/*
 *  net/dccp/options.c
 *
 *  An implementation of the DCCP protocol
 *  Copyright (c) 2005 Aristeu Sergio Rozanski Filho <aris@cathedrallabs.org>
 *  Copyright (c) 2005 Arnaldo Carvalho de Melo <acme@ghostprotocols.net>
 *  Copyright (c) 2005 Ian McDonald <ian.mcdonald@jandi.co.nz>
 *
 *      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/dccp.h>
#include <linux/module.h>
#include <linux/types.h>
#include <asm/unaligned.h>
#include <linux/kernel.h>
#include <linux/skbuff.h>

#include "ackvec.h"
#include "ccid.h"
#include "dccp.h"
#include "feat.h"

int sysctl_dccp_feat_sequence_window = DCCPF_INITIAL_SEQUENCE_WINDOW;
int sysctl_dccp_feat_rx_ccid          = DCCPF_INITIAL_CCID;
int sysctl_dccp_feat_tx_ccid          = DCCPF_INITIAL_CCID;
int sysctl_dccp_feat_ack_ratio        = DCCPF_INITIAL_ACK_RATIO;
int sysctl_dccp_feat_send_ack_vector = DCCPF_INITIAL_SEND_ACK_VECTOR;
int sysctl_dccp_feat_send_ndp_count  = DCCPF_INITIAL_SEND_NDP_COUNT;

static u32 dccp_decode_value_var(const unsigned char *bf, const u8 len)
{
        u32 value = 0;

        if (len > 3)
                value += *bf++ << 24;
        if (len > 2)
                value += *bf++ << 16;
        if (len > 1)
                value += *bf++ << 8;
        if (len > 0)
                value += *bf;

        return value;
}

int dccp_parse_options(struct sock *sk, struct sk_buff *skb)
{
        struct dccp_sock *dp = dccp_sk(sk);
        const struct dccp_hdr *dh = dccp_hdr(skb);
        const u8 pkt_type = DCCP_SKB_CB(skb)->dccpd_type;
        u64 ackno = DCCP_SKB_CB(skb)->dccpd_ack_seq;
        unsigned char *options = (unsigned char *)dh + dccp_hdr_len(skb);
        unsigned char *opt_ptr = options;
        const unsigned char *opt_end = (unsigned char *)dh +
                                        (dh->dccph_doff * 4);
        struct dccp_options_received *opt_recv = &dp->dccps_options_received;
        unsigned char opt, len;
        unsigned char *value;
        u32 elapsed_time;
        __be32 opt_val;
        int rc;
        int mandatory = 0;

        memset(opt_recv, 0, sizeof(*opt_recv));

        opt = len = 0;
        while (opt_ptr != opt_end) {
                opt   = *opt_ptr++;
                len   = 0;
                value = NULL;

                /* Check if this isn't a single byte option */
                if (opt > DCCPO_MAX_RESERVED) {
                        if (opt_ptr == opt_end)
                                goto out_invalid_option;

                        len = *opt_ptr++;
                        if (len < 3)
                                goto out_invalid_option;
                        /*
                         * Remove the type and len fields, leaving
                         * just the value size
                         */
                        len     -= 2;
                        value   = opt_ptr;
                        opt_ptr += len;

                        if (opt_ptr > opt_end)
                                goto out_invalid_option;
                }

                switch (opt) {
                case DCCPO_PADDING:
                        break;
                case DCCPO_MANDATORY:
                        if (mandatory)
                                goto out_invalid_option;
                        if (pkt_type != DCCP_PKT_DATA)
                                mandatory = 1;
                        break;
                case DCCPO_NDP_COUNT:
                        if (len > 3)
                                goto out_invalid_option;

