// SPDX-License-Identifier: GPL-2.0-only
#define pr_fmt(fmt) "IPsec: " fmt

#include <crypto/aead.h>
#include <crypto/authenc.h>
#include <linux/err.h>
#include <linux/module.h>
#include <net/ip.h>
#include <net/xfrm.h>
#include <net/esp.h>
#include <linux/scatterlist.h>
#include <linux/kernel.h>
#include <linux/pfkeyv2.h>
#include <linux/rtnetlink.h>
#include <linux/slab.h>
#include <linux/spinlock.h>
#include <linux/in6.h>
#include <net/icmp.h>
#include <net/protocol.h>
#include <net/udp.h>
#include <net/tcp.h>
#include <net/espintcp.h>

#include <linux/highmem.h>

struct esp_skb_cb {
        struct xfrm_skb_cb xfrm;
        void *tmp;
};

struct esp_output_extra {
        __be32 seqhi;
        u32 esphoff;
};

#define ESP_SKB_CB(__skb) ((struct esp_skb_cb *)&((__skb)->cb[0]))

/*
 * Allocate an AEAD request structure with extra space for SG and IV.
 *
 * For alignment considerations the IV is placed at the front, followed
 * by the request and finally the SG list.
 *
 * TODO: Use spare space in skb for this where possible.
 */
static void *esp_alloc_tmp(struct crypto_aead *aead, int nfrags, int extralen)
{
        unsigned int len;

        len = extralen;

        len += crypto_aead_ivsize(aead);

        if (len) {
                len += crypto_aead_alignmask(aead) &
                       ~(crypto_tfm_ctx_alignment() - 1);
                len = ALIGN(len, crypto_tfm_ctx_alignment());
        }

        len += sizeof(struct aead_request) + crypto_aead_reqsize(aead);
        len = ALIGN(len, __alignof__(struct scatterlist));

        len += sizeof(struct scatterlist) * nfrags;

        return kmalloc(len, GFP_ATOMIC);
}

static inline void *esp_tmp_extra(void *tmp)
{
        return PTR_ALIGN(tmp, __alignof__(struct esp_output_extra));
}

static inline u8 *esp_tmp_iv(struct crypto_aead *aead, void *tmp, int extralen)
{
        return crypto_aead_ivsize(aead) ?
               PTR_ALIGN((u8 *)tmp + extralen,
                         crypto_aead_alignmask(aead) + 1) : tmp + extralen;
}

static inline struct aead_request *esp_tmp_req(struct crypto_aead *aead, u8 *iv)
{
        struct aead_request *req;

        req = (void *)PTR_ALIGN(iv + crypto_aead_ivsize(aead),
                                crypto_tfm_ctx_alignment());
        aead_request_set_tfm(req, aead);
        return req;
}

static inline struct scatterlist *esp_req_sg(struct crypto_aead *aead,
                                             struct aead_request *req)
{
        return (void *)ALIGN((unsigned long)(req + 1) +
                             crypto_aead_reqsize(aead),
                             __alignof__(struct scatterlist));
}

static void esp_ssg_unref(struct xfrm_state *x, void *tmp)
{
        struct esp_output_extra *extra = esp_tmp_extra(tmp);
        struct crypto_aead *aead = x->data;
        int extralen = 0;
        u8 *iv;
        struct aead_request *req;
        struct scatterlist *sg;

        if (x->props.flags & XFRM_STATE_ESN)
                extralen += sizeof(*extra);

        extra = esp_tmp_extra(tmp);
        iv = esp_tmp_iv(aead, tmp, extralen);
        req = esp_tmp_req(aead, iv);

        /* Unref skb_frag_pages in the src scatterlist if necessary.
         * Skip the first sg which comes from skb->data.
         */
        if (req->src != req->dst)
                for (sg = sg_next(req->src); sg; sg = sg_next(sg))
                        put_page(sg_page(sg));
}

#ifdef CONFIG_INET_ESPINTCP
struct esp_tcp_sk {
        struct sock *sk;
        struct rcu_head rcu;
};

static void esp_free_tcp_sk(struct rcu_head *head)
{
        struct esp_tcp_sk *esk = container_of(head, struct esp_tcp_sk, rcu);

        sock_put(esk->sk);
        kfree(esk);
}

static struct sock *esp_find_tcp_sk(struct xfrm_state *x)
{
        struct xfrm_encap_tmpl *encap = x->encap;
        struct esp_tcp_sk *esk;
        __be16 sport, dport;
        struct sock *nsk;
        struct sock *sk;

        sk = rcu_dereference(x->encap_sk);
        if (sk && sk->sk_state == TCP_ESTABLISHED)
                return sk;

