/*
 *  net/dccp/feat.c
 *
 *  An implementation of the DCCP protocol
 *  Andrea Bittau <a.bittau@cs.ucl.ac.uk>
 *
 *      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/module.h>

#include "ccid.h"
#include "feat.h"

#define DCCP_FEAT_SP_NOAGREE (-123)

int dccp_feat_change(struct dccp_minisock *dmsk, u8 type, u8 feature,
                     u8 *val, u8 len, gfp_t gfp)
{
        struct dccp_opt_pend *opt;

        dccp_feat_debug(type, feature, *val);

        if (!dccp_feat_is_valid_type(type)) {
                DCCP_WARN("option type %d invalid in negotiation\n", type);
                return 1;
        }
        if (!dccp_feat_is_valid_length(type, feature, len)) {
                DCCP_WARN("invalid length %d\n", len);
                return 1;
        }
        /* XXX add further sanity checks */

        /* check if that feature is already being negotiated */
        list_for_each_entry(opt, &dmsk->dccpms_pending, dccpop_node) {
                /* ok we found a negotiation for this option already */
                if (opt->dccpop_feat == feature && opt->dccpop_type == type) {
                        dccp_pr_debug("Replacing old\n");
                        /* replace */
                        BUG_ON(opt->dccpop_val == NULL);
                        kfree(opt->dccpop_val);
                        opt->dccpop_val  = val;
                        opt->dccpop_len  = len;
                        opt->dccpop_conf = 0;
                        return 0;
                }
        }

        /* negotiation for a new feature */
        opt = kmalloc(sizeof(*opt), gfp);
        if (opt == NULL)
                return -ENOMEM;

        opt->dccpop_type = type;
        opt->dccpop_feat = feature;
        opt->dccpop_len  = len;
        opt->dccpop_val  = val;
        opt->dccpop_conf = 0;
        opt->dccpop_sc   = NULL;

        BUG_ON(opt->dccpop_val == NULL);

        list_add_tail(&opt->dccpop_node, &dmsk->dccpms_pending);
        return 0;
}

EXPORT_SYMBOL_GPL(dccp_feat_change);

static int dccp_feat_update_ccid(struct sock *sk, u8 type, u8 new_ccid_nr)
{
        struct dccp_sock *dp = dccp_sk(sk);
        struct dccp_minisock *dmsk = dccp_msk(sk);
        /* figure out if we are changing our CCID or the peer's */
        const int rx = type == DCCPO_CHANGE_R;
        const u8 ccid_nr = rx ? dmsk->dccpms_rx_ccid : dmsk->dccpms_tx_ccid;
        struct ccid *new_ccid;

        /* Check if nothing is being changed. */
        if (ccid_nr == new_ccid_nr)
                return 0;

        new_ccid = ccid_new(new_ccid_nr, sk, rx, GFP_ATOMIC);
        if (new_ccid == NULL)
                return -ENOMEM;

        if (rx) {
                ccid_hc_rx_delete(dp->dccps_hc_rx_ccid, sk);
                dp->dccps_hc_rx_ccid = new_ccid;
                dmsk->dccpms_rx_ccid = new_ccid_nr;
        } else {
                ccid_hc_tx_delete(dp->dccps_hc_tx_ccid, sk);
                dp->dccps_hc_tx_ccid = new_ccid;
                dmsk->dccpms_tx_ccid = new_ccid_nr;
        }

        return 0;
}

/* XXX taking only u8 vals */
static int dccp_feat_update(struct sock *sk, u8 type, u8 feat, u8 val)
{
        dccp_feat_debug(type, feat, val);

        switch (feat) {
        case DCCPF_CCID:
                return dccp_feat_update_ccid(sk, type, val);
        default:
                dccp_pr_debug("UNIMPLEMENTED: %s(%d, ...)\n",
                              dccp_feat_typename(type), feat);
                break;
        }
        return 0;
}

static int dccp_feat_reconcile(struct sock *sk, struct dccp_opt_pend *opt,
                               u8 *rpref, u8 rlen)
{
        struct dccp_sock *dp = dccp_sk(sk);
        u8 *spref, slen, *res = NULL;
        int i, j, rc, agree = 1;

        BUG_ON(rpref == NULL);

