/*
 *      Extension Header handling for IPv6
 *      Linux INET6 implementation
 *
 *      Authors:
 *      Pedro Roque             <roque@di.fc.ul.pt>
 *      Andi Kleen              <ak@muc.de>
 *      Alexey Kuznetsov        <kuznet@ms2.inr.ac.ru>
 *
 *      This program is free software; you can redistribute it and/or
 *      modify it under the terms of the GNU General Public License
 *      as published by the Free Software Foundation; either version
 *      2 of the License, or (at your option) any later version.
 */

/* Changes:
 *      yoshfuji                : ensure not to overrun while parsing
 *                                tlv options.
 *      Mitsuru KANDA @USAGI and: Remove ipv6_parse_exthdrs().
 *      YOSHIFUJI Hideaki @USAGI  Register inbound extension header
 *                                handlers as inet6_protocol{}.
 */

#include <linux/errno.h>
#include <linux/types.h>
#include <linux/socket.h>
#include <linux/sockios.h>
#include <linux/net.h>
#include <linux/netdevice.h>
#include <linux/in6.h>
#include <linux/icmpv6.h>
#include <linux/slab.h>
#include <linux/export.h>

#include <net/dst.h>
#include <net/sock.h>
#include <net/snmp.h>

#include <net/ipv6.h>
#include <net/protocol.h>
#include <net/transp_v6.h>
#include <net/rawv6.h>
#include <net/ndisc.h>
#include <net/ip6_route.h>
#include <net/addrconf.h>
#include <net/calipso.h>
#if IS_ENABLED(CONFIG_IPV6_MIP6)
#include <net/xfrm.h>
#endif
#include <linux/seg6.h>
#include <net/seg6.h>
#ifdef CONFIG_IPV6_SEG6_HMAC
#include <net/seg6_hmac.h>
#endif

#include <linux/uaccess.h>

/*
 *      Parsing tlv encoded headers.
 *
 *      Parsing function "func" returns true, if parsing succeed
 *      and false, if it failed.
 *      It MUST NOT touch skb->h.
 */

struct tlvtype_proc {
        int     type;
        bool    (*func)(struct sk_buff *skb, int offset);
};

/*********************
  Generic functions
 *********************/

/* An unknown option is detected, decide what to do */

static bool ip6_tlvopt_unknown(struct sk_buff *skb, int optoff,
                               bool disallow_unknowns)
{
        if (disallow_unknowns) {
                /* If unknown TLVs are disallowed by configuration
                 * then always silently drop packet. Note this also
                 * means no ICMP parameter problem is sent which
                 * could be a good property to mitigate a reflection DOS
                 * attack.
                 */

                goto drop;
        }

        switch ((skb_network_header(skb)[optoff] & 0xC0) >> 6) {
        case 0: /* ignore */
                return true;

        case 1: /* drop packet */
                break;

        case 3: /* Send ICMP if not a multicast address and drop packet */
                /* Actually, it is redundant check. icmp_send
                   will recheck in any case.
                 */
                if (ipv6_addr_is_multicast(&ipv6_hdr(skb)->daddr))
                        break;
                /* fall through */
        case 2: /* send ICMP PARM PROB regardless and drop packet */
                icmpv6_param_prob(skb, ICMPV6_UNK_OPTION, optoff);
                return false;
        }

drop:
        kfree_skb(skb);
        return false;
}

/* Parse tlv encoded option header (hop-by-hop or destination) */

static bool ip6_parse_tlv(const struct tlvtype_proc *procs,
                          struct sk_buff *skb,
                          int max_count)
{
        int len = (skb_transport_header(skb)[1] + 1) << 3;
        const unsigned char *nh = skb_network_header(skb);
        int off = skb_network_header_len(skb);
        const struct tlvtype_proc *curr;
        bool disallow_unknowns = false;
        int tlv_count = 0;
        int padlen = 0;

        if (unlikely(max_count < 0)) {
                disallow_unknowns = true;
                max_count = -max_count;
        }

        if (skb_transport_offset(skb) + len > skb_headlen(skb))
                goto bad;

        off += 2;
        len -= 2;

        while (len > 0) {
                int optlen = nh[off + 1] + 2;
                int i;

                switch (nh[off]) {
                case IPV6_TLV_PAD1:
                        optlen = 1;
                        padlen++;
                        if (padlen > 7)
                                goto bad;
                        break;

                case IPV6_TLV_PADN:
                        /* RFC 2460 states that the purpose of PadN is
                         * to align the containing header to multiples
                         * of 8. 7 is therefore the highest valid value.
                         * See also RFC 4942, Section 2.1.9.5.
                         */
                        padlen += optlen;
                        if (padlen > 7)
                                goto bad;
                        /* RFC 4942 recommends receiving hosts to
                         * actively check PadN payload to contain
                         * only zeroes.
                         */
                        for (i = 2; i < optlen; i++) {
                                if (nh[off + i] != 0)
                                        goto bad;
                        }
                        break;

                default: /* Other TLV code so scan list */
                        if (optlen > len)
                                goto bad;

                        tlv_count++;
                        if (tlv_count > max_count)
                                goto bad;

