/*
 * xfrm_output.c - Common IPsec encapsulation code.
 *
 * Copyright (c) 2007 Herbert Xu <herbert@gondor.apana.org.au>
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version
 * 2 of the License, or (at your option) any later version.
 */

#include <linux/errno.h>
#include <linux/module.h>
#include <linux/netdevice.h>
#include <linux/netfilter.h>
#include <linux/skbuff.h>
#include <linux/slab.h>
#include <linux/spinlock.h>
#include <net/dst.h>
#include <net/xfrm.h>

static int xfrm_output2(struct net *net, struct sock *sk, struct sk_buff *skb);

static int xfrm_skb_check_space(struct sk_buff *skb)
{
        struct dst_entry *dst = skb_dst(skb);
        int nhead = dst->header_len + LL_RESERVED_SPACE(dst->dev)
                - skb_headroom(skb);
        int ntail = dst->dev->needed_tailroom - skb_tailroom(skb);

        if (nhead <= 0) {
                if (ntail <= 0)
                        return 0;
                nhead = 0;
        } else if (ntail < 0)
                ntail = 0;

        return pskb_expand_head(skb, nhead, ntail, GFP_ATOMIC);
}

/* Children define the path of the packet through the
 * Linux networking.  Thus, destinations are stackable.
 */

static struct dst_entry *skb_dst_pop(struct sk_buff *skb)
{
        struct dst_entry *child = dst_clone(skb_dst(skb)->child);

        skb_dst_drop(skb);
        return child;
}

static int xfrm_output_one(struct sk_buff *skb, int err)
{
        struct dst_entry *dst = skb_dst(skb);
        struct xfrm_state *x = dst->xfrm;
        struct net *net = xs_net(x);

        if (err <= 0)
                goto resume;

        do {
                err = xfrm_skb_check_space(skb);
                if (err) {
                        XFRM_INC_STATS(net, LINUX_MIB_XFRMOUTERROR);
                        goto error_nolock;
                }

                err = x->outer_mode->output(x, skb);
                if (err) {
                        XFRM_INC_STATS(net, LINUX_MIB_XFRMOUTSTATEMODEERROR);
                        goto error_nolock;
                }

                spin_lock_bh(&x->lock);

                if (unlikely(x->km.state != XFRM_STATE_VALID)) {
                        XFRM_INC_STATS(net, LINUX_MIB_XFRMOUTSTATEINVALID);
                        err = -EINVAL;
                        goto error;
                }

                err = xfrm_state_check_expire(x);
                if (err) {
                        XFRM_INC_STATS(net, LINUX_MIB_XFRMOUTSTATEEXPIRED);
                        goto error;
                }

                err = x->repl->overflow(x, skb);
                if (err) {
                        XFRM_INC_STATS(net, LINUX_MIB_XFRMOUTSTATESEQERROR);
                        goto error;
                }

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

                spin_unlock_bh(&x->lock);

                skb_dst_force(skb);

                /* Inner headers are invalid now. */
                skb->encapsulation = 0;

                err = x->type->output(x, skb);
                if (err == -EINPROGRESS)
                        goto out;

resume:
                if (err) {
                        XFRM_INC_STATS(net, LINUX_MIB_XFRMOUTSTATEPROTOERROR);
                        goto error_nolock;
                }

                dst = skb_dst_pop(skb);
                if (!dst) {
                        XFRM_INC_STATS(net, LINUX_MIB_XFRMOUTERROR);
                        err = -EHOSTUNREACH;
                        goto error_nolock;
                }
                skb_dst_set(skb, dst);
                x = dst->xfrm;
        } while (x && !(x->outer_mode->flags & XFRM_MODE_FLAG_TUNNEL));

        return 0;

error:
        spin_unlock_bh(&x->lock);
error_nolock:
        kfree_skb(skb);
out:
        return err;
}

int xfrm_output_resume(struct sk_buff *skb, int err)
{
        struct net *net = xs_net(skb_dst(skb)->xfrm);

        while (likely((err = xfrm_output_one(skb, err)) == 0)) {
                nf_reset(skb);

                err = skb_dst(skb)->ops->local_out(net, skb->sk, skb);
                if (unlikely(err != 1))
                        goto out;

                if (!skb_dst(skb)->xfrm)
                        return dst_output(net, skb->sk, skb);

                err = nf_hook(skb_dst(skb)->ops->family,
                              NF_INET_POST_ROUTING, net, skb->sk, skb,
                              NULL, skb_dst(skb)->dev, xfrm_output2);
                if (unlikely(err != 1))
                        goto out;
        }

        if (err == -EINPROGRESS)
                err = 0;

out:
        return err;
}
EXPORT_SYMBOL_GPL(xfrm_output_resume);

static int xfrm_output2(struct net *net, struct sock *sk, struct sk_buff *skb)
{
        return xfrm_output_resume(skb, 1);
}

static int xfrm_output_gso(struct net *net, struct sock *sk, struct sk_buff *skb)
{
        struct sk_buff *segs;

        BUILD_BUG_ON(sizeof(*IPCB(skb)) > SKB_SGO_CB_OFFSET);
        BUILD_BUG_ON(sizeof(*IP6CB(skb)) > SKB_SGO_CB_OFFSET);
        segs = skb_gso_segment(skb, 0);
        kfree_skb(skb);
        if (IS_ERR(segs))
                return PTR_ERR(segs);
        if (segs == NULL)
                return -EINVAL;

        do {
                struct sk_buff *nskb = segs->next;
                int err;

                segs->next = NULL;
                err = xfrm_output2(net, sk, segs);

                if (unlikely(err)) {
                        kfree_skb_list(nskb);
                        return err;
                }

                segs = nskb;
        } while (segs);

        return 0;
}

int xfrm_output(struct sock *sk, struct sk_buff *skb)
{
        struct net *net = dev_net(skb_dst(skb)->dev);
        int err;

        if (skb_is_gso(skb))
                return xfrm_output_gso(net, sk, skb);

        if (skb->ip_summed == CHECKSUM_PARTIAL) {
                err = skb_checksum_help(skb);
                if (err) {
                        XFRM_INC_STATS(net, LINUX_MIB_XFRMOUTERROR);
                        kfree_skb(skb);
                        return err;
                }
        }

        return xfrm_output2(net, sk, skb);
}
EXPORT_SYMBOL_GPL(xfrm_output);

int xfrm_inner_extract_output(struct xfrm_state *x, struct sk_buff *skb)
{
        struct xfrm_mode *inner_mode;
        if (x->sel.family == AF_UNSPEC)
                inner_mode = xfrm_ip2inner_mode(x,
                                xfrm_af2proto(skb_dst(skb)->ops->family));
        else
                inner_mode = x->inner_mode;

        if (inner_mode == NULL)
                return -EAFNOSUPPORT;
        return inner_mode->afinfo->extract_output(x, skb);
}
EXPORT_SYMBOL_GPL(xfrm_inner_extract_output);

void xfrm_local_error(struct sk_buff *skb, int mtu)
{
        unsigned int proto;
        struct xfrm_state_afinfo *afinfo;

        if (skb->protocol == htons(ETH_P_IP))
                proto = AF_INET;
        else if (skb->protocol == htons(ETH_P_IPV6))
                proto = AF_INET6;
        else
                return;

        afinfo = xfrm_state_get_afinfo(proto);
        if (!afinfo)
                return;

        afinfo->local_error(skb, mtu);
        xfrm_state_put_afinfo(afinfo);
}
EXPORT_SYMBOL_GPL(xfrm_local_error);