/*      $NetBSD: xform_ipip.c,v 1.80 2025/06/11 02:44:13 ozaki-r Exp $  */
/*      $FreeBSD: xform_ipip.c,v 1.3.2.1 2003/01/24 05:11:36 sam Exp $  */
/*      $OpenBSD: ip_ipip.c,v 1.25 2002/06/10 18:04:55 itojun Exp $ */

/*
 * The authors of this code are John Ioannidis (ji@tla.org),
 * Angelos D. Keromytis (kermit@csd.uch.gr) and
 * Niels Provos (provos@physnet.uni-hamburg.de).
 *
 * The original version of this code was written by John Ioannidis
 * for BSD/OS in Athens, Greece, in November 1995.
 *
 * Ported to OpenBSD and NetBSD, with additional transforms, in December 1996,
 * by Angelos D. Keromytis.
 *
 * Additional transforms and features in 1997 and 1998 by Angelos D. Keromytis
 * and Niels Provos.
 *
 * Additional features in 1999 by Angelos D. Keromytis.
 *
 * Copyright (C) 1995, 1996, 1997, 1998, 1999 by John Ioannidis,
 * Angelos D. Keromytis and Niels Provos.
 * Copyright (c) 2001, Angelos D. Keromytis.
 *
 * Permission to use, copy, and modify this software with or without fee
 * is hereby granted, provided that this entire notice is included in
 * all copies of any software which is or includes a copy or
 * modification of this software.
 * You may use this code under the GNU public license if you so wish. Please
 * contribute changes back to the authors under this freer than GPL license
 * so that we may further the use of strong encryption without limitations to
 * all.
 *
 * THIS SOFTWARE IS BEING PROVIDED "AS IS", WITHOUT ANY EXPRESS OR
 * IMPLIED WARRANTY. IN PARTICULAR, NONE OF THE AUTHORS MAKES ANY
 * REPRESENTATION OR WARRANTY OF ANY KIND CONCERNING THE
 * MERCHANTABILITY OF THIS SOFTWARE OR ITS FITNESS FOR ANY PARTICULAR
 * PURPOSE.
 */

#include <sys/cdefs.h>
__KERNEL_RCSID(0, "$NetBSD: xform_ipip.c,v 1.80 2025/06/11 02:44:13 ozaki-r Exp $");

#if defined(_KERNEL_OPT)
#include "opt_inet.h"
#endif

/*
 * IP-inside-IP processing.
 *
 * The input point is encapsw{4,6}, called via the encap callback. The
 * output point is ipip_output, called directly. XF_IP4 has no more
 * meaning here, ipe4_xformsw is dummy.
 */

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/mbuf.h>
#include <sys/kernel.h>
#include <sys/protosw.h>

#include <net/if.h>

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

#include <netipsec/ipsec.h>
#include <netipsec/ipsec_private.h>
#include <netipsec/xform.h>

#include <netipsec/ipip_var.h>

#ifdef INET6
#include <netinet/ip6.h>
#include <netipsec/ipsec6.h>
#include <netinet6/in6_var.h>
#include <netinet6/ip6protosw.h>
#endif

#include <netipsec/key.h>
#include <netipsec/key_debug.h>

/* XXX IPCOMP */
#define M_IPSEC (M_AUTHIPHDR|M_DECRYPTED)

int ipip_spoofcheck = 1;
percpu_t *ipipstat_percpu;

static void _ipip_input(struct mbuf *, int);

#ifdef INET6
static int
ip4_input6(struct mbuf **m, int *offp, int proto, void *eparg __unused)
{
        _ipip_input(*m, *offp);
        return IPPROTO_DONE;
}
#endif

#ifdef INET
static void
ip4_input(struct mbuf *m, int off, int proto, void *eparg __unused)
{
        _ipip_input(m, off);
}
#endif

/*
 * _ipip_input gets called when we receive an IP{46} encapsulated packet,
 * because AH or ESP were being used in tunnel mode.
 */
static void
_ipip_input(struct mbuf *m, int iphlen)
{
        register struct sockaddr_in *sin;
        register struct ifnet *ifp;
        register struct ifaddr *ifa;
        pktqueue_t *pktq = NULL;
        struct ip *ip4 = NULL;
#ifdef INET6
        register struct sockaddr_in6 *sin6;
        struct ip6_hdr *ip6 = NULL;
        uint8_t itos;
#endif
        uint8_t otos;
        uint8_t v;
        int hlen;