                        for (curr = procs; curr->type >= 0; curr++) {
                                if (curr->type == nh[off]) {
                                        /* type specific length/alignment
                                           checks will be performed in the
                                           func(). */
                                        if (curr->func(skb, off) == false)
                                                return false;
                                        break;
                                }
                        }
                        if (curr->type < 0 &&
                            !ip6_tlvopt_unknown(skb, off, disallow_unknowns))
                                return false;

                        padlen = 0;
                        break;
                }
                off += optlen;
                len -= optlen;
        }

        if (len == 0)
                return true;
bad:
        kfree_skb(skb);
        return false;
}

/*****************************
  Destination options header.
 *****************************/

#if IS_ENABLED(CONFIG_IPV6_MIP6)
static bool ipv6_dest_hao(struct sk_buff *skb, int optoff)
{
        struct ipv6_destopt_hao *hao;
        struct inet6_skb_parm *opt = IP6CB(skb);
        struct ipv6hdr *ipv6h = ipv6_hdr(skb);
        int ret;

        if (opt->dsthao) {
                net_dbg_ratelimited("hao duplicated\n");
                goto discard;
        }
        opt->dsthao = opt->dst1;
        opt->dst1 = 0;

        hao = (struct ipv6_destopt_hao *)(skb_network_header(skb) + optoff);

        if (hao->length != 16) {
                net_dbg_ratelimited("hao invalid option length = %d\n",
                                    hao->length);
                goto discard;
        }

        if (!(ipv6_addr_type(&hao->addr) & IPV6_ADDR_UNICAST)) {
                net_dbg_ratelimited("hao is not an unicast addr: %pI6\n",
                                    &hao->addr);
                goto discard;
        }

        ret = xfrm6_input_addr(skb, (xfrm_address_t *)&ipv6h->daddr,
                               (xfrm_address_t *)&hao->addr, IPPROTO_DSTOPTS);
        if (unlikely(ret < 0))
                goto discard;

        if (skb_cloned(skb)) {
                if (pskb_expand_head(skb, 0, 0, GFP_ATOMIC))
                        goto discard;

                /* update all variable using below by copied skbuff */
                hao = (struct ipv6_destopt_hao *)(skb_network_header(skb) +
                                                  optoff);
                ipv6h = ipv6_hdr(skb);
        }

        if (skb->ip_summed == CHECKSUM_COMPLETE)
                skb->ip_summed = CHECKSUM_NONE;

        swap(ipv6h->saddr, hao->addr);

        if (skb->tstamp == 0)
                __net_timestamp(skb);

        return true;

 discard:
        kfree_skb(skb);
        return false;
}
#endif

static const struct tlvtype_proc tlvprocdestopt_lst[] = {
#if IS_ENABLED(CONFIG_IPV6_MIP6)
        {
                .type   = IPV6_TLV_HAO,
                .func   = ipv6_dest_hao,
        },
#endif
        {-1,                    NULL}
};

static int ipv6_destopt_rcv(struct sk_buff *skb)
{
        struct inet6_skb_parm *opt = IP6CB(skb);
#if IS_ENABLED(CONFIG_IPV6_MIP6)
        __u16 dstbuf;
#endif
        struct dst_entry *dst = skb_dst(skb);
        struct net *net = dev_net(skb->dev);
        int extlen;

        if (!pskb_may_pull(skb, skb_transport_offset(skb) + 8) ||
            !pskb_may_pull(skb, (skb_transport_offset(skb) +
                                 ((skb_transport_header(skb)[1] + 1) << 3)))) {
                __IP6_INC_STATS(dev_net(dst->dev), ip6_dst_idev(dst),
                                IPSTATS_MIB_INHDRERRORS);
fail_and_free:
                kfree_skb(skb);
                return -1;
        }

        extlen = (skb_transport_header(skb)[1] + 1) << 3;
        if (extlen > net->ipv6.sysctl.max_dst_opts_len)
                goto fail_and_free;

        opt->lastopt = opt->dst1 = skb_network_header_len(skb);
#if IS_ENABLED(CONFIG_IPV6_MIP6)
        dstbuf = opt->dst1;
#endif

        if (ip6_parse_tlv(tlvprocdestopt_lst, skb,
                          init_net.ipv6.sysctl.max_dst_opts_cnt)) {
                skb->transport_header += extlen;
                opt = IP6CB(skb);
#if IS_ENABLED(CONFIG_IPV6_MIP6)
                opt->nhoff = dstbuf;
#else
                opt->nhoff = opt->dst1;
#endif
                return 1;
        }

        __IP6_INC_STATS(dev_net(dst->dev),
                        ip6_dst_idev(dst), IPSTATS_MIB_INHDRERRORS);
        return -1;
}

static void seg6_update_csum(struct sk_buff *skb)
{
        struct ipv6_sr_hdr *hdr;
        struct in6_addr *addr;
        __be32 from, to;

        /* srh is at transport offset and seg_left is already decremented
         * but daddr is not yet updated with next segment
         */

        hdr = (struct ipv6_sr_hdr *)skb_transport_header(skb);
        addr = hdr->segments + hdr->segments_left;

        hdr->segments_left++;
        from = *(__be32 *)hdr;

        hdr->segments_left--;
        to = *(__be32 *)hdr;

        /* update skb csum with diff resulting from seg_left decrement */

        update_csum_diff4(skb, from, to);

