/*
 *  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"

u64 dccp_decode_value_var(const u8 *bf, const u8 len)
{
        u64 value = 0;

        if (len >= DCCP_OPTVAL_MAXLEN)
                value += ((u64)*bf++) << 40;
        if (len > 4)
                value += ((u64)*bf++) << 32;
        if (len > 3)
                value += ((u64)*bf++) << 24;
        if (len > 2)
                value += ((u64)*bf++) << 16;
        if (len > 1)
                value += ((u64)*bf++) << 8;
        if (len > 0)
                value += *bf;

        return value;
}

/**
 * dccp_parse_options  -  Parse DCCP options present in @skb
 * @sk: client|server|listening dccp socket (when @dreq != NULL)
 * @dreq: request socket to use during connection setup, or NULL
 */
int dccp_parse_options(struct sock *sk, struct dccp_request_sock *dreq,
                       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;
        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 *uninitialized_var(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_nonsensical_length;

                        len = *opt_ptr++;
                        if (len < 2)
                                goto out_nonsensical_length;
                        /*
                         * 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_nonsensical_length;
                }

                /*
                 * CCID-specific options are ignored during connection setup, as
                 * negotiation may still be in progress (see RFC 4340, 10.3).
                 * The same applies to Ack Vectors, as these depend on the CCID.
                 */
                if (dreq != NULL && (opt >= DCCPO_MIN_RX_CCID_SPECIFIC ||
                    opt == DCCPO_ACK_VECTOR_0 || opt == DCCPO_ACK_VECTOR_1))
                        goto ignore_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 > 6)
                                goto out_invalid_option;

                        opt_recv->dccpor_ndp = dccp_decode_value_var(value, len);
                        dccp_pr_debug("%s opt: NDP count=%llu\n", dccp_role(sk),
                                      (unsigned long long)opt_recv->dccpor_ndp);
                        break;
                case DCCPO_CHANGE_L ... DCCPO_CONFIRM_R:
                        if (pkt_type == DCCP_PKT_DATA)      /* RFC 4340, 6 */
                                break;
                        rc = dccp_feat_parse_options(sk, dreq, mandatory, opt,
                                                    *value, value + 1, len - 1);
                        if (rc)
                                goto out_featneg_failed;
                        break;
                case DCCPO_TIMESTAMP:
                        if (len != 4)
                                goto out_invalid_option;
                        /*
                         * RFC 4340 13.1: "The precise time corresponding to
                         * Timestamp Value zero is not specified". We use
                         * zero to indicate absence of a meaningful timestamp.
                         */
                        opt_val = get_unaligned((__be32 *)value);
                        if (unlikely(opt_val == 0)) {
                                DCCP_WARN("Timestamp with zero value\n");
                                break;
                        }

                        if (dreq != NULL) {
                                dreq->dreq_timestamp_echo = ntohl(opt_val);
                                dreq->dreq_timestamp_time = dccp_timestamp();
                        } else {
                                opt_recv->dccpor_timestamp =
                                        dp->dccps_timestamp_echo = ntohl(opt_val);
                                dp->dccps_timestamp_time = dccp_timestamp();
                        }
                        dccp_pr_debug("%s rx opt: TIMESTAMP=%u, ackno=%llu\n",
                                      dccp_role(sk), ntohl(opt_val),
                                      (unsigned long long)
                                      DCCP_SKB_CB(skb)->dccpd_ack_seq);
                        /* schedule an Ack in case this sender is quiescent */
                        inet_csk_schedule_ack(sk);
                        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 (dccp_packet_without_ack(skb))   /* RFC 4340, 13.2 */
                                break;

                        if (len == 2) {
                                __be16 opt_val2 = get_unaligned((__be16 *)value);
                                elapsed_time = ntohs(opt_val2);
                        } else if (len == 4) {
                                opt_val = get_unaligned((__be32 *)value);
                                elapsed_time = ntohl(opt_val);
                        } else {
                                goto out_invalid_option;
                        }

                        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;
                case DCCPO_MIN_RX_CCID_SPECIFIC ... DCCPO_MAX_RX_CCID_SPECIFIC:
                        if (ccid_hc_rx_parse_options(dp->dccps_hc_rx_ccid, sk,
                                                     pkt_type, opt, value, len))
                                goto out_invalid_option;
                        break;
                case DCCPO_ACK_VECTOR_0:
                case DCCPO_ACK_VECTOR_1:
                        if (dccp_packet_without_ack(skb))   /* RFC 4340, 11.4 */
                                break;
                        /*
                         * Ack vectors are processed by the TX CCID if it is
                         * interested. The RX CCID need not parse Ack Vectors,
                         * since it is only interested in clearing old state.
                         * Fall through.
                         */
                case DCCPO_MIN_TX_CCID_SPECIFIC ... DCCPO_MAX_TX_CCID_SPECIFIC:
                        if (ccid_hc_tx_parse_options(dp->dccps_hc_tx_ccid, sk,
                                                     pkt_type, opt, value, len))
                                goto out_invalid_option;
                        break;
                default:
                        DCCP_CRIT("DCCP(%p): option %d(len=%d) not "
                                  "implemented, ignoring", sk, opt, len);
                        break;
                }
ignore_option:
                if (opt != DCCPO_MANDATORY)
                        mandatory = 0;
        }

