// SPDX-License-Identifier: GPL-2.0
/*
 * xfrm6_input.c: based on net/ipv4/xfrm4_input.c
 *
 * Authors:
 *      Mitsuru KANDA @USAGI
 *      Kazunori MIYAZAWA @USAGI
 *      Kunihiro Ishiguro <kunihiro@ipinfusion.com>
 *      YOSHIFUJI Hideaki @USAGI
 *              IPv6 support
 */

#include <linux/module.h>
#include <linux/string.h>
#include <linux/netfilter.h>
#include <linux/netfilter_ipv6.h>
#include <net/ipv6.h>
#include <net/xfrm.h>
#include <net/protocol.h>
#include <net/gro.h>

int xfrm6_rcv_spi(struct sk_buff *skb, int nexthdr, __be32 spi,
                  struct ip6_tnl *t)
{
        XFRM_TUNNEL_SKB_CB(skb)->tunnel.ip6 = t;
        XFRM_SPI_SKB_CB(skb)->family = AF_INET6;
        XFRM_SPI_SKB_CB(skb)->daddroff = offsetof(struct ipv6hdr, daddr);
        return xfrm_input(skb, nexthdr, spi, 0);
}
EXPORT_SYMBOL(xfrm6_rcv_spi);

static int xfrm6_transport_finish2(struct net *net, struct sock *sk,
                                   struct sk_buff *skb)
{
        if (xfrm_trans_queue(skb, ip6_rcv_finish)) {
                kfree_skb(skb);
                return NET_RX_DROP;
        }

        return 0;
}

int xfrm6_transport_finish(struct sk_buff *skb, int async)
{
        struct xfrm_offload *xo = xfrm_offload(skb);
        struct net_device *dev = skb->dev;
        int nhlen = -skb_network_offset(skb);

        skb_network_header(skb)[IP6CB(skb)->nhoff] =
                XFRM_MODE_SKB_CB(skb)->protocol;

#ifndef CONFIG_NETFILTER
        if (!async)
                return 1;
#endif

        __skb_push(skb, nhlen);
        ipv6_hdr(skb)->payload_len = htons(skb->len - sizeof(struct ipv6hdr));
        skb_postpush_rcsum(skb, skb_network_header(skb), nhlen);

        if (xo && (xo->flags & XFRM_GRO)) {
                /* The full l2 header needs to be preserved so that re-injecting the packet at l2
                 * works correctly in the presence of vlan tags.
                 */
                skb_mac_header_rebuild_full(skb, xo->orig_mac_len);
                skb_reset_network_header(skb);
                skb_reset_transport_header(skb);
                return 0;
        }

        NF_HOOK(NFPROTO_IPV6, NF_INET_PRE_ROUTING,
                dev_net(dev), NULL, skb, dev, NULL,
                xfrm6_transport_finish2);
        return 0;
}

static int __xfrm6_udp_encap_rcv(struct sock *sk, struct sk_buff *skb, bool pull)
{
        struct udp_sock *up = udp_sk(sk);
        struct udphdr *uh;
        struct ipv6hdr *ip6h;
        int len;
        int ip6hlen = sizeof(struct ipv6hdr);
        __u8 *udpdata;
        __be32 *udpdata32;
        u16 encap_type;

        encap_type = READ_ONCE(up->encap_type);
        /* if this is not encapsulated socket, then just return now */
        if (!encap_type)
                return 1;

        /* If this is a paged skb, make sure we pull up
         * whatever data we need to look at. */
        len = skb->len - sizeof(struct udphdr);
        if (!pskb_may_pull(skb, sizeof(struct udphdr) + min(len, 8)))
                return 1;

        /* Now we can get the pointers */
        uh = udp_hdr(skb);
        udpdata = (__u8 *)uh + sizeof(struct udphdr);
        udpdata32 = (__be32 *)udpdata;

        switch (encap_type) {
        default:
        case UDP_ENCAP_ESPINUDP:
                /* Check if this is a keepalive packet.  If so, eat it. */
                if (len == 1 && udpdata[0] == 0xff) {
                        return -EINVAL;
                } else if (len > sizeof(struct ip_esp_hdr) && udpdata32[0] != 0) {
                        /* ESP Packet without Non-ESP header */
                        len = sizeof(struct udphdr);
                } else
                        /* Must be an IKE packet.. pass it through */
                        return 1;
                break;
        }

        /* At this point we are sure that this is an ESPinUDP packet,
         * so we need to remove 'len' bytes from the packet (the UDP
         * header and optional ESP marker bytes) and then modify the
         * protocol to ESP, and then call into the transform receiver.
         */
        if (skb_unclone(skb, GFP_ATOMIC))
                return -EINVAL;

        /* Now we can update and verify the packet length... */
        ip6h = ipv6_hdr(skb);
        ip6h->payload_len = htons(ntohs(ip6h->payload_len) - len);
        if (skb->len < ip6hlen + len) {
                /* packet is too small!?! */
                return -EINVAL;
        }

        /* pull the data buffer up to the ESP header and set the
         * transport header to point to ESP.  Keep UDP on the stack
         * for later.
         */
        if (pull) {
                __skb_pull(skb, len);
                skb_reset_transport_header(skb);
        } else {
                skb_set_transport_header(skb, len);
        }

