sizeof(struct ip));
                if (m == NULL) {
                        error = ENOBUFS;
                        goto err;
                }
                ip = mtod(m, struct ip *);
                ip_ecn_ingress((ifp->if_flags & IFF_LINK1) ? ECN_ALLOWED:
                    ECN_NOCARE, &ecn, &ip->ip_tos);
                break;
#endif
#ifdef INET6
        case AF_INET6:
                proto = IPPROTO_IPV6;
                if (m->m_len < sizeof(struct ip6_hdr))
                        m = m_pullup(m, sizeof(struct ip6_hdr));
                if (m == NULL) {
                        error = ENOBUFS;
                        goto err;
                }
                t = 0;
                ip6 = mtod(m, struct ip6_hdr *);
                ip6_ecn_ingress((ifp->if_flags & IFF_LINK1) ? ECN_ALLOWED:
                    ECN_NOCARE, &t, &ip6->ip6_flow);
                ecn = (ntohl(t) >> 20) & 0xff;
                break;
#endif
        case AF_LINK:
                KASSERT(ifp->if_bridge != NULL,
                    ("%s: bridge not attached", __func__));
                proto = IPPROTO_ETHERIP;
                M_PREPEND(m, sizeof(struct etherip_header), M_NOWAIT);
                if (m == NULL) {
                        error = ENOBUFS;
                        goto err;
                }
                eth = mtod(m, struct etherip_header *);
                eth->eip_resvh = 0;
                eth->eip_ver = ETHERIP_VERSION;
                eth->eip_resvl = 0;
                break;
        default:
                error = EAFNOSUPPORT;
                m_freem(m);
                goto err;
        }
        /* XXX should we check if our outer source is legal? */
        /* dispatch to output logic based on outer AF */
        switch (sc->gif_family) {
#ifdef INET
        case AF_INET:
                error = in_gif_output(ifp, m, proto, ecn);
                break;
#endif
#ifdef INET6
        case AF_INET6:
                error = in6_gif_output(ifp, m, proto, ecn);
                break;
#endif
        default:
                m_freem(m);
        }
err:
        if (error)
                if_inc_counter(ifp, IFCOUNTER_OERRORS, 1);
        return (error);
}

static void
gif_qflush(struct ifnet *ifp __unused)
{

}

int
gif_output(struct ifnet *ifp, struct mbuf *m, const struct sockaddr *dst,
        struct route *ro)
{
        uint32_t af;

        /* BPF writes need to be handled specially. */
        if (dst->sa_family == AF_UNSPEC || dst->sa_family == pseudo_AF_HDRCMPLT)
                memcpy(&af, dst->sa_data, sizeof(af));
        else
                af = RO_GET_FAMILY(ro, dst);
        /*
         * Now save the af in the inbound pkt csum data, this is a cheat since
         * we are using the inbound csum_data field to carry the af over to
         * the gif_transmit() routine, avoiding using yet another mtag.
         */
        m->m_pkthdr.csum_data = af;
        return (ifp->if_transmit(ifp, m));
}

void
gif_input(struct mbuf *m, struct ifnet *ifp, int proto, uint8_t ecn)
{
        struct etherip_header *eip;
#ifdef INET
        struct ip *ip;
#endif
#ifdef INET6
        struct ip6_hdr *ip6;
        uint32_t t;
#endif
        struct ether_header *eh;
        struct ifnet *oldifp;
        int isr, n, af;

        NET_EPOCH_ASSERT();