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

out_nonsensical_length:
        /* RFC 4340, 5.8: ignore option and all remaining option space */
        return 0;

out_invalid_option:
        DCCP_INC_STATS_BH(DCCP_MIB_INVALIDOPT);
        rc = DCCP_RESET_CODE_OPTION_ERROR;
out_featneg_failed:
        DCCP_WARN("DCCP(%p): Option %d (len=%d) error=%u\n", sk, opt, len, rc);
        DCCP_SKB_CB(skb)->dccpd_reset_code = rc;
        DCCP_SKB_CB(skb)->dccpd_reset_data[0] = opt;
        DCCP_SKB_CB(skb)->dccpd_reset_data[1] = len > 0 ? value[0] : 0;
        DCCP_SKB_CB(skb)->dccpd_reset_data[2] = len > 1 ? value[1] : 0;
        return -1;
}

EXPORT_SYMBOL_GPL(dccp_parse_options);

void dccp_encode_value_var(const u64 value, u8 *to, const u8 len)
{
        if (len >= DCCP_OPTVAL_MAXLEN)
                *to++ = (value & 0xFF0000000000ull) >> 40;
        if (len > 4)
                *to++ = (value & 0xFF00000000ull) >> 32;
        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 u8 dccp_ndp_len(const u64 ndp)
{
        if (likely(ndp <= 0xFF))
                return 1;
        return likely(ndp <= USHRT_MAX) ? 2 : (ndp <= UINT_MAX ? 4 : 6);
}

int dccp_insert_option(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);
        u64 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;
}

/* FIXME: This function is currently not used anywhere */
int dccp_insert_option_elapsed_time(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);

static int dccp_insert_option_timestamp(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(skb, DCCPO_TIMESTAMP, &now, sizeof(now));
}

static int dccp_insert_option_timestamp_echo(struct dccp_sock *dp,
                                             struct dccp_request_sock *dreq,
                                             struct sk_buff *skb)
{
        __be32 tstamp_echo;
        unsigned char *to;
        u32 elapsed_time, elapsed_time_len, len;

        if (dreq != NULL) {
                elapsed_time = dccp_timestamp() - dreq->dreq_timestamp_time;
                tstamp_echo  = htonl(dreq->dreq_timestamp_echo);
                dreq->dreq_timestamp_echo = 0;
        } else {
                elapsed_time = dccp_timestamp() - dp->dccps_timestamp_time;
                tstamp_echo  = htonl(dp->dccps_timestamp_echo);
                dp->dccps_timestamp_echo = 0;
        }

        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;

        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);
        }

        return 0;
}

static int dccp_insert_option_ackvec(struct sock *sk, struct sk_buff *skb)
{
        struct dccp_sock *dp = dccp_sk(sk);
        struct dccp_ackvec *av = dp->dccps_hc_rx_ackvec;
        struct dccp_skb_cb *dcb = DCCP_SKB_CB(skb);
        const u16 buflen = dccp_ackvec_buflen(av);
        /* Figure out how many options do we need to represent the ackvec */
        const u8 nr_opts = DIV_ROUND_UP(buflen, DCCP_SINGLE_OPT_MAXLEN);
        u16 len = buflen + 2 * nr_opts;
        u8 i, nonce = 0;
        const unsigned char *tail, *from;
        unsigned char *to;

        if (dcb->dccpd_opt_len + len > DCCP_MAX_OPT_LEN) {
                DCCP_WARN("Lacking space for %u bytes on %s packet\n", len,
                          dccp_packet_name(dcb->dccpd_type));
                return -1;
        }
        /*
         * Since Ack Vectors are variable-length, we can not always predict
         * their size. To catch exception cases where the space is running out
         * on the skb, a separate Sync is scheduled to carry the Ack Vector.
         */
        if (len > DCCPAV_MIN_OPTLEN &&
            len + dcb->dccpd_opt_len + skb->len > dp->dccps_mss_cache) {
                DCCP_WARN("No space left for Ack Vector (%u) on skb (%u+%u), "
                          "MPS=%u ==> reduce payload size?\n", len, skb->len,
                          dcb->dccpd_opt_len, dp->dccps_mss_cache);
                dp->dccps_sync_scheduled = 1;
                return 0;
        }
        dcb->dccpd_opt_len += len;

        to   = skb_push(skb, len);
        len  = buflen;
        from = av->av_buf + av->av_buf_head;
        tail = av->av_buf + DCCPAV_MAX_ACKVEC_LEN;

        for (i = 0; i < nr_opts; ++i) {
                int copylen = len;

                if (len > DCCP_SINGLE_OPT_MAXLEN)
                        copylen = DCCP_SINGLE_OPT_MAXLEN;