        /* compute csum diff between current and next segment and update */

        update_csum_diff16(skb, (__be32 *)(&ipv6_hdr(skb)->daddr),
                           (__be32 *)addr);
}

static int ipv6_srh_rcv(struct sk_buff *skb)
{
        struct inet6_skb_parm *opt = IP6CB(skb);
        struct net *net = dev_net(skb->dev);
        struct ipv6_sr_hdr *hdr;
        struct inet6_dev *idev;
        struct in6_addr *addr;
        int accept_seg6;

        hdr = (struct ipv6_sr_hdr *)skb_transport_header(skb);

        idev = __in6_dev_get(skb->dev);

        accept_seg6 = net->ipv6.devconf_all->seg6_enabled;
        if (accept_seg6 > idev->cnf.seg6_enabled)
                accept_seg6 = idev->cnf.seg6_enabled;

        if (!accept_seg6) {
                kfree_skb(skb);
                return -1;
        }

#ifdef CONFIG_IPV6_SEG6_HMAC
        if (!seg6_hmac_validate_skb(skb)) {
                kfree_skb(skb);
                return -1;
        }
#endif

looped_back:
        if (hdr->segments_left == 0) {
                if (hdr->nexthdr == NEXTHDR_IPV6) {
                        int offset = (hdr->hdrlen + 1) << 3;

                        skb_postpull_rcsum(skb, skb_network_header(skb),
                                           skb_network_header_len(skb));

                        if (!pskb_pull(skb, offset)) {
                                kfree_skb(skb);
                                return -1;
                        }
                        skb_postpull_rcsum(skb, skb_transport_header(skb),
                                           offset);

                        skb_reset_network_header(skb);
                        skb_reset_transport_header(skb);
                        skb->encapsulation = 0;

                        __skb_tunnel_rx(skb, skb->dev, net);

                        netif_rx(skb);
                        return -1;
                }

                opt->srcrt = skb_network_header_len(skb);
                opt->lastopt = opt->srcrt;
                skb->transport_header += (hdr->hdrlen + 1) << 3;
                opt->nhoff = (&hdr->nexthdr) - skb_network_header(skb);

                return 1;
        }

        if (hdr->segments_left >= (hdr->hdrlen >> 1)) {
                __IP6_INC_STATS(net, ip6_dst_idev(skb_dst(skb)),
                                IPSTATS_MIB_INHDRERRORS);
                icmpv6_param_prob(skb, ICMPV6_HDR_FIELD,
                                  ((&hdr->segments_left) -
                                   skb_network_header(skb)));
                return -1;
        }

        if (skb_cloned(skb)) {
                if (pskb_expand_head(skb, 0, 0, GFP_ATOMIC)) {
                        __IP6_INC_STATS(net, ip6_dst_idev(skb_dst(skb)),
                                        IPSTATS_MIB_OUTDISCARDS);
                        kfree_skb(skb);
                        return -1;
                }
        }

        hdr = (struct ipv6_sr_hdr *)skb_transport_header(skb);

        hdr->segments_left--;
        addr = hdr->segments + hdr->segments_left;

        skb_push(skb, sizeof(struct ipv6hdr));

        if (skb->ip_summed == CHECKSUM_COMPLETE)
                seg6_update_csum(skb);

        ipv6_hdr(skb)->daddr = *addr;

        skb_dst_drop(skb);

        ip6_route_input(skb);

        if (skb_dst(skb)->error) {
                dst_input(skb);
                return -1;
        }

        if (skb_dst(skb)->dev->flags & IFF_LOOPBACK) {
                if (ipv6_hdr(skb)->hop_limit <= 1) {
                        __IP6_INC_STATS(net, ip6_dst_idev(skb_dst(skb)),
                                        IPSTATS_MIB_INHDRERRORS);
                        icmpv6_send(skb, ICMPV6_TIME_EXCEED,
                                    ICMPV6_EXC_HOPLIMIT, 0);
                        kfree_skb(skb);
                        return -1;
                }
                ipv6_hdr(skb)->hop_limit--;

                skb_pull(skb, sizeof(struct ipv6hdr));
                goto looped_back;
        }

        dst_input(skb);

        return -1;
}

/********************************
  Routing header.
 ********************************/

/* called with rcu_read_lock() */
static int ipv6_rthdr_rcv(struct sk_buff *skb)
{
        struct inet6_skb_parm *opt = IP6CB(skb);
        struct in6_addr *addr = NULL;
        struct in6_addr daddr;
        struct inet6_dev *idev;
        int n, i;
        struct ipv6_rt_hdr *hdr;
        struct rt0_hdr *rthdr;
        struct net *net = dev_net(skb->dev);
        int accept_source_route = net->ipv6.devconf_all->accept_source_route;

        idev = __in6_dev_get(skb->dev);
        if (idev && accept_source_route > idev->cnf.accept_source_route)
                accept_source_route = idev->cnf.accept_source_route;

        if (!pskb_may_pull(skb, skb_transport_offset(skb) + 8) ||
            !pskb_may_pull(skb, (skb_transport_offset(skb) +
                                 ((skb_transport_header(skb)[1] + 1) << 3)))) {
                __IP6_INC_STATS(net, ip6_dst_idev(skb_dst(skb)),
                                IPSTATS_MIB_INHDRERRORS);
                kfree_skb(skb);
                return -1;
        }

        hdr = (struct ipv6_rt_hdr *)skb_transport_header(skb);

        if (ipv6_addr_is_multicast(&ipv6_hdr(skb)->daddr) ||
            skb->pkt_type != PACKET_HOST) {
                __IP6_INC_STATS(net, ip6_dst_idev(skb_dst(skb)),
                                IPSTATS_MIB_INADDRERRORS);
                kfree_skb(skb);
                return -1;
        }