        spin_lock_bh(&x->lock);
        sport = encap->encap_sport;
        dport = encap->encap_dport;
        nsk = rcu_dereference_protected(x->encap_sk,
                                        lockdep_is_held(&x->lock));
        if (sk && sk == nsk) {
                esk = kmalloc(sizeof(*esk), GFP_ATOMIC);
                if (!esk) {
                        spin_unlock_bh(&x->lock);
                        return ERR_PTR(-ENOMEM);
                }
                RCU_INIT_POINTER(x->encap_sk, NULL);
                esk->sk = sk;
                call_rcu(&esk->rcu, esp_free_tcp_sk);
        }
        spin_unlock_bh(&x->lock);

        sk = inet_lookup_established(xs_net(x), &tcp_hashinfo, x->id.daddr.a4,
                                     dport, x->props.saddr.a4, sport, 0);
        if (!sk)
                return ERR_PTR(-ENOENT);

        if (!tcp_is_ulp_esp(sk)) {
                sock_put(sk);
                return ERR_PTR(-EINVAL);
        }

        spin_lock_bh(&x->lock);
        nsk = rcu_dereference_protected(x->encap_sk,
                                        lockdep_is_held(&x->lock));
        if (encap->encap_sport != sport ||
            encap->encap_dport != dport) {
                sock_put(sk);
                sk = nsk ?: ERR_PTR(-EREMCHG);
        } else if (sk == nsk) {
                sock_put(sk);
        } else {
                rcu_assign_pointer(x->encap_sk, sk);
        }
        spin_unlock_bh(&x->lock);

        return sk;
}

static int esp_output_tcp_finish(struct xfrm_state *x, struct sk_buff *skb)
{
        struct sock *sk;
        int err;

        rcu_read_lock();

        sk = esp_find_tcp_sk(x);
        err = PTR_ERR_OR_ZERO(sk);
        if (err)
                goto out;

        bh_lock_sock(sk);
        if (sock_owned_by_user(sk))
                err = espintcp_queue_out(sk, skb);
        else
                err = espintcp_push_skb(sk, skb);
        bh_unlock_sock(sk);

out:
        rcu_read_unlock();
        return err;
}

static int esp_output_tcp_encap_cb(struct net *net, struct sock *sk,
                                   struct sk_buff *skb)
{
        struct dst_entry *dst = skb_dst(skb);
        struct xfrm_state *x = dst->xfrm;

        return esp_output_tcp_finish(x, skb);
}

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

        local_bh_disable();
        err = xfrm_trans_queue_net(xs_net(x), skb, esp_output_tcp_encap_cb);
        local_bh_enable();

        /* EINPROGRESS just happens to do the right thing.  It
         * actually means that the skb has been consumed and
         * isn't coming back.
         */
        return err ?: -EINPROGRESS;
}
#else
static int esp_output_tail_tcp(struct xfrm_state *x, struct sk_buff *skb)
{
        kfree_skb(skb);

        return -EOPNOTSUPP;
}
#endif

static void esp_output_done(struct crypto_async_request *base, int err)
{
        struct sk_buff *skb = base->data;
        struct xfrm_offload *xo = xfrm_offload(skb);
        void *tmp;
        struct xfrm_state *x;

        if (xo && (xo->flags & XFRM_DEV_RESUME)) {
                struct sec_path *sp = skb_sec_path(skb);

                x = sp->xvec[sp->len - 1];
        } else {
                x = skb_dst(skb)->xfrm;
        }

        tmp = ESP_SKB_CB(skb)->tmp;
        esp_ssg_unref(x, tmp);
        kfree(tmp);

        if (xo && (xo->flags & XFRM_DEV_RESUME)) {
                if (err) {
                        XFRM_INC_STATS(xs_net(x), LINUX_MIB_XFRMOUTSTATEPROTOERROR);
                        kfree_skb(skb);
                        return;
                }

                skb_push(skb, skb->data - skb_mac_header(skb));
                secpath_reset(skb);
                xfrm_dev_resume(skb);
        } else {
                if (!err &&
                    x->encap && x->encap->encap_type == TCP_ENCAP_ESPINTCP)
                        esp_output_tail_tcp(x, skb);
                else
                        xfrm_output_resume(skb, err);
        }
}

/* Move ESP header back into place. */
static void esp_restore_header(struct sk_buff *skb, unsigned int offset)
{
        struct ip_esp_hdr *esph = (void *)(skb->data + offset);
        void *tmp = ESP_SKB_CB(skb)->tmp;
        __be32 *seqhi = esp_tmp_extra(tmp);

        esph->seq_no = esph->spi;
        esph->spi = *seqhi;
}

static void esp_output_restore_header(struct sk_buff *skb)
{
        void *tmp = ESP_SKB_CB(skb)->tmp;
        struct esp_output_extra *extra = esp_tmp_extra(tmp);

        esp_restore_header(skb, skb_transport_offset(skb) + extra->esphoff -
                                sizeof(__be32));
}

static struct ip_esp_hdr *esp_output_set_extra(struct sk_buff *skb,
                                               struct xfrm_state *x,
                                               struct ip_esp_hdr *esph,
                                               struct esp_output_extra *extra)
{
        /* For ESN we move the header forward by 4 bytes to
         * accomodate the high bits.  We will move it back after
         * encryption.
         */
        if ((x->props.flags & XFRM_STATE_ESN)) {
                __u32 seqhi;
                struct xfrm_offload *xo = xfrm_offload(skb);

