/*
   *  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
  ", 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;

  			if (len == 0)
  				goto out_invalid_option;

  			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
  ");
  				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
  ",

  				      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("
  ");

  				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
  ", 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
  ",
  				      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(DCCP_MIB_INVALIDOPT);

  	rc = DCCP_RESET_CODE_OPTION_ERROR;
  out_featneg_failed:
  	DCCP_WARN("DCCP(%p): Option %d (len=%d) error=%u
  ", 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;

  }

  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
  ", 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?
  ", 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
  ", len, feat);

  		return -1;

  	}

  	if (unlikely(val == NULL || len == 0))

  		len = repeat_first = false;

  	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!
  ", 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;

  }