        /* segment routing */
        if (hdr->type == IPV6_SRCRT_TYPE_4)
                return ipv6_srh_rcv(skb);

looped_back:
        if (hdr->segments_left == 0) {
                switch (hdr->type) {
#if IS_ENABLED(CONFIG_IPV6_MIP6)
                case IPV6_SRCRT_TYPE_2:
                        /* Silently discard type 2 header unless it was
                         * processed by own
                         */
                        if (!addr) {
                                __IP6_INC_STATS(net, ip6_dst_idev(skb_dst(skb)),
                                                IPSTATS_MIB_INADDRERRORS);
                                kfree_skb(skb);
                                return -1;
                        }
                        break;
#endif
                default:
                        break;
                }

                opt->lastopt = opt->srcrt = skb_network_header_len(skb);
                skb->transport_header += (hdr->hdrlen + 1) << 3;
                opt->dst0 = opt->dst1;
                opt->dst1 = 0;
                opt->nhoff = (&hdr->nexthdr) - skb_network_header(skb);
                return 1;
        }

        switch (hdr->type) {
#if IS_ENABLED(CONFIG_IPV6_MIP6)
        case IPV6_SRCRT_TYPE_2:
                if (accept_source_route < 0)
                        goto unknown_rh;
                /* Silently discard invalid RTH type 2 */
                if (hdr->hdrlen != 2 || hdr->segments_left != 1) {
                        __IP6_INC_STATS(net, ip6_dst_idev(skb_dst(skb)),
                                        IPSTATS_MIB_INHDRERRORS);
                        kfree_skb(skb);
                        return -1;
                }
                break;
#endif
        default:
                goto unknown_rh;
        }

        /*
         *      This is the routing header forwarding algorithm from
         *      RFC 2460, page 16.
         */

        n = hdr->hdrlen >> 1;

        if (hdr->segments_left > n) {
                __IP6_INC_STATS(net, ip6_dst_idev(skb_dst(skb)),
                                IPSTATS_MIB_INHDRERRORS);
                icmpv6_param_prob(skb, ICMPV6_HDR_FIELD,
                                  ((&hdr->segments_left) -
                                   skb_network_header(skb)));
                return -1;
        }

        /* We are about to mangle packet header. Be careful!
           Do not damage packets queued somewhere.
         */
        if (skb_cloned(skb)) {
                /* the copy is a forwarded packet */
                if (pskb_expand_head(skb, 0, 0, GFP_ATOMIC)) {
                        __IP6_INC_STATS(net, ip6_dst_idev(skb_dst(skb)),
                                        IPSTATS_MIB_OUTDISCARDS);
                        kfree_skb(skb);
                        return -1;
                }
                hdr = (struct ipv6_rt_hdr *)skb_transport_header(skb);
        }

        if (skb->ip_summed == CHECKSUM_COMPLETE)
                skb->ip_summed = CHECKSUM_NONE;

        i = n - --hdr->segments_left;

        rthdr = (struct rt0_hdr *) hdr;
        addr = rthdr->addr;
        addr += i - 1;

        switch (hdr->type) {
#if IS_ENABLED(CONFIG_IPV6_MIP6)
        case IPV6_SRCRT_TYPE_2:
                if (xfrm6_input_addr(skb, (xfrm_address_t *)addr,
                                     (xfrm_address_t *)&ipv6_hdr(skb)->saddr,
                                     IPPROTO_ROUTING) < 0) {
                        __IP6_INC_STATS(net, ip6_dst_idev(skb_dst(skb)),
                                        IPSTATS_MIB_INADDRERRORS);
                        kfree_skb(skb);
                        return -1;
                }
                if (!ipv6_chk_home_addr(dev_net(skb_dst(skb)->dev), addr)) {
                        __IP6_INC_STATS(net, ip6_dst_idev(skb_dst(skb)),
                                        IPSTATS_MIB_INADDRERRORS);
                        kfree_skb(skb);
                        return -1;
                }
                break;
#endif
        default:
                break;
        }

        if (ipv6_addr_is_multicast(addr)) {
                __IP6_INC_STATS(net, ip6_dst_idev(skb_dst(skb)),
                                IPSTATS_MIB_INADDRERRORS);
                kfree_skb(skb);
                return -1;
        }

        daddr = *addr;
        *addr = ipv6_hdr(skb)->daddr;
        ipv6_hdr(skb)->daddr = daddr;

        skb_dst_drop(skb);
        ip6_route_input(skb);
        if (skb_dst(skb)->error) {
                skb_push(skb, skb->data - skb_network_header(skb));
                dst_input(skb);
                return -1;
        }

        if (skb_dst(skb)->dev->flags&IFF_LOOPBACK) {
                if (ipv6_hdr(skb)->hop_limit <= 1) {
                        __IP6_INC_STATS(net, ip6_dst_idev(skb_dst(skb)),
                                        IPSTATS_MIB_INHDRERRORS);
                        icmpv6_send(skb, ICMPV6_TIME_EXCEED, ICMPV6_EXC_HOPLIMIT,
                                    0);
                        kfree_skb(skb);
                        return -1;
                }
                ipv6_hdr(skb)->hop_limit--;
                goto looped_back;
        }

