// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * xfrm_output.c - Common IPsec encapsulation code.
 *
 * Copyright (c) 2007 Herbert Xu <herbert@gondor.apana.org.au>
 */

#include <linux/errno.h>
#include <linux/module.h>
#include <linux/netdevice.h>
#include <linux/netfilter.h>
#include <linux/skbuff.h>
#include <linux/slab.h>
#include <linux/spinlock.h>
#include <net/dst.h>
#include <net/gso.h>
#include <net/icmp.h>
#include <net/inet_ecn.h>
#include <net/xfrm.h>

#if IS_ENABLED(CONFIG_IPV6)
#include <net/ip6_route.h>
#include <net/ipv6_stubs.h>
#endif

#include "xfrm_inout.h"

static int xfrm_output2(struct net *net, struct sock *sk, struct sk_buff *skb);
static int xfrm_inner_extract_output(struct xfrm_state *x, struct sk_buff *skb);

static int xfrm_skb_check_space(struct sk_buff *skb)
{
        struct dst_entry *dst = skb_dst(skb);
        int nhead = dst->header_len + LL_RESERVED_SPACE(dst->dev)
                - skb_headroom(skb);
        int ntail = dst->dev->needed_tailroom - skb_tailroom(skb);

        if (nhead <= 0) {
                if (ntail <= 0)
                        return 0;
                nhead = 0;
        } else if (ntail < 0)
                ntail = 0;

        return pskb_expand_head(skb, nhead, ntail, GFP_ATOMIC);
}

/* Children define the path of the packet through the
 * Linux networking.  Thus, destinations are stackable.
 */

static struct dst_entry *skb_dst_pop(struct sk_buff *skb)
{
        struct dst_entry *child = dst_clone(xfrm_dst_child(skb_dst(skb)));

        skb_dst_drop(skb);
        return child;
}

/* Add encapsulation header.
 *
 * The IP header will be moved forward to make space for the encapsulation
 * header.
 */
static int xfrm4_transport_output(struct xfrm_state *x, struct sk_buff *skb)
{
        struct iphdr *iph = ip_hdr(skb);
        int ihl = iph->ihl * 4;

        skb_set_inner_transport_header(skb, skb_transport_offset(skb));

        skb_set_network_header(skb, -x->props.header_len);
        skb->mac_header = skb->network_header +
                          offsetof(struct iphdr, protocol);
        skb->transport_header = skb->network_header + ihl;
        __skb_pull(skb, ihl);
        memmove(skb_network_header(skb), iph, ihl);
        return 0;
}

#if IS_ENABLED(CONFIG_IPV6_MIP6)
static int mip6_rthdr_offset(struct sk_buff *skb, u8 **nexthdr, int type)
{
        const unsigned char *nh = skb_network_header(skb);
        unsigned int offset = sizeof(struct ipv6hdr);
        unsigned int packet_len;
        int found_rhdr = 0;

        packet_len = skb_tail_pointer(skb) - nh;
        *nexthdr = &ipv6_hdr(skb)->nexthdr;

        while (offset <= packet_len) {
                struct ipv6_opt_hdr *exthdr;

                switch (**nexthdr) {
                case NEXTHDR_HOP:
                        break;
                case NEXTHDR_ROUTING:
                        if (type == IPPROTO_ROUTING && offset + 3 <= packet_len) {
                                struct ipv6_rt_hdr *rt;

                                rt = (struct ipv6_rt_hdr *)(nh + offset);
                                if (rt->type != 0)
                                        return offset;
                        }
                        found_rhdr = 1;
                        break;
                case NEXTHDR_DEST:
                        /* HAO MUST NOT appear more than once.
                         * XXX: It is better to try to find by the end of
                         * XXX: packet if HAO exists.
                         */
                        if (ipv6_find_tlv(skb, offset, IPV6_TLV_HAO) >= 0) {
                                net_dbg_ratelimited("mip6: hao exists already, override\n");
                                return offset;
                        }

                        if (found_rhdr)
                                return offset;