                        opt_recv->dccpor_ndp = dccp_decode_value_var(value, len);
                        dccp_pr_debug("%s rx opt: NDP count=%d\n", dccp_role(sk),
                                      opt_recv->dccpor_ndp);
                        break;
                case DCCPO_CHANGE_L:
                        /* fall through */
                case DCCPO_CHANGE_R:
                        if (len < 2)
                                goto out_invalid_option;
                        rc = dccp_feat_change_recv(sk, opt, *value, value + 1,
                                                   len - 1);
                        /*
                         * When there is a change error, change_recv is
                         * responsible for dealing with it.  i.e. reply with an
                         * empty confirm.
                         * If the change was mandatory, then we need to die.
                         */
                        if (rc && mandatory)
                                goto out_invalid_option;
                        break;
                case DCCPO_CONFIRM_L:
                        /* fall through */
                case DCCPO_CONFIRM_R:
                        if (len < 2)
                                goto out_invalid_option;
                        if (dccp_feat_confirm_recv(sk, opt, *value,
                                                   value + 1, len - 1))
                                goto out_invalid_option;
                        break;
                case DCCPO_ACK_VECTOR_0:
                case DCCPO_ACK_VECTOR_1:
                        if (pkt_type == DCCP_PKT_DATA)
                                break;

                        if (dccp_msk(sk)->dccpms_send_ack_vector &&
                            dccp_ackvec_parse(sk, skb, &ackno, opt, value, len))
                                goto out_invalid_option;
                        break;
                case DCCPO_TIMESTAMP:
                        if (len != 4)
                                goto out_invalid_option;

                        opt_val = get_unaligned((__be32 *)value);
                        opt_recv->dccpor_timestamp = ntohl(opt_val);

                        dp->dccps_timestamp_echo = opt_recv->dccpor_timestamp;
                        dp->dccps_timestamp_time = ktime_get_real();

                        dccp_pr_debug("%s rx opt: TIMESTAMP=%u, ackno=%llu\n",
                                      dccp_role(sk), opt_recv->dccpor_timestamp,
                                      (unsigned long long)
                                      DCCP_SKB_CB(skb)->dccpd_ack_seq);
                        break;
                case DCCPO_TIMESTAMP_ECHO:
                        if (len != 4 && len != 6 && len != 8)
                                goto out_invalid_option;

                        opt_val = get_unaligned((__be32 *)value);
                        opt_recv->dccpor_timestamp_echo = ntohl(opt_val);

                        dccp_pr_debug("%s rx opt: TIMESTAMP_ECHO=%u, len=%d, "
                                      "ackno=%llu", dccp_role(sk),
                                      opt_recv->dccpor_timestamp_echo,
                                      len + 2,
                                      (unsigned long long)
                                      DCCP_SKB_CB(skb)->dccpd_ack_seq);

                        value += 4;

                        if (len == 4) {         /* no elapsed time included */
                                dccp_pr_debug_cat("\n");
                                break;
                        }

                        if (len == 6) {         /* 2-byte elapsed time */
                                __be16 opt_val2 = get_unaligned((__be16 *)value);
                                elapsed_time = ntohs(opt_val2);
                        } else {                /* 4-byte elapsed time */
                                opt_val = get_unaligned((__be32 *)value);
                                elapsed_time = ntohl(opt_val);
                        }

                        dccp_pr_debug_cat(", ELAPSED_TIME=%u\n", elapsed_time);

                        /* Give precedence to the biggest ELAPSED_TIME */
                        if (elapsed_time > opt_recv->dccpor_elapsed_time)
                                opt_recv->dccpor_elapsed_time = elapsed_time;
                        break;
                case DCCPO_ELAPSED_TIME:
                        if (len != 2 && len != 4)
                                goto out_invalid_option;

                        if (pkt_type == DCCP_PKT_DATA)
                                continue;

                        if (len == 2) {
                                __be16 opt_val2 = get_unaligned((__be16 *)value);
                                elapsed_time = ntohs(opt_val2);
                        } else {
                                opt_val = get_unaligned((__be32 *)value);
                                elapsed_time = ntohl(opt_val);
                        }

                        if (elapsed_time > opt_recv->dccpor_elapsed_time)
                                opt_recv->dccpor_elapsed_time = elapsed_time;