                if (xo)
                        seqhi = xo->seq.hi;
                else
                        seqhi = XFRM_SKB_CB(skb)->seq.output.hi;

                extra->esphoff = (unsigned char *)esph -
                                 skb_transport_header(skb);
                esph = (struct ip_esp_hdr *)((unsigned char *)esph - 4);
                extra->seqhi = esph->spi;
                esph->seq_no = htonl(seqhi);
        }

        esph->spi = x->id.spi;

        return esph;
}

static void esp_output_done_esn(struct crypto_async_request *base, int err)
{
        struct sk_buff *skb = base->data;

        esp_output_restore_header(skb);
        esp_output_done(base, err);
}

static struct ip_esp_hdr *esp_output_udp_encap(struct sk_buff *skb,
                                               int encap_type,
                                               struct esp_info *esp,
                                               __be16 sport,
                                               __be16 dport)
{
        struct udphdr *uh;
        __be32 *udpdata32;
        unsigned int len;

        len = skb->len + esp->tailen - skb_transport_offset(skb);
        if (len + sizeof(struct iphdr) > IP_MAX_MTU)
                return ERR_PTR(-EMSGSIZE);

        uh = (struct udphdr *)esp->esph;
        uh->source = sport;
        uh->dest = dport;
        uh->len = htons(len);
        uh->check = 0;

        *skb_mac_header(skb) = IPPROTO_UDP;

        if (encap_type == UDP_ENCAP_ESPINUDP_NON_IKE) {
                udpdata32 = (__be32 *)(uh + 1);
                udpdata32[0] = udpdata32[1] = 0;
                return (struct ip_esp_hdr *)(udpdata32 + 2);
        }

        return (struct ip_esp_hdr *)(uh + 1);
}

#ifdef CONFIG_INET_ESPINTCP
static struct ip_esp_hdr *esp_output_tcp_encap(struct xfrm_state *x,
                                                    struct sk_buff *skb,
                                                    struct esp_info *esp)
{
        __be16 *lenp = (void *)esp->esph;
        struct ip_esp_hdr *esph;
        unsigned int len;
        struct sock *sk;

        len = skb->len + esp->tailen - skb_transport_offset(skb);
        if (len > IP_MAX_MTU)
                return ERR_PTR(-EMSGSIZE);

        rcu_read_lock();
        sk = esp_find_tcp_sk(x);
        rcu_read_unlock();

        if (IS_ERR(sk))
                return ERR_CAST(sk);

        *lenp = htons(len);
        esph = (struct ip_esp_hdr *)(lenp + 1);

        return esph;
}
#else
static struct ip_esp_hdr *esp_output_tcp_encap(struct xfrm_state *x,
                                                    struct sk_buff *skb,
                                                    struct esp_info *esp)
{
        return ERR_PTR(-EOPNOTSUPP);
}
#endif

static int esp_output_encap(struct xfrm_state *x, struct sk_buff *skb,
                            struct esp_info *esp)
{
        struct xfrm_encap_tmpl *encap = x->encap;
        struct ip_esp_hdr *esph;
        __be16 sport, dport;
        int encap_type;

        spin_lock_bh(&x->lock);
        sport = encap->encap_sport;
        dport = encap->encap_dport;
        encap_type = encap->encap_type;
        spin_unlock_bh(&x->lock);

        switch (encap_type) {
        default:
        case UDP_ENCAP_ESPINUDP:
        case UDP_ENCAP_ESPINUDP_NON_IKE:
                esph = esp_output_udp_encap(skb, encap_type, esp, sport, dport);
                break;
        case TCP_ENCAP_ESPINTCP:
                esph = esp_output_tcp_encap(x, skb, esp);
                break;
        }

        if (IS_ERR(esph))
                return PTR_ERR(esph);

        esp->esph = esph;

        return 0;
}

int esp_output_head(struct xfrm_state *x, struct sk_buff *skb, struct esp_info *esp)
{
        u8 *tail;
        u8 *vaddr;
        int nfrags;
        int esph_offset;
        struct page *page;
        struct sk_buff *trailer;
        int tailen = esp->tailen;

        /* this is non-NULL only with TCP/UDP Encapsulation */
        if (x->encap) {
                int err = esp_output_encap(x, skb, esp);

                if (err < 0)
                        return err;
        }

        if (!skb_cloned(skb)) {
                if (tailen <= skb_tailroom(skb)) {
                        nfrags = 1;
                        trailer = skb;
                        tail = skb_tail_pointer(trailer);

                        goto skip_cow;
                } else if ((skb_shinfo(skb)->nr_frags < MAX_SKB_FRAGS)
                           && !skb_has_frag_list(skb)) {
                        int allocsize;
                        struct sock *sk = skb->sk;
                        struct page_frag *pfrag = &x->xfrag;

                        esp->inplace = false;

