#include <linux/errno.h>
#include <linux/ip.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/skbuff.h>
#include <linux/socket.h>
#include <linux/types.h>
#include <net/checksum.h>
#include <net/ip.h>
#include <net/ip6_fib.h>
#include <net/lwtunnel.h>
#include <net/protocol.h>
#include <uapi/linux/ila.h>
#include "ila.h"

static __wsum get_csum_diff(struct ipv6hdr *ip6h, struct ila_params *p)
{
        struct ila_addr *iaddr = ila_a2i(&ip6h->daddr);

        if (p->locator_match.v64)
                return p->csum_diff;
        else
                return compute_csum_diff8((__be32 *)&iaddr->loc,
                                          (__be32 *)&p->locator);
}

static void ila_csum_do_neutral(struct ila_addr *iaddr,
                                struct ila_params *p)
{
        __sum16 *adjust = (__force __sum16 *)&iaddr->ident.v16[3];
        __wsum diff, fval;

        /* Check if checksum adjust value has been cached */
        if (p->locator_match.v64) {
                diff = p->csum_diff;
        } else {
                diff = compute_csum_diff8((__be32 *)&p->locator,
                                          (__be32 *)iaddr);
        }

        fval = (__force __wsum)(ila_csum_neutral_set(iaddr->ident) ?
                        CSUM_NEUTRAL_FLAG : ~CSUM_NEUTRAL_FLAG);

        diff = csum_add(diff, fval);

        *adjust = ~csum_fold(csum_add(diff, csum_unfold(*adjust)));

        /* Flip the csum-neutral bit. Either we are doing a SIR->ILA
         * translation with ILA_CSUM_NEUTRAL_MAP as the csum_method
         * and the C-bit is not set, or we are doing an ILA-SIR
         * tranlsation and the C-bit is set.
         */
        iaddr->ident.csum_neutral ^= 1;
}

static void ila_csum_adjust_transport(struct sk_buff *skb,
                                      struct ila_params *p)
{
        __wsum diff;
        struct ipv6hdr *ip6h = ipv6_hdr(skb);
        struct ila_addr *iaddr = ila_a2i(&ip6h->daddr);
        size_t nhoff = sizeof(struct ipv6hdr);

        switch (ip6h->nexthdr) {
        case NEXTHDR_TCP:
                if (likely(pskb_may_pull(skb, nhoff + sizeof(struct tcphdr)))) {
                        struct tcphdr *th = (struct tcphdr *)
                                        (skb_network_header(skb) + nhoff);

                        diff = get_csum_diff(ip6h, p);
                        inet_proto_csum_replace_by_diff(&th->check, skb,
                                                        diff, true);
                }
                break;
        case NEXTHDR_UDP:
                if (likely(pskb_may_pull(skb, nhoff + sizeof(struct udphdr)))) {
                        struct udphdr *uh = (struct udphdr *)
                                        (skb_network_header(skb) + nhoff);

                        if (uh->check || skb->ip_summed == CHECKSUM_PARTIAL) {
                                diff = get_csum_diff(ip6h, p);
                                inet_proto_csum_replace_by_diff(&uh->check, skb,
                                                                diff, true);
                                if (!uh->check)
                                        uh->check = CSUM_MANGLED_0;
                        }
                }
                break;
        case NEXTHDR_ICMP:
                if (likely(pskb_may_pull(skb,
                                         nhoff + sizeof(struct icmp6hdr)))) {
                        struct icmp6hdr *ih = (struct icmp6hdr *)
                                        (skb_network_header(skb) + nhoff);

                        diff = get_csum_diff(ip6h, p);
                        inet_proto_csum_replace_by_diff(&ih->icmp6_cksum, skb,
                                                        diff, true);
                }
                break;
        }

        /* Now change destination address */
        iaddr->loc = p->locator;
}

void ila_update_ipv6_locator(struct sk_buff *skb, struct ila_params *p,
                             bool set_csum_neutral)
{
        struct ipv6hdr *ip6h = ipv6_hdr(skb);
        struct ila_addr *iaddr = ila_a2i(&ip6h->daddr);

        /* First deal with the transport checksum */
        if (ila_csum_neutral_set(iaddr->ident)) {
                /* C-bit is set in the locator indicating that this
                 * is a locator being translated to a SIR address.
                 * Perform (receiver) checksum-neutral translation.
                 */
                if (!set_csum_neutral)
                        ila_csum_do_neutral(iaddr, p);
        } else {
                switch (p->csum_mode) {
                case ILA_CSUM_ADJUST_TRANSPORT:
                        ila_csum_adjust_transport(skb, p);
                        break;
                case ILA_CSUM_NEUTRAL_MAP:
                        ila_csum_do_neutral(iaddr, p);
                        break;
                case ILA_CSUM_NO_ACTION:
                        break;
                }
        }

        /* Now change destination address */
        iaddr->loc = p->locator;
}

void ila_init_saved_csum(struct ila_params *p)
{
        if (!p->locator_match.v64)
                return;

        p->csum_diff = compute_csum_diff8(
                                (__be32 *)&p->locator,
                                (__be32 *)&p->locator_match);
}

static int __init ila_init(void)
{
        int ret;

        ret = ila_lwt_init();

        if (ret)
                goto fail_lwt;

        ret = ila_xlat_init();
        if (ret)
                goto fail_xlat;

        return 0;
fail_xlat:
        ila_lwt_fini();
fail_lwt:
        return ret;
}

static void __exit ila_fini(void)
{
        ila_xlat_fini();
        ila_lwt_fini();
}

module_init(ila_init);
module_exit(ila_fini);
MODULE_AUTHOR("Tom Herbert <tom@herbertland.com>");
MODULE_LICENSE("GPL");