                        dccp_pr_debug("%s rx opt: ELAPSED_TIME=%d\n",
                                      dccp_role(sk), elapsed_time);
                        break;
                        /*
                         * From RFC 4340, sec. 10.3:
                         *
                         *      Option numbers 128 through 191 are for
                         *      options sent from the HC-Sender to the
                         *      HC-Receiver; option numbers 192 through 255
                         *      are for options sent from the HC-Receiver to
                         *      the HC-Sender.
                         */
                case 128 ... 191: {
                        const u16 idx = value - options;

                        if (ccid_hc_rx_parse_options(dp->dccps_hc_rx_ccid, sk,
                                                     opt, len, idx,
                                                     value) != 0)
                                goto out_invalid_option;
                }
                        break;
                case 192 ... 255: {
                        const u16 idx = value - options;

                        if (ccid_hc_tx_parse_options(dp->dccps_hc_tx_ccid, sk,
                                                     opt, len, idx,
                                                     value) != 0)
                                goto out_invalid_option;
                }
                        break;
                default:
                        DCCP_CRIT("DCCP(%p): option %d(len=%d) not "
                                  "implemented, ignoring", sk, opt, len);
                        break;
                }

                if (opt != DCCPO_MANDATORY)
                        mandatory = 0;
        }

        /* mandatory was the last byte in option list -> reset connection */
        if (mandatory)
                goto out_invalid_option;

        return 0;

out_invalid_option:
        DCCP_INC_STATS_BH(DCCP_MIB_INVALIDOPT);
        DCCP_SKB_CB(skb)->dccpd_reset_code = DCCP_RESET_CODE_OPTION_ERROR;
        DCCP_WARN("DCCP(%p): invalid option %d, len=%d", sk, opt, len);
        return -1;
}

EXPORT_SYMBOL_GPL(dccp_parse_options);

static void dccp_encode_value_var(const u32 value, unsigned char *to,
                                  const unsigned int len)
{
        if (len > 3)
                *to++ = (value & 0xFF000000) >> 24;
        if (len > 2)
                *to++ = (value & 0xFF0000) >> 16;
        if (len > 1)
                *to++ = (value & 0xFF00) >> 8;
        if (len > 0)
                *to++ = (value & 0xFF);
}

static inline int dccp_ndp_len(const int ndp)
{
        return likely(ndp <= 0xFF) ? 1 : ndp <= 0xFFFF ? 2 : 3;
}

int dccp_insert_option(struct sock *sk, struct sk_buff *skb,
                        const unsigned char option,
                        const void *value, const unsigned char len)
{
        unsigned char *to;

        if (DCCP_SKB_CB(skb)->dccpd_opt_len + len + 2 > DCCP_MAX_OPT_LEN)
                return -1;

        DCCP_SKB_CB(skb)->dccpd_opt_len += len + 2;

        to    = skb_push(skb, len + 2);
        *to++ = option;
        *to++ = len + 2;

        memcpy(to, value, len);
        return 0;
}

EXPORT_SYMBOL_GPL(dccp_insert_option);

static int dccp_insert_option_ndp(struct sock *sk, struct sk_buff *skb)
{
        struct dccp_sock *dp = dccp_sk(sk);
        int ndp = dp->dccps_ndp_count;

        if (dccp_non_data_packet(skb))
                ++dp->dccps_ndp_count;
        else
                dp->dccps_ndp_count = 0;

        if (ndp > 0) {
                unsigned char *ptr;
                const int ndp_len = dccp_ndp_len(ndp);
                const int len = ndp_len + 2;

                if (DCCP_SKB_CB(skb)->dccpd_opt_len + len > DCCP_MAX_OPT_LEN)
                        return -1;

                DCCP_SKB_CB(skb)->dccpd_opt_len += len;

                ptr = skb_push(skb, len);
                *ptr++ = DCCPO_NDP_COUNT;
                *ptr++ = len;
                dccp_encode_value_var(ndp, ptr, ndp_len);
        }

        return 0;
}

static inline int dccp_elapsed_time_len(const u32 elapsed_time)
{
        return elapsed_time == 0 ? 0 : elapsed_time <= 0xFFFF ? 2 : 4;
}

int dccp_insert_option_elapsed_time(struct sock *sk, struct sk_buff *skb,
                                    u32 elapsed_time)
{
        const int elapsed_time_len = dccp_elapsed_time_len(elapsed_time);
        const int len = 2 + elapsed_time_len;
        unsigned char *to;

        if (elapsed_time_len == 0)
                return 0;

        if (DCCP_SKB_CB(skb)->dccpd_opt_len + len > DCCP_MAX_OPT_LEN)
                return -1;