                        break;
                default:
                        return offset;
                }

                if (offset + sizeof(struct ipv6_opt_hdr) > packet_len)
                        return -EINVAL;

                exthdr = (struct ipv6_opt_hdr *)(skb_network_header(skb) +
                                                 offset);
                offset += ipv6_optlen(exthdr);
                if (offset > IPV6_MAXPLEN)
                        return -EINVAL;
                *nexthdr = &exthdr->nexthdr;
        }

        return -EINVAL;
}
#endif

#if IS_ENABLED(CONFIG_IPV6)
static int xfrm6_hdr_offset(struct xfrm_state *x, struct sk_buff *skb, u8 **prevhdr)
{
        switch (x->type->proto) {
#if IS_ENABLED(CONFIG_IPV6_MIP6)
        case IPPROTO_DSTOPTS:
        case IPPROTO_ROUTING:
                return mip6_rthdr_offset(skb, prevhdr, x->type->proto);
#endif
        default:
                break;
        }

        return ip6_find_1stfragopt(skb, prevhdr);
}
#endif

/* Add encapsulation header.
 *
 * The IP header and mutable extension headers will be moved forward to make
 * space for the encapsulation header.
 */
static int xfrm6_transport_output(struct xfrm_state *x, struct sk_buff *skb)
{
#if IS_ENABLED(CONFIG_IPV6)
        struct ipv6hdr *iph;
        u8 *prevhdr;
        int hdr_len;

        iph = ipv6_hdr(skb);
        skb_set_inner_transport_header(skb, skb_transport_offset(skb));

        hdr_len = xfrm6_hdr_offset(x, skb, &prevhdr);
        if (hdr_len < 0)
                return hdr_len;
        skb_set_mac_header(skb,
                           (prevhdr - x->props.header_len) - skb->data);
        skb_set_network_header(skb, -x->props.header_len);
        skb->transport_header = skb->network_header + hdr_len;
        __skb_pull(skb, hdr_len);
        memmove(ipv6_hdr(skb), iph, hdr_len);
        return 0;
#else
        WARN_ON_ONCE(1);
        return -EAFNOSUPPORT;
#endif
}

/* Add route optimization header space.
 *
 * The IP header and mutable extension headers will be moved forward to make
 * space for the route optimization header.
 */
static int xfrm6_ro_output(struct xfrm_state *x, struct sk_buff *skb)
{
#if IS_ENABLED(CONFIG_IPV6)
        struct ipv6hdr *iph;
        u8 *prevhdr;
        int hdr_len;

        iph = ipv6_hdr(skb);

        hdr_len = xfrm6_hdr_offset(x, skb, &prevhdr);
        if (hdr_len < 0)
                return hdr_len;
        skb_set_mac_header(skb,
                           (prevhdr - x->props.header_len) - skb->data);
        skb_set_network_header(skb, -x->props.header_len);
        skb->transport_header = skb->network_header + hdr_len;
        __skb_pull(skb, hdr_len);
        memmove(ipv6_hdr(skb), iph, hdr_len);

        return 0;
#else
        WARN_ON_ONCE(1);
        return -EAFNOSUPPORT;
#endif
}

/* Add encapsulation header.
 *
 * The top IP header will be constructed per draft-nikander-esp-beet-mode-06.txt.
 */
static int xfrm4_beet_encap_add(struct xfrm_state *x, struct sk_buff *skb)
{
        struct ip_beet_phdr *ph;
        struct iphdr *top_iph;
        int hdrlen, optlen;

        hdrlen = 0;
        optlen = XFRM_MODE_SKB_CB(skb)->optlen;
        if (unlikely(optlen))
                hdrlen += IPV4_BEET_PHMAXLEN - (optlen & 4);

        skb_set_network_header(skb, -x->props.header_len - hdrlen +
                               (XFRM_MODE_SKB_CB(skb)->ihl - sizeof(*top_iph)));
        if (x->sel.family != AF_INET6)
                skb->network_header += IPV4_BEET_PHMAXLEN;
        skb->mac_header = skb->network_header +
                          offsetof(struct iphdr, protocol);
        skb->transport_header = skb->network_header + sizeof(*top_iph);

        xfrm4_beet_make_header(skb);

        ph = __skb_pull(skb, XFRM_MODE_SKB_CB(skb)->ihl - hdrlen);

        top_iph = ip_hdr(skb);

