path: root/net/dccp/feat.c

/*
 *  net/dccp/feat.c
 *
 *  Feature negotiation for the DCCP protocol (RFC 4340, section 6)
 *
 *  Copyright (c) 2008 Gerrit Renker <gerrit@erg.abdn.ac.uk>
 *  Rewrote from scratch, some bits from earlier code by
 *  Copyright (c) 2005 Andrea Bittau <a.bittau@cs.ucl.ac.uk>
 *
 *
 *  ASSUMPTIONS
 *  -----------
 *  o Feature negotiation is coordinated with connection setup (as in TCP), wild
 *    changes of parameters of an established connection are not supported.
 *  o All currently known SP features have 1-byte quantities. If in the future
 *    extensions of RFCs 4340..42 define features with item lengths larger than
 *    one byte, a feature-specific extension of the code will be required.
 *
 *  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"

/*
 * Feature activation handlers.
 *
 * These all use an u64 argument, to provide enough room for NN/SP features. At
 * this stage the negotiated values have been checked to be within their range.
 */
static int dccp_hdlr_ccid(struct sock *sk, u64 ccid, bool rx)
{
	struct dccp_sock *dp = dccp_sk(sk);
	struct ccid *new_ccid = ccid_new(ccid, sk, rx, gfp_any());

	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;
	} else {
		ccid_hc_tx_delete(dp->dccps_hc_tx_ccid, sk);
		dp