/*-
 * SPDX-License-Identifier: BSD-2-Clause
 *
 * Copyright (c) 1998 The NetBSD Foundation, Inc.
 * Copyright (c) 2014, 2018 Andrey V. Elsukov <ae@FreeBSD.org>
 * All rights reserved.
 *
 * This code is derived from software contributed to The NetBSD Foundation
 * by Heiko W.Rupp <hwr@pilhuhn.de>
 *
 * IPv6-over-GRE contributed by Gert Doering <gert@greenie.muc.de>
 *
 * 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.
 *
 * $NetBSD: ip_gre.c,v 1.29 2003/09/05 23:02:43 itojun Exp $
 */

#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>
#include <netinet/in_var.h>
#include <netinet/in_pcb.h>
#include <netinet/ip.h>
#include <netinet/ip_encap.h>
#include <netinet/ip_var.h>
#include <netinet/udp.h>
#include <netinet/udp_var.h>

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

#include <net/if_gre.h>
#include <machine/in_cksum.h>

#define GRE_TTL                 30
VNET_DEFINE(int, ip_gre_ttl) = GRE_TTL;
#define V_ip_gre_ttl            VNET(ip_gre_ttl)
SYSCTL_INT(_net_inet_ip, OID_AUTO, grettl, CTLFLAG_VNET | CTLFLAG_RW,
    &VNET_NAME(ip_gre_ttl), 0, "Default TTL value for encapsulated packets");

struct in_gre_socket {
        struct gre_socket               base;
        in_addr_t                       addr;
};
VNET_DEFINE_STATIC(struct gre_sockets *, ipv4_sockets) = NULL;
VNET_DEFINE_STATIC(struct gre_list *, ipv4_hashtbl) = NULL;
VNET_DEFINE_STATIC(struct gre_list *, ipv4_srchashtbl) = NULL;
#define V_ipv4_sockets          VNET(ipv4_sockets)
#define V_ipv4_hashtbl          VNET(ipv4_hashtbl)
#define V_ipv4_srchashtbl       VNET(ipv4_srchashtbl)
#define GRE_HASH(src, dst)      (V_ipv4_hashtbl[\
    in_gre_hashval((src), (dst)) & (GRE_HASH_SIZE - 1)])
#define GRE_SRCHASH(src)        (V_ipv4_srchashtbl[\
    fnv_32_buf(&(src), sizeof(src), FNV1_32_INIT) & (GRE_HASH_SIZE - 1)])
#define GRE_SOCKHASH(src)       (V_ipv4_sockets[\
    fnv_32_buf(&(src), sizeof(src), FNV1_32_INIT) & (GRE_HASH_SIZE - 1)])
#define GRE_HASH_SC(sc)         GRE_HASH((sc)->gre_oip.ip_src.s_addr,\
    (sc)->gre_oip.ip_dst.s_addr)

static uint32_t
in_gre_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 struct gre_socket*
in_gre_lookup_socket(in_addr_t addr)
{
        struct gre_socket *gs;
        struct in_gre_socket *s;

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

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

        if (sc->gre_family == AF_INET &&
            sc->gre_oip.ip_src.s_addr == src &&
            sc->gre_oip.ip_dst.s_addr == dst &&
            (sc->gre_options & GRE_UDPENCAP) == (opts & GRE_UDPENCAP))
                return (EEXIST);

        if (opts & GRE_UDPENCAP) {
                gs = in_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 (tmp->gre_oip.ip_src.s_addr == src &&
                    tmp->gre_oip.ip_dst.s_addr == dst)
                        return (EADDRNOTAVAIL);
        }
        return (0);
}

static int
in_gre_lookup(const struct mbuf *m, int off, int proto, void **arg)
{
        const struct ip *ip;
        struct gre_softc *sc;

