// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * IP Payload Compression Protocol (IPComp) for IPv6 - RFC3173
 *
 * Copyright (C)2003 USAGI/WIDE Project
 *
 * Author       Mitsuru KANDA  <mk@linux-ipv6.org>
 */
/*
 * [Memo]
 *
 * Outbound:
 *  The compression of IP datagram MUST be done before AH/ESP processing,
 *  fragmentation, and the addition of Hop-by-Hop/Routing header.
 *
 * Inbound:
 *  The decompression of IP datagram MUST be done after the reassembly,
 *  AH/ESP processing.
 */

#define pr_fmt(fmt) "IPv6: " fmt

#include <linux/module.h>
#include <net/ip.h>
#include <net/xfrm.h>
#include <net/ipcomp.h>
#include <linux/crypto.h>
#include <linux/err.h>
#include <linux/pfkeyv2.h>
#include <linux/random.h>
#include <linux/percpu.h>
#include <linux/smp.h>
#include <linux/list.h>
#include <linux/vmalloc.h>
#include <linux/rtnetlink.h>
#include <net/ip6_route.h>
#include <net/icmp.h>
#include <net/ipv6.h>
#include <net/protocol.h>
#include <linux/ipv6.h>
#include <linux/icmpv6.h>
#include <linux/mutex.h>

static int ipcomp6_err(struct sk_buff *skb, struct inet6_skb_parm *opt,
                                u8 type, u8 code, int offset, __be32 info)
{
        struct net *net = dev_net(skb->dev);
        __be32 spi;
        const struct ipv6hdr *iph = (const struct ipv6hdr *)skb->data;
        struct ip_comp_hdr *ipcomph =
                (struct ip_comp_hdr *)(skb->data + offset);
        struct xfrm_state *x;

        if (type != ICMPV6_PKT_TOOBIG &&
            type != NDISC_REDIRECT)
                return 0;

        spi = htonl(ntohs(ipcomph->cpi));
        x = xfrm_state_lookup(net, skb->mark, (const xfrm_address_t *)&iph->daddr,
                              spi, IPPROTO_COMP, AF_INET6);
        if (!x)
                return 0;

        if (type == NDISC_REDIRECT)
                ip6_redirect(skb, net, skb->dev->ifindex, 0,
                             sock_net_uid(net, NULL));
        else
                ip6_update_pmtu(skb, net, info, 0, 0, sock_net_uid(net, NULL));
        xfrm_state_put(x);

        return 0;
}

static struct lock_class_key xfrm_state_lock_key;
static struct xfrm_state *ipcomp6_tunnel_create(struct xfrm_state *x)
{
        struct net *net = xs_net(x);
        struct xfrm_state *t = NULL;

        t = xfrm_state_alloc(net);
        if (!t)
                goto out;
        lockdep_set_class(&t->lock, &xfrm_state_lock_key);

        t->id.proto = IPPROTO_IPV6;
        t->id.spi = xfrm6_tunnel_alloc_spi(net, (xfrm_address_t *)&x->props.saddr);
        if (!t->id.spi)
                goto error;

        memcpy(t->id.daddr.a6, x->id.daddr.a6, sizeof(struct in6_addr));
        memcpy(&t->sel, &x->sel, sizeof(t->sel));
        t->props.family = AF_INET6;
        t->props.mode = x->props.mode;
        memcpy(t->props.saddr.a6, x->props.saddr.a6, sizeof(struct in6_addr));
        memcpy(&t->mark, &x->mark, sizeof(t->mark));
        t->if_id = x->if_id;

        if (xfrm_init_state(t, NULL))
                goto error;

        atomic_set(&t->tunnel_users, 1);

out:
        return t;

error:
        t->km.state = XFRM_STATE_DEAD;
        xfrm_state_put(t);
        t = NULL;
        goto out;
}

static int ipcomp6_tunnel_attach(struct xfrm_state *x)
{
        struct net *net = xs_net(x);
        int err = 0;
        struct xfrm_state *t = NULL;
        __be32 spi;
        u32 mark = x->mark.m & x->mark.v;

        spi = xfrm6_tunnel_spi_lookup(net, (xfrm_address_t *)&x->props.saddr);
        if (spi)
                t = xfrm_state_lookup(net, mark, (xfrm_address_t *)&x->id.daddr,
                                              spi, IPPROTO_IPV6, AF_INET6);
        if (!t) {
                t = ipcomp6_tunnel_create(x);
                if (!t) {
                        err = -EINVAL;
                        goto out;
                }
                xfrm_state_insert(t);
                xfrm_state_hold(t);
        }
        x->tunnel = t;
        atomic_inc(&t->tunnel_users);

out:
        return err;
}

static int ipcomp6_init_state(struct xfrm_state *x,
                              struct netlink_ext_ack *extack)
{
        int err = -EINVAL;

        x->props.header_len = 0;
        switch (x->props.mode) {
        case XFRM_MODE_TRANSPORT:
                break;
        case XFRM_MODE_TUNNEL:
                x->props.header_len += sizeof(struct ipv6hdr);
                break;
        default:
                NL_SET_ERR_MSG(extack, "Unsupported XFRM mode for IPcomp");
                goto out;
        }

        err = ipcomp_init_state(x, extack);
        if (err)
                goto out;

        if (x->props.mode == XFRM_MODE_TUNNEL) {
                err = ipcomp6_tunnel_attach(x);
                if (err) {
                        NL_SET_ERR_MSG(extack, "Kernel error: failed to initialize the associated state");
                        goto out;
                }
        }

        err = 0;
out:
        return err;
}

static int ipcomp6_rcv_cb(struct sk_buff *skb, int err)
{
        return 0;
}

static const struct xfrm_type ipcomp6_type = {
        .owner          = THIS_MODULE,
        .proto          = IPPROTO_COMP,
        .init_state     = ipcomp6_init_state,
        .destructor     = ipcomp_destroy,
        .input          = ipcomp_input,
        .output         = ipcomp_output,
};

static struct xfrm6_protocol ipcomp6_protocol = {
        .handler        = xfrm6_rcv,
        .input_handler  = xfrm_input,
        .cb_handler     = ipcomp6_rcv_cb,
        .err_handler    = ipcomp6_err,
        .priority       = 0,
};

static int __init ipcomp6_init(void)
{
        if (xfrm_register_type(&ipcomp6_type, AF_INET6) < 0) {
                pr_info("%s: can't add xfrm type\n", __func__);
                return -EAGAIN;
        }
        if (xfrm6_protocol_register(&ipcomp6_protocol, IPPROTO_COMP) < 0) {
                pr_info("%s: can't add protocol\n", __func__);
                xfrm_unregister_type(&ipcomp6_type, AF_INET6);
                return -EAGAIN;
        }
        return 0;
}

static void __exit ipcomp6_fini(void)
{
        if (xfrm6_protocol_deregister(&ipcomp6_protocol, IPPROTO_COMP) < 0)
                pr_info("%s: can't remove protocol\n", __func__);
        xfrm_unregister_type(&ipcomp6_type, AF_INET6);
}

module_init(ipcomp6_init);
module_exit(ipcomp6_fini);
MODULE_LICENSE("GPL");
MODULE_DESCRIPTION("IP Payload Compression Protocol (IPComp) for IPv6 - RFC3173");
MODULE_AUTHOR("Mitsuru KANDA <mk@linux-ipv6.org>");

MODULE_ALIAS_XFRM_TYPE(AF_INET6, XFRM_PROTO_COMP);