/*-
 * Copyright (c) 2014, 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.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``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 AUTHOR 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.
 */

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

#include <sys/param.h>
#include <sys/jail.h>
#include <sys/systm.h>
#include <sys/socket.h>
#include <sys/socketvar.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/if.h>
#include <net/if_var.h>
#include <net/if_private.h>
#include <net/vnet.h>

#include <netinet/in.h>
#ifdef INET
#include <net/ethernet.h>
#include <netinet/ip.h>
#endif
#include <netinet/in_pcb.h>
#include <netinet/ip_encap.h>
#include <netinet/ip_var.h>
#include <netinet/ip6.h>
#include <netinet/udp.h>
#include <netinet/udp_var.h>
#include <netinet6/ip6_var.h>
#include <netinet6/in6_var.h>
#include <netinet6/scope6_var.h>
#include <net/if_gre.h>

VNET_DEFINE(int, ip6_gre_hlim) = IPV6_DEFHLIM;
#define V_ip6_gre_hlim          VNET(ip6_gre_hlim)

SYSCTL_DECL(_net_inet6_ip6);
SYSCTL_INT(_net_inet6_ip6, OID_AUTO, grehlim, CTLFLAG_VNET | CTLFLAG_RW,
    &VNET_NAME(ip6_gre_hlim), 0, "Default hop limit for encapsulated packets");

struct in6_gre_socket {
        struct gre_socket       base;
        struct in6_addr         addr; /* scope zone id is embedded */
};
VNET_DEFINE_STATIC(struct gre_sockets *, ipv6_sockets) = NULL;
VNET_DEFINE_STATIC(struct gre_list *, ipv6_hashtbl) = NULL;
VNET_DEFINE_STATIC(struct gre_list *, ipv6_srchashtbl) = NULL;
#define V_ipv6_sockets          VNET(ipv6_sockets)
#define V_ipv6_hashtbl          VNET(ipv6_hashtbl)
#define V_ipv6_srchashtbl       VNET(ipv6_srchashtbl)
#define GRE_HASH(src, dst)      (V_ipv6_hashtbl[\
    in6_gre_hashval((src), (dst)) & (GRE_HASH_SIZE - 1)])
#define GRE_SRCHASH(src)        (V_ipv6_srchashtbl[\
    fnv_32_buf((src), sizeof(*src), FNV1_32_INIT) & (GRE_HASH_SIZE - 1)])
#define GRE_SOCKHASH(src)       (V_ipv6_sockets[\
    fnv_32_buf((src), sizeof(*src), FNV1_32_INIT) & (GRE_HASH_SIZE - 1)])
#define GRE_HASH_SC(sc)         GRE_HASH(&(sc)->gre_oip6.ip6_src,\
    &(sc)->gre_oip6.ip6_dst)

static uint32_t
in6_gre_hashval(const struct in6_addr *src, const struct in6_addr *dst)
{
        uint32_t ret;

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

static struct gre_socket*
in6_gre_lookup_socket(const struct in6_addr *addr)
{
        struct gre_socket *gs;
        struct in6_gre_socket *s;

        CK_LIST_FOREACH(gs, &GRE_SOCKHASH(addr), chain) {
                s = __containerof(gs, struct in6_gre_socket, base);
                if (IN6_ARE_ADDR_EQUAL(&s->addr, addr))
                        break;
        }
        return (gs);
}

static int
in6_gre_checkdup(const struct gre_softc *sc, const struct in6_addr *src,
    const struct in6_addr *dst, uint32_t opts)
{
        struct gre_list *head;
        struct gre_softc *tmp;
        struct gre_socket *gs;

        if (sc->gre_family == AF_INET6 &&
            IN6_ARE_ADDR_EQUAL(&sc->gre_oip6.ip6_src, src) &&
            IN6_ARE_ADDR_EQUAL(&sc->gre_oip6.ip6_dst, dst) &&
            (sc->gre_options & GRE_UDPENCAP) == (opts & GRE_UDPENCAP))
                return (EEXIST);

        if (opts & GRE_UDPENCAP) {
                gs = in6_gre_lookup_socket(src);
                if (gs == NULL)
                        return (0);
                head = &gs->list;
        } else
                head = &GRE_HASH(src, dst);