        if (unlikely(optlen)) {
                if (WARN_ON(optlen < 0))
                        return -EINVAL;

                ph->padlen = 4 - (optlen & 4);
                ph->hdrlen = optlen / 8;
                ph->nexthdr = top_iph->protocol;
                if (ph->padlen)
                        memset(ph + 1, IPOPT_NOP, ph->padlen);

                top_iph->protocol = IPPROTO_BEETPH;
                top_iph->ihl = sizeof(struct iphdr) / 4;
        }

        top_iph->saddr = x->props.saddr.a4;
        top_iph->daddr = x->id.daddr.a4;

        return 0;
}

/* Add encapsulation header.
 *
 * The top IP header will be constructed per RFC 2401.
 */
static int xfrm4_tunnel_encap_add(struct xfrm_state *x, struct sk_buff *skb)
{
        bool small_ipv6 = (skb->protocol == htons(ETH_P_IPV6)) && (skb->len <= IPV6_MIN_MTU);
        struct dst_entry *dst = skb_dst(skb);
        struct iphdr *top_iph;
        int flags;

        skb_set_inner_network_header(skb, skb_network_offset(skb));
        skb_set_inner_transport_header(skb, skb_transport_offset(skb));

        skb_set_network_header(skb, -x->props.header_len);
        skb->mac_header = skb->network_header +
                          offsetof(struct iphdr, protocol);
        skb->transport_header = skb->network_header + sizeof(*top_iph);
        top_iph = ip_hdr(skb);

        top_iph->ihl = 5;
        top_iph->version = 4;

        top_iph->protocol = xfrm_af2proto(skb_dst(skb)->ops->family);

        /* DS disclosing depends on XFRM_SA_XFLAG_DONT_ENCAP_DSCP */
        if (x->props.extra_flags & XFRM_SA_XFLAG_DONT_ENCAP_DSCP)
                top_iph->tos = 0;
        else
                top_iph->tos = XFRM_MODE_SKB_CB(skb)->tos;
        top_iph->tos = INET_ECN_encapsulate(top_iph->tos,
                                            XFRM_MODE_SKB_CB(skb)->tos);

        flags = x->props.flags;
        if (flags & XFRM_STATE_NOECN)
                IP_ECN_clear(top_iph);

        top_iph->frag_off = (flags & XFRM_STATE_NOPMTUDISC) || small_ipv6 ?
                0 : (XFRM_MODE_SKB_CB(skb)->frag_off & htons(IP_DF));

        top_iph->ttl = ip4_dst_hoplimit(xfrm_dst_child(dst));

        top_iph->saddr = x->props.saddr.a4;
        top_iph->daddr = x->id.daddr.a4;
        ip_select_ident(dev_net(dst->dev), skb, NULL);

        return 0;
}

#if IS_ENABLED(CONFIG_IPV6)
static int xfrm6_tunnel_encap_add(struct xfrm_state *x, struct sk_buff *skb)
{
        struct dst_entry *dst = skb_dst(skb);
        struct ipv6hdr *top_iph;
        int dsfield;

        skb_set_inner_network_header(skb, skb_network_offset(skb));
        skb_set_inner_transport_header(skb, skb_transport_offset(skb));

        skb_set_network_header(skb, -x->props.header_len);
        skb->mac_header = skb->network_header +
                          offsetof(struct ipv6hdr, nexthdr);
        skb->transport_header = skb->network_header + sizeof(*top_iph);
        top_iph = ipv6_hdr(skb);

        top_iph->version = 6;

        memcpy(top_iph->flow_lbl, XFRM_MODE_SKB_CB(skb)->flow_lbl,
               sizeof(top_iph->flow_lbl));
        top_iph->nexthdr = xfrm_af2proto(skb_dst(skb)->ops->family);

        if (x->props.extra_flags & XFRM_SA_XFLAG_DONT_ENCAP_DSCP)
                dsfield = 0;
        else
                dsfield = XFRM_MODE_SKB_CB(skb)->tos;
        dsfield = INET_ECN_encapsulate(dsfield, XFRM_MODE_SKB_CB(skb)->tos);
        if (x->props.flags & XFRM_STATE_NOECN)
                dsfield &= ~INET_ECN_MASK;
        ipv6_change_dsfield(top_iph, 0, dsfield);
        top_iph->hop_limit = ip6_dst_hoplimit(xfrm_dst_child(dst));
        top_iph->saddr = *(struct in6_addr *)&x->props.saddr;
        top_iph->daddr = *(struct in6_addr *)&x->id.daddr;
        return 0;
}