        /* check if we are the black sheep */
        if (dp->dccps_role == DCCP_ROLE_CLIENT) {
                spref = rpref;
                slen  = rlen;
                rpref = opt->dccpop_val;
                rlen  = opt->dccpop_len;
        } else {
                spref = opt->dccpop_val;
                slen  = opt->dccpop_len;
        }
        /*
         * Now we have server preference list in spref and client preference in
         * rpref
         */
        BUG_ON(spref == NULL);
        BUG_ON(rpref == NULL);

        /* FIXME sanity check vals */

        /* Are values in any order?  XXX Lame "algorithm" here */
        /* XXX assume values are 1 byte */
        for (i = 0; i < slen; i++) {
                for (j = 0; j < rlen; j++) {
                        if (spref[i] == rpref[j]) {
                                res = &spref[i];
                                break;
                        }
                }
                if (res)
                        break;
        }

        /* we didn't agree on anything */
        if (res == NULL) {
                /* confirm previous value */
                switch (opt->dccpop_feat) {
                case DCCPF_CCID:
                        /* XXX did i get this right? =P */
                        if (opt->dccpop_type == DCCPO_CHANGE_L)
                                res = &dccp_msk(sk)->dccpms_tx_ccid;
                        else
                                res = &dccp_msk(sk)->dccpms_rx_ccid;
                        break;

                default:
                        DCCP_BUG("Fell through, feat=%d", opt->dccpop_feat);
                        /* XXX implement res */
                        return -EFAULT;
                }

                dccp_pr_debug("Don't agree... reconfirming %d\n", *res);
                agree = 0; /* this is used for mandatory options... */
        }

        /* need to put result and our preference list */
        /* XXX assume 1 byte vals */
        rlen = 1 + opt->dccpop_len;
        rpref = kmalloc(rlen, GFP_ATOMIC);
        if (rpref == NULL)
                return -ENOMEM;

        *rpref = *res;
        memcpy(&rpref[1], opt->dccpop_val, opt->dccpop_len);

        /* put it in the "confirm queue" */
        if (opt->dccpop_sc == NULL) {
                opt->dccpop_sc = kmalloc(sizeof(*opt->dccpop_sc), GFP_ATOMIC);
                if (opt->dccpop_sc == NULL) {
                        kfree(rpref);
                        return -ENOMEM;
                }
        } else {
                /* recycle the confirm slot */
                BUG_ON(opt->dccpop_sc->dccpoc_val == NULL);
                kfree(opt->dccpop_sc->dccpoc_val);
                dccp_pr_debug("recycling confirm slot\n");
        }
        memset(opt->dccpop_sc, 0, sizeof(*opt->dccpop_sc));

        opt->dccpop_sc->dccpoc_val = rpref;
        opt->dccpop_sc->dccpoc_len = rlen;

        /* update the option on our side [we are about to send the confirm] */
        rc = dccp_feat_update(sk, opt->dccpop_type, opt->dccpop_feat, *res);
        if (rc) {
                kfree(opt->dccpop_sc->dccpoc_val);
                kfree(opt->dccpop_sc);
                opt->dccpop_sc = NULL;
                return rc;
        }

        dccp_pr_debug("Will confirm %d\n", *rpref);

        /* say we want to change to X but we just got a confirm X, suppress our
         * change
         */
        if (!opt->dccpop_conf) {
                if (*opt->dccpop_val == *res)
                        opt->dccpop_conf = 1;
                dccp_pr_debug("won't ask for change of same feature\n");
        }

        return agree ? 0 : DCCP_FEAT_SP_NOAGREE; /* used for mandatory opts */
}

static int dccp_feat_sp(struct sock *sk, u8 type, u8 feature, u8 *val, u8 len)
{
        struct dccp_minisock *dmsk = dccp_msk(sk);
        struct dccp_opt_pend *opt;
        int rc = 1;
        u8 t;

        /*
         * We received a CHANGE.  We gotta match it against our own preference
         * list.  If we got a CHANGE_R it means it's a change for us, so we need
         * to compare our CHANGE_L list.
         */
        if (type == DCCPO_CHANGE_L)
                t = DCCPO_CHANGE_R;
        else
                t = DCCPO_CHANGE_L;

        /* find our preference list for this feature */
        list_for_each_entry(opt, &dmsk->dccpms_pending, dccpop_node) {
                if (opt->dccpop_type != t || opt->dccpop_feat != feature)
                        continue;

                /* find the winner from the two preference lists */
                rc = dccp_feat_reconcile(sk, opt, val, len);
                break;
        }