        if (ifp == NULL) {
                /* just in case */
                m_freem(m);
                return;
        }
        m->m_pkthdr.rcvif = ifp;
        m_clrprotoflags(m);
        switch (proto) {
#ifdef INET
        case IPPROTO_IPV4:
                af = AF_INET;
                if (m->m_len < sizeof(struct ip))
                        m = m_pullup(m, sizeof(struct ip));
                if (m == NULL)
                        goto drop;
                ip = mtod(m, struct ip *);
                if (ip_ecn_egress((ifp->if_flags & IFF_LINK1) ? ECN_ALLOWED:
                    ECN_NOCARE, &ecn, &ip->ip_tos) == 0) {
                        m_freem(m);
                        goto drop;
                }
                break;
#endif
#ifdef INET6
        case IPPROTO_IPV6:
                af = AF_INET6;
                if (m->m_len < sizeof(struct ip6_hdr))
                        m = m_pullup(m, sizeof(struct ip6_hdr));
                if (m == NULL)
                        goto drop;
                t = htonl((uint32_t)ecn << 20);
                ip6 = mtod(m, struct ip6_hdr *);
                if (ip6_ecn_egress((ifp->if_flags & IFF_LINK1) ? ECN_ALLOWED:
                    ECN_NOCARE, &t, &ip6->ip6_flow) == 0) {
                        m_freem(m);
                        goto drop;
                }
                break;
#endif
        case IPPROTO_ETHERIP:
                af = AF_LINK;
                break;
        default:
                m_freem(m);
                goto drop;
        }

#ifdef MAC
        mac_ifnet_create_mbuf(ifp, m);
#endif

        if (bpf_peers_present(ifp->if_bpf)) {
                uint32_t af1 = af;
                bpf_mtap2(ifp->if_bpf, &af1, sizeof(af1), m);
        }

        if ((ifp->if_flags & IFF_MONITOR) != 0) {
                if_inc_counter(ifp, IFCOUNTER_IPACKETS, 1);
                if_inc_counter(ifp, IFCOUNTER_IBYTES, m->m_pkthdr.len);
                m_freem(m);
                return;
        }

        if (ng_gif_input_p != NULL) {
                (*ng_gif_input_p)(ifp, &m, af);
                if (m == NULL)
                        goto drop;
        }

        /*
         * Put the packet to the network layer input queue according to the
         * specified address family.
         * Note: older versions of gif_input directly called network layer
         * input functions, e.g. ip6_input, here.  We changed the policy to
         * prevent too many recursive calls of such input functions, which
         * might cause kernel panic.  But the change may introduce another
         * problem; if the input queue is full, packets are discarded.
         * The kernel stack overflow really happened, and we believed
         * queue-full rarely occurs, so we changed the policy.
         */
        switch (af) {
#ifdef INET
        case AF_INET:
                isr = NETISR_IP;
                break;
#endif
#ifdef INET6
        case AF_INET6:
                isr = NETISR_IPV6;
                break;
#endif
        case AF_LINK:
                n = sizeof(struct etherip_header) +
                    sizeof(struct ether_header);
                if (n > m->m_len)
                        m = m_pullup(m, n);
                if (m == NULL)
                        goto drop;
                eip = mtod(m, struct etherip_header *);
                if (eip->eip_ver != ETHERIP_VERSION) {
                        /* discard unknown versions */
                        m_freem(m);
                        goto drop;
                }

                m_adj_decap(m, sizeof(struct etherip_header));

                m->m_flags &= ~(M_BCAST|M_MCAST);
                m->m_pkthdr.rcvif = ifp;

                if (ifp->if_bridge) {
                        oldifp = ifp;
                        eh = mtod(m, struct ether_header *);
                        if (ETHER_IS_MULTICAST(eh->ether_dhost)) {
                                if (ETHER_IS_BROADCAST(eh->ether_dhost))
                                        m->m_flags |= M_BCAST;
                                else
                                        m->m_flags |= M_MCAST;
                                if_inc_counter(ifp, IFCOUNTER_IMCASTS, 1);
                        }
                        BRIDGE_INPUT(ifp, m);

                        if (m != NULL && ifp != oldifp) {
                                /*
                                 * The bridge gave us back itself or one of the
                                 * members for which the frame is addressed.
                                 */
                                ether_demux(ifp, m);
                                return;
                        }
                }
                if (m != NULL)
                        m_freem(m);
                return;

        default:
                if (ng_gif_input_orphan_p != NULL)
                        (*ng_gif_input_orphan_p)(ifp, m, af);
                else
                        m_freem(m);
                return;
        }

        if_inc_counter(ifp, IFCOUNTER_IPACKETS, 1);
        if_inc_counter(ifp, IFCOUNTER_IBYTES, m->m_pkthdr.len);
        M_SETFIB(m, ifp->if_fib);
        netisr_dispatch(isr, m);
        return;
drop:
        if_inc_counter(ifp, IFCOUNTER_IERRORS, 1);
}