                        allocsize = ALIGN(tailen, L1_CACHE_BYTES);

                        spin_lock_bh(&x->lock);

                        if (unlikely(!skb_page_frag_refill(allocsize, pfrag, GFP_ATOMIC))) {
                                spin_unlock_bh(&x->lock);
                                goto cow;
                        }

                        page = pfrag->page;
                        get_page(page);

                        vaddr = kmap_atomic(page);

                        tail = vaddr + pfrag->offset;

                        esp_output_fill_trailer(tail, esp->tfclen, esp->plen, esp->proto);

                        kunmap_atomic(vaddr);

                        nfrags = skb_shinfo(skb)->nr_frags;

                        __skb_fill_page_desc(skb, nfrags, page, pfrag->offset,
                                             tailen);
                        skb_shinfo(skb)->nr_frags = ++nfrags;

                        pfrag->offset = pfrag->offset + allocsize;

                        spin_unlock_bh(&x->lock);

                        nfrags++;

                        skb->len += tailen;
                        skb->data_len += tailen;
                        skb->truesize += tailen;
                        if (sk && sk_fullsock(sk))
                                refcount_add(tailen, &sk->sk_wmem_alloc);

                        goto out;
                }
        }

cow:
        esph_offset = (unsigned char *)esp->esph - skb_transport_header(skb);

        nfrags = skb_cow_data(skb, tailen, &trailer);
        if (nfrags < 0)
                goto out;
        tail = skb_tail_pointer(trailer);
        esp->esph = (struct ip_esp_hdr *)(skb_transport_header(skb) + esph_offset);

skip_cow:
        esp_output_fill_trailer(tail, esp->tfclen, esp->plen, esp->proto);
        pskb_put(skb, trailer, tailen);

out:
        return nfrags;
}
EXPORT_SYMBOL_GPL(esp_output_head);

int esp_output_tail(struct xfrm_state *x, struct sk_buff *skb, struct esp_info *esp)
{
        u8 *iv;
        int alen;
        void *tmp;
        int ivlen;
        int assoclen;
        int extralen;
        struct page *page;
        struct ip_esp_hdr *esph;
        struct crypto_aead *aead;
        struct aead_request *req;
        struct scatterlist *sg, *dsg;
        struct esp_output_extra *extra;
        int err = -ENOMEM;

        assoclen = sizeof(struct ip_esp_hdr);
        extralen = 0;

        if (x->props.flags & XFRM_STATE_ESN) {
                extralen += sizeof(*extra);
                assoclen += sizeof(__be32);
        }

        aead = x->data;
        alen = crypto_aead_authsize(aead);
        ivlen = crypto_aead_ivsize(aead);

        tmp = esp_alloc_tmp(aead, esp->nfrags + 2, extralen);
        if (!tmp)
                goto error;

        extra = esp_tmp_extra(tmp);
        iv = esp_tmp_iv(aead, tmp, extralen);
        req = esp_tmp_req(aead, iv);
        sg = esp_req_sg(aead, req);

        if (esp->inplace)
                dsg = sg;
        else
                dsg = &sg[esp->nfrags];

        esph = esp_output_set_extra(skb, x, esp->esph, extra);
        esp->esph = esph;

        sg_init_table(sg, esp->nfrags);
        err = skb_to_sgvec(skb, sg,
                           (unsigned char *)esph - skb->data,
                           assoclen + ivlen + esp->clen + alen);
        if (unlikely(err < 0))
                goto error_free;

        if (!esp->inplace) {
                int allocsize;
                struct page_frag *pfrag = &x->xfrag;

                allocsize = ALIGN(skb->data_len, L1_CACHE_BYTES);

                spin_lock_bh(&x->lock);
                if (unlikely(!skb_page_frag_refill(allocsize, pfrag, GFP_ATOMIC))) {
                        spin_unlock_bh(&x->lock);
                        goto error_free;
                }

                skb_shinfo(skb)->nr_frags = 1;

                page = pfrag->page;
                get_page(page);
                /* replace page frags in skb with new page */
                __skb_fill_page_desc(skb, 0, page, pfrag->offset, skb->data_len);
                pfrag->offset = pfrag->offset + allocsize;
                spin_unlock_bh(&x->lock);

                sg_init_table(dsg, skb_shinfo(skb)->nr_frags + 1);
                err = skb_to_sgvec(skb, dsg,
                                   (unsigned char *)esph - skb->data,
                                   assoclen + ivlen + esp->clen + alen);
                if (unlikely(err < 0))
                        goto error_free;
        }

        if ((x->props.flags & XFRM_STATE_ESN))
                aead_request_set_callback(req, 0, esp_output_done_esn, skb);
        else
                aead_request_set_callback(req, 0, esp_output_done, skb);

        aead_request_set_crypt(req, sg, dsg, ivlen + esp->clen, iv);
        aead_request_set_ad(req, assoclen);

        memset(iv, 0, ivlen);
        memcpy(iv + ivlen - min(ivlen, 8), (u8 *)&esp->seqno + 8 - min(ivlen, 8),
               min(ivlen, 8));

