/*-
 * 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: in_gif.c,v 1.54 2001/05/14 14:02:16 itojun Exp $
 */

#include "opt_inet.h"
#include "opt_inet6.h"

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/jail.h>
#include <sys/socket.h>
#include <sys/sockio.h>
#include <sys/mbuf.h>
#include <sys/errno.h>
#include <sys/kernel.h>
#include <sys/sysctl.h>
#include <sys/malloc.h>
#include <sys/proc.h>

#include <net/ethernet.h>
#include <net/if.h>
#include <net/if_var.h>
#include <net/if_private.h>
#include <net/route.h>
#include <net/vnet.h>

#include <netinet/in.h>
#include <netinet/in_systm.h>
#include <netinet/ip.h>
#include <netinet/ip_var.h>
#include <netinet/in_var.h>
#include <netinet/ip_encap.h>
#include <netinet/ip_ecn.h>
#include <netinet/in_fib.h>

#ifdef INET6
#include <netinet/ip6.h>
#endif

#include <net/if_gif.h>

#define GIF_TTL         30
VNET_DEFINE_STATIC(int, ip_gif_ttl) = GIF_TTL;
#define V_ip_gif_ttl            VNET(ip_gif_ttl)
SYSCTL_INT(_net_inet_ip, IPCTL_GIF_TTL, gifttl, CTLFLAG_VNET | CTLFLAG_RW,
    &VNET_NAME(ip_gif_ttl), 0, "Default TTL value for encapsulated packets");

/*
 * We keep interfaces in a hash table using src+dst as key.
 * Interfaces with GIF_IGNORE_SOURCE flag are linked into plain list.
 */
VNET_DEFINE_STATIC(struct gif_list *, ipv4_hashtbl) = NULL;
VNET_DEFINE_STATIC(struct gif_list *, ipv4_srchashtbl) = NULL;
VNET_DEFINE_STATIC(struct gif_list, ipv4_list) = CK_LIST_HEAD_INITIALIZER();
#define V_ipv4_hashtbl          VNET(ipv4_hashtbl)
#define V_ipv4_srchashtbl       VNET(ipv4_srchashtbl)
#define V_ipv4_list             VNET(ipv4_list)

#define GIF_HASH(src, dst)      (V_ipv4_hashtbl[\
    in_gif_hashval((src), (dst)) & (GIF_HASH_SIZE - 1)])
#define GIF_SRCHASH(src)        (V_ipv4_srchashtbl[\
    fnv_32_buf(&(src), sizeof(src), FNV1_32_INIT) & (GIF_HASH_SIZE - 1)])
#define GIF_HASH_SC(sc)         GIF_HASH((sc)->gif_iphdr->ip_src.s_addr,\
    (sc)->gif_iphdr->ip_dst.s_addr)
static uint32_t
in_gif_hashval(in_addr_t src, in_addr_t dst)
{
        uint32_t ret;

        ret = fnv_32_buf(&src, sizeof(src), FNV1_32_INIT);
        return (fnv_32_buf(&dst, sizeof(dst), ret));
}

static int
in_gif_checkdup(const struct gif_softc *sc, in_addr_t src, in_addr_t dst)
{
        struct gif_softc *tmp;

        if (sc->gif_family == AF_INET &&
            sc->gif_iphdr->ip_src.s_addr == src &&
            sc->gif_iphdr->ip_dst.s_addr == dst)
                return (EEXIST);

        CK_LIST_FOREACH(tmp, &GIF_HASH(src, dst), chain) {
                if (tmp == sc)
                        continue;
                if (tmp->gif_iphdr->ip_src.s_addr == src &&
                    tmp->gif_iphdr->ip_dst.s_addr == dst)
                        return (EADDRNOTAVAIL);
        }
        return (0);
}

/*
 * Check that ingress address belongs to local host.
 */
static void
in_gif_set_running(struct gif_softc *sc)
{

        if (in_localip(sc->gif_iphdr->ip_src))
                GIF2IFP(sc)->if_drv_flags |= IFF_DRV_RUNNING;
        else
                GIF2IFP(sc)->if_drv_flags &= ~IFF_DRV_RUNNING;
}

/*
 * ifaddr_event handler.
 * Clear IFF_DRV_RUNNING flag when ingress address disappears to prevent
 * source address spoofing.
 */
static void
in_gif_srcaddr(void *arg __unused, const struct sockaddr *sa,
    int event __unused)
{
        const struct sockaddr_in *sin;
        struct gif_softc *sc;

        /* Check that VNET is ready */
        if (V_ipv4_hashtbl == NULL)
                return;

        NET_EPOCH_ASSERT();
        sin = (const struct sockaddr_in *)sa;
        CK_LIST_FOREACH(sc, &GIF_SRCHASH(sin->sin_addr.s_addr), srchash) {
                if (sc->gif_iphdr->ip_src.s_addr != sin->sin_addr.s_addr)
                        continue;
                in_gif_set_running(sc);
        }
}

static void
in_gif_attach(struct gif_softc *sc)
{

        if (sc->gif_options & GIF_IGNORE_SOURCE)
                CK_LIST_INSERT_HEAD(&V_ipv4_list, sc, chain);
        else
                CK_LIST_INSERT_HEAD(&GIF_HASH_SC(sc), sc, chain);