static int
gif_ioctl(struct ifnet *ifp, u_long cmd, caddr_t data)
{
        struct ifreq *ifr = (struct ifreq*)data;
        struct gif_softc *sc;
        u_int options;
        int error;

        switch (cmd) {
        case SIOCSIFADDR:
                ifp->if_flags |= IFF_UP;
        case SIOCADDMULTI:
        case SIOCDELMULTI:
        case SIOCGIFMTU:
        case SIOCSIFFLAGS:
                return (0);
        case SIOCSIFMTU:
                if (ifr->ifr_mtu < GIF_MTU_MIN ||
                    ifr->ifr_mtu > GIF_MTU_MAX)
                        return (EINVAL);
                else
                        ifp->if_mtu = ifr->ifr_mtu;
                return (0);
        }
        sx_xlock(&gif_ioctl_sx);
        sc = ifp->if_softc;
        if (sc == NULL) {
                error = ENXIO;
                goto bad;
        }
        error = 0;
        switch (cmd) {
        case SIOCDIFPHYADDR:
                if (sc->gif_family == 0)
                        break;
                gif_delete_tunnel(sc);
                break;
#ifdef INET
        case SIOCSIFPHYADDR:
        case SIOCGIFPSRCADDR:
        case SIOCGIFPDSTADDR:
                error = in_gif_ioctl(sc, cmd, data);
                break;
#endif
#ifdef INET6
        case SIOCSIFPHYADDR_IN6:
        case SIOCGIFPSRCADDR_IN6:
        case SIOCGIFPDSTADDR_IN6:
                error = in6_gif_ioctl(sc, cmd, data);
                break;
#endif
        case SIOCGTUNFIB:
                ifr->ifr_fib = sc->gif_fibnum;
                break;
        case SIOCSTUNFIB:
                if ((error = priv_check(curthread, PRIV_NET_GIF)) != 0)
                        break;
                if (ifr->ifr_fib >= rt_numfibs)
                        error = EINVAL;
                else
                        sc->gif_fibnum = ifr->ifr_fib;
                break;
        case GIFGOPTS:
                options = sc->gif_options;
                error = copyout(&options, ifr_data_get_ptr(ifr),
                    sizeof(options));
                break;
        case GIFSOPTS:
                if ((error = priv_check(curthread, PRIV_NET_GIF)) != 0)
                        break;
                error = copyin(ifr_data_get_ptr(ifr), &options,
                    sizeof(options));
                if (error)
                        break;
                if (options & ~GIF_OPTMASK) {
                        error = EINVAL;
                        break;
                }
                if (sc->gif_options != options) {
                        switch (sc->gif_family) {
#ifdef INET
                        case AF_INET:
                                error = in_gif_setopts(sc, options);
                                break;
#endif
#ifdef INET6
                        case AF_INET6:
                                error = in6_gif_setopts(sc, options);
                                break;
#endif
                        default:
                                /* No need to invoke AF-handler */
                                sc->gif_options = options;
                        }
                }
                break;
        default:
                error = EINVAL;
                break;
        }
        if (error == 0 && sc->gif_family != 0) {
                if (
#ifdef INET
                    cmd == SIOCSIFPHYADDR ||
#endif
#ifdef INET6
                    cmd == SIOCSIFPHYADDR_IN6 ||
#endif
                    0) {
                        if_link_state_change(ifp, LINK_STATE_UP);
                }
        }
bad:
        sx_xunlock(&gif_ioctl_sx);
        return (error);
}

static void
gif_delete_tunnel(struct gif_softc *sc)
{

        sx_assert(&gif_ioctl_sx, SA_XLOCKED);
        if (sc->gif_family != 0) {
                CK_LIST_REMOVE(sc, srchash);
                CK_LIST_REMOVE(sc, chain);
                /* Wait until it become safe to free gif_hdr */
                GIF_WAIT();
                free(sc->gif_hdr, M_GIF);
        }
        sc->gif_family = 0;
        GIF2IFP(sc)->if_drv_flags &= ~IFF_DRV_RUNNING;
        if_link_state_change(GIF2IFP(sc), LINK_STATE_DOWN);
}