static int xfrm6_beet_encap_add(struct xfrm_state *x, struct sk_buff *skb)
{
        struct ipv6hdr *top_iph;
        struct ip_beet_phdr *ph;
        int optlen, hdr_len;

        hdr_len = 0;
        optlen = XFRM_MODE_SKB_CB(skb)->optlen;
        if (unlikely(optlen))
                hdr_len += IPV4_BEET_PHMAXLEN - (optlen & 4);

        skb_set_network_header(skb, -x->props.header_len - hdr_len);
        if (x->sel.family != AF_INET6)
                skb->network_header += IPV4_BEET_PHMAXLEN;
        skb->mac_header = skb->network_header +
                          offsetof(struct ipv6hdr, nexthdr);
        skb->transport_header = skb->network_header + sizeof(*top_iph);
        ph = __skb_pull(skb, XFRM_MODE_SKB_CB(skb)->ihl - hdr_len);

        xfrm6_beet_make_header(skb);

        top_iph = ipv6_hdr(skb);
        if (unlikely(optlen)) {
                if (WARN_ON(optlen < 0))
                        return -EINVAL;

                ph->padlen = 4 - (optlen & 4);
                ph->hdrlen = optlen / 8;
                ph->nexthdr = top_iph->nexthdr;
                if (ph->padlen)
                        memset(ph + 1, IPOPT_NOP, ph->padlen);

                top_iph->nexthdr = IPPROTO_BEETPH;
        }

        top_iph->saddr = *(struct in6_addr *)&x->props.saddr;
        top_iph->daddr = *(struct in6_addr *)&x->id.daddr;
        return 0;
}
#endif

/* Add encapsulation header.
 *
 * On exit, the transport header will be set to the start of the
 * encapsulation header to be filled in by x->type->output and the mac
 * header will be set to the nextheader (protocol for IPv4) field of the
 * extension header directly preceding the encapsulation header, or in
 * its absence, that of the top IP header.
 * The value of the network header will always point to the top IP header
 * while skb->data will point to the payload.
 */
static int xfrm4_prepare_output(struct xfrm_state *x, struct sk_buff *skb)
{
        int err;

        err = xfrm_inner_extract_output(x, skb);
        if (err)
                return err;

        IPCB(skb)->flags |= IPSKB_XFRM_TUNNEL_SIZE;
        skb->protocol = htons(ETH_P_IP);

        switch (x->props.mode) {
        case XFRM_MODE_BEET:
                return xfrm4_beet_encap_add(x, skb);
        case XFRM_MODE_TUNNEL:
                return xfrm4_tunnel_encap_add(x, skb);
        }

        WARN_ON_ONCE(1);
        return -EOPNOTSUPP;
}

static int xfrm6_prepare_output(struct xfrm_state *x, struct sk_buff *skb)
{
#if IS_ENABLED(CONFIG_IPV6)
        int err;

        err = xfrm_inner_extract_output(x, skb);
        if (err)
                return err;

        skb->ignore_df = 1;
        skb->protocol = htons(ETH_P_IPV6);

        switch (x->props.mode) {
        case XFRM_MODE_BEET:
                return xfrm6_beet_encap_add(x, skb);
        case XFRM_MODE_TUNNEL:
                return xfrm6_tunnel_encap_add(x, skb);
        default:
                WARN_ON_ONCE(1);
                return -EOPNOTSUPP;
        }
#endif
        WARN_ON_ONCE(1);
        return -EAFNOSUPPORT;
}