                /*
                 * RFC 4340, 12.2: Encode the Nonce Echo for this Ack Vector via
                 * its type; ack_nonce is the sum of all individual buf_nonce's.
                 */
                nonce ^= av->av_buf_nonce[i];

                *to++ = DCCPO_ACK_VECTOR_0 + av->av_buf_nonce[i];
                *to++ = copylen + 2;

                /* Check if buf_head wraps */
                if (from + copylen > tail) {
                        const u16 tailsize = tail - from;

                        memcpy(to, from, tailsize);
                        to      += tailsize;
                        len     -= tailsize;
                        copylen -= tailsize;
                        from    = av->av_buf;
                }

                memcpy(to, from, copylen);
                from += copylen;
                to   += copylen;
                len  -= copylen;
        }
        /*
         * Each sent Ack Vector is recorded in the list, as per A.2 of RFC 4340.
         */
        if (dccp_ackvec_update_records(av, dcb->dccpd_seq, nonce))
                return -ENOBUFS;
        return 0;
}

/**
 * dccp_insert_option_mandatory  -  Mandatory option (5.8.2)
 * Note that since we are using skb_push, this function needs to be called
 * _after_ inserting the option it is supposed to influence (stack order).
 */
int dccp_insert_option_mandatory(struct sk_buff *skb)
{
        if (DCCP_SKB_CB(skb)->dccpd_opt_len >= DCCP_MAX_OPT_LEN)
                return -1;

        DCCP_SKB_CB(skb)->dccpd_opt_len++;
        *skb_push(skb, 1) = DCCPO_MANDATORY;
        return 0;
}

/**
 * dccp_insert_fn_opt  -  Insert single Feature-Negotiation option into @skb
 * @type: %DCCPO_CHANGE_L, %DCCPO_CHANGE_R, %DCCPO_CONFIRM_L, %DCCPO_CONFIRM_R
 * @feat: one out of %dccp_feature_numbers
 * @val: NN value or SP array (preferred element first) to copy
 * @len: true length of @val in bytes (excluding first element repetition)
 * @repeat_first: whether to copy the first element of @val twice
 * The last argument is used to construct Confirm options, where the preferred
 * value and the preference list appear separately (RFC 4340, 6.3.1). Preference
 * lists are kept such that the preferred entry is always first, so we only need
 * to copy twice, and avoid the overhead of cloning into a bigger array.
 */
int dccp_insert_fn_opt(struct sk_buff *skb, u8 type, u8 feat,
                       u8 *val, u8 len, bool repeat_first)
{
        u8 tot_len, *to;

        /* take the `Feature' field and possible repetition into account */
        if (len > (DCCP_SINGLE_OPT_MAXLEN - 2)) {
                DCCP_WARN("length %u for feature %u too large\n", len, feat);
                return -1;
        }

        if (unlikely(val == NULL || len == 0))
                len = repeat_first = 0;
        tot_len = 3 + repeat_first + len;

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

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

        if (repeat_first)
                *to++ = *val;
        if (len)
                memcpy(to, val, len);
        return 0;
}

/* The length of all options needs to be a multiple of 4 (5.8) */
static void dccp_insert_option_padding(struct sk_buff *skb)
{
        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;
        }
}

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

        DCCP_SKB_CB(skb)->dccpd_opt_len = 0;

        if (dp->dccps_send_ndp_count && dccp_insert_option_ndp(sk, skb))
                return -1;

        if (DCCP_SKB_CB(skb)->dccpd_type != DCCP_PKT_DATA) {

                /* Feature Negotiation */
                if (dccp_feat_insert_opts(dp, NULL, skb))
                        return -1;

                if (DCCP_SKB_CB(skb)->dccpd_type == DCCP_PKT_REQUEST) {
                        /*
                         * Obtain RTT sample from Request/Response exchange.
                         * This is currently used for TFRC initialisation.
                         */
                        if (dccp_insert_option_timestamp(skb))
                                return -1;

                } else if (dccp_ackvec_pending(sk) &&
                           dccp_insert_option_ackvec(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;
        }

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

        dccp_insert_option_padding(skb);
        return 0;
}

int dccp_insert_options_rsk(struct dccp_request_sock *dreq, struct sk_buff *skb)
{
        DCCP_SKB_CB(skb)->dccpd_opt_len = 0;

        if (dccp_feat_insert_opts(NULL, dreq, skb))
                return -1;

        /* Obtain RTT sample from Response/Ack exchange (used by TFRC). */
        if (dccp_insert_option_timestamp(skb))
                return -1;

        if (dreq->dreq_timestamp_echo != 0 &&
            dccp_insert_option_timestamp_echo(NULL, dreq, skb))
                return -1;

        dccp_insert_option_padding(skb);
        return 0;
}