        ESP_SKB_CB(skb)->tmp = tmp;
        err = crypto_aead_encrypt(req);

        switch (err) {
        case -EINPROGRESS:
                goto error;

        case -ENOSPC:
                err = NET_XMIT_DROP;
                break;

        case 0:
                if ((x->props.flags & XFRM_STATE_ESN))
                        esp_output_restore_header(skb);
        }

        if (sg != dsg)
                esp_ssg_unref(x, tmp);

        if (!err && x->encap && x->encap->encap_type == TCP_ENCAP_ESPINTCP)
                err = esp_output_tail_tcp(x, skb);

error_free:
        kfree(tmp);
error:
        return err;
}
EXPORT_SYMBOL_GPL(esp_output_tail);

static int esp_output(struct xfrm_state *x, struct sk_buff *skb)
{
        int alen;
        int blksize;
        struct ip_esp_hdr *esph;
        struct crypto_aead *aead;
        struct esp_info esp;

        esp.inplace = true;

        esp.proto = *skb_mac_header(skb);
        *skb_mac_header(skb) = IPPROTO_ESP;

        /* skb is pure payload to encrypt */

        aead = x->data;
        alen = crypto_aead_authsize(aead);

        esp.tfclen = 0;
        if (x->tfcpad) {
                struct xfrm_dst *dst = (struct xfrm_dst *)skb_dst(skb);
                u32 padto;

                padto = min(x->tfcpad, xfrm_state_mtu(x, dst->child_mtu_cached));
                if (skb->len < padto)
                        esp.tfclen = padto - skb->len;
        }
        blksize = ALIGN(crypto_aead_blocksize(aead), 4);
        esp.clen = ALIGN(skb->len + 2 + esp.tfclen, blksize);
        esp.plen = esp.clen - skb->len - esp.tfclen;
        esp.tailen = esp.tfclen + esp.plen + alen;

        esp.esph = ip_esp_hdr(skb);

        esp.nfrags = esp_output_head(x, skb, &esp);
        if (esp.nfrags < 0)
                return esp.nfrags;

        esph = esp.esph;
        esph->spi = x->id.spi;

        esph->seq_no = htonl(XFRM_SKB_CB(skb)->seq.output.low);
        esp.seqno = cpu_to_be64(XFRM_SKB_CB(skb)->seq.output.low +
                                 ((u64)XFRM_SKB_CB(skb)->seq.output.hi << 32));

        skb_push(skb, -skb_network_offset(skb));

        return esp_output_tail(x, skb, &esp);
}

static inline int esp_remove_trailer(struct sk_buff *skb)
{
        struct xfrm_state *x = xfrm_input_state(skb);
        struct xfrm_offload *xo = xfrm_offload(skb);
        struct crypto_aead *aead = x->data;
        int alen, hlen, elen;
        int padlen, trimlen;
        __wsum csumdiff;
        u8 nexthdr[2];
        int ret;

        alen = crypto_aead_authsize(aead);
        hlen = sizeof(struct ip_esp_hdr) + crypto_aead_ivsize(aead);
        elen = skb->len - hlen;

        if (xo && (xo->flags & XFRM_ESP_NO_TRAILER)) {
                ret = xo->proto;
                goto out;
        }

        if (skb_copy_bits(skb, skb->len - alen - 2, nexthdr, 2))
                BUG();

        ret = -EINVAL;
        padlen = nexthdr[0];
        if (padlen + 2 + alen >= elen) {
                net_dbg_ratelimited("ipsec esp packet is garbage padlen=%d, elen=%d\n",
                                    padlen + 2, elen - alen);
                goto out;
        }

        trimlen = alen + padlen + 2;
        if (skb->ip_summed == CHECKSUM_COMPLETE) {
                csumdiff = skb_checksum(skb, skb->len - trimlen, trimlen, 0);
                skb->csum = csum_block_sub(skb->csum, csumdiff,
                                           skb->len - trimlen);
        }
        pskb_trim(skb, skb->len - trimlen);

        ret = nexthdr[1];

out:
        return ret;
}

int esp_input_done2(struct sk_buff *skb, int err)
{
        const struct iphdr *iph;
        struct xfrm_state *x = xfrm_input_state(skb);
        struct xfrm_offload *xo = xfrm_offload(skb);
        struct crypto_aead *aead = x->data;
        int hlen = sizeof(struct ip_esp_hdr) + crypto_aead_ivsize(aead);
        int ihl;

        if (!xo || (xo && !(xo->flags & CRYPTO_DONE)))
                kfree(ESP_SKB_CB(skb)->tmp);

        if (unlikely(err))
                goto out;

        err = esp_remove_trailer(skb);
        if (unlikely(err < 0))
                goto out;

        iph = ip_hdr(skb);
        ihl = iph->ihl * 4;

        if (x->encap) {
                struct xfrm_encap_tmpl *encap = x->encap;
                struct tcphdr *th = (void *)(skb_network_header(skb) + ihl);
                struct udphdr *uh = (void *)(skb_network_header(skb) + ihl);
                __be16 source;

                switch (x->encap->encap_type) {
                case TCP_ENCAP_ESPINTCP:
                        source = th->source;
                        break;
                case UDP_ENCAP_ESPINUDP:
                case UDP_ENCAP_ESPINUDP_NON_IKE:
                        source = uh->source;
                        break;
                default:
                        WARN_ON_ONCE(1);
                        err = -EINVAL;
                        goto out;
                }