        CK_LIST_INSERT_HEAD(&GIF_SRCHASH(sc->gif_iphdr->ip_src.s_addr),
            sc, srchash);
}

int
in_gif_setopts(struct gif_softc *sc, u_int options)
{

        /* NOTE: we are protected with gif_ioctl_sx lock */
        MPASS(sc->gif_family == AF_INET);
        MPASS(sc->gif_options != options);

        if ((options & GIF_IGNORE_SOURCE) !=
            (sc->gif_options & GIF_IGNORE_SOURCE)) {
                CK_LIST_REMOVE(sc, srchash);
                CK_LIST_REMOVE(sc, chain);
                sc->gif_options = options;
                in_gif_attach(sc);
        }
        return (0);
}

int
in_gif_ioctl(struct gif_softc *sc, u_long cmd, caddr_t data)
{
        struct ifreq *ifr = (struct ifreq *)data;
        struct epoch_tracker et;
        struct sockaddr_in *dst, *src;
        struct ip *ip;
        int error;

        /* NOTE: we are protected with gif_ioctl_sx lock */
        error = EINVAL;
        switch (cmd) {
        case SIOCSIFPHYADDR:
                src = &((struct in_aliasreq *)data)->ifra_addr;
                dst = &((struct in_aliasreq *)data)->ifra_dstaddr;

                /* sanity checks */
                if (src->sin_family != dst->sin_family ||
                    src->sin_family != AF_INET ||
                    src->sin_len != dst->sin_len ||
                    src->sin_len != sizeof(*src))
                        break;
                if (src->sin_addr.s_addr == INADDR_ANY ||
                    dst->sin_addr.s_addr == INADDR_ANY) {
                        error = EADDRNOTAVAIL;
                        break;
                }
                if (V_ipv4_hashtbl == NULL) {
                        V_ipv4_hashtbl = gif_hashinit();
                        V_ipv4_srchashtbl = gif_hashinit();
                }
                error = in_gif_checkdup(sc, src->sin_addr.s_addr,
                    dst->sin_addr.s_addr);
                if (error == EADDRNOTAVAIL)
                        break;
                if (error == EEXIST) {
                        /* Addresses are the same. Just return. */
                        error = 0;
                        break;
                }
                ip = malloc(sizeof(*ip), M_GIF, M_WAITOK | M_ZERO);
                ip->ip_src.s_addr = src->sin_addr.s_addr;
                ip->ip_dst.s_addr = dst->sin_addr.s_addr;
                if (sc->gif_family != 0) {
                        /* Detach existing tunnel first */
                        CK_LIST_REMOVE(sc, srchash);
                        CK_LIST_REMOVE(sc, chain);
                        GIF_WAIT();
                        free(sc->gif_hdr, M_GIF);
                        /* XXX: should we notify about link state change? */
                }
                sc->gif_family = AF_INET;
                sc->gif_iphdr = ip;
                in_gif_attach(sc);
                NET_EPOCH_ENTER(et);
                in_gif_set_running(sc);
                NET_EPOCH_EXIT(et);
                break;
        case SIOCGIFPSRCADDR:
        case SIOCGIFPDSTADDR:
                if (sc->gif_family != AF_INET) {
                        error = EADDRNOTAVAIL;
                        break;
                }
                src = (struct sockaddr_in *)&ifr->ifr_addr;
                memset(src, 0, sizeof(*src));
                src->sin_family = AF_INET;
                src->sin_len = sizeof(*src);
                src->sin_addr = (cmd == SIOCGIFPSRCADDR) ?
                    sc->gif_iphdr->ip_src: sc->gif_iphdr->ip_dst;
                error = prison_if(curthread->td_ucred, (struct sockaddr *)src);
                if (error != 0)
                        memset(src, 0, sizeof(*src));
                break;
        }
        return (error);
}

int
in_gif_output(struct ifnet *ifp, struct mbuf *m, int proto, uint8_t ecn)
{
        struct gif_softc *sc = ifp->if_softc;
        struct ip *ip;

        /* prepend new IP header */
        NET_EPOCH_ASSERT();
        M_PREPEND(m, sizeof(struct ip), M_NOWAIT);
        if (m == NULL)
                return (ENOBUFS);
        ip = mtod(m, struct ip *);

        MPASS(sc->gif_family == AF_INET);
        memcpy(ip, sc->gif_iphdr, sizeof(struct ip));
        ip->ip_p = proto;
        /* version will be set in ip_output() */
        ip->ip_ttl = V_ip_gif_ttl;
        ip->ip_len = htons(m->m_pkthdr.len);
        ip->ip_tos = ecn;

        return (ip_output(m, NULL, NULL, 0, NULL, NULL));
}

static int
in_gif_input(struct mbuf *m, int off, int proto, void *arg)
{
        struct gif_softc *sc = arg;
        struct ifnet *gifp;
        struct ip *ip;
        uint8_t ecn;

