// SPDX-License-Identifier: GPL-2.0-only
/*
 * IPV4 GSO/GRO offload support
 * Linux INET implementation
 *
 * Copyright (C) 2016 secunet Security Networks AG
 * Author: Steffen Klassert <steffen.klassert@secunet.com>
 *
 * ESP GRO support
 */

#include <linux/skbuff.h>
#include <linux/init.h>
#include <net/protocol.h>
#include <crypto/aead.h>
#include <crypto/authenc.h>
#include <linux/err.h>
#include <linux/module.h>
#include <net/gro.h>
#include <net/gso.h>
#include <net/ip.h>
#include <net/xfrm.h>
#include <net/esp.h>
#include <linux/scatterlist.h>
#include <linux/kernel.h>
#include <linux/slab.h>
#include <linux/spinlock.h>
#include <net/udp.h>

static struct sk_buff *esp4_gro_receive(struct list_head *head,
                                        struct sk_buff *skb)
{
        int offset = skb_gro_offset(skb);
        struct xfrm_offload *xo;
        struct xfrm_state *x;
        int encap_type = 0;
        __be32 seq;
        __be32 spi;

        if (!pskb_pull(skb, offset))
                return NULL;

        if (xfrm_parse_spi(skb, IPPROTO_ESP, &spi, &seq) != 0)
                goto out;

        xo = xfrm_offload(skb);
        if (!xo || !(xo->flags & CRYPTO_DONE)) {
                struct sec_path *sp = secpath_set(skb);

                if (!sp)
                        goto out;

                if (sp->len == XFRM_MAX_DEPTH)
                        goto out_reset;

                x = xfrm_input_state_lookup(dev_net(skb->dev), skb->mark,
                                            (xfrm_address_t *)&ip_hdr(skb)->daddr,
                                            spi, IPPROTO_ESP, AF_INET);

                if (unlikely(x && x->dir && x->dir != XFRM_SA_DIR_IN)) {
                        /* non-offload path will record the error and audit log */
                        xfrm_state_put(x);
                        x = NULL;
                }

                if (!x)
                        goto out_reset;

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

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

                xo = xfrm_offload(skb);
                if (!xo)
                        goto out_reset;
        }

        xo->flags |= XFRM_GRO;

        if (NAPI_GRO_CB(skb)->proto == IPPROTO_UDP)
                encap_type = UDP_ENCAP_ESPINUDP;

        XFRM_TUNNEL_SKB_CB(skb)->tunnel.ip4 = NULL;
        XFRM_SPI_SKB_CB(skb)->family = AF_INET;
        XFRM_SPI_SKB_CB(skb)->daddroff = offsetof(struct iphdr, daddr);
        XFRM_SPI_SKB_CB(skb)->seq = seq;

        /* We don't need to handle errors from xfrm_input, it does all
         * the error handling and frees the resources on error. */
        xfrm_input(skb, IPPROTO_ESP, spi, encap_type);

        return ERR_PTR(-EINPROGRESS);
out_reset:
        secpath_reset(skb);
out:
        skb_push(skb, offset);
        NAPI_GRO_CB(skb)->same_flow = 0;
        NAPI_GRO_CB(skb)->flush = 1;

        return NULL;
}

static void esp4_gso_encap(struct xfrm_state *x, struct sk_buff *skb)
{
        struct ip_esp_hdr *esph;
        struct iphdr *iph = ip_hdr(skb);
        struct xfrm_offload *xo = xfrm_offload(skb);
        int proto = iph->protocol;

        skb_push(skb, -skb_network_offset(skb));
        esph = ip_esp_hdr(skb);
        *skb_mac_header(skb) = IPPROTO_ESP;

        esph->spi = x->id.spi;
        esph->seq_no = htonl(XFRM_SKB_CB(skb)->seq.output.low);

        xo->proto = proto;
}

static struct sk_buff *xfrm4_tunnel_gso_segment(struct xfrm_state *x,
                                                struct sk_buff *skb,
                                                netdev_features_t features)
{
        struct xfrm_offload *xo = xfrm_offload(skb);
        const struct xfrm_mode *inner_mode = xfrm_ip2inner_mode(x, xo->proto);
        __be16 type = inner_mode->family == AF_INET6 ? htons(ETH_P_IPV6)
                                                     : htons(ETH_P_IP);

        return skb_eth_gso_segment(skb, features, type);
}

static struct sk_buff *xfrm4_transport_gso_segment(struct xfrm_state *x,
                                                   struct sk_buff *skb,
                                                   netdev_features_t features)
{
        const struct net_offload *ops;
        struct sk_buff *segs = ERR_PTR(-EINVAL);
        struct xfrm_offload *xo = xfrm_offload(skb);

