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Commit 44e6fd9e authored by Gerrit Renker's avatar Gerrit Renker
Browse files

dccp: support for exchanging of NN options in established state 2/2 



This patch adds the receiver side and the (fast-path) activation part for
dynamic changes of non-negotiable (NN) parameters in (PART)OPEN state.

Signed-off-by: default avatarGerrit Renker <gerrit@erg.abdn.ac.uk>
Signed-off-by: default avatarSamuel Jero <sj323707@ohio.edu>
Acked-by: default avatarIan McDonald <ian.mcdonald@jandi.co.uk>
parent d6916f87

net/dccp/feat.c

+116 −0
Original line number Diff line number Diff line
@@ -344,6 +344,20 @@ static int __dccp_feat_activate(struct sock *sk, const int idx, 
	return dccp_feat_table[idx].activation_hdlr(sk, val, rx);

}



/**

 * dccp_feat_activate  -  Activate feature value on socket

 * @sk: fully connected DCCP socket (after handshake is complete)

 * @feat_num: feature to activate, one of %dccp_feature_numbers

 * @local: whether local (1) or remote (0) @feat_num is meant

 * @fval: the value (SP or NN) to activate, or NULL to use the default value

 * For general use this function is preferable over __dccp_feat_activate().

 */

static int dccp_feat_activate(struct sock *sk, u8 feat_num, bool local,

			      dccp_feat_val const *fval)

{

	return __dccp_feat_activate(sk, dccp_feat_index(feat_num), local, fval);

}



/* Test for "Req'd" feature (RFC 4340, 6.4) */

static inline int dccp_feat_must_be_understood(u8 feat_num)

{
@@ -1251,6 +1265,100 @@ static u8 dccp_feat_confirm_recv(struct list_head *fn, u8 is_mandatory, u8 opt, 
			    : DCCP_RESET_CODE_OPTION_ERROR;

}



/**

 * dccp_feat_handle_nn_established  -  Fast-path reception of NN options

 * @sk:		socket of an established DCCP connection

 * @mandatory:	whether @opt was preceded by a Mandatory option

 * @opt:	%DCCPO_CHANGE_L | %DCCPO_CONFIRM_R (NN only)

 * @feat:	NN number, one of %dccp_feature_numbers

 * @val:	NN value

 * @len:	length of @val in bytes

 * This function combines the functionality of change_recv/confirm_recv, with

 * the following differences (reset codes are the same):

 *    - cleanup after receiving the Confirm;

 *    - values are directly activated after successful parsing;

 *    - deliberately restricted to NN features.

 * The restriction to NN features is essential since SP features can have non-

 * predictable outcomes (depending on the remote configuration), and are inter-

 * dependent (CCIDs for instance cause further dependencies).

 */

static u8 dccp_feat_handle_nn_established(struct sock *sk, u8 mandatory, u8 opt,

					  u8 feat, u8 *val, u8 len)

{

	struct list_head *fn = &dccp_sk(sk)->dccps_featneg;

	const bool local = (opt == DCCPO_CONFIRM_R);

	struct dccp_feat_entry *entry;

	u8 type = dccp_feat_type(feat);

	dccp_feat_val fval;



	dccp_feat_print_opt(opt, feat, val, len, mandatory);



	/* Ignore non-mandatory unknown and non-NN features */

	if (type == FEAT_UNKNOWN) {

		if (local && !mandatory)

			return 0;

		goto fast_path_unknown;

	} else if (type != FEAT_NN) {

		return 0;

	}



	/*

	 * We don't accept empty Confirms, since in fast-path feature

	 * negotiation the values are enabled immediately after sending

	 * the Change option.

	 * Empty Changes on the other hand are invalid (RFC 4340, 6.1).

	 */

	if (len == 0 || len > sizeof(fval.nn))

		goto fast_path_unknown;



	if (opt == DCCPO_CHANGE_L) {

		fval.nn = dccp_decode_value_var(val, len);

		if (!dccp_feat_is_valid_nn_val(feat, fval.nn))

			goto fast_path_unknown;



		if (dccp_feat_push_confirm(fn, feat, local, &fval) ||

		    dccp_feat_activate(sk, feat, local, &fval))

			return DCCP_RESET_CODE_TOO_BUSY;



		/* set the `Ack Pending' flag to piggyback a Confirm */

		inet_csk_schedule_ack(sk);



	} else if (opt == DCCPO_CONFIRM_R) {

		entry = dccp_feat_list_lookup(fn, feat, local);

		if (entry == NULL || entry->state != FEAT_CHANGING)

			return 0;



		fval.nn = dccp_decode_value_var(val, len);

		/*

		 * Just ignore a value that doesn't match our current value.

		 * If the option changes twice within two RTTs, then at least

		 * one CONFIRM will be received for the old value after a

		 * new CHANGE was sent.

		 */

		if (fval.nn != entry->val.nn)

			return 0;



		/* Only activate after receiving the Confirm option (6.6.1). */

		dccp_feat_activate(sk, feat, local, &fval);



		/* It has been confirmed - so remove the entry */

		dccp_feat_list_pop(entry);



	} else {

		DCCP_WARN("Received illegal option %u\n", opt);

		goto fast_path_failed;

	}

	return 0;



fast_path_unknown:

	if (!mandatory)

		return dccp_push_empty_confirm(fn, feat, local);



fast_path_failed:

	return mandatory ? DCCP_RESET_CODE_MANDATORY_ERROR

			 : DCCP_RESET_CODE_OPTION_ERROR;

}



/**

 * dccp_feat_parse_options  -  Process Feature-Negotiation Options

 * @sk: for general use and used by the client during connection setup
@@ -1286,6 +1394,14 @@ int dccp_feat_parse_options(struct sock *sk, struct dccp_request_sock *dreq, 
			return dccp_feat_confirm_recv(fn, mandatory, opt, feat,

						      val, len, server);

		}

		break;

	/*

	 *	Support for exchanging NN options on an established connection.

	 */

	case DCCP_OPEN:

	case DCCP_PARTOPEN:

		return dccp_feat_handle_nn_established(sk, mandatory, opt, feat,

						       val, len);

	}

	return 0;	/* ignore FN options in all other states */

}