/*-
 * SPDX-License-Identifier: BSD-2-Clause
 *
 * Copyright (c) 2022 Alexander V. Chernikov <melifaro@FreeBSD.org>
 *
 * 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 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 AUTHOR 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.
 */

#include <sys/cdefs.h>
#include "opt_inet.h"
#include "opt_inet6.h"
#include <sys/types.h>
#include <sys/eventhandler.h>
#include <sys/kernel.h>
#include <sys/malloc.h>
#include <sys/socket.h>
#include <sys/syslog.h>

#include <net/if.h>
#include <net/if_var.h>
#include <net/if_llatbl.h>
#include <netlink/netlink.h>
#include <netlink/netlink_ctl.h>
#include <netlink/netlink_route.h>
#include <netlink/route/route_var.h>

#include <netinet6/in6_var.h>           /* nd6.h requires this */
#include <netinet6/nd6.h>               /* nd6 state machine */
#include <netinet6/scope6_var.h>        /* scope deembedding */

#define DEBUG_MOD_NAME  nl_neigh
#define DEBUG_MAX_LEVEL LOG_DEBUG3
#include <netlink/netlink_debug.h>
_DECLARE_DEBUG(LOG_INFO);

static int lle_families[] = { AF_INET, AF_INET6 };

static eventhandler_tag lle_event_p;

struct netlink_walkargs {
        struct nl_writer *nw;
        struct nlmsghdr hdr;
        struct nlpcb *so;
        if_t ifp;
        int family;
        int error;
        int count;
        int dumped;
};

static int
lle_state_to_nl_state(int family, struct llentry *lle)
{
        int state = lle->ln_state;

        switch (family) {
        case AF_INET:
                if (lle->la_flags & (LLE_STATIC | LLE_IFADDR))
                        state = 1;
                switch (state) {
                case 0: /* ARP_LLINFO_INCOMPLETE */
                        return (NUD_INCOMPLETE);
                case 1: /* ARP_LLINFO_REACHABLE  */
                        return (NUD_REACHABLE);
                case 2: /* ARP_LLINFO_VERIFY */
                        return (NUD_PROBE);
                }
                break;
        case AF_INET6:
                switch (state) {
                case ND6_LLINFO_INCOMPLETE:
                        return (NUD_INCOMPLETE);
                case ND6_LLINFO_REACHABLE:
                        return (NUD_REACHABLE);
                case ND6_LLINFO_STALE:
                        return (NUD_STALE);
                case ND6_LLINFO_DELAY:
                        return (NUD_DELAY);
                case ND6_LLINFO_PROBE:
                        return (NUD_PROBE);
                }
                break;
        }

        return (NUD_NONE);
}

static uint32_t
lle_flags_to_nl_flags(const struct llentry *lle)
{
        uint32_t nl_flags = 0;

        if (lle->la_flags & LLE_IFADDR)
                nl_flags |= NTF_SELF;
        if (lle->la_flags & LLE_PUB)
                nl_flags |= NTF_PROXY;
        if (lle->la_flags & LLE_STATIC)
                nl_flags |= NTF_STICKY;
        if (lle->ln_router != 0)
                nl_flags |= NTF_ROUTER;

        return (nl_flags);
}

static uint32_t
get_lle_next_ts(const struct llentry *lle)
{
        if (lle->la_expire == 0)
                return (0);
        return (lle->la_expire + lle->lle_remtime / hz + time_second - time_uptime);
}

static int
dump_lle_locked(struct llentry *lle, void *arg)
{
        struct netlink_walkargs *wa = (struct netlink_walkargs *)arg;
        struct nlmsghdr *hdr = &wa->hdr;
        struct nl_writer *nw = wa->nw;
        struct ndmsg *ndm;
#if defined(INET) || defined(INET6)
        union {
                struct in_addr  in;
                struct in6_addr in6;
        } addr;
#endif