        IPIP_STATINC(IPIP_STAT_IPACKETS);

        m_copydata(m, 0, 1, &v);

        switch (v >> 4) {
#ifdef INET
        case 4:
                hlen = sizeof(struct ip);
                break;
#endif
#ifdef INET6
        case 6:
                hlen = sizeof(struct ip6_hdr);
                break;
#endif
        default:
                DPRINTF("bad protocol version 0x%x (%u) "
                    "for outer header\n", v, v>>4);
                IPIP_STATINC(IPIP_STAT_FAMILY);
                m_freem(m);
                return;
        }

        /* Bring the IP header in the first mbuf, if not there already */
        if (m->m_len < hlen) {
                if ((m = m_pullup(m, hlen)) == NULL) {
                        DPRINTF("m_pullup (1) failed\n");
                        IPIP_STATINC(IPIP_STAT_HDROPS);
                        return;
                }
        }

        /* Keep outer ecn field. */
        switch (v >> 4) {
#ifdef INET
        case 4:
                otos = mtod(m, struct ip *)->ip_tos;
                break;
#endif
#ifdef INET6
        case 6:
                otos = (ntohl(mtod(m, struct ip6_hdr *)->ip6_flow) >> 20) & 0xff;
                break;
#endif
        default:
                panic("%s: impossible (1)", __func__);
        }

        /* Remove outer IP header */
        m_adj(m, iphlen);

        /* Sanity check */
        if (m->m_pkthdr.len < sizeof(struct ip))  {
                IPIP_STATINC(IPIP_STAT_HDROPS);
                m_freem(m);
                return;
        }

        m_copydata(m, 0, 1, &v);

        switch (v >> 4) {
#ifdef INET
        case 4:
                hlen = sizeof(struct ip);
                pktq = ip_pktq;
                break;
#endif
#ifdef INET6
        case 6:
                hlen = sizeof(struct ip6_hdr);
                pktq = ip6_pktq;
                break;
#endif
        default:
                DPRINTF("bad protocol version %#x (%u) "
                    "for inner header\n", v, v >> 4);
                IPIP_STATINC(IPIP_STAT_FAMILY);
                m_freem(m);
                return;
        }

        /*
         * Bring the inner IP header in the first mbuf, if not there already.
         */
        if (m->m_len < hlen) {
                if ((m = m_pullup(m, hlen)) == NULL) {
                        DPRINTF("m_pullup (2) failed\n");
                        IPIP_STATINC(IPIP_STAT_HDROPS);
                        return;
                }
        }

        /*
         * RFC 1853 specifies that the inner TTL should not be touched on
         * decapsulation. There's no reason this comment should be here, but
         * this is as good as any a position.
         */

        /* Some sanity checks in the inner IP header */
        switch (v >> 4) {
#ifdef INET
        case 4:
                ip4 = mtod(m, struct ip *);
                ip_ecn_egress(ip4_ipsec_ecn, &otos, &ip4->ip_tos);
                break;
#endif
#ifdef INET6
        case 6:
                ip6 = mtod(m, struct ip6_hdr *);
                itos = (ntohl(ip6->ip6_flow) >> 20) & 0xff;
                ip_ecn_egress(ip6_ipsec_ecn, &otos, &itos);
                ip6->ip6_flow &= ~htonl(0xff << 20);
                ip6->ip6_flow |= htonl((uint32_t)itos << 20);
                break;
#endif
        default:
                panic("%s: impossible (2)", __func__);
        }

        /* Check for local address spoofing. */
        if ((m_get_rcvif_NOMPSAFE(m) == NULL ||
            !(m_get_rcvif_NOMPSAFE(m)->if_flags & IFF_LOOPBACK)) &&
            ipip_spoofcheck) {
                int s = pserialize_read_enter();
                IFNET_READER_FOREACH(ifp) {
                        IFADDR_READER_FOREACH(ifa, ifp) {
#ifdef INET
                                if (ip4) {
                                        if (ifa->ifa_addr->sa_family !=
                                            AF_INET)
                                                continue;