        CK_LIST_FOREACH(tmp, head, chain) {
                if (tmp == sc)
                        continue;
                if (IN6_ARE_ADDR_EQUAL(&tmp->gre_oip6.ip6_src, src) &&
                    IN6_ARE_ADDR_EQUAL(&tmp->gre_oip6.ip6_dst, dst))
                        return (EADDRNOTAVAIL);
        }
        return (0);
}

static int
in6_gre_lookup(const struct mbuf *m, int off, int proto, void **arg)
{
        const struct ip6_hdr *ip6;
        struct gre_softc *sc;

        if (V_ipv6_hashtbl == NULL)
                return (0);

        NET_EPOCH_ASSERT();
        ip6 = mtod(m, const struct ip6_hdr *);
        CK_LIST_FOREACH(sc, &GRE_HASH(&ip6->ip6_dst, &ip6->ip6_src), chain) {
                /*
                 * This is an inbound packet, its ip6_dst is source address
                 * in softc.
                 */
                if (IN6_ARE_ADDR_EQUAL(&sc->gre_oip6.ip6_src,
                    &ip6->ip6_dst) &&
                    IN6_ARE_ADDR_EQUAL(&sc->gre_oip6.ip6_dst,
                    &ip6->ip6_src)) {
                        if ((GRE2IFP(sc)->if_flags & IFF_UP) == 0)
                                return (0);
                        *arg = sc;
                        return (ENCAP_DRV_LOOKUP);
                }
        }
        return (0);
}

/*
 * Check that ingress address belongs to local host.
 */
static void
in6_gre_set_running(struct gre_softc *sc)
{

        if (in6_localip(&sc->gre_oip6.ip6_src))
                GRE2IFP(sc)->if_drv_flags |= IFF_DRV_RUNNING;
        else
                GRE2IFP(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
in6_gre_srcaddr(void *arg __unused, const struct sockaddr *sa,
    int event __unused)
{
        const struct sockaddr_in6 *sin;
        struct gre_softc *sc;

        /* Check that VNET is ready */
        if (V_ipv6_hashtbl == NULL)
                return;

        NET_EPOCH_ASSERT();
        sin = (const struct sockaddr_in6 *)sa;
        CK_LIST_FOREACH(sc, &GRE_SRCHASH(&sin->sin6_addr), srchash) {
                if (IN6_ARE_ADDR_EQUAL(&sc->gre_oip6.ip6_src,
                    &sin->sin6_addr) == 0)
                        continue;
                in6_gre_set_running(sc);
        }
}

static bool
in6_gre_udp_input(struct mbuf *m, int off, struct inpcb *inp,
    const struct sockaddr *sa, void *ctx)
{
        struct gre_socket *gs;
        struct gre_softc *sc;
        struct sockaddr_in6 dst;

        NET_EPOCH_ASSERT();

        gs = (struct gre_socket *)ctx;
        dst = *(const struct sockaddr_in6 *)sa;
        if (sa6_embedscope(&dst, 0)) {
                m_freem(m);
                return (true);
        }
        CK_LIST_FOREACH(sc, &gs->list, chain) {
                if (IN6_ARE_ADDR_EQUAL(&sc->gre_oip6.ip6_dst, &dst.sin6_addr))
                        break;
        }
        if (sc != NULL && (GRE2IFP(sc)->if_flags & IFF_UP) != 0){
                gre_input(m, off + sizeof(struct udphdr), IPPROTO_UDP, sc);
                return (true);
        }
        m_freem(m);

        return (true);
}

static int
in6_gre_setup_socket(struct gre_softc *sc)
{
        struct sockopt sopt;
        struct sockaddr_in6 sin6;
        struct in6_gre_socket *s;
        struct gre_socket *gs;
        int error, value;