                /*
                 * 1) if the NAT-T peer's IP or port changed then
                 *    advertize the change to the keying daemon.
                 *    This is an inbound SA, so just compare
                 *    SRC ports.
                 */
                if (iph->saddr != x->props.saddr.a4 ||
                    source != encap->encap_sport) {
                        xfrm_address_t ipaddr;

                        ipaddr.a4 = iph->saddr;
                        km_new_mapping(x, &ipaddr, source);

                        /* XXX: perhaps add an extra
                         * policy check here, to see
                         * if we should allow or
                         * reject a packet from a
                         * different source
                         * address/port.
                         */
                }

                /*
                 * 2) ignore UDP/TCP checksums in case
                 *    of NAT-T in Transport Mode, or
                 *    perform other post-processing fixes
                 *    as per draft-ietf-ipsec-udp-encaps-06,
                 *    section 3.1.2
                 */
                if (x->props.mode == XFRM_MODE_TRANSPORT)
                        skb->ip_summed = CHECKSUM_UNNECESSARY;
        }

        skb_pull_rcsum(skb, hlen);
        if (x->props.mode == XFRM_MODE_TUNNEL)
                skb_reset_transport_header(skb);
        else
                skb_set_transport_header(skb, -ihl);

        /* RFC4303: Drop dummy packets without any error */
        if (err == IPPROTO_NONE)
                err = -EINVAL;

out:
        return err;
}
EXPORT_SYMBOL_GPL(esp_input_done2);

static void esp_input_done(struct crypto_async_request *base, int err)
{
        struct sk_buff *skb = base->data;

        xfrm_input_resume(skb, esp_input_done2(skb, err));
}

static void esp_input_restore_header(struct sk_buff *skb)
{
        esp_restore_header(skb, 0);
        __skb_pull(skb, 4);
}

static void esp_input_set_header(struct sk_buff *skb, __be32 *seqhi)
{
        struct xfrm_state *x = xfrm_input_state(skb);
        struct ip_esp_hdr *esph;

        /* For ESN we move the header forward by 4 bytes to
         * accomodate the high bits.  We will move it back after
         * decryption.
         */
        if ((x->props.flags & XFRM_STATE_ESN)) {
                esph = skb_push(skb, 4);
                *seqhi = esph->spi;
                esph->spi = esph->seq_no;
                esph->seq_no = XFRM_SKB_CB(skb)->seq.input.hi;
        }
}

static void esp_input_done_esn(struct crypto_async_request *base, int err)
{
        struct sk_buff *skb = base->data;

        esp_input_restore_header(skb);
        esp_input_done(base, err);
}

/*
 * Note: detecting truncated vs. non-truncated authentication data is very
 * expensive, so we only support truncated data, which is the recommended
 * and common case.
 */
static int esp_input(struct xfrm_state *x, struct sk_buff *skb)
{
        struct crypto_aead *aead = x->data;
        struct aead_request *req;
        struct sk_buff *trailer;
        int ivlen = crypto_aead_ivsize(aead);
        int elen = skb->len - sizeof(struct ip_esp_hdr) - ivlen;
        int nfrags;
        int assoclen;
        int seqhilen;
        __be32 *seqhi;
        void *tmp;
        u8 *iv;
        struct scatterlist *sg;
        int err = -EINVAL;

        if (!pskb_may_pull(skb, sizeof(struct ip_esp_hdr) + ivlen))
                goto out;

        if (elen <= 0)
                goto out;

        assoclen = sizeof(struct ip_esp_hdr);
        seqhilen = 0;

        if (x->props.flags & XFRM_STATE_ESN) {
                seqhilen += sizeof(__be32);
                assoclen += seqhilen;
        }

        if (!skb_cloned(skb)) {
                if (!skb_is_nonlinear(skb)) {
                        nfrags = 1;

                        goto skip_cow;
                } else if (!skb_has_frag_list(skb)) {
                        nfrags = skb_shinfo(skb)->nr_frags;
                        nfrags++;

                        goto skip_cow;
                }
        }

        err = skb_cow_data(skb, 0, &trailer);
        if (err < 0)
                goto out;

        nfrags = err;

skip_cow:
        err = -ENOMEM;
        tmp = esp_alloc_tmp(aead, nfrags, seqhilen);
        if (!tmp)
                goto out;