        /* We didn't deal with the change.  This can happen if we have no
         * preference list for the feature.  In fact, it just shouldn't
         * happen---if we understand a feature, we should have a preference list
         * with at least the default value.
         */
        BUG_ON(rc == 1);

        return rc;
}

static int dccp_feat_nn(struct sock *sk, u8 type, u8 feature, u8 *val, u8 len)
{
        struct dccp_opt_pend *opt;
        struct dccp_minisock *dmsk = dccp_msk(sk);
        u8 *copy;
        int rc;

        /* NN features must be Change L (sec. 6.3.2) */
        if (type != DCCPO_CHANGE_L) {
                dccp_pr_debug("received %s for NN feature %d\n",
                                dccp_feat_typename(type), feature);
                return -EFAULT;
        }

        /* XXX sanity check opt val */

        /* copy option so we can confirm it */
        opt = kzalloc(sizeof(*opt), GFP_ATOMIC);
        if (opt == NULL)
                return -ENOMEM;

        copy = kmemdup(val, len, GFP_ATOMIC);
        if (copy == NULL) {
                kfree(opt);
                return -ENOMEM;
        }

        opt->dccpop_type = DCCPO_CONFIRM_R; /* NN can only confirm R */
        opt->dccpop_feat = feature;
        opt->dccpop_val  = copy;
        opt->dccpop_len  = len;

        /* change feature */
        rc = dccp_feat_update(sk, type, feature, *val);
        if (rc) {
                kfree(opt->dccpop_val);
                kfree(opt);
                return rc;
        }

        dccp_feat_debug(type, feature, *copy);

        list_add_tail(&opt->dccpop_node, &dmsk->dccpms_conf);

        return 0;
}

static void dccp_feat_empty_confirm(struct dccp_minisock *dmsk,
                                    u8 type, u8 feature)
{
        /* XXX check if other confirms for that are queued and recycle slot */
        struct dccp_opt_pend *opt = kzalloc(sizeof(*opt), GFP_ATOMIC);

        if (opt == NULL) {
                /* XXX what do we do?  Ignoring should be fine.  It's a change
                 * after all =P
                 */
                return;
        }

        switch (type) {
        case DCCPO_CHANGE_L:
                opt->dccpop_type = DCCPO_CONFIRM_R;
                break;
        case DCCPO_CHANGE_R:
                opt->dccpop_type = DCCPO_CONFIRM_L;
                break;
        default:
                DCCP_WARN("invalid type %d\n", type);
                kfree(opt);
                return;
        }
        opt->dccpop_feat = feature;
        opt->dccpop_val  = NULL;
        opt->dccpop_len  = 0;

        /* change feature */
        dccp_pr_debug("Empty %s(%d)\n", dccp_feat_typename(type), feature);

        list_add_tail(&opt->dccpop_node, &dmsk->dccpms_conf);
}

static void dccp_feat_flush_confirm(struct sock *sk)
{
        struct dccp_minisock *dmsk = dccp_msk(sk);
        /* Check if there is anything to confirm in the first place */
        int yes = !list_empty(&dmsk->dccpms_conf);

        if (!yes) {
                struct dccp_opt_pend *opt;

                list_for_each_entry(opt, &dmsk->dccpms_pending, dccpop_node) {
                        if (opt->dccpop_conf) {
                                yes = 1;
                                break;
                        }
                }
        }

        if (!yes)
                return;

        /* OK there is something to confirm... */
        /* XXX check if packet is in flight?  Send delayed ack?? */
        if (sk->sk_state == DCCP_OPEN)
                dccp_send_ack(sk);
}

int dccp_feat_change_recv(struct sock *sk, u8 type, u8 feature, u8 *val, u8 len)
{
        int rc;

        dccp_feat_debug(type, feature, *val);

        /* figure out if it's SP or NN feature */
        switch (feature) {
        /* deal with SP features */
        case DCCPF_CCID:
                rc = dccp_feat_sp(sk, type, feature, val, len);
                break;

        /* deal with NN features */
        case DCCPF_ACK_RATIO:
                rc = dccp_feat_nn(sk, type, feature, val, len);
                break;

        /* XXX implement other features */
        default:
                dccp_pr_debug("UNIMPLEMENTED: not handling %s(%d, ...)\n",
                              dccp_feat_typename(type), feature);
                rc = -EFAULT;
                break;
        }