        /*
         * NOTE: we are protected with gre_ioctl_sx lock.
         *
         * First check that socket is already configured.
         * If so, check that source address was not changed.
         * If address is different, check that there are no other tunnels
         * and close socket.
         */
        gs = sc->gre_so;
        if (gs != NULL) {
                s = __containerof(gs, struct in6_gre_socket, base);
                if (!IN6_ARE_ADDR_EQUAL(&s->addr, &sc->gre_oip6.ip6_src)) {
                        if (CK_LIST_EMPTY(&gs->list)) {
                                CK_LIST_REMOVE(gs, chain);
                                soclose(gs->so);
                                NET_EPOCH_CALL(gre_sofree, &gs->epoch_ctx);
                        }
                        gs = sc->gre_so = NULL;
                }
        }

        if (gs == NULL) {
                /*
                 * Check that socket for given address is already
                 * configured.
                 */
                gs = in6_gre_lookup_socket(&sc->gre_oip6.ip6_src);
                if (gs == NULL) {
                        s = malloc(sizeof(*s), M_GRE, M_WAITOK | M_ZERO);
                        s->addr = sc->gre_oip6.ip6_src;
                        gs = &s->base;

                        error = socreate(sc->gre_family, &gs->so,
                            SOCK_DGRAM, IPPROTO_UDP, curthread->td_ucred,
                            curthread);
                        if (error != 0) {
                                if_printf(GRE2IFP(sc),
                                    "cannot create socket: %d\n", error);
                                free(s, M_GRE);
                                return (error);
                        }

                        error = udp_set_kernel_tunneling(gs->so,
                            in6_gre_udp_input, NULL, gs);
                        if (error != 0) {
                                if_printf(GRE2IFP(sc),
                                    "cannot set UDP tunneling: %d\n", error);
                                goto fail;
                        }

                        memset(&sopt, 0, sizeof(sopt));
                        sopt.sopt_dir = SOPT_SET;
                        sopt.sopt_level = IPPROTO_IPV6;
                        sopt.sopt_name = IPV6_BINDANY;
                        sopt.sopt_val = &value;
                        sopt.sopt_valsize = sizeof(value);
                        value = 1;
                        error = sosetopt(gs->so, &sopt);
                        if (error != 0) {
                                if_printf(GRE2IFP(sc),
                                    "cannot set IPV6_BINDANY opt: %d\n",
                                    error);
                                goto fail;
                        }

                        memset(&sin6, 0, sizeof(sin6));
                        sin6.sin6_family = AF_INET6;
                        sin6.sin6_len = sizeof(sin6);
                        sin6.sin6_addr = sc->gre_oip6.ip6_src;
                        sin6.sin6_port = htons(GRE_UDPPORT);
                        error = sa6_recoverscope(&sin6);
                        if (error != 0) {
                                if_printf(GRE2IFP(sc),
                                    "cannot determine scope zone id: %d\n",
                                    error);
                                goto fail;
                        }
                        error = sobind(gs->so, (struct sockaddr *)&sin6,
                            curthread);
                        if (error != 0) {
                                if_printf(GRE2IFP(sc),
                                    "cannot bind socket: %d\n", error);
                                goto fail;
                        }
                        /* Add socket to the chain */
                        CK_LIST_INSERT_HEAD(
                            &GRE_SOCKHASH(&sc->gre_oip6.ip6_src), gs, chain);
                }
        }

        /* Add softc to the socket's list */
        CK_LIST_INSERT_HEAD(&gs->list, sc, chain);
        sc->gre_so = gs;
        return (0);
fail:
        soclose(gs->so);
        free(s, M_GRE);
        return (error);
}

static int
in6_gre_attach(struct gre_softc *sc)
{
        struct grehdr *gh;
        int error;

        if (sc->gre_options & GRE_UDPENCAP) {
                sc->gre_csumflags = CSUM_UDP_IPV6;
                sc->gre_hlen = sizeof(struct greudp6);
                sc->gre_oip6.ip6_nxt = IPPROTO_UDP;
                gh = &sc->gre_udp6hdr->gi6_gre;
                gre_update_udphdr(sc, &sc->gre_udp6,
                    in6_cksum_pseudo(&sc->gre_oip6, 0, 0, 0));
        } else {
                sc->gre_hlen = sizeof(struct greip6);
                sc->gre_oip6.ip6_nxt = IPPROTO_GRE;
                gh = &sc->gre_ip6hdr->gi6_gre;
        }
        sc->gre_oip6.ip6_vfc = IPV6_VERSION;
        gre_update_hdr(sc, gh);