        skb_push(skb, skb->data - skb_network_header(skb));
        dst_input(skb);
        return -1;

unknown_rh:
        __IP6_INC_STATS(net, ip6_dst_idev(skb_dst(skb)), IPSTATS_MIB_INHDRERRORS);
        icmpv6_param_prob(skb, ICMPV6_HDR_FIELD,
                          (&hdr->type) - skb_network_header(skb));
        return -1;
}

static const struct inet6_protocol rthdr_protocol = {
        .handler        =       ipv6_rthdr_rcv,
        .flags          =       INET6_PROTO_NOPOLICY,
};

static const struct inet6_protocol destopt_protocol = {
        .handler        =       ipv6_destopt_rcv,
        .flags          =       INET6_PROTO_NOPOLICY,
};

static const struct inet6_protocol nodata_protocol = {
        .handler        =       dst_discard,
        .flags          =       INET6_PROTO_NOPOLICY,
};

int __init ipv6_exthdrs_init(void)
{
        int ret;

        ret = inet6_add_protocol(&rthdr_protocol, IPPROTO_ROUTING);
        if (ret)
                goto out;

        ret = inet6_add_protocol(&destopt_protocol, IPPROTO_DSTOPTS);
        if (ret)
                goto out_rthdr;

        ret = inet6_add_protocol(&nodata_protocol, IPPROTO_NONE);
        if (ret)
                goto out_destopt;

out:
        return ret;
out_destopt:
        inet6_del_protocol(&destopt_protocol, IPPROTO_DSTOPTS);
out_rthdr:
        inet6_del_protocol(&rthdr_protocol, IPPROTO_ROUTING);
        goto out;
};

void ipv6_exthdrs_exit(void)
{
        inet6_del_protocol(&nodata_protocol, IPPROTO_NONE);
        inet6_del_protocol(&destopt_protocol, IPPROTO_DSTOPTS);
        inet6_del_protocol(&rthdr_protocol, IPPROTO_ROUTING);
}

/**********************************
  Hop-by-hop options.
 **********************************/

/*
 * Note: we cannot rely on skb_dst(skb) before we assign it in ip6_route_input().
 */
static inline struct inet6_dev *ipv6_skb_idev(struct sk_buff *skb)
{
        return skb_dst(skb) ? ip6_dst_idev(skb_dst(skb)) : __in6_dev_get(skb->dev);
}

static inline struct net *ipv6_skb_net(struct sk_buff *skb)
{
        return skb_dst(skb) ? dev_net(skb_dst(skb)->dev) : dev_net(skb->dev);
}

/* Router Alert as of RFC 2711 */

static bool ipv6_hop_ra(struct sk_buff *skb, int optoff)
{
        const unsigned char *nh = skb_network_header(skb);

        if (nh[optoff + 1] == 2) {
                IP6CB(skb)->flags |= IP6SKB_ROUTERALERT;
                memcpy(&IP6CB(skb)->ra, nh + optoff + 2, sizeof(IP6CB(skb)->ra));
                return true;
        }
        net_dbg_ratelimited("ipv6_hop_ra: wrong RA length %d\n",
                            nh[optoff + 1]);
        kfree_skb(skb);
        return false;
}

/* Jumbo payload */

static bool ipv6_hop_jumbo(struct sk_buff *skb, int optoff)
{
        const unsigned char *nh = skb_network_header(skb);
        struct net *net = ipv6_skb_net(skb);
        u32 pkt_len;

        if (nh[optoff + 1] != 4 || (optoff & 3) != 2) {
                net_dbg_ratelimited("ipv6_hop_jumbo: wrong jumbo opt length/alignment %d\n",
                                    nh[optoff+1]);
                __IP6_INC_STATS(net, ipv6_skb_idev(skb),
                                IPSTATS_MIB_INHDRERRORS);
                goto drop;
        }

        pkt_len = ntohl(*(__be32 *)(nh + optoff + 2));
        if (pkt_len <= IPV6_MAXPLEN) {
                __IP6_INC_STATS(net, ipv6_skb_idev(skb),
                                IPSTATS_MIB_INHDRERRORS);
                icmpv6_param_prob(skb, ICMPV6_HDR_FIELD, optoff+2);
                return false;
        }
        if (ipv6_hdr(skb)->payload_len) {
                __IP6_INC_STATS(net, ipv6_skb_idev(skb),
                                IPSTATS_MIB_INHDRERRORS);
                icmpv6_param_prob(skb, ICMPV6_HDR_FIELD, optoff);
                return false;
        }

        if (pkt_len > skb->len - sizeof(struct ipv6hdr)) {
                __IP6_INC_STATS(net, ipv6_skb_idev(skb),
                                IPSTATS_MIB_INTRUNCATEDPKTS);
                goto drop;
        }

        if (pskb_trim_rcsum(skb, pkt_len + sizeof(struct ipv6hdr)))
                goto drop;