        skb->transport_header += x->props.header_len;
        ops = rcu_dereference(inet_offloads[xo->proto]);
        if (likely(ops && ops->callbacks.gso_segment))
                segs = ops->callbacks.gso_segment(skb, features);

        return segs;
}

static struct sk_buff *xfrm4_beet_gso_segment(struct xfrm_state *x,
                                              struct sk_buff *skb,
                                              netdev_features_t features)
{
        struct xfrm_offload *xo = xfrm_offload(skb);
        struct sk_buff *segs = ERR_PTR(-EINVAL);
        const struct net_offload *ops;
        u8 proto = xo->proto;

        skb->transport_header += x->props.header_len;

        if (x->sel.family != AF_INET6) {
                if (proto == IPPROTO_BEETPH) {
                        struct ip_beet_phdr *ph =
                                (struct ip_beet_phdr *)skb->data;

                        skb->transport_header += ph->hdrlen * 8;
                        proto = ph->nexthdr;
                } else {
                        skb->transport_header -= IPV4_BEET_PHMAXLEN;
                }
        } else {
                __be16 frag;

                skb->transport_header +=
                        ipv6_skip_exthdr(skb, 0, &proto, &frag);
                if (proto == IPPROTO_TCP)
                        skb_shinfo(skb)->gso_type |= SKB_GSO_TCPV4;
        }

        if (proto == IPPROTO_IPV6)
                skb_shinfo(skb)->gso_type |= SKB_GSO_IPXIP4;

        __skb_pull(skb, skb_transport_offset(skb));
        ops = rcu_dereference(inet_offloads[proto]);
        if (likely(ops && ops->callbacks.gso_segment))
                segs = ops->callbacks.gso_segment(skb, features);

        return segs;
}

static struct sk_buff *xfrm4_outer_mode_gso_segment(struct xfrm_state *x,
                                                    struct sk_buff *skb,
                                                    netdev_features_t features)
{
        switch (x->outer_mode.encap) {
        case XFRM_MODE_TUNNEL:
                return xfrm4_tunnel_gso_segment(x, skb, features);
        case XFRM_MODE_TRANSPORT:
                return xfrm4_transport_gso_segment(x, skb, features);
        case XFRM_MODE_BEET:
                return xfrm4_beet_gso_segment(x, skb, features);
        }

        return ERR_PTR(-EOPNOTSUPP);
}

static struct sk_buff *esp4_gso_segment(struct sk_buff *skb,
                                        netdev_features_t features)
{
        struct xfrm_state *x;
        struct ip_esp_hdr *esph;
        struct crypto_aead *aead;
        netdev_features_t esp_features = features;
        struct xfrm_offload *xo = xfrm_offload(skb);
        struct sec_path *sp;

        if (!xo)
                return ERR_PTR(-EINVAL);

        if (!(skb_shinfo(skb)->gso_type & SKB_GSO_ESP))
                return ERR_PTR(-EINVAL);

        sp = skb_sec_path(skb);
        x = sp->xvec[sp->len - 1];
        aead = x->data;
        esph = ip_esp_hdr(skb);

        if (esph->spi != x->id.spi)
                return ERR_PTR(-EINVAL);

        if (!pskb_may_pull(skb, sizeof(*esph) + crypto_aead_ivsize(aead)))
                return ERR_PTR(-EINVAL);

        __skb_pull(skb, sizeof(*esph) + crypto_aead_ivsize(aead));

        skb->encap_hdr_csum = 1;

        if ((!(skb->dev->gso_partial_features & NETIF_F_HW_ESP) &&
             !(features & NETIF_F_HW_ESP)) || x->xso.dev != skb->dev)
                esp_features = features & ~(NETIF_F_SG | NETIF_F_CSUM_MASK |
                                            NETIF_F_SCTP_CRC);
        else if (!(features & NETIF_F_HW_ESP_TX_CSUM) &&
                 !(skb->dev->gso_partial_features & NETIF_F_HW_ESP_TX_CSUM))
                esp_features = features & ~(NETIF_F_CSUM_MASK |
                                            NETIF_F_SCTP_CRC);

        xo->flags |= XFRM_GSO_SEGMENT;

        return xfrm4_outer_mode_gso_segment(x, skb, esp_features);
}

static int esp_input_tail(struct xfrm_state *x, struct sk_buff *skb)
{
        struct crypto_aead *aead = x->data;
        struct xfrm_offload *xo = xfrm_offload(skb);

        if (!pskb_may_pull(skb, sizeof(struct ip_esp_hdr) + crypto_aead_ivsize(aead)))
                return -EINVAL;