static int xfrm_outer_mode_output(struct xfrm_state *x, struct sk_buff *skb)
{
        switch (x->props.mode) {
        case XFRM_MODE_BEET:
        case XFRM_MODE_TUNNEL:
                if (x->props.family == AF_INET)
                        return xfrm4_prepare_output(x, skb);
                if (x->props.family == AF_INET6)
                        return xfrm6_prepare_output(x, skb);
                break;
        case XFRM_MODE_TRANSPORT:
                if (x->props.family == AF_INET)
                        return xfrm4_transport_output(x, skb);
                if (x->props.family == AF_INET6)
                        return xfrm6_transport_output(x, skb);
                break;
        case XFRM_MODE_ROUTEOPTIMIZATION:
                if (x->props.family == AF_INET6)
                        return xfrm6_ro_output(x, skb);
                WARN_ON_ONCE(1);
                break;
        default:
                if (x->mode_cbs && x->mode_cbs->prepare_output)
                        return x->mode_cbs->prepare_output(x, skb);
                WARN_ON_ONCE(1);
                break;
        }

        return -EOPNOTSUPP;
}

#if IS_ENABLED(CONFIG_NET_PKTGEN)
int pktgen_xfrm_outer_mode_output(struct xfrm_state *x, struct sk_buff *skb)
{
        return xfrm_outer_mode_output(x, skb);
}
EXPORT_SYMBOL_GPL(pktgen_xfrm_outer_mode_output);
#endif

static int xfrm_output_one(struct sk_buff *skb, int err)
{
        struct dst_entry *dst = skb_dst(skb);
        struct xfrm_state *x = dst->xfrm;
        struct net *net = xs_net(x);

        if (err <= 0 || x->xso.type == XFRM_DEV_OFFLOAD_PACKET)
                goto resume;

        do {
                err = xfrm_skb_check_space(skb);
                if (err) {
                        XFRM_INC_STATS(net, LINUX_MIB_XFRMOUTERROR);
                        goto error_nolock;
                }

                skb->mark = xfrm_smark_get(skb->mark, x);

                err = xfrm_outer_mode_output(x, skb);
                if (err) {
                        XFRM_INC_STATS(net, LINUX_MIB_XFRMOUTSTATEMODEERROR);
                        goto error_nolock;
                }

                spin_lock_bh(&x->lock);

                if (unlikely(x->km.state != XFRM_STATE_VALID)) {
                        XFRM_INC_STATS(net, LINUX_MIB_XFRMOUTSTATEINVALID);
                        err = -EINVAL;
                        goto error;
                }

                err = xfrm_state_check_expire(x);
                if (err) {
                        XFRM_INC_STATS(net, LINUX_MIB_XFRMOUTSTATEEXPIRED);
                        goto error;
                }

                err = xfrm_replay_overflow(x, skb);
                if (err) {
                        XFRM_INC_STATS(net, LINUX_MIB_XFRMOUTSTATESEQERROR);
                        goto error;
                }

                x->curlft.bytes += skb->len;
                x->curlft.packets++;
                x->lastused = ktime_get_real_seconds();

                spin_unlock_bh(&x->lock);

                skb_dst_force(skb);
                if (!skb_dst(skb)) {
                        XFRM_INC_STATS(net, LINUX_MIB_XFRMOUTERROR);
                        err = -EHOSTUNREACH;
                        goto error_nolock;
                }

                if (xfrm_offload(skb)) {
                        x->type_offload->encap(x, skb);
                } else {
                        /* Inner headers are invalid now. */
                        skb->encapsulation = 0;

                        err = x->type->output(x, skb);
                        if (err == -EINPROGRESS)
                                goto out;
                }

resume:
                if (err) {
                        XFRM_INC_STATS(net, LINUX_MIB_XFRMOUTSTATEPROTOERROR);
                        goto error_nolock;
                }

                dst = skb_dst_pop(skb);
                if (!dst) {
                        XFRM_INC_STATS(net, LINUX_MIB_XFRMOUTERROR);
                        err = -EHOSTUNREACH;
                        goto error_nolock;
                }
                skb_dst_set(skb, dst);
                x = dst->xfrm;
        } while (x && !(x->outer_mode.flags & XFRM_MODE_FLAG_TUNNEL));

        return 0;

error:
        spin_unlock_bh(&x->lock);
error_nolock:
        kfree_skb(skb);
out:
        return err;
}

int xfrm_output_resume(struct sock *sk, struct sk_buff *skb, int err)
{
        struct net *net = xs_net(skb_dst(skb)->xfrm);