        IF_DEBUG_LEVEL(LOG_DEBUG2) {
                char llebuf[NHOP_PRINT_BUFSIZE];
                llentry_print_buf_lltable(lle, llebuf, sizeof(llebuf));
                NL_LOG(LOG_DEBUG2, "dumping %s", llebuf);
        }

        if (!nlmsg_reply(nw, hdr, sizeof(struct ndmsg)))
                goto enomem;

        ndm = nlmsg_reserve_object(nw, struct ndmsg);
        ndm->ndm_family = wa->family;
        ndm->ndm_ifindex = if_getindex(wa->ifp);
        ndm->ndm_state = lle_state_to_nl_state(wa->family, lle);
        ndm->ndm_flags = lle_flags_to_nl_flags(lle);

        switch (wa->family) {
#ifdef INET
        case AF_INET:
                addr.in = lle->r_l3addr.addr4;
                nlattr_add(nw, NDA_DST, 4, &addr);
                break;
#endif
#ifdef INET6
        case AF_INET6:
                addr.in6 = lle->r_l3addr.addr6;
                in6_clearscope(&addr.in6);
                nlattr_add(nw, NDA_DST, 16, &addr);
                break;
#endif
        }

        if (lle->r_flags & RLLE_VALID) {
                /* Has L2 */
                int addrlen = if_getaddrlen(wa->ifp);
                nlattr_add(nw, NDA_LLADDR, addrlen, lle->ll_addr);
        }

        nlattr_add_u32(nw, NDA_PROBES, lle->la_asked);

        struct nda_cacheinfo *cache;
        cache = nlmsg_reserve_attr(nw, NDA_CACHEINFO, struct nda_cacheinfo);
        if (cache == NULL)
                goto enomem;
        /* TODO: provide confirmed/updated */
        cache->ndm_refcnt = lle->lle_refcnt;

        int off = nlattr_add_nested(nw, NDA_FREEBSD);
        if (off != 0) {
                nlattr_add_u32(nw, NDAF_NEXT_STATE_TS, get_lle_next_ts(lle));

                nlattr_set_len(nw, off);
        }

        if (nlmsg_end(nw))
                return (0);
enomem:
        NL_LOG(LOG_DEBUG, "unable to dump lle state (ENOMEM)");
        nlmsg_abort(nw);
        return (ENOMEM);
}

static int
dump_lle(struct lltable *llt, struct llentry *lle, void *arg)
{
        int error;

        LLE_RLOCK(lle);
        error = dump_lle_locked(lle, arg);
        LLE_RUNLOCK(lle);
        return (error);
}

static bool
dump_llt(struct lltable *llt, struct netlink_walkargs *wa)
{
        lltable_foreach_lle(llt, dump_lle, wa);

        return (true);
}

static int
dump_llts_iface(struct netlink_walkargs *wa, if_t ifp, int family)
{
        int error = 0;

        wa->ifp = ifp;
        for (int i = 0; i < sizeof(lle_families) / sizeof(int); i++) {
                int fam = lle_families[i];
                struct lltable *llt = lltable_get(ifp, fam);
                if (llt != NULL && (family == 0 || family == fam)) {
                        wa->count++;
                        wa->family = fam;
                        if (!dump_llt(llt, wa)) {
                                error = ENOMEM;
                                break;
                        }
                        wa->dumped++;
                }
        }
        return (error);
}

static int
dump_llts(struct netlink_walkargs *wa, if_t ifp, int family)
{
        NL_LOG(LOG_DEBUG2, "Start dump ifp=%s family=%d", ifp ? if_name(ifp) : "NULL", family);

        wa->hdr.nlmsg_flags |= NLM_F_MULTI;

        if (ifp != NULL) {
                dump_llts_iface(wa, ifp, family);
        } else {
                struct if_iter it;

                for (ifp = if_iter_start(&it); ifp != NULL; ifp = if_iter_next(&it)) {
                        dump_llts_iface(wa, ifp, family);
                }
                if_iter_finish(&it);
        }

        NL_LOG(LOG_DEBUG2, "End dump, iterated %d dumped %d", wa->count, wa->dumped);

        if (!nlmsg_end_dump(wa->nw, wa->error, &wa->hdr)) {
                NL_LOG(LOG_DEBUG, "Unable to add new message");
                return (ENOMEM);
        }

        return (0);
}

static int
get_lle(struct netlink_walkargs *wa, if_t ifp, int family, struct sockaddr *dst)
{
        struct lltable *llt = lltable_get(ifp, family);
        if (llt == NULL)
                return (ESRCH);

        struct llentry *lle = lla_lookup(llt, LLE_UNLOCKED, dst);
        if (lle == NULL)
                return (ESRCH);

        wa->ifp = ifp;
        wa->family = family;