                                        sin = (struct sockaddr_in *)ifa->ifa_addr;

                                        if (sin->sin_addr.s_addr ==
                                            ip4->ip_src.s_addr) {
                                                pserialize_read_exit(s);
                                                IPIP_STATINC(IPIP_STAT_SPOOF);
                                                m_freem(m);
                                                return;
                                        }
                                }
#endif

#ifdef INET6
                                if (ip6) {
                                        if (ifa->ifa_addr->sa_family !=
                                            AF_INET6)
                                                continue;

                                        sin6 = (struct sockaddr_in6 *)ifa->ifa_addr;

                                        if (IN6_ARE_ADDR_EQUAL(&sin6->sin6_addr, &ip6->ip6_src)) {
                                                pserialize_read_exit(s);
                                                IPIP_STATINC(IPIP_STAT_SPOOF);
                                                m_freem(m);
                                                return;
                                        }

                                }
#endif
                        }
                }
                pserialize_read_exit(s);
        }

        /* Statistics: m->m_pkthdr.len is the length of the inner packet */
        IPIP_STATADD(IPIP_STAT_IBYTES, m->m_pkthdr.len);

        /*
         * Interface pointer stays the same; if no IPsec processing has
         * been done (or will be done), this will point to a normal
         * interface. Otherwise, it'll point to an enc interface, which
         * will allow a packet filter to distinguish between secure and
         * untrusted packets.
         */

        int s = splnet();
        if (__predict_false(!pktq_enqueue(pktq, m, 0))) {
                IPIP_STATINC(IPIP_STAT_QFULL);
                m_freem(m);
        }
        splx(s);
}

int
ipip_output(struct mbuf *m, struct secasvar *sav, struct mbuf **mp)
{
        char buf[IPSEC_ADDRSTRLEN];
        uint8_t tp, otos;
        struct secasindex *saidx;
        int error, iphlen;
#ifdef INET
        uint8_t itos;
        struct ip *ipo;
#endif
#ifdef INET6
        struct ip6_hdr *ip6, *ip6o;
#endif

        KASSERT(sav != NULL);

        /* XXX Deal with empty TDB source/destination addresses. */

        m_copydata(m, 0, 1, &tp);
        tp = (tp >> 4) & 0xff;  /* Get the IP version number. */

        saidx = &sav->sah->saidx;
        switch (saidx->dst.sa.sa_family) {
#ifdef INET
        case AF_INET:
                if (saidx->src.sa.sa_family != AF_INET ||
                    saidx->src.sin.sin_addr.s_addr == INADDR_ANY ||
                    saidx->dst.sin.sin_addr.s_addr == INADDR_ANY) {
                        DPRINTF("unspecified tunnel endpoint "
                            "address in SA %s/%08lx\n",
                            ipsec_address(&saidx->dst, buf, sizeof(buf)),
                            (u_long)ntohl(sav->spi));
                        IPIP_STATINC(IPIP_STAT_UNSPEC);
                        error = EINVAL;
                        goto bad;
                }

                M_PREPEND(m, sizeof(struct ip), M_DONTWAIT);
                if (m == NULL) {
                        DPRINTF("M_PREPEND failed\n");
                        IPIP_STATINC(IPIP_STAT_HDROPS);
                        error = ENOBUFS;
                        goto bad;
                }

                iphlen = sizeof(struct ip);

                ipo = mtod(m, struct ip *);
                ipo->ip_v = IPVERSION;
                ipo->ip_hl = 5;
                ipo->ip_len = htons(m->m_pkthdr.len);
                ipo->ip_ttl = ip_defttl;
                ipo->ip_sum = 0;
                ipo->ip_src = saidx->src.sin.sin_addr;
                ipo->ip_dst = saidx->dst.sin.sin_addr;
                ipo->ip_id = ip_newid();

                /* If the inner protocol is IP... */
                if (tp == IPVERSION) {
                        /* Save ECN notification */
                        m_copydata(m, sizeof(struct ip) +
                            offsetof(struct ip, ip_tos),
                            sizeof(uint8_t), &itos);