        while (likely((err = xfrm_output_one(skb, err)) == 0)) {
                nf_reset_ct(skb);

                err = skb_dst(skb)->ops->local_out(net, sk, skb);
                if (unlikely(err != 1))
                        goto out;

                if (!skb_dst(skb)->xfrm)
                        return dst_output(net, sk, skb);

                err = nf_hook(skb_dst(skb)->ops->family,
                              NF_INET_POST_ROUTING, net, sk, skb,
                              NULL, skb_dst(skb)->dev, xfrm_output2);
                if (unlikely(err != 1))
                        goto out;
        }

        if (err == -EINPROGRESS)
                err = 0;

out:
        return err;
}
EXPORT_SYMBOL_GPL(xfrm_output_resume);

static int xfrm_dev_direct_output(struct sock *sk, struct xfrm_state *x,
                                  struct sk_buff *skb)
{
        struct dst_entry *dst = skb_dst(skb);
        struct net *net = xs_net(x);
        int err;

        dst = skb_dst_pop(skb);
        if (!dst) {
                XFRM_INC_STATS(net, LINUX_MIB_XFRMOUTERROR);
                kfree_skb(skb);
                return -EHOSTUNREACH;
        }
        skb_dst_set(skb, dst);
        nf_reset_ct(skb);

        err = skb_dst(skb)->ops->local_out(net, sk, skb);
        if (unlikely(err != 1)) {
                kfree_skb(skb);
                return err;
        }

        /* In transport mode, network destination is
         * directly reachable, while in tunnel mode,
         * inner packet network may not be. In packet
         * offload type, HW is responsible for hard
         * header packet mangling so directly xmit skb
         * to netdevice.
         */
        skb->dev = x->xso.dev;
        __skb_push(skb, skb->dev->hard_header_len);
        return dev_queue_xmit(skb);
}

static int xfrm_output2(struct net *net, struct sock *sk, struct sk_buff *skb)
{
        return xfrm_output_resume(sk, skb, 1);
}

static int xfrm_output_gso(struct net *net, struct sock *sk, struct sk_buff *skb)
{
        struct sk_buff *segs, *nskb;

        BUILD_BUG_ON(sizeof(*IPCB(skb)) > SKB_GSO_CB_OFFSET);
        BUILD_BUG_ON(sizeof(*IP6CB(skb)) > SKB_GSO_CB_OFFSET);
        segs = skb_gso_segment(skb, 0);
        kfree_skb(skb);
        if (IS_ERR(segs))
                return PTR_ERR(segs);
        if (segs == NULL)
                return -EINVAL;

        skb_list_walk_safe(segs, segs, nskb) {
                int err;

                skb_mark_not_on_list(segs);
                err = xfrm_output2(net, sk, segs);

                if (unlikely(err)) {
                        kfree_skb_list(nskb);
                        return err;
                }
        }

        return 0;
}

/* For partial checksum offload, the outer header checksum is calculated
 * by software and the inner header checksum is calculated by hardware.
 * This requires hardware to know the inner packet type to calculate
 * the inner header checksum. Save inner ip protocol here to avoid
 * traversing the packet in the vendor's xmit code.
 * For IPsec tunnel mode save the ip protocol from the IP header of the
 * plain text packet. Otherwise If the encap type is IPIP, just save
 * skb->inner_ipproto in any other case get the ip protocol from the IP
 * header.
 */
static void xfrm_get_inner_ipproto(struct sk_buff *skb, struct xfrm_state *x)
{
        struct xfrm_offload *xo = xfrm_offload(skb);
        const struct ethhdr *eth;

        if (!xo)
                return;

        if (x->outer_mode.encap == XFRM_MODE_TUNNEL) {
                switch (skb_dst(skb)->ops->family) {
                case AF_INET:
                        xo->inner_ipproto = ip_hdr(skb)->protocol;
                        break;
                case AF_INET6:
                        xo->inner_ipproto = ipv6_hdr(skb)->nexthdr;
                        break;
                default:
                        break;
                }

                return;
        }
        if (x->outer_mode.encap == XFRM_MODE_IPTFS) {
                xo->inner_ipproto = IPPROTO_AGGFRAG;
                return;
        }