        IP6CB(skb)->flags |= IP6SKB_JUMBOGRAM;
        return true;

drop:
        kfree_skb(skb);
        return false;
}

/* CALIPSO RFC 5570 */

static bool ipv6_hop_calipso(struct sk_buff *skb, int optoff)
{
        const unsigned char *nh = skb_network_header(skb);

        if (nh[optoff + 1] < 8)
                goto drop;

        if (nh[optoff + 6] * 4 + 8 > nh[optoff + 1])
                goto drop;

        if (!calipso_validate(skb, nh + optoff))
                goto drop;

        return true;

drop:
        kfree_skb(skb);
        return false;
}

static const struct tlvtype_proc tlvprochopopt_lst[] = {
        {
                .type   = IPV6_TLV_ROUTERALERT,
                .func   = ipv6_hop_ra,
        },
        {
                .type   = IPV6_TLV_JUMBO,
                .func   = ipv6_hop_jumbo,
        },
        {
                .type   = IPV6_TLV_CALIPSO,
                .func   = ipv6_hop_calipso,
        },
        { -1, }
};

int ipv6_parse_hopopts(struct sk_buff *skb)
{
        struct inet6_skb_parm *opt = IP6CB(skb);
        struct net *net = dev_net(skb->dev);
        int extlen;

        /*
         * skb_network_header(skb) is equal to skb->data, and
         * skb_network_header_len(skb) is always equal to
         * sizeof(struct ipv6hdr) by definition of
         * hop-by-hop options.
         */
        if (!pskb_may_pull(skb, sizeof(struct ipv6hdr) + 8) ||
            !pskb_may_pull(skb, (sizeof(struct ipv6hdr) +
                                 ((skb_transport_header(skb)[1] + 1) << 3)))) {
fail_and_free:
                kfree_skb(skb);
                return -1;
        }

        extlen = (skb_transport_header(skb)[1] + 1) << 3;
        if (extlen > net->ipv6.sysctl.max_hbh_opts_len)
                goto fail_and_free;

        opt->flags |= IP6SKB_HOPBYHOP;
        if (ip6_parse_tlv(tlvprochopopt_lst, skb,
                          init_net.ipv6.sysctl.max_hbh_opts_cnt)) {
                skb->transport_header += extlen;
                opt = IP6CB(skb);
                opt->nhoff = sizeof(struct ipv6hdr);
                return 1;
        }
        return -1;
}

/*
 *      Creating outbound headers.
 *
 *      "build" functions work when skb is filled from head to tail (datagram)
 *      "push"  functions work when headers are added from tail to head (tcp)
 *
 *      In both cases we assume, that caller reserved enough room
 *      for headers.
 */

static void ipv6_push_rthdr0(struct sk_buff *skb, u8 *proto,
                             struct ipv6_rt_hdr *opt,
                             struct in6_addr **addr_p, struct in6_addr *saddr)
{
        struct rt0_hdr *phdr, *ihdr;
        int hops;

        ihdr = (struct rt0_hdr *) opt;

        phdr = skb_push(skb, (ihdr->rt_hdr.hdrlen + 1) << 3);
        memcpy(phdr, ihdr, sizeof(struct rt0_hdr));

        hops = ihdr->rt_hdr.hdrlen >> 1;

        if (hops > 1)
                memcpy(phdr->addr, ihdr->addr + 1,
                       (hops - 1) * sizeof(struct in6_addr));

        phdr->addr[hops - 1] = **addr_p;
        *addr_p = ihdr->addr;

        phdr->rt_hdr.nexthdr = *proto;
        *proto = NEXTHDR_ROUTING;
}

static void ipv6_push_rthdr4(struct sk_buff *skb, u8 *proto,
                             struct ipv6_rt_hdr *opt,
                             struct in6_addr **addr_p, struct in6_addr *saddr)
{
        struct ipv6_sr_hdr *sr_phdr, *sr_ihdr;
        int plen, hops;

        sr_ihdr = (struct ipv6_sr_hdr *)opt;
        plen = (sr_ihdr->hdrlen + 1) << 3;

        sr_phdr = skb_push(skb, plen);
        memcpy(sr_phdr, sr_ihdr, sizeof(struct ipv6_sr_hdr));

        hops = sr_ihdr->first_segment + 1;
        memcpy(sr_phdr->segments + 1, sr_ihdr->segments + 1,
               (hops - 1) * sizeof(struct in6_addr));

        sr_phdr->segments[0] = **addr_p;
        *addr_p = &sr_ihdr->segments[sr_ihdr->segments_left];

        if (sr_ihdr->hdrlen > hops * 2) {
                int tlvs_offset, tlvs_length;

                tlvs_offset = (1 + hops * 2) << 3;
                tlvs_length = (sr_ihdr->hdrlen - hops * 2) << 3;
                memcpy((char *)sr_phdr + tlvs_offset,
                       (char *)sr_ihdr + tlvs_offset, tlvs_length);
        }

#ifdef CONFIG_IPV6_SEG6_HMAC
        if (sr_has_hmac(sr_phdr)) {
                struct net *net = NULL;

                if (skb->dev)
                        net = dev_net(skb->dev);
                else if (skb->sk)
                        net = sock_net(skb->sk);