                        ipo->ip_p = IPPROTO_IPIP;

                        /*
                         * We should be keeping tunnel soft-state and
                         * send back ICMPs if needed.
                         */
                        m_copydata(m, sizeof(struct ip) +
                            offsetof(struct ip, ip_off),
                            sizeof(uint16_t), &ipo->ip_off);
                        ipo->ip_off &= ~ htons(IP_DF | IP_MF | IP_OFFMASK);
                }
#ifdef INET6
                else if (tp == (IPV6_VERSION >> 4)) {
                        uint32_t itos32;

                        /* Save ECN notification. */
                        m_copydata(m, sizeof(struct ip) +
                            offsetof(struct ip6_hdr, ip6_flow),
                            sizeof(uint32_t), &itos32);
                        itos = ntohl(itos32) >> 20;
                        ipo->ip_p = IPPROTO_IPV6;
                        ipo->ip_off = 0;
                }
#endif
                else {
                        goto nofamily;
                }

                otos = 0;
                ip_ecn_ingress(ECN_ALLOWED, &otos, &itos);
                ipo->ip_tos = otos;
                break;
#endif /* INET */

#ifdef INET6
        case AF_INET6:
                if (IN6_IS_ADDR_UNSPECIFIED(&saidx->dst.sin6.sin6_addr) ||
                    saidx->src.sa.sa_family != AF_INET6 ||
                    IN6_IS_ADDR_UNSPECIFIED(&saidx->src.sin6.sin6_addr)) {
                        DPRINTF("unspecified tunnel endpoint "
                            "address in SA %s/%08lx\n",
                            ipsec_address(&saidx->dst, buf, sizeof(buf)),
                            (u_long)ntohl(sav->spi));
                        IPIP_STATINC(IPIP_STAT_UNSPEC);
                        error = ENOBUFS;
                        goto bad;
                }

                if (tp == (IPV6_VERSION >> 4)) {
                        /* scoped address handling */
                        ip6 = mtod(m, struct ip6_hdr *);
                        if (IN6_IS_SCOPE_LINKLOCAL(&ip6->ip6_src))
                                ip6->ip6_src.s6_addr16[1] = 0;
                        if (IN6_IS_SCOPE_LINKLOCAL(&ip6->ip6_dst))
                                ip6->ip6_dst.s6_addr16[1] = 0;
                }

                M_PREPEND(m, sizeof(struct ip6_hdr), M_DONTWAIT);
                if (m == NULL) {
                        DPRINTF("M_PREPEND failed\n");
                        IPIP_STATINC(IPIP_STAT_HDROPS);
                        error = ENOBUFS;
                        goto bad;
                }

                iphlen = sizeof(struct ip6_hdr);

                /* Initialize IPv6 header */
                ip6o = mtod(m, struct ip6_hdr *);
                ip6o->ip6_flow = 0;
                ip6o->ip6_vfc &= ~IPV6_VERSION_MASK;
                ip6o->ip6_vfc |= IPV6_VERSION;
                ip6o->ip6_plen = htons(m->m_pkthdr.len - sizeof(*ip6o));
                ip6o->ip6_hlim = ip_defttl;
                ip6o->ip6_dst = saidx->dst.sin6.sin6_addr;
                ip6o->ip6_src = saidx->src.sin6.sin6_addr;
                if (IN6_IS_SCOPE_LINKLOCAL(&ip6o->ip6_dst))
                        ip6o->ip6_dst.s6_addr16[1] = htons(saidx->dst.sin6.sin6_scope_id);
                if (IN6_IS_SCOPE_LINKLOCAL(&ip6o->ip6_src))
                        ip6o->ip6_src.s6_addr16[1] = htons(saidx->src.sin6.sin6_scope_id);

#ifdef INET
                if (tp == IPVERSION) {
                        /* Save ECN notification */
                        m_copydata(m, sizeof(struct ip6_hdr) +
                            offsetof(struct ip, ip_tos), sizeof(uint8_t),
                            &itos);

                        /* This is really IPVERSION. */
                        ip6o->ip6_nxt = IPPROTO_IPIP;
                } else
#endif
                if (tp == (IPV6_VERSION >> 4)) {
                        uint32_t itos32;