        /* check if there were problems changing features */
        if (rc) {
                /* If we don't agree on SP, we sent a confirm for old value.
                 * However we propagate rc to caller in case option was
                 * mandatory
                 */
                if (rc != DCCP_FEAT_SP_NOAGREE)
                        dccp_feat_empty_confirm(dccp_msk(sk), type, feature);
        }

        /* generate the confirm [if required] */
        dccp_feat_flush_confirm(sk);

        return rc;
}

EXPORT_SYMBOL_GPL(dccp_feat_change_recv);

int dccp_feat_confirm_recv(struct sock *sk, u8 type, u8 feature,
                           u8 *val, u8 len)
{
        u8 t;
        struct dccp_opt_pend *opt;
        struct dccp_minisock *dmsk = dccp_msk(sk);
        int found = 0;
        int all_confirmed = 1;

        dccp_feat_debug(type, feature, *val);

        /* locate our change request */
        switch (type) {
        case DCCPO_CONFIRM_L: t = DCCPO_CHANGE_R; break;
        case DCCPO_CONFIRM_R: t = DCCPO_CHANGE_L; break;
        default:              DCCP_WARN("invalid type %d\n", type);
                              return 1;

        }
        /* XXX sanity check feature value */

        list_for_each_entry(opt, &dmsk->dccpms_pending, dccpop_node) {
                if (!opt->dccpop_conf && opt->dccpop_type == t &&
                    opt->dccpop_feat == feature) {
                        found = 1;
                        dccp_pr_debug("feature %d found\n", opt->dccpop_feat);

                        /* XXX do sanity check */

                        opt->dccpop_conf = 1;

                        /* We got a confirmation---change the option */
                        dccp_feat_update(sk, opt->dccpop_type,
                                         opt->dccpop_feat, *val);

                        /* XXX check the return value of dccp_feat_update */
                        break;
                }

                if (!opt->dccpop_conf)
                        all_confirmed = 0;
        }

        /* fix re-transmit timer */
        /* XXX gotta make sure that no option negotiation occurs during
         * connection shutdown.  Consider that the CLOSEREQ is sent and timer is
         * on.  if all options are confirmed it might kill timer which should
         * remain alive until close is received.
         */
        if (all_confirmed) {
                dccp_pr_debug("clear feat negotiation timer %p\n", sk);
                inet_csk_clear_xmit_timer(sk, ICSK_TIME_RETRANS);
        }

        if (!found)
                dccp_pr_debug("%s(%d, ...) never requested\n",
                              dccp_feat_typename(type), feature);
        return 0;
}

EXPORT_SYMBOL_GPL(dccp_feat_confirm_recv);

void dccp_feat_clean(struct dccp_minisock *dmsk)
{
        struct dccp_opt_pend *opt, *next;

        list_for_each_entry_safe(opt, next, &dmsk->dccpms_pending,
                                 dccpop_node) {
                BUG_ON(opt->dccpop_val == NULL);
                kfree(opt->dccpop_val);

                if (opt->dccpop_sc != NULL) {
                        BUG_ON(opt->dccpop_sc->dccpoc_val == NULL);
                        kfree(opt->dccpop_sc->dccpoc_val);
                        kfree(opt->dccpop_sc);
                }

                kfree(opt);
        }
        INIT_LIST_HEAD(&dmsk->dccpms_pending);

        list_for_each_entry_safe(opt, next, &dmsk->dccpms_conf, dccpop_node) {
                BUG_ON(opt == NULL);
                if (opt->dccpop_val != NULL)
                        kfree(opt->dccpop_val);
                kfree(opt);
        }
        INIT_LIST_HEAD(&dmsk->dccpms_conf);
}

EXPORT_SYMBOL_GPL(dccp_feat_clean);

/* this is to be called only when a listening sock creates its child.  It is
 * assumed by the function---the confirm is not duplicated, but rather it is
 * "passed on".
 */
int dccp_feat_clone(struct sock *oldsk, struct sock *newsk)
{
        struct dccp_minisock *olddmsk = dccp_msk(oldsk);
        struct dccp_minisock *newdmsk = dccp_msk(newsk);
        struct dccp_opt_pend *opt;
        int rc = 0;