        DCCP_SKB_CB(skb)->dccpd_opt_len += len;

        to    = skb_push(skb, len);
        *to++ = DCCPO_ELAPSED_TIME;
        *to++ = len;

        if (elapsed_time_len == 2) {
                const __be16 var16 = htons((u16)elapsed_time);
                memcpy(to, &var16, 2);
        } else {
                const __be32 var32 = htonl(elapsed_time);
                memcpy(to, &var32, 4);
        }

        return 0;
}

EXPORT_SYMBOL_GPL(dccp_insert_option_elapsed_time);

int dccp_insert_option_timestamp(struct sock *sk, struct sk_buff *skb)
{
        __be32 now = htonl(dccp_timestamp());
        /* yes this will overflow but that is the point as we want a
         * 10 usec 32 bit timer which mean it wraps every 11.9 hours */

        return dccp_insert_option(sk, skb, DCCPO_TIMESTAMP, &now, sizeof(now));
}

EXPORT_SYMBOL_GPL(dccp_insert_option_timestamp);

static int dccp_insert_option_timestamp_echo(struct sock *sk,
                                             struct sk_buff *skb)
{
        struct dccp_sock *dp = dccp_sk(sk);
        __be32 tstamp_echo;
        int len, elapsed_time_len;
        unsigned char *to;
        const suseconds_t delta = ktime_us_delta(ktime_get_real(),
                                                 dp->dccps_timestamp_time);
        u32 elapsed_time = delta / 10;
        elapsed_time_len = dccp_elapsed_time_len(elapsed_time);
        len = 6 + elapsed_time_len;

        if (DCCP_SKB_CB(skb)->dccpd_opt_len + len > DCCP_MAX_OPT_LEN)
                return -1;

        DCCP_SKB_CB(skb)->dccpd_opt_len += len;

        to    = skb_push(skb, len);
        *to++ = DCCPO_TIMESTAMP_ECHO;
        *to++ = len;

        tstamp_echo = htonl(dp->dccps_timestamp_echo);
        memcpy(to, &tstamp_echo, 4);
        to += 4;

        if (elapsed_time_len == 2) {
                const __be16 var16 = htons((u16)elapsed_time);
                memcpy(to, &var16, 2);
        } else if (elapsed_time_len == 4) {
                const __be32 var32 = htonl(elapsed_time);
                memcpy(to, &var32, 4);
        }

        dp->dccps_timestamp_echo = 0;
        dp->dccps_timestamp_time = ktime_set(0, 0);
        return 0;
}

static int dccp_insert_feat_opt(struct sk_buff *skb, u8 type, u8 feat,
                                u8 *val, u8 len)
{
        u8 *to;

        if (DCCP_SKB_CB(skb)->dccpd_opt_len + len + 3 > DCCP_MAX_OPT_LEN) {
                DCCP_WARN("packet too small for feature %d option!\n", feat);
                return -1;
        }

        DCCP_SKB_CB(skb)->dccpd_opt_len += len + 3;

        to    = skb_push(skb, len + 3);
        *to++ = type;
        *to++ = len + 3;
        *to++ = feat;

        if (len)
                memcpy(to, val, len);

        dccp_pr_debug("%s(%s (%d), ...), length %d\n",
                      dccp_feat_typename(type),
                      dccp_feat_name(feat), feat, len);
        return 0;
}

static int dccp_insert_options_feat(struct sock *sk, struct sk_buff *skb)
{
        struct dccp_sock *dp = dccp_sk(sk);
        struct dccp_minisock *dmsk = dccp_msk(sk);
        struct dccp_opt_pend *opt, *next;
        int change = 0;