        /* non-Tunnel Mode */
        if (!skb->encapsulation)
                return;

        if (skb->inner_protocol_type == ENCAP_TYPE_IPPROTO) {
                xo->inner_ipproto = skb->inner_ipproto;
                return;
        }

        if (skb->inner_protocol_type != ENCAP_TYPE_ETHER)
                return;

        eth = (struct ethhdr *)skb_inner_mac_header(skb);

        switch (ntohs(eth->h_proto)) {
        case ETH_P_IPV6:
                xo->inner_ipproto = inner_ipv6_hdr(skb)->nexthdr;
                break;
        case ETH_P_IP:
                xo->inner_ipproto = inner_ip_hdr(skb)->protocol;
                break;
        }
}

int xfrm_output(struct sock *sk, struct sk_buff *skb)
{
        struct net *net = dev_net(skb_dst(skb)->dev);
        struct xfrm_state *x = skb_dst(skb)->xfrm;
        int family;
        int err;

        family = (x->xso.type != XFRM_DEV_OFFLOAD_PACKET) ? x->outer_mode.family
                : skb_dst(skb)->ops->family;

        switch (family) {
        case AF_INET:
                memset(IPCB(skb), 0, sizeof(*IPCB(skb)));
                IPCB(skb)->flags |= IPSKB_XFRM_TRANSFORMED;
                break;
        case AF_INET6:
                memset(IP6CB(skb), 0, sizeof(*IP6CB(skb)));

                IP6CB(skb)->flags |= IP6SKB_XFRM_TRANSFORMED;
                break;
        }

        if (x->xso.type == XFRM_DEV_OFFLOAD_PACKET) {
                if (!xfrm_dev_offload_ok(skb, x)) {
                        XFRM_INC_STATS(net, LINUX_MIB_XFRMOUTERROR);
                        kfree_skb(skb);
                        return -EHOSTUNREACH;
                }

                /* Exclusive direct xmit for tunnel mode, as
                 * some filtering or matching rules may apply
                 * in transport mode.
                 * Locally generated packets also require
                 * the normal XFRM path for L2 header setup,
                 * as the hardware needs the L2 header to match
                 * for encryption, so skip direct output as well.
                 */
                if (x->props.mode == XFRM_MODE_TUNNEL && !skb->sk)
                        return xfrm_dev_direct_output(sk, x, skb);

                return xfrm_output_resume(sk, skb, 0);
        }

        secpath_reset(skb);

        if (xfrm_dev_offload_ok(skb, x)) {
                struct sec_path *sp;

                sp = secpath_set(skb);
                if (!sp) {
                        XFRM_INC_STATS(net, LINUX_MIB_XFRMOUTERROR);
                        kfree_skb(skb);
                        return -ENOMEM;
                }

                sp->olen++;
                sp->xvec[sp->len++] = x;
                xfrm_state_hold(x);

                xfrm_get_inner_ipproto(skb, x);
                skb->encapsulation = 1;

                if (skb_is_gso(skb)) {
                        if (skb->inner_protocol && x->props.mode == XFRM_MODE_TUNNEL)
                                return xfrm_output_gso(net, sk, skb);

                        skb_shinfo(skb)->gso_type |= SKB_GSO_ESP;
                        goto out;
                }

                if (x->xso.dev && x->xso.dev->features & NETIF_F_HW_ESP_TX_CSUM)
                        goto out;
        } else {
                if (skb_is_gso(skb))
                        return xfrm_output_gso(net, sk, skb);
        }

        if (skb->ip_summed == CHECKSUM_PARTIAL) {
                err = skb_checksum_help(skb);
                if (err) {
                        XFRM_INC_STATS(net, LINUX_MIB_XFRMOUTERROR);
                        kfree_skb(skb);
                        return err;
                }
        }

out:
        return xfrm_output2(net, sk, skb);
}
EXPORT_SYMBOL_GPL(xfrm_output);

int xfrm4_tunnel_check_size(struct sk_buff *skb)
{
        int mtu, ret = 0;

        if (IPCB(skb)->flags & IPSKB_XFRM_TUNNEL_SIZE)
                goto out;

        if (!(ip_hdr(skb)->frag_off & htons(IP_DF)) || skb->ignore_df)
                goto out;