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

        NET_EPOCH_ASSERT();
        ip = mtod(m, const struct ip *);
        CK_LIST_FOREACH(sc, &GRE_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->gre_oip.ip_src.s_addr == ip->ip_dst.s_addr &&
                    sc->gre_oip.ip_dst.s_addr == ip->ip_src.s_addr) {
                        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
in_gre_set_running(struct gre_softc *sc)
{

        if (in_localip(sc->gre_oip.ip_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
in_gre_srcaddr(void *arg __unused, const struct sockaddr *sa,
    int event __unused)
{
        const struct sockaddr_in *sin;
        struct gre_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, &GRE_SRCHASH(sin->sin_addr.s_addr), srchash) {
                if (sc->gre_oip.ip_src.s_addr != sin->sin_addr.s_addr)
                        continue;
                in_gre_set_running(sc);
        }
}

static bool
in_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;
        in_addr_t dst;

        NET_EPOCH_ASSERT();

        gs = (struct gre_socket *)ctx;
        dst = ((const struct sockaddr_in *)sa)->sin_addr.s_addr;
        CK_LIST_FOREACH(sc, &gs->list, chain) {
                if (sc->gre_oip.ip_dst.s_addr == dst)
                        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
in_gre_setup_socket(struct gre_softc *sc)
{
        struct sockopt sopt;
        struct sockaddr_in sin;
        struct in_gre_socket *s;
        struct gre_socket *gs;
        in_addr_t addr;
        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.
         */
        addr = sc->gre_oip.ip_src.s_addr;
        gs = sc->gre_so;
        if (gs != NULL) {
                s = __containerof(gs, struct in_gre_socket, base);
                if (s->addr != addr) {
                        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 = in_gre_lookup_socket(addr);
                if (gs == NULL) {
                        s = malloc(sizeof(*s), M_GRE, M_WAITOK | M_ZERO);
                        s->addr = addr;
                        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,
                            in_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_IP;
                        sopt.sopt_name = IP_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 IP_BINDANY opt: %d\n", error);
                                goto fail;
                        }

                        memset(&sin, 0, sizeof(sin));
                        sin.sin_family = AF_INET;
                        sin.sin_len = sizeof(sin);
                        sin.sin_addr.s_addr = addr;
                        sin.sin_port = htons(GRE_UDPPORT);
                        error = sobind(gs->so, (struct sockaddr *)&sin,
                            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(addr), 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
in_gre_attach(struct gre_softc *sc)
{
        struct epoch_tracker et;
        struct grehdr *gh;
        int error;

        if (sc->gre_options & GRE_UDPENCAP) {
                sc->gre_csumflags = CSUM_UDP;
                sc->gre_hlen = sizeof(struct greudp);
                sc->gre_oip.ip_p = IPPROTO_UDP;
                gh = &sc->gre_udphdr->gi_gre;
                gre_update_udphdr(sc, &sc->gre_udp,
                    in_pseudo(sc->gre_oip.ip_src.s_addr,
                    sc->gre_oip.ip_dst.s_addr, 0));
        } else {
                sc->gre_hlen = sizeof(struct greip);
                sc->gre_oip.ip_p = IPPROTO_GRE;
                gh = &sc->gre_iphdr->gi_gre;
        }
        sc->gre_oip.ip_v = IPVERSION;
        sc->gre_oip.ip_hl = sizeof(struct ip) >> 2;
        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 = in_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_oip.ip_src.s_addr),
            sc, srchash);

        /* Set IFF_DRV_RUNNING if interface is ready */
        NET_EPOCH_ENTER(et);
        in_gre_set_running(sc);
        NET_EPOCH_EXIT(et);
        return (0);
}

int
in_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_INET);

        /*
         * 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) &&
            in_gre_checkdup(sc, sc->gre_oip.ip_src.s_addr,
                sc->gre_oip.ip_dst.s_addr, 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 = in_gre_attach(sc);
        if (error != 0) {
                sc->gre_family = 0;
                free(sc->gre_hdr, M_GRE);
        }
        return (error);
}

int
in_gre_ioctl(struct gre_softc *sc, u_long cmd, caddr_t data)
{
        struct ifreq *ifr = (struct ifreq *)data;
        struct sockaddr_in *dst, *src;
        struct ip *ip;
        int error;