        /*
         * If we return error, this means that sc is not linked,
         * and caller should reset gre_family and free(sc->gre_hdr).
         */
        if (sc->gre_options & GRE_UDPENCAP) {
                error = in6_gre_setup_socket(sc);
                if (error != 0)
                        return (error);
        } else
                CK_LIST_INSERT_HEAD(&GRE_HASH_SC(sc), sc, chain);
        CK_LIST_INSERT_HEAD(&GRE_SRCHASH(&sc->gre_oip6.ip6_src), sc, srchash);

        /* Set IFF_DRV_RUNNING if interface is ready */
        in6_gre_set_running(sc);
        return (0);
}

int
in6_gre_setopts(struct gre_softc *sc, u_long cmd, uint32_t value)
{
        int error;

        /* NOTE: we are protected with gre_ioctl_sx lock */
        MPASS(cmd == GRESKEY || cmd == GRESOPTS || cmd == GRESPORT);
        MPASS(sc->gre_family == AF_INET6);

        /*
         * If we are going to change encapsulation protocol, do check
         * for duplicate tunnels. Return EEXIST here to do not confuse
         * user.
         */
        if (cmd == GRESOPTS &&
            (sc->gre_options & GRE_UDPENCAP) != (value & GRE_UDPENCAP) &&
            in6_gre_checkdup(sc, &sc->gre_oip6.ip6_src,
                &sc->gre_oip6.ip6_dst, value) == EADDRNOTAVAIL)
                return (EEXIST);

        CK_LIST_REMOVE(sc, chain);
        CK_LIST_REMOVE(sc, srchash);
        GRE_WAIT();
        switch (cmd) {
        case GRESKEY:
                sc->gre_key = value;
                break;
        case GRESOPTS:
                sc->gre_options = value;
                break;
        case GRESPORT:
                sc->gre_port = value;
                break;
        }
        error = in6_gre_attach(sc);
        if (error != 0) {
                sc->gre_family = 0;
                free(sc->gre_hdr, M_GRE);
        }
        return (error);
}

int
in6_gre_ioctl(struct gre_softc *sc, u_long cmd, caddr_t data)
{
        struct in6_ifreq *ifr = (struct in6_ifreq *)data;
        struct sockaddr_in6 *dst, *src;
        struct ip6_hdr *ip6;
        int error;

        /* NOTE: we are protected with gre_ioctl_sx lock */
        error = EINVAL;
        switch (cmd) {
        case SIOCSIFPHYADDR_IN6:
                src = &((struct in6_aliasreq *)data)->ifra_addr;
                dst = &((struct in6_aliasreq *)data)->ifra_dstaddr;

                /* sanity checks */
                if (src->sin6_family != dst->sin6_family ||
                    src->sin6_family != AF_INET6 ||
                    src->sin6_len != dst->sin6_len ||
                    src->sin6_len != sizeof(*src))
                        break;
                if (IN6_IS_ADDR_UNSPECIFIED(&src->sin6_addr) ||
                    IN6_IS_ADDR_UNSPECIFIED(&dst->sin6_addr)) {
                        error = EADDRNOTAVAIL;
                        break;
                }
                /*
                 * Check validity of the scope zone ID of the
                 * addresses, and convert it into the kernel
                 * internal form if necessary.
                 */
                if ((error = sa6_embedscope(src, 0)) != 0 ||
                    (error = sa6_embedscope(dst, 0)) != 0)
                        break;