        mtu = dst_mtu(skb_dst(skb));
        if ((!skb_is_gso(skb) && skb->len > mtu) ||
            (skb_is_gso(skb) &&
             !skb_gso_validate_network_len(skb, ip_skb_dst_mtu(skb->sk, skb)))) {
                skb->protocol = htons(ETH_P_IP);

                if (skb->sk && sk_fullsock(skb->sk))
                        xfrm_local_error(skb, mtu);
                else
                        icmp_send(skb, ICMP_DEST_UNREACH,
                                  ICMP_FRAG_NEEDED, htonl(mtu));
                ret = -EMSGSIZE;
        }
out:
        return ret;
}
EXPORT_SYMBOL_GPL(xfrm4_tunnel_check_size);

static int xfrm4_extract_output(struct xfrm_state *x, struct sk_buff *skb)
{
        int err;

        if (x->outer_mode.encap == XFRM_MODE_BEET &&
            ip_is_fragment(ip_hdr(skb))) {
                net_warn_ratelimited("BEET mode doesn't support inner IPv4 fragments\n");
                return -EAFNOSUPPORT;
        }

        err = xfrm4_tunnel_check_size(skb);
        if (err)
                return err;

        XFRM_MODE_SKB_CB(skb)->protocol = ip_hdr(skb)->protocol;

        xfrm4_extract_header(skb);
        return 0;
}

#if IS_ENABLED(CONFIG_IPV6)
int xfrm6_tunnel_check_size(struct sk_buff *skb)
{
        int mtu, ret = 0;
        struct dst_entry *dst = skb_dst(skb);
        struct sock *sk = skb_to_full_sk(skb);

        if (skb->ignore_df)
                goto out;

        mtu = dst_mtu(dst);
        if (mtu < IPV6_MIN_MTU)
                mtu = IPV6_MIN_MTU;

        if ((!skb_is_gso(skb) && skb->len > mtu) ||
            (skb_is_gso(skb) &&
             !skb_gso_validate_network_len(skb, ip6_skb_dst_mtu(skb)))) {
                skb->dev = dst->dev;
                skb->protocol = htons(ETH_P_IPV6);

                if (xfrm6_local_dontfrag(sk))
                        ipv6_stub->xfrm6_local_rxpmtu(skb, mtu);
                else if (sk)
                        xfrm_local_error(skb, mtu);
                else
                        icmpv6_send(skb, ICMPV6_PKT_TOOBIG, 0, mtu);
                ret = -EMSGSIZE;
        }
out:
        return ret;
}
EXPORT_SYMBOL_GPL(xfrm6_tunnel_check_size);
#endif

static int xfrm6_extract_output(struct xfrm_state *x, struct sk_buff *skb)
{
#if IS_ENABLED(CONFIG_IPV6)
        int err;

        err = xfrm6_tunnel_check_size(skb);
        if (err)
                return err;

        XFRM_MODE_SKB_CB(skb)->protocol = ipv6_hdr(skb)->nexthdr;

        xfrm6_extract_header(skb);
        return 0;
#else
        WARN_ON_ONCE(1);
        return -EAFNOSUPPORT;
#endif
}

static int xfrm_inner_extract_output(struct xfrm_state *x, struct sk_buff *skb)
{
        switch (skb->protocol) {
        case htons(ETH_P_IP):
                return xfrm4_extract_output(x, skb);
        case htons(ETH_P_IPV6):
                return xfrm6_extract_output(x, skb);
        }

        return -EAFNOSUPPORT;
}

void xfrm_local_error(struct sk_buff *skb, int mtu)
{
        unsigned int proto;
        struct xfrm_state_afinfo *afinfo;

        if (skb->protocol == htons(ETH_P_IP))
                proto = AF_INET;
        else if (skb->protocol == htons(ETH_P_IPV6) &&
                 skb->sk->sk_family == AF_INET6)
                proto = AF_INET6;
        else
                return;

        afinfo = xfrm_state_get_afinfo(proto);
        if (afinfo) {
                afinfo->local_error(skb, mtu);
                rcu_read_unlock();
        }
}
EXPORT_SYMBOL_GPL(xfrm_local_error);