        /* NOTE: we are protected with gre_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 = gre_hashinit();
                        V_ipv4_srchashtbl = gre_hashinit();
                        V_ipv4_sockets = (struct gre_sockets *)gre_hashinit();
                }
                error = in_gre_checkdup(sc, src->sin_addr.s_addr,
                    dst->sin_addr.s_addr, sc->gre_options);
                if (error == EADDRNOTAVAIL)
                        break;
                if (error == EEXIST) {
                        /* Addresses are the same. Just return. */
                        error = 0;
                        break;
                }
                ip = malloc(sizeof(struct greudp) + 3 * sizeof(uint32_t),
                    M_GRE, 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->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_INET;
                sc->gre_hdr = ip;
                sc->gre_oseq = 0;
                sc->gre_iseq = UINT32_MAX;
                error = in_gre_attach(sc);
                if (error != 0) {
                        sc->gre_family = 0;
                        free(sc->gre_hdr, M_GRE);
                }
                break;
        case SIOCGIFPSRCADDR:
        case SIOCGIFPDSTADDR:
                if (sc->gre_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->gre_oip.ip_src: sc->gre_oip.ip_dst;
                error = prison_if(curthread->td_ucred, (struct sockaddr *)src);
                if (error != 0)
                        memset(src, 0, sizeof(*src));
                break;
        }
        return (error);
}

int
in_gre_output(struct mbuf *m, int af, int hlen)
{
        struct greip *gi;

        gi = mtod(m, struct greip *);
        switch (af) {
        case AF_INET:
                /*
                 * gre_transmit() has used M_PREPEND() that doesn't guarantee
                 * m_data is contiguous more than hlen bytes. Use m_copydata()
                 * here to avoid m_pullup().
                 */
                m_copydata(m, hlen + offsetof(struct ip, ip_tos),
                    sizeof(u_char), &gi->gi_ip.ip_tos);
                m_copydata(m, hlen + offsetof(struct ip, ip_id),
                    sizeof(u_short), (caddr_t)&gi->gi_ip.ip_id);
                break;
#ifdef INET6
        case AF_INET6:
                gi->gi_ip.ip_tos = 0; /* XXX */
                ip_fillid(&gi->gi_ip, V_ip_random_id);
                break;
#endif
        }
        gi->gi_ip.ip_ttl = V_ip_gre_ttl;
        gi->gi_ip.ip_len = htons(m->m_pkthdr.len);
        return (ip_output(m, NULL, NULL, IP_FORWARDING, NULL, NULL));
}

static const struct srcaddrtab *ipv4_srcaddrtab = NULL;
static const struct encaptab *ecookie = NULL;
static const struct encap_config ipv4_encap_cfg = {
        .proto = IPPROTO_GRE,
        .min_length = sizeof(struct greip) + sizeof(struct ip),
        .exact_match = ENCAP_DRV_LOOKUP,
        .lookup = in_gre_lookup,
        .input = gre_input
};

void
in_gre_init(void)
{

        if (!IS_DEFAULT_VNET(curvnet))
                return;
        ipv4_srcaddrtab = ip_encap_register_srcaddr(in_gre_srcaddr,
            NULL, M_WAITOK);
        ecookie = ip_encap_attach(&ipv4_encap_cfg, NULL, M_WAITOK);
}

void
in_gre_uninit(void)
{

        if (IS_DEFAULT_VNET(curvnet)) {
                ip_encap_detach(ecookie);
                ip_encap_unregister_srcaddr(ipv4_srcaddrtab);
        }
        if (V_ipv4_hashtbl != NULL) {
                gre_hashdestroy(V_ipv4_hashtbl);
                V_ipv4_hashtbl = NULL;
                GRE_WAIT();
                gre_hashdestroy(V_ipv4_srchashtbl);
                gre_hashdestroy((struct gre_list *)V_ipv4_sockets);
        }
}