        return (dump_lle(llt, lle, wa));
}

static void
set_scope6(struct sockaddr *sa, if_t ifp)
{
#ifdef INET6
        if (sa != NULL && sa->sa_family == AF_INET6 && ifp != NULL) {
                struct sockaddr_in6 *sa6 = (struct sockaddr_in6 *)sa;

                if (IN6_IS_ADDR_LINKLOCAL(&sa6->sin6_addr))
                        in6_set_unicast_scopeid(&sa6->sin6_addr, if_getindex(ifp));
        }
#endif
}

struct nl_parsed_neigh {
        struct sockaddr *nda_dst;
        struct ifnet    *nda_ifp;
        struct nlattr   *nda_lladdr;
        uint32_t        ndaf_next_ts;
        uint32_t        ndm_flags;
        uint16_t        ndm_state;
        uint8_t         ndm_family;
};

#define _IN(_field)     offsetof(struct ndmsg, _field)
#define _OUT(_field)    offsetof(struct nl_parsed_neigh, _field)
static const struct nlattr_parser nla_p_neigh_fbsd[] = {
        { .type = NDAF_NEXT_STATE_TS, .off = _OUT(ndaf_next_ts), .cb = nlattr_get_uint32 },
};
NL_DECLARE_ATTR_PARSER(neigh_fbsd_parser, nla_p_neigh_fbsd);

static const struct nlfield_parser nlf_p_neigh[] = {
        { .off_in = _IN(ndm_family), .off_out = _OUT(ndm_family), .cb = nlf_get_u8 },
        { .off_in = _IN(ndm_flags), .off_out = _OUT(ndm_flags), .cb = nlf_get_u8_u32 },
        { .off_in = _IN(ndm_state), .off_out = _OUT(ndm_state), .cb = nlf_get_u16 },
        { .off_in = _IN(ndm_ifindex), .off_out = _OUT(nda_ifp), .cb = nlf_get_ifpz },
};

static const struct nlattr_parser nla_p_neigh[] = {
        { .type = NDA_DST, .off = _OUT(nda_dst), .cb = nlattr_get_ip },
        { .type = NDA_LLADDR, .off = _OUT(nda_lladdr), .cb = nlattr_get_nla },
        { .type = NDA_IFINDEX, .off = _OUT(nda_ifp), .cb = nlattr_get_ifp },
        { .type = NDA_FLAGS_EXT, .off = _OUT(ndm_flags), .cb = nlattr_get_uint32 },
        { .type = NDA_FREEBSD, .arg = &neigh_fbsd_parser, .cb = nlattr_get_nested },
};
#undef _IN
#undef _OUT

static bool
post_p_neigh(void *_attrs, struct nl_pstate *npt __unused)
{
        struct nl_parsed_neigh *attrs = (struct nl_parsed_neigh *)_attrs;

        set_scope6(attrs->nda_dst, attrs->nda_ifp);
        return (true);
}
NL_DECLARE_PARSER_EXT(ndmsg_parser, struct ndmsg, NULL, nlf_p_neigh, nla_p_neigh, post_p_neigh);


/*
 * type=RTM_NEWNEIGH, flags=NLM_F_REQUEST|NLM_F_ACK|NLM_F_EXCL|NLM_F_CREATE, seq=1661941473, pid=0},
 * {ndm_family=AF_INET6, ndm_ifindex=if_nametoindex("enp0s31f6"), ndm_state=NUD_PERMANENT, ndm_flags=0, ndm_type=RTN_UNSPEC},
 * [
 *  {{nla_len=20, nla_type=NDA_DST}, inet_pton(AF_INET6, "2a01:4f8:13a:70c::3")},
 *  {{nla_len=10, nla_type=NDA_LLADDR}, 20:4e:71:62:ae:f2}]}, iov_len=60}
 */

static int
rtnl_handle_newneigh(struct nlmsghdr *hdr, struct nlpcb *nlp, struct nl_pstate *npt)
{
        int error;

        struct nl_parsed_neigh attrs = {};
        error = nl_parse_nlmsg(hdr, &ndmsg_parser, npt, &attrs);
        if (error != 0)
                return (error);

        if (attrs.nda_ifp == NULL || attrs.nda_dst == NULL || attrs.nda_lladdr == NULL) {
                if (attrs.nda_ifp == NULL)
                        NLMSG_REPORT_ERR_MSG(npt, "NDA_IFINDEX / ndm_ifindex not set");
                if (attrs.nda_dst == NULL)
                        NLMSG_REPORT_ERR_MSG(npt, "NDA_DST not set");
                if (attrs.nda_lladdr == NULL)
                        NLMSG_REPORT_ERR_MSG(npt, "NDA_LLADDR not set");
                return (EINVAL);
        }