                WARN_ON(!net);

                if (net)
                        seg6_push_hmac(net, saddr, sr_phdr);
        }
#endif

        sr_phdr->nexthdr = *proto;
        *proto = NEXTHDR_ROUTING;
}

static void ipv6_push_rthdr(struct sk_buff *skb, u8 *proto,
                            struct ipv6_rt_hdr *opt,
                            struct in6_addr **addr_p, struct in6_addr *saddr)
{
        switch (opt->type) {
        case IPV6_SRCRT_TYPE_0:
        case IPV6_SRCRT_STRICT:
        case IPV6_SRCRT_TYPE_2:
                ipv6_push_rthdr0(skb, proto, opt, addr_p, saddr);
                break;
        case IPV6_SRCRT_TYPE_4:
                ipv6_push_rthdr4(skb, proto, opt, addr_p, saddr);
                break;
        default:
                break;
        }
}

static void ipv6_push_exthdr(struct sk_buff *skb, u8 *proto, u8 type, struct ipv6_opt_hdr *opt)
{
        struct ipv6_opt_hdr *h = skb_push(skb, ipv6_optlen(opt));

        memcpy(h, opt, ipv6_optlen(opt));
        h->nexthdr = *proto;
        *proto = type;
}

void ipv6_push_nfrag_opts(struct sk_buff *skb, struct ipv6_txoptions *opt,
                          u8 *proto,
                          struct in6_addr **daddr, struct in6_addr *saddr)
{
        if (opt->srcrt) {
                ipv6_push_rthdr(skb, proto, opt->srcrt, daddr, saddr);
                /*
                 * IPV6_RTHDRDSTOPTS is ignored
                 * unless IPV6_RTHDR is set (RFC3542).
                 */
                if (opt->dst0opt)
                        ipv6_push_exthdr(skb, proto, NEXTHDR_DEST, opt->dst0opt);
        }
        if (opt->hopopt)
                ipv6_push_exthdr(skb, proto, NEXTHDR_HOP, opt->hopopt);
}

void ipv6_push_frag_opts(struct sk_buff *skb, struct ipv6_txoptions *opt, u8 *proto)
{
        if (opt->dst1opt)
                ipv6_push_exthdr(skb, proto, NEXTHDR_DEST, opt->dst1opt);
}
EXPORT_SYMBOL(ipv6_push_frag_opts);

struct ipv6_txoptions *
ipv6_dup_options(struct sock *sk, struct ipv6_txoptions *opt)
{
        struct ipv6_txoptions *opt2;

        opt2 = sock_kmalloc(sk, opt->tot_len, GFP_ATOMIC);
        if (opt2) {
                long dif = (char *)opt2 - (char *)opt;
                memcpy(opt2, opt, opt->tot_len);
                if (opt2->hopopt)
                        *((char **)&opt2->hopopt) += dif;
                if (opt2->dst0opt)
                        *((char **)&opt2->dst0opt) += dif;
                if (opt2->dst1opt)
                        *((char **)&opt2->dst1opt) += dif;
                if (opt2->srcrt)
                        *((char **)&opt2->srcrt) += dif;
                refcount_set(&opt2->refcnt, 1);
        }
        return opt2;
}
EXPORT_SYMBOL_GPL(ipv6_dup_options);

static int ipv6_renew_option(void *ohdr,
                             struct ipv6_opt_hdr __user *newopt, int newoptlen,
                             int inherit,
                             struct ipv6_opt_hdr **hdr,
                             char **p)
{
        if (inherit) {
                if (ohdr) {
                        memcpy(*p, ohdr, ipv6_optlen((struct ipv6_opt_hdr *)ohdr));
                        *hdr = (struct ipv6_opt_hdr *)*p;
                        *p += CMSG_ALIGN(ipv6_optlen(*hdr));
                }
        } else {
                if (newopt) {
                        if (copy_from_user(*p, newopt, newoptlen))
                                return -EFAULT;
                        *hdr = (struct ipv6_opt_hdr *)*p;
                        if (ipv6_optlen(*hdr) > newoptlen)
                                return -EINVAL;
                        *p += CMSG_ALIGN(newoptlen);
                }
        }
        return 0;
}

/**
 * ipv6_renew_options - replace a specific ext hdr with a new one.
 *
 * @sk: sock from which to allocate memory
 * @opt: original options
 * @newtype: option type to replace in @opt
 * @newopt: new option of type @newtype to replace (user-mem)
 * @newoptlen: length of @newopt
 *
 * Returns a new set of options which is a copy of @opt with the
 * option type @newtype replaced with @newopt.
 *
 * @opt may be NULL, in which case a new set of options is returned
 * containing just @newopt.
 *
 * @newopt may be NULL, in which case the specified option type is
 * not copied into the new set of options.
 *
 * The new set of options is allocated from the socket option memory
 * buffer of @sk.
 */
struct ipv6_txoptions *
ipv6_renew_options(struct sock *sk, struct ipv6_txoptions *opt,
                   int newtype,
                   struct ipv6_opt_hdr __user *newopt, int newoptlen)
{
        int tot_len = 0;
        char *p;
        struct ipv6_txoptions *opt2;
        int err;

        if (opt) {
                if (newtype != IPV6_HOPOPTS && opt->hopopt)
                        tot_len += CMSG_ALIGN(ipv6_optlen(opt->hopopt));
                if (newtype != IPV6_RTHDRDSTOPTS && opt->dst0opt)
                        tot_len += CMSG_ALIGN(ipv6_optlen(opt->dst0opt));
                if (newtype != IPV6_RTHDR && opt->srcrt)
                        tot_len += CMSG_ALIGN(ipv6_optlen(opt->srcrt));
                if (newtype != IPV6_DSTOPTS && opt->dst1opt)
                        tot_len += CMSG_ALIGN(ipv6_optlen(opt->dst1opt));
        }