        INIT_LIST_HEAD(&newdmsk->dccpms_pending);
        INIT_LIST_HEAD(&newdmsk->dccpms_conf);

        list_for_each_entry(opt, &olddmsk->dccpms_pending, dccpop_node) {
                struct dccp_opt_pend *newopt;
                /* copy the value of the option */
                u8 *val = kmemdup(opt->dccpop_val, opt->dccpop_len, GFP_ATOMIC);

                if (val == NULL)
                        goto out_clean;

                newopt = kmemdup(opt, sizeof(*newopt), GFP_ATOMIC);
                if (newopt == NULL) {
                        kfree(val);
                        goto out_clean;
                }

                /* insert the option */
                newopt->dccpop_val = val;
                list_add_tail(&newopt->dccpop_node, &newdmsk->dccpms_pending);

                /* XXX what happens with backlogs and multiple connections at
                 * once...
                 */
                /* the master socket no longer needs to worry about confirms */
                opt->dccpop_sc = NULL; /* it's not a memleak---new socket has it */

                /* reset state for a new socket */
                opt->dccpop_conf = 0;
        }

        /* XXX not doing anything about the conf queue */

out:
        return rc;

out_clean:
        dccp_feat_clean(newdmsk);
        rc = -ENOMEM;
        goto out;
}

EXPORT_SYMBOL_GPL(dccp_feat_clone);

static int __dccp_feat_init(struct dccp_minisock *dmsk, u8 type, u8 feat,
                            u8 *val, u8 len)
{
        int rc = -ENOMEM;
        u8 *copy = kmemdup(val, len, GFP_KERNEL);

        if (copy != NULL) {
                rc = dccp_feat_change(dmsk, type, feat, copy, len, GFP_KERNEL);
                if (rc)
                        kfree(copy);
        }
        return rc;
}

int dccp_feat_init(struct dccp_minisock *dmsk)
{
        int rc;

        INIT_LIST_HEAD(&dmsk->dccpms_pending);
        INIT_LIST_HEAD(&dmsk->dccpms_conf);

        /* CCID L */
        rc = __dccp_feat_init(dmsk, DCCPO_CHANGE_L, DCCPF_CCID,
                              &dmsk->dccpms_tx_ccid, 1);
        if (rc)
                goto out;

        /* CCID R */
        rc = __dccp_feat_init(dmsk, DCCPO_CHANGE_R, DCCPF_CCID,
                              &dmsk->dccpms_rx_ccid, 1);
        if (rc)
                goto out;

        /* Ack ratio */
        rc = __dccp_feat_init(dmsk, DCCPO_CHANGE_L, DCCPF_ACK_RATIO,
                              &dmsk->dccpms_ack_ratio, 1);
out:
        return rc;
}

EXPORT_SYMBOL_GPL(dccp_feat_init);

#ifdef CONFIG_IP_DCCP_DEBUG
const char *dccp_feat_typename(const u8 type)
{
        switch(type) {
        case DCCPO_CHANGE_L:  return("ChangeL");
        case DCCPO_CONFIRM_L: return("ConfirmL");
        case DCCPO_CHANGE_R:  return("ChangeR");
        case DCCPO_CONFIRM_R: return("ConfirmR");
        /* the following case must not appear in feature negotation  */
        default:              dccp_pr_debug("unknown type %d [BUG!]\n", type);
        }
        return NULL;
}

EXPORT_SYMBOL_GPL(dccp_feat_typename);

const char *dccp_feat_name(const u8 feat)
{
        static const char *feature_names[] = {
                [DCCPF_RESERVED]        = "Reserved",
                [DCCPF_CCID]            = "CCID",
                [DCCPF_SHORT_SEQNOS]    = "Allow Short Seqnos",
                [DCCPF_SEQUENCE_WINDOW] = "Sequence Window",
                [DCCPF_ECN_INCAPABLE]   = "ECN Incapable",
                [DCCPF_ACK_RATIO]       = "Ack Ratio",
                [DCCPF_SEND_ACK_VECTOR] = "Send ACK Vector",
                [DCCPF_SEND_NDP_COUNT]  = "Send NDP Count",
                [DCCPF_MIN_CSUM_COVER]  = "Min. Csum Coverage",
                [DCCPF_DATA_CHECKSUM]   = "Send Data Checksum",
        };
        if (feat >= DCCPF_MIN_CCID_SPECIFIC)
                return "CCID-specific";

        if (dccp_feat_is_reserved(feat))
                return feature_names[DCCPF_RESERVED];

        return feature_names[feat];
}

EXPORT_SYMBOL_GPL(dccp_feat_name);
#endif /* CONFIG_IP_DCCP_DEBUG */