        /* confirm any options [NN opts] */
        list_for_each_entry_safe(opt, next, &dmsk->dccpms_conf, dccpop_node) {
                dccp_insert_feat_opt(skb, opt->dccpop_type,
                                     opt->dccpop_feat, opt->dccpop_val,
                                     opt->dccpop_len);
                /* fear empty confirms */
                if (opt->dccpop_val)
                        kfree(opt->dccpop_val);
                kfree(opt);
        }
        INIT_LIST_HEAD(&dmsk->dccpms_conf);

        /* see which features we need to send */
        list_for_each_entry(opt, &dmsk->dccpms_pending, dccpop_node) {
                /* see if we need to send any confirm */
                if (opt->dccpop_sc) {
                        dccp_insert_feat_opt(skb, opt->dccpop_type + 1,
                                             opt->dccpop_feat,
                                             opt->dccpop_sc->dccpoc_val,
                                             opt->dccpop_sc->dccpoc_len);

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

                /* any option not confirmed, re-send it */
                if (!opt->dccpop_conf) {
                        dccp_insert_feat_opt(skb, opt->dccpop_type,
                                             opt->dccpop_feat, opt->dccpop_val,
                                             opt->dccpop_len);
                        change++;
                }
        }

        /* Retransmit timer.
         * If this is the master listening sock, we don't set a timer on it.  It
         * should be fine because if the dude doesn't receive our RESPONSE
         * [which will contain the CHANGE] he will send another REQUEST which
         * will "retrnasmit" the change.
         */
        if (change && dp->dccps_role != DCCP_ROLE_LISTEN) {
                dccp_pr_debug("reset feat negotiation timer %p\n", sk);

                /* XXX don't reset the timer on re-transmissions.  I.e. reset it
                 * only when sending new stuff i guess.  Currently the timer
                 * never backs off because on re-transmission it just resets it!
                 */
                inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS,
                                          inet_csk(sk)->icsk_rto, DCCP_RTO_MAX);
        }

        return 0;
}

int dccp_insert_options(struct sock *sk, struct sk_buff *skb)
{
        struct dccp_sock *dp = dccp_sk(sk);
        struct dccp_minisock *dmsk = dccp_msk(sk);

        DCCP_SKB_CB(skb)->dccpd_opt_len = 0;

        if (dmsk->dccpms_send_ndp_count &&
            dccp_insert_option_ndp(sk, skb))
                return -1;

        if (!dccp_packet_without_ack(skb)) {
                if (dmsk->dccpms_send_ack_vector &&
                    dccp_ackvec_pending(dp->dccps_hc_rx_ackvec) &&
                    dccp_insert_option_ackvec(sk, skb))
                        return -1;

                if (dp->dccps_timestamp_echo != 0 &&
                    dccp_insert_option_timestamp_echo(sk, skb))
                        return -1;
        }

        if (dp->dccps_hc_rx_insert_options) {
                if (ccid_hc_rx_insert_options(dp->dccps_hc_rx_ccid, sk, skb))
                        return -1;
                dp->dccps_hc_rx_insert_options = 0;
        }

        /* Feature negotiation */
        /* Data packets can't do feat negotiation */
        if (DCCP_SKB_CB(skb)->dccpd_type != DCCP_PKT_DATA &&
            DCCP_SKB_CB(skb)->dccpd_type != DCCP_PKT_DATAACK &&
            dccp_insert_options_feat(sk, skb))
                return -1;

        /*
         * Obtain RTT sample from Request/Response exchange.
         * This is currently used in CCID 3 initialisation.
         */
        if (DCCP_SKB_CB(skb)->dccpd_type == DCCP_PKT_REQUEST &&
            dccp_insert_option_timestamp(sk, skb))
                return -1;

        /* XXX: insert other options when appropriate */

        if (DCCP_SKB_CB(skb)->dccpd_opt_len != 0) {
                /* The length of all options has to be a multiple of 4 */
                int padding = DCCP_SKB_CB(skb)->dccpd_opt_len % 4;

                if (padding != 0) {
                        padding = 4 - padding;
                        memset(skb_push(skb, padding), 0, padding);
                        DCCP_SKB_CB(skb)->dccpd_opt_len += padding;
                }
        }

        return 0;
}