        if (newopt && newoptlen)
                tot_len += CMSG_ALIGN(newoptlen);

        if (!tot_len)
                return NULL;

        tot_len += sizeof(*opt2);
        opt2 = sock_kmalloc(sk, tot_len, GFP_ATOMIC);
        if (!opt2)
                return ERR_PTR(-ENOBUFS);

        memset(opt2, 0, tot_len);
        refcount_set(&opt2->refcnt, 1);
        opt2->tot_len = tot_len;
        p = (char *)(opt2 + 1);

        err = ipv6_renew_option(opt ? opt->hopopt : NULL, newopt, newoptlen,
                                newtype != IPV6_HOPOPTS,
                                &opt2->hopopt, &p);
        if (err)
                goto out;

        err = ipv6_renew_option(opt ? opt->dst0opt : NULL, newopt, newoptlen,
                                newtype != IPV6_RTHDRDSTOPTS,
                                &opt2->dst0opt, &p);
        if (err)
                goto out;

        err = ipv6_renew_option(opt ? opt->srcrt : NULL, newopt, newoptlen,
                                newtype != IPV6_RTHDR,
                                (struct ipv6_opt_hdr **)&opt2->srcrt, &p);
        if (err)
                goto out;

        err = ipv6_renew_option(opt ? opt->dst1opt : NULL, newopt, newoptlen,
                                newtype != IPV6_DSTOPTS,
                                &opt2->dst1opt, &p);
        if (err)
                goto out;

        opt2->opt_nflen = (opt2->hopopt ? ipv6_optlen(opt2->hopopt) : 0) +
                          (opt2->dst0opt ? ipv6_optlen(opt2->dst0opt) : 0) +
                          (opt2->srcrt ? ipv6_optlen(opt2->srcrt) : 0);
        opt2->opt_flen = (opt2->dst1opt ? ipv6_optlen(opt2->dst1opt) : 0);

        return opt2;
out:
        sock_kfree_s(sk, opt2, opt2->tot_len);
        return ERR_PTR(err);
}

/**
 * ipv6_renew_options_kern - replace a specific ext hdr with a new one.
 *
 * @sk: sock from which to allocate memory
 * @opt: original options
 * @newtype: option type to replace in @opt
 * @newopt: new option of type @newtype to replace (kernel-mem)
 * @newoptlen: length of @newopt
 *
 * See ipv6_renew_options().  The difference is that @newopt is
 * kernel memory, rather than user memory.
 */
struct ipv6_txoptions *
ipv6_renew_options_kern(struct sock *sk, struct ipv6_txoptions *opt,
                        int newtype, struct ipv6_opt_hdr *newopt,
                        int newoptlen)
{
        struct ipv6_txoptions *ret_val;
        const mm_segment_t old_fs = get_fs();

        set_fs(KERNEL_DS);
        ret_val = ipv6_renew_options(sk, opt, newtype,
                                     (struct ipv6_opt_hdr __user *)newopt,
                                     newoptlen);
        set_fs(old_fs);
        return ret_val;
}

struct ipv6_txoptions *ipv6_fixup_options(struct ipv6_txoptions *opt_space,
                                          struct ipv6_txoptions *opt)
{
        /*
         * ignore the dest before srcrt unless srcrt is being included.
         * --yoshfuji
         */
        if (opt && opt->dst0opt && !opt->srcrt) {
                if (opt_space != opt) {
                        memcpy(opt_space, opt, sizeof(*opt_space));
                        opt = opt_space;
                }
                opt->opt_nflen -= ipv6_optlen(opt->dst0opt);
                opt->dst0opt = NULL;
        }

        return opt;
}
EXPORT_SYMBOL_GPL(ipv6_fixup_options);

/**
 * fl6_update_dst - update flowi destination address with info given
 *                  by srcrt option, if any.
 *
 * @fl6: flowi6 for which daddr is to be updated
 * @opt: struct ipv6_txoptions in which to look for srcrt opt
 * @orig: copy of original daddr address if modified
 *
 * Returns NULL if no txoptions or no srcrt, otherwise returns orig
 * and initial value of fl6->daddr set in orig
 */
struct in6_addr *fl6_update_dst(struct flowi6 *fl6,
                                const struct ipv6_txoptions *opt,
                                struct in6_addr *orig)
{
        if (!opt || !opt->srcrt)
                return NULL;

        *orig = fl6->daddr;

        switch (opt->srcrt->type) {
        case IPV6_SRCRT_TYPE_0:
        case IPV6_SRCRT_STRICT:
        case IPV6_SRCRT_TYPE_2:
                fl6->daddr = *((struct rt0_hdr *)opt->srcrt)->addr;
                break;
        case IPV6_SRCRT_TYPE_4:
        {
                struct ipv6_sr_hdr *srh = (struct ipv6_sr_hdr *)opt->srcrt;

                fl6->daddr = srh->segments[srh->segments_left];
                break;
        }
        default:
                return NULL;
        }

        return orig;
}
EXPORT_SYMBOL_GPL(fl6_update_dst);