        /* process ESP */
        return 0;
}

/* If it's a keepalive packet, then just eat it.
 * If it's an encapsulated packet, then pass it to the
 * IPsec xfrm input.
 * Returns 0 if skb passed to xfrm or was dropped.
 * Returns >0 if skb should be passed to UDP.
 * Returns <0 if skb should be resubmitted (-ret is protocol)
 */
int xfrm6_udp_encap_rcv(struct sock *sk, struct sk_buff *skb)
{
        int ret;

        if (skb->protocol == htons(ETH_P_IP))
                return xfrm4_udp_encap_rcv(sk, skb);

        ret = __xfrm6_udp_encap_rcv(sk, skb, true);
        if (!ret)
                return xfrm6_rcv_encap(skb, IPPROTO_ESP, 0,
                                       udp_sk(sk)->encap_type);

        if (ret < 0) {
                kfree_skb(skb);
                return 0;
        }

        return ret;
}

struct sk_buff *xfrm6_gro_udp_encap_rcv(struct sock *sk, struct list_head *head,
                                        struct sk_buff *skb)
{
        int offset = skb_gro_offset(skb);
        const struct net_offload *ops;
        struct sk_buff *pp = NULL;
        int len, dlen;
        __u8 *udpdata;
        __be32 *udpdata32;

        if (skb->protocol == htons(ETH_P_IP))
                return xfrm4_gro_udp_encap_rcv(sk, head, skb);

        len = skb->len - offset;
        dlen = offset + min(len, 8);
        udpdata = skb_gro_header(skb, dlen, offset);
        udpdata32 = (__be32 *)udpdata;
        if (unlikely(!udpdata))
                return NULL;

        rcu_read_lock();
        ops = rcu_dereference(inet6_offloads[IPPROTO_ESP]);
        if (!ops || !ops->callbacks.gro_receive)
                goto out;

        /* check if it is a keepalive or IKE packet */
        if (len <= sizeof(struct ip_esp_hdr) || udpdata32[0] == 0)
                goto out;

        /* set the transport header to ESP */
        skb_set_transport_header(skb, offset);

        NAPI_GRO_CB(skb)->proto = IPPROTO_UDP;

        pp = call_gro_receive(ops->callbacks.gro_receive, head, skb);
        rcu_read_unlock();

        return pp;

out:
        rcu_read_unlock();
        NAPI_GRO_CB(skb)->same_flow = 0;
        NAPI_GRO_CB(skb)->flush = 1;

        return NULL;
}

int xfrm6_rcv_tnl(struct sk_buff *skb, struct ip6_tnl *t)
{
        return xfrm6_rcv_spi(skb, skb_network_header(skb)[IP6CB(skb)->nhoff],
                             0, t);
}
EXPORT_SYMBOL(xfrm6_rcv_tnl);

int xfrm6_rcv(struct sk_buff *skb)
{
        return xfrm6_rcv_tnl(skb, NULL);
}
EXPORT_SYMBOL(xfrm6_rcv);
int xfrm6_input_addr(struct sk_buff *skb, xfrm_address_t *daddr,
                     xfrm_address_t *saddr, u8 proto)
{
        struct net *net = dev_net(skb->dev);
        struct xfrm_state *x = NULL;
        struct sec_path *sp;
        int i = 0;

        sp = secpath_set(skb);
        if (!sp) {
                XFRM_INC_STATS(net, LINUX_MIB_XFRMINERROR);
                goto drop;
        }

        if (1 + sp->len == XFRM_MAX_DEPTH) {
                XFRM_INC_STATS(net, LINUX_MIB_XFRMINBUFFERERROR);
                goto drop;
        }

        for (i = 0; i < 3; i++) {
                xfrm_address_t *dst, *src;

                switch (i) {
                case 0:
                        dst = daddr;
                        src = saddr;
                        break;
                case 1:
                        /* lookup state with wild-card source address */
                        dst = daddr;
                        src = (xfrm_address_t *)&in6addr_any;
                        break;
                default:
                        /* lookup state with wild-card addresses */
                        dst = (xfrm_address_t *)&in6addr_any;
                        src = (xfrm_address_t *)&in6addr_any;
                        break;
                }

                x = xfrm_state_lookup_byaddr(net, skb->mark, dst, src, proto, AF_INET6);
                if (!x)
                        continue;

                if (unlikely(x->dir && x->dir != XFRM_SA_DIR_IN)) {
                        XFRM_INC_STATS(net, LINUX_MIB_XFRMINSTATEDIRERROR);
                        xfrm_state_put(x);
                        x = NULL;
                        continue;
                }

                spin_lock(&x->lock);

                if ((!i || (x->props.flags & XFRM_STATE_WILDRECV)) &&
                    likely(x->km.state == XFRM_STATE_VALID) &&
                    !xfrm_state_check_expire(x)) {
                        spin_unlock(&x->lock);
                        if (x->type->input(x, skb) > 0) {
                                /* found a valid state */
                                break;
                        }
                } else
                        spin_unlock(&x->lock);

                xfrm_state_put(x);
                x = NULL;
        }

        if (!x) {
                XFRM_INC_STATS(net, LINUX_MIB_XFRMINNOSTATES);
                xfrm_audit_state_notfound_simple(skb, AF_INET6);
                goto drop;
        }

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

        spin_lock(&x->lock);

        x->curlft.bytes += skb->len;
        x->curlft.packets++;

        spin_unlock(&x->lock);

        return 1;

drop:
        return -1;
}
EXPORT_SYMBOL(xfrm6_input_addr);