                        /* Save ECN notification. */
                        m_copydata(m, sizeof(struct ip6_hdr) +
                            offsetof(struct ip6_hdr, ip6_flow),
                            sizeof(uint32_t), &itos32);
                        itos = ntohl(itos32) >> 20;

                        ip6o->ip6_nxt = IPPROTO_IPV6;
                } else {
                        goto nofamily;
                }

                otos = 0;
                ip_ecn_ingress(ECN_ALLOWED, &otos, &itos);
                ip6o->ip6_flow |= htonl((uint32_t)otos << 20);
                break;
#endif /* INET6 */

        default:
nofamily:
                DPRINTF("unsupported protocol family %u\n",
                    saidx->dst.sa.sa_family);
                IPIP_STATINC(IPIP_STAT_FAMILY);
                error = EAFNOSUPPORT;
                goto bad;
        }

        IPIP_STATINC(IPIP_STAT_OPACKETS);
        IPIP_STATADD(IPIP_STAT_OBYTES, m->m_pkthdr.len - iphlen);

        *mp = m;
        return 0;

bad:
        m_freem(m);
        *mp = NULL;
        return error;
}

#ifdef INET
static struct encapsw ipe4_encapsw = {
        .encapsw4 = {
                .pr_input = ip4_input,
                .pr_ctlinput = NULL,
        }
};
#endif
#ifdef INET6
static struct encapsw ipe4_encapsw6 = {
        .encapsw6 = {
                .pr_input = ip4_input6,
                .pr_ctlinput = NULL,
        }
};
#endif

/*
 * Check the encapsulated packet to see if we want it
 */
static int
ipe4_encapcheck(struct mbuf *m, int off, int proto, void *arg)
{
        /*
         * Only take packets coming from IPSEC tunnels; the rest
         * must be handled by the gif tunnel code.  Note that we
         * also return a minimum priority when we want the packet
         * so any explicit gif tunnels take precedence.
         */
        return ((m->m_flags & M_IPSEC) != 0 ? 1 : 0);
}

/* -------------------------------------------------------------------------- */

static int
ipe4_init(struct secasvar *sav, const struct xformsw *xsp)
{
        sav->tdb_xform = xsp;
        return 0;
}

static void
ipe4_zeroize(struct secasvar *sav)
{
        sav->tdb_xform = NULL;
}

static int
ipe4_input(struct mbuf *m, struct secasvar *sav, int skip, int protoff)
{
        /* This is a rather serious mistake, so no conditional printing. */
        printf("should never be called\n");
        m_freem(m);
        return EOPNOTSUPP;
}

static int
ipe4_output(struct mbuf *m, const struct ipsecrequest *isr,
    struct secasvar *sav, int skip, int protoff, int flags)
{
        panic("%s: should not have been called", __func__);
}

static struct xformsw ipe4_xformsw = {
        .xf_type        = XF_IP4,
        .xf_flags       = 0,
        .xf_name        = "IPv4 Simple Encapsulation",
        .xf_init        = ipe4_init,
        .xf_zeroize     = ipe4_zeroize,
        .xf_input       = ipe4_input,
        .xf_output      = ipe4_output,
        .xf_next        = NULL,
};

/* -------------------------------------------------------------------------- */

void
ipe4_attach(void)
{

        ipipstat_percpu = percpu_alloc(sizeof(uint64_t) * IPIP_NSTATS);

        xform_register(&ipe4_xformsw);
        /* attach to encapsulation framework */
        /* XXX save return cookie for detach on module remove */

        encapinit();
        /* This function is called before ifinit(). Who else gets lock? */
        (void)encap_lock_enter();
        /* ipe4_encapsw and ipe4_encapsw must be added atomically */
#ifdef INET
        (void)encap_attach_func(AF_INET, -1, ipe4_encapcheck, &ipe4_encapsw,
            NULL);
#endif
#ifdef INET6
        (void)encap_attach_func(AF_INET6, -1, ipe4_encapcheck, &ipe4_encapsw6,
            NULL);
#endif
        encap_lock_exit();
}