        if (attrs.nda_dst->sa_family != attrs.ndm_family) {
                NLMSG_REPORT_ERR_MSG(npt,
                    "NDA_DST family (%d) is different from ndm_family (%d)",
                    attrs.nda_dst->sa_family, attrs.ndm_family);
                return (EINVAL);
        }

        int addrlen = if_getaddrlen(attrs.nda_ifp);
        if (attrs.nda_lladdr->nla_len != sizeof(struct nlattr) + addrlen) {
                NLMSG_REPORT_ERR_MSG(npt,
                    "NDA_LLADDR address length (%d) is different from expected (%d)",
                    (int)attrs.nda_lladdr->nla_len - (int)sizeof(struct nlattr), addrlen);
                return (EINVAL);
        }

        const uint16_t supported_flags = NTF_PROXY | NTF_STICKY;
        if ((attrs.ndm_flags & supported_flags) != attrs.ndm_flags) {
                NLMSG_REPORT_ERR_MSG(npt, "ndm_flags %X not supported",
                    attrs.ndm_flags &~ supported_flags);
                return (ENOTSUP);
        }

        /* Replacement requires new entry creation anyway */
        if ((hdr->nlmsg_flags & (NLM_F_CREATE | NLM_F_REPLACE)) == 0)
                return (ENOTSUP);

        struct lltable *llt = lltable_get(attrs.nda_ifp, attrs.ndm_family);
        if (llt == NULL)
                return (EAFNOSUPPORT);


        uint8_t linkhdr[LLE_MAX_LINKHDR];
        size_t linkhdrsize = sizeof(linkhdr);
        int lladdr_off = 0;
        if (lltable_calc_llheader(attrs.nda_ifp, attrs.ndm_family,
            (char *)(attrs.nda_lladdr + 1), linkhdr, &linkhdrsize, &lladdr_off) != 0) {
                NLMSG_REPORT_ERR_MSG(npt, "unable to calculate lle prepend data");
                return (EINVAL);
        }

        int lle_flags = (attrs.ndm_flags & NTF_PROXY) ? LLE_PUB : 0;
        if (attrs.ndm_flags & NTF_STICKY)
                lle_flags |= LLE_STATIC;
        struct llentry *lle = lltable_alloc_entry(llt, lle_flags, attrs.nda_dst);
        if (lle == NULL)
                return (ENOMEM);
        lltable_set_entry_addr(attrs.nda_ifp, lle, linkhdr, linkhdrsize, lladdr_off);

        if (attrs.ndm_flags & NTF_STICKY)
                lle->la_expire = 0;
        else
                lle->la_expire = attrs.ndaf_next_ts - time_second + time_uptime;

        /* llentry created, try to insert or update */
        LLTABLE_LOCK(llt);
        LLE_WLOCK(lle);
        struct llentry *lle_tmp = lla_lookup(llt, LLE_EXCLUSIVE, attrs.nda_dst);
        if (lle_tmp != NULL) {
                error = EEXIST;
                if (hdr->nlmsg_flags & NLM_F_REPLACE) {
                        error = EPERM;
                        if ((lle_tmp->la_flags & LLE_IFADDR) == 0) {
                                error = 0; /* success */
                                lltable_unlink_entry(llt, lle_tmp);
                                llentry_free(lle_tmp);
                                lle_tmp = NULL;
                                lltable_link_entry(llt, lle);
                        }
                }
                if (lle_tmp)
                        LLE_WUNLOCK(lle_tmp);
        } else {
                if (hdr->nlmsg_flags & NLM_F_CREATE)
                        lltable_link_entry(llt, lle);
                else
                        error = ENOENT;
        }
        LLTABLE_UNLOCK(llt);

        if (error != 0) {
                /* throw away the newly allocated llentry */
                llentry_free(lle);
                return (error);
        }