        if (!(xo->flags & CRYPTO_DONE))
                skb->ip_summed = CHECKSUM_NONE;

        return esp_input_done2(skb, 0);
}

static int esp_xmit(struct xfrm_state *x, struct sk_buff *skb,  netdev_features_t features)
{
        int err;
        int alen;
        int blksize;
        struct xfrm_offload *xo;
        struct ip_esp_hdr *esph;
        struct crypto_aead *aead;
        struct esp_info esp;
        bool hw_offload = true;
        __u32 seq;
        int encap_type = 0;

        esp.inplace = true;

        xo = xfrm_offload(skb);

        if (!xo)
                return -EINVAL;

        if ((!(features & NETIF_F_HW_ESP) &&
             !(skb->dev->gso_partial_features & NETIF_F_HW_ESP)) ||
            x->xso.dev != skb->dev) {
                xo->flags |= CRYPTO_FALLBACK;
                hw_offload = false;
        }

        esp.proto = xo->proto;

        /* skb is pure payload to encrypt */

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

        esp.tfclen = 0;
        /* XXX: Add support for tfc padding here. */

        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);

        if (x->encap)
                encap_type = x->encap->encap_type;

        if (!hw_offload || !skb_is_gso(skb) || (hw_offload && encap_type == UDP_ENCAP_ESPINUDP)) {
                esp.nfrags = esp_output_head(x, skb, &esp);
                if (esp.nfrags < 0)
                        return esp.nfrags;
        }

        seq = xo->seq.low;

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

        skb_push(skb, -skb_network_offset(skb));

        if (xo->flags & XFRM_GSO_SEGMENT) {
                esph->seq_no = htonl(seq);

                if (!skb_is_gso(skb))
                        xo->seq.low++;
                else
                        xo->seq.low += skb_shinfo(skb)->gso_segs;
        }

        if (xo->seq.low < seq)
                xo->seq.hi++;

        esp.seqno = cpu_to_be64(seq + ((u64)xo->seq.hi << 32));

        if (hw_offload && encap_type == UDP_ENCAP_ESPINUDP) {
                /* In the XFRM stack, the encapsulation protocol is set to iphdr->protocol by
                 * setting *skb_mac_header(skb) (see esp_output_udp_encap()) where skb->mac_header
                 * points to iphdr->protocol (see xfrm4_tunnel_encap_add()).
                 * However, in esp_xmit(), skb->mac_header doesn't point to iphdr->protocol.
                 * Therefore, the protocol field needs to be corrected.
                 */
                ip_hdr(skb)->protocol = IPPROTO_UDP;

                esph->seq_no = htonl(seq);
        }

        ip_hdr(skb)->tot_len = htons(skb->len);
        ip_send_check(ip_hdr(skb));

        if (hw_offload) {
                if (!skb_ext_add(skb, SKB_EXT_SEC_PATH))
                        return -ENOMEM;

                xo = xfrm_offload(skb);
                if (!xo)
                        return -EINVAL;

                xo->flags |= XFRM_XMIT;
                return 0;
        }

        err = esp_output_tail(x, skb, &esp);
        if (err)
                return err;

        secpath_reset(skb);

        if (skb_needs_linearize(skb, skb->dev->features) &&
            __skb_linearize(skb))
                return -ENOMEM;
        return 0;
}

static const struct net_offload esp4_offload = {
        .callbacks = {
                .gro_receive = esp4_gro_receive,
                .gso_segment = esp4_gso_segment,
        },
};

static const struct xfrm_type_offload esp_type_offload = {
        .owner          = THIS_MODULE,
        .proto          = IPPROTO_ESP,
        .input_tail     = esp_input_tail,
        .xmit           = esp_xmit,
        .encap          = esp4_gso_encap,
};

static int __init esp4_offload_init(void)
{
        if (xfrm_register_type_offload(&esp_type_offload, AF_INET) < 0) {
                pr_info("%s: can't add xfrm type offload\n", __func__);
                return -EAGAIN;
        }

        return inet_add_offload(&esp4_offload, IPPROTO_ESP);
}

static void __exit esp4_offload_exit(void)
{
        xfrm_unregister_type_offload(&esp_type_offload, AF_INET);
        inet_del_offload(&esp4_offload, IPPROTO_ESP);
}

module_init(esp4_offload_init);
module_exit(esp4_offload_exit);
MODULE_LICENSE("GPL");
MODULE_AUTHOR("Steffen Klassert <steffen.klassert@secunet.com>");
MODULE_ALIAS_XFRM_OFFLOAD_TYPE(AF_INET, XFRM_PROTO_ESP);
MODULE_DESCRIPTION("IPV4 GSO/GRO offload support");