        NET_EPOCH_ASSERT();
        if (sc == NULL) {
                m_freem(m);
                KMOD_IPSTAT_INC(ips_nogif);
                return (IPPROTO_DONE);
        }
        gifp = GIF2IFP(sc);
        if ((gifp->if_flags & IFF_UP) != 0) {
                ip = mtod(m, struct ip *);
                ecn = ip->ip_tos;
                m_adj(m, off);
                gif_input(m, gifp, proto, ecn);
        } else {
                m_freem(m);
                KMOD_IPSTAT_INC(ips_nogif);
        }
        return (IPPROTO_DONE);
}

static int
in_gif_lookup(const struct mbuf *m, int off, int proto, void **arg)
{
        const struct ip *ip;
        struct gif_softc *sc;
        int ret;

        if (V_ipv4_hashtbl == NULL)
                return (0);

        NET_EPOCH_ASSERT();
        ip = mtod(m, const struct ip *);
        /*
         * NOTE: it is safe to iterate without any locking here, because softc
         * can be reclaimed only when we are not within net_epoch_preempt
         * section, but ip_encap lookup+input are executed in epoch section.
         */
        ret = 0;
        CK_LIST_FOREACH(sc, &GIF_HASH(ip->ip_dst.s_addr,
            ip->ip_src.s_addr), chain) {
                /*
                 * This is an inbound packet, its ip_dst is source address
                 * in softc.
                 */
                if (sc->gif_iphdr->ip_src.s_addr == ip->ip_dst.s_addr &&
                    sc->gif_iphdr->ip_dst.s_addr == ip->ip_src.s_addr) {
                        ret = ENCAP_DRV_LOOKUP;
                        goto done;
                }
        }
        /*
         * No exact match.
         * Check the list of interfaces with GIF_IGNORE_SOURCE flag.
         */
        CK_LIST_FOREACH(sc, &V_ipv4_list, chain) {
                if (sc->gif_iphdr->ip_src.s_addr == ip->ip_dst.s_addr) {
                        ret = 32 + 8; /* src + proto */
                        goto done;
                }
        }
        return (0);
done:
        if ((GIF2IFP(sc)->if_flags & IFF_UP) == 0)
                return (0);
        /* ingress filters on outer source */
        if ((GIF2IFP(sc)->if_flags & IFF_LINK2) == 0) {
                if (fib4_check_urpf(sc->gif_fibnum, ip->ip_src, 0, NHR_NONE,
                                        m->m_pkthdr.rcvif) == 0)
                        return (0);
        }
        *arg = sc;
        return (ret);
}

static const struct srcaddrtab *ipv4_srcaddrtab;
static struct {
        const struct encap_config encap;
        const struct encaptab *cookie;
} ipv4_encap_cfg[] = {
        {
                .encap = {
                        .proto = IPPROTO_IPV4,
                        .min_length = 2 * sizeof(struct ip),
                        .exact_match = ENCAP_DRV_LOOKUP,
                        .lookup = in_gif_lookup,
                        .input = in_gif_input
                },
        },
#ifdef INET6
        {
                .encap = {
                        .proto = IPPROTO_IPV6,
                        .min_length = sizeof(struct ip) +
                            sizeof(struct ip6_hdr),
                        .exact_match = ENCAP_DRV_LOOKUP,
                        .lookup = in_gif_lookup,
                        .input = in_gif_input
                },
        },
#endif
        {
                .encap = {
                        .proto = IPPROTO_ETHERIP,
                        .min_length = sizeof(struct ip) +
                            sizeof(struct etherip_header) +
                            sizeof(struct ether_header),
                        .exact_match = ENCAP_DRV_LOOKUP,
                        .lookup = in_gif_lookup,
                        .input = in_gif_input
                },
        }
};

void
in_gif_init(void)
{
        int i;

        if (!IS_DEFAULT_VNET(curvnet))
                return;

        ipv4_srcaddrtab = ip_encap_register_srcaddr(in_gif_srcaddr,
            NULL, M_WAITOK);
        for (i = 0; i < nitems(ipv4_encap_cfg); i++)
                ipv4_encap_cfg[i].cookie = ip_encap_attach(
                    &ipv4_encap_cfg[i].encap, NULL, M_WAITOK);
}

void
in_gif_uninit(void)
{
        int i;

        if (IS_DEFAULT_VNET(curvnet)) {
                for (i = 0; i < nitems(ipv4_encap_cfg); i++)
                        ip_encap_detach(ipv4_encap_cfg[i].cookie);
                ip_encap_unregister_srcaddr(ipv4_srcaddrtab);
        }
        if (V_ipv4_hashtbl != NULL) {
                gif_hashdestroy(V_ipv4_hashtbl);
                V_ipv4_hashtbl = NULL;
                GIF_WAIT();
                gif_hashdestroy(V_ipv4_srchashtbl);
        }
}