        /* XXX: We're inside epoch */
        EVENTHANDLER_INVOKE(lle_event, lle, LLENTRY_RESOLVED);
        LLE_WUNLOCK(lle);
        llt->llt_post_resolved(llt, lle);

        return (0);
}

static int
rtnl_handle_delneigh(struct nlmsghdr *hdr, struct nlpcb *nlp, struct nl_pstate *npt)
{
        int error;

        struct nl_parsed_neigh attrs = {};
        error = nl_parse_nlmsg(hdr, &ndmsg_parser, npt, &attrs);
        if (error != 0)
                return (error);

        if (attrs.nda_dst == NULL) {
                NLMSG_REPORT_ERR_MSG(npt, "NDA_DST not set");
                return (EINVAL);
        }

        if (attrs.nda_ifp == NULL) {
                NLMSG_REPORT_ERR_MSG(npt, "no ifindex provided");
                return (EINVAL);
        }

        struct lltable *llt = lltable_get(attrs.nda_ifp, attrs.ndm_family);
        if (llt == NULL)
                return (EAFNOSUPPORT);

        return (lltable_delete_addr(llt, 0, attrs.nda_dst));
}

static int
rtnl_handle_getneigh(struct nlmsghdr *hdr, struct nlpcb *nlp, struct nl_pstate *npt)
{
        int error;

        struct nl_parsed_neigh attrs = {};
        error = nl_parse_nlmsg(hdr, &ndmsg_parser, npt, &attrs);
        if (error != 0)
                return (error);

        if (attrs.nda_dst != NULL && attrs.nda_ifp == NULL) {
                NLMSG_REPORT_ERR_MSG(npt, "has NDA_DST but no ifindex provided");
                return (EINVAL);
        }

        struct netlink_walkargs wa = {
                .so = nlp,
                .nw = npt->nw,
                .hdr.nlmsg_pid = hdr->nlmsg_pid,
                .hdr.nlmsg_seq = hdr->nlmsg_seq,
                .hdr.nlmsg_flags = hdr->nlmsg_flags,
                .hdr.nlmsg_type = NL_RTM_NEWNEIGH,
        };

        if (attrs.nda_dst == NULL)
                error = dump_llts(&wa, attrs.nda_ifp, attrs.ndm_family);
        else
                error = get_lle(&wa, attrs.nda_ifp, attrs.ndm_family, attrs.nda_dst);

        return (error);
}

static const struct rtnl_cmd_handler cmd_handlers[] = {
        {
                .cmd = NL_RTM_NEWNEIGH,
                .name = "RTM_NEWNEIGH",
                .cb = &rtnl_handle_newneigh,
                .priv = PRIV_NET_ROUTE,
        },
        {
                .cmd = NL_RTM_DELNEIGH,
                .name = "RTM_DELNEIGH",
                .cb = &rtnl_handle_delneigh,
                .priv = PRIV_NET_ROUTE,
        },
        {
                .cmd = NL_RTM_GETNEIGH,
                .name = "RTM_GETNEIGH",
                .cb = &rtnl_handle_getneigh,
        }
};

static void
rtnl_lle_event(void *arg __unused, struct llentry *lle, int evt)
{
        struct nl_writer nw;
        if_t ifp;
        int family;

        LLE_WLOCK_ASSERT(lle);

        ifp = lltable_get_ifp(lle->lle_tbl);
        family = lltable_get_af(lle->lle_tbl);

        if (family != AF_INET && family != AF_INET6)
                return;

        int nlmsgs_type = evt == LLENTRY_RESOLVED ? NL_RTM_NEWNEIGH : NL_RTM_DELNEIGH;

        if (!nl_writer_group(&nw, NLMSG_SMALL, NETLINK_ROUTE, RTNLGRP_NEIGH, 0,
            false)) {
                NL_LOG(LOG_DEBUG, "error allocating group writer");
                return;
        }

        struct netlink_walkargs wa = {
                .hdr.nlmsg_type = nlmsgs_type,
                .nw = &nw,
                .ifp = ifp,
                .family = family,
        };

        dump_lle_locked(lle, &wa);
        nlmsg_flush(&nw);
}

static const struct nlhdr_parser *all_parsers[] = { &ndmsg_parser, &neigh_fbsd_parser };

void
rtnl_neighs_init(void)
{
        NL_VERIFY_PARSERS(all_parsers);
        rtnl_register_messages(cmd_handlers, nitems(cmd_handlers));
        lle_event_p = EVENTHANDLER_REGISTER(lle_event, rtnl_lle_event, NULL,
            EVENTHANDLER_PRI_ANY);
}

void
rtnl_neighs_destroy(void)
{
        EVENTHANDLER_DEREGISTER(lle_event, lle_event_p);
}