                if (V_ipv6_hashtbl == NULL) {
                        V_ipv6_hashtbl = gre_hashinit();
                        V_ipv6_srchashtbl = gre_hashinit();
                        V_ipv6_sockets = (struct gre_sockets *)gre_hashinit();
                }
                error = in6_gre_checkdup(sc, &src->sin6_addr,
                    &dst->sin6_addr, sc->gre_options);
                if (error == EADDRNOTAVAIL)
                        break;
                if (error == EEXIST) {
                        /* Addresses are the same. Just return. */
                        error = 0;
                        break;
                }
                ip6 = malloc(sizeof(struct greudp6) + 3 * sizeof(uint32_t),
                    M_GRE, M_WAITOK | M_ZERO);
                ip6->ip6_src = src->sin6_addr;
                ip6->ip6_dst = dst->sin6_addr;
                if (sc->gre_family != 0) {
                        /* Detach existing tunnel first */
                        CK_LIST_REMOVE(sc, chain);
                        CK_LIST_REMOVE(sc, srchash);
                        GRE_WAIT();
                        free(sc->gre_hdr, M_GRE);
                        /* XXX: should we notify about link state change? */
                }
                sc->gre_family = AF_INET6;
                sc->gre_hdr = ip6;
                sc->gre_oseq = 0;
                sc->gre_iseq = UINT32_MAX;
                error = in6_gre_attach(sc);
                if (error != 0) {
                        sc->gre_family = 0;
                        free(sc->gre_hdr, M_GRE);
                }
                break;
        case SIOCGIFPSRCADDR_IN6:
        case SIOCGIFPDSTADDR_IN6:
                if (sc->gre_family != AF_INET6) {
                        error = EADDRNOTAVAIL;
                        break;
                }
                src = (struct sockaddr_in6 *)&ifr->ifr_addr;
                memset(src, 0, sizeof(*src));
                src->sin6_family = AF_INET6;
                src->sin6_len = sizeof(*src);
                src->sin6_addr = (cmd == SIOCGIFPSRCADDR_IN6) ?
                    sc->gre_oip6.ip6_src: sc->gre_oip6.ip6_dst;
                error = prison_if(curthread->td_ucred, (struct sockaddr *)src);
                if (error == 0)
                        error = sa6_recoverscope(src);
                if (error != 0)
                        memset(src, 0, sizeof(*src));
                break;
        }
        return (error);
}

int
in6_gre_output(struct mbuf *m, int af __unused, int hlen __unused,
    uint32_t flowid)
{
        struct greip6 *gi6;

        gi6 = mtod(m, struct greip6 *);
        gi6->gi6_ip6.ip6_hlim = V_ip6_gre_hlim;
        gi6->gi6_ip6.ip6_flow |= flowid & IPV6_FLOWLABEL_MASK;
        return (ip6_output(m, NULL, NULL, IPV6_MINMTU, NULL, NULL, NULL));
}

static const struct srcaddrtab *ipv6_srcaddrtab = NULL;
static const struct encaptab *ecookie = NULL;
static const struct encap_config ipv6_encap_cfg = {
        .proto = IPPROTO_GRE,
        .min_length = sizeof(struct greip6) +
#ifdef INET
            sizeof(struct ip),
#else
            sizeof(struct ip6_hdr),
#endif
        .exact_match = ENCAP_DRV_LOOKUP,
        .lookup = in6_gre_lookup,
        .input = gre_input
};

void
in6_gre_init(void)
{

        if (!IS_DEFAULT_VNET(curvnet))
                return;
        ipv6_srcaddrtab = ip6_encap_register_srcaddr(in6_gre_srcaddr,
            NULL, M_WAITOK);
        ecookie = ip6_encap_attach(&ipv6_encap_cfg, NULL, M_WAITOK);
}

void
in6_gre_uninit(void)
{

        if (IS_DEFAULT_VNET(curvnet)) {
                ip6_encap_detach(ecookie);
                ip6_encap_unregister_srcaddr(ipv6_srcaddrtab);
        }
        if (V_ipv6_hashtbl != NULL) {
                gre_hashdestroy(V_ipv6_hashtbl);
                V_ipv6_hashtbl = NULL;
                GRE_WAIT();
                gre_hashdestroy(V_ipv6_srchashtbl);
                gre_hashdestroy((struct gre_list *)V_ipv6_sockets);
        }
}