        ESP_SKB_CB(skb)->tmp = tmp;
        seqhi = esp_tmp_extra(tmp);
        iv = esp_tmp_iv(aead, tmp, seqhilen);
        req = esp_tmp_req(aead, iv);
        sg = esp_req_sg(aead, req);

        esp_input_set_header(skb, seqhi);

        sg_init_table(sg, nfrags);
        err = skb_to_sgvec(skb, sg, 0, skb->len);
        if (unlikely(err < 0)) {
                kfree(tmp);
                goto out;
        }

        skb->ip_summed = CHECKSUM_NONE;

        if ((x->props.flags & XFRM_STATE_ESN))
                aead_request_set_callback(req, 0, esp_input_done_esn, skb);
        else
                aead_request_set_callback(req, 0, esp_input_done, skb);

        aead_request_set_crypt(req, sg, sg, elen + ivlen, iv);
        aead_request_set_ad(req, assoclen);

        err = crypto_aead_decrypt(req);
        if (err == -EINPROGRESS)
                goto out;

        if ((x->props.flags & XFRM_STATE_ESN))
                esp_input_restore_header(skb);

        err = esp_input_done2(skb, err);

out:
        return err;
}

static int esp4_err(struct sk_buff *skb, u32 info)
{
        struct net *net = dev_net(skb->dev);
        const struct iphdr *iph = (const struct iphdr *)skb->data;
        struct ip_esp_hdr *esph = (struct ip_esp_hdr *)(skb->data+(iph->ihl<<2));
        struct xfrm_state *x;

        switch (icmp_hdr(skb)->type) {
        case ICMP_DEST_UNREACH:
                if (icmp_hdr(skb)->code != ICMP_FRAG_NEEDED)
                        return 0;
        case ICMP_REDIRECT:
                break;
        default:
                return 0;
        }

        x = xfrm_state_lookup(net, skb->mark, (const xfrm_address_t *)&iph->daddr,
                              esph->spi, IPPROTO_ESP, AF_INET);
        if (!x)
                return 0;

        if (icmp_hdr(skb)->type == ICMP_DEST_UNREACH)
                ipv4_update_pmtu(skb, net, info, 0, IPPROTO_ESP);
        else
                ipv4_redirect(skb, net, 0, IPPROTO_ESP);
        xfrm_state_put(x);

        return 0;
}

static void esp_destroy(struct xfrm_state *x)
{
        struct crypto_aead *aead = x->data;

        if (!aead)
                return;

        crypto_free_aead(aead);
}

static int esp_init_aead(struct xfrm_state *x)
{
        char aead_name[CRYPTO_MAX_ALG_NAME];
        struct crypto_aead *aead;
        int err;

        err = -ENAMETOOLONG;
        if (snprintf(aead_name, CRYPTO_MAX_ALG_NAME, "%s(%s)",
                     x->geniv, x->aead->alg_name) >= CRYPTO_MAX_ALG_NAME)
                goto error;

        aead = crypto_alloc_aead(aead_name, 0, 0);
        err = PTR_ERR(aead);
        if (IS_ERR(aead))
                goto error;

        x->data = aead;

        err = crypto_aead_setkey(aead, x->aead->alg_key,
                                 (x->aead->alg_key_len + 7) / 8);
        if (err)
                goto error;

        err = crypto_aead_setauthsize(aead, x->aead->alg_icv_len / 8);
        if (err)
                goto error;

error:
        return err;
}

static int esp_init_authenc(struct xfrm_state *x)
{
        struct crypto_aead *aead;
        struct crypto_authenc_key_param *param;
        struct rtattr *rta;
        char *key;
        char *p;
        char authenc_name[CRYPTO_MAX_ALG_NAME];
        unsigned int keylen;
        int err;

        err = -EINVAL;
        if (!x->ealg)
                goto error;

        err = -ENAMETOOLONG;

        if ((x->props.flags & XFRM_STATE_ESN)) {
                if (snprintf(authenc_name, CRYPTO_MAX_ALG_NAME,
                             "%s%sauthencesn(%s,%s)%s",
                             x->geniv ?: "", x->geniv ? "(" : "",
                             x->aalg ? x->aalg->alg_name : "digest_null",
                             x->ealg->alg_name,
                             x->geniv ? ")" : "") >= CRYPTO_MAX_ALG_NAME)
                        goto error;
        } else {
                if (snprintf(authenc_name, CRYPTO_MAX_ALG_NAME,
                             "%s%sauthenc(%s,%s)%s",
                             x->geniv ?: "", x->geniv ? "(" : "",
                             x->aalg ? x->aalg->alg_name : "digest_null",
                             x->ealg->alg_name,
                             x->geniv ? ")" : "") >= CRYPTO_MAX_ALG_NAME)
                        goto error;
        }

        aead = crypto_alloc_aead(authenc_name, 0, 0);
        err = PTR_ERR(aead);
        if (IS_ERR(aead))
                goto error;

        x->data = aead;

        keylen = (x->aalg ? (x->aalg->alg_key_len + 7) / 8 : 0) +
                 (x->ealg->alg_key_len + 7) / 8 + RTA_SPACE(sizeof(*param));
        err = -ENOMEM;
        key = kmalloc(keylen, GFP_KERNEL);
        if (!key)
                goto error;

        p = key;
        rta = (void *)p;
        rta->rta_type = CRYPTO_AUTHENC_KEYA_PARAM;
        rta->rta_len = RTA_LENGTH(sizeof(*param));
        param = RTA_DATA(rta);
        p += RTA_SPACE(sizeof(*param));

        if (x->aalg) {
                struct xfrm_algo_desc *aalg_desc;

                memcpy(p, x->aalg->alg_key, (x->aalg->alg_key_len + 7) / 8);
                p += (x->aalg->alg_key_len + 7) / 8;

                aalg_desc = xfrm_aalg_get_byname(x->aalg->alg_name, 0);
                BUG_ON(!aalg_desc);

                err = -EINVAL;
                if (aalg_desc->uinfo.auth.icv_fullbits / 8 !=
                    crypto_aead_authsize(aead)) {
                        pr_info("ESP: %s digestsize %u != %hu\n",
                                x->aalg->alg_name,
                                crypto_aead_authsize(aead),
                                aalg_desc->uinfo.auth.icv_fullbits / 8);
                        goto free_key;
                }

                err = crypto_aead_setauthsize(
                        aead, x->aalg->alg_trunc_len / 8);
                if (err)
                        goto free_key;
        }

        param->enckeylen = cpu_to_be32((x->ealg->alg_key_len + 7) / 8);
        memcpy(p, x->ealg->alg_key, (x->ealg->alg_key_len + 7) / 8);

        err = crypto_aead_setkey(aead, key, keylen);

free_key:
        kfree(key);

error:
        return err;
}

static int esp_init_state(struct xfrm_state *x)
{
        struct crypto_aead *aead;
        u32 align;
        int err;

        x->data = NULL;

        if (x->aead)
                err = esp_init_aead(x);
        else
                err = esp_init_authenc(x);

        if (err)
                goto error;

        aead = x->data;

        x->props.header_len = sizeof(struct ip_esp_hdr) +
                              crypto_aead_ivsize(aead);
        if (x->props.mode == XFRM_MODE_TUNNEL)
                x->props.header_len += sizeof(struct iphdr);
        else if (x->props.mode == XFRM_MODE_BEET && x->sel.family != AF_INET6)
                x->props.header_len += IPV4_BEET_PHMAXLEN;
        if (x->encap) {
                struct xfrm_encap_tmpl *encap = x->encap;

                switch (encap->encap_type) {
                default:
                        err = -EINVAL;
                        goto error;
                case UDP_ENCAP_ESPINUDP:
                        x->props.header_len += sizeof(struct udphdr);
                        break;
                case UDP_ENCAP_ESPINUDP_NON_IKE:
                        x->props.header_len += sizeof(struct udphdr) + 2 * sizeof(u32);
                        break;
#ifdef CONFIG_INET_ESPINTCP
                case TCP_ENCAP_ESPINTCP:
                        /* only the length field, TCP encap is done by
                         * the socket
                         */
                        x->props.header_len += 2;
                        break;
#endif
                }
        }

        align = ALIGN(crypto_aead_blocksize(aead), 4);
        x->props.trailer_len = align + 1 + crypto_aead_authsize(aead);

error:
        return err;
}

static int esp4_rcv_cb(struct sk_buff *skb, int err)
{
        return 0;
}

static const struct xfrm_type esp_type =
{
        .description    = "ESP4",
        .owner          = THIS_MODULE,
        .proto          = IPPROTO_ESP,
        .flags          = XFRM_TYPE_REPLAY_PROT,
        .init_state     = esp_init_state,
        .destructor     = esp_destroy,
        .input          = esp_input,
        .output         = esp_output,
};

static struct xfrm4_protocol esp4_protocol = {
        .handler        =       xfrm4_rcv,
        .input_handler  =       xfrm_input,
        .cb_handler     =       esp4_rcv_cb,
        .err_handler    =       esp4_err,
        .priority       =       0,
};

static int __init esp4_init(void)
{
        if (xfrm_register_type(&esp_type, AF_INET) < 0) {
                pr_info("%s: can't add xfrm type\n", __func__);
                return -EAGAIN;
        }
        if (xfrm4_protocol_register(&esp4_protocol, IPPROTO_ESP) < 0) {
                pr_info("%s: can't add protocol\n", __func__);
                xfrm_unregister_type(&esp_type, AF_INET);
                return -EAGAIN;
        }
        return 0;
}

static void __exit esp4_fini(void)
{
        if (xfrm4_protocol_deregister(&esp4_protocol, IPPROTO_ESP) < 0)
                pr_info("%s: can't remove protocol\n", __func__);
        xfrm_unregister_type(&esp_type, AF_INET);
}

module_init(esp4_init);
module_exit(esp4_fini);
MODULE_LICENSE("GPL");
MODULE_ALIAS_XFRM_TYPE(AF_INET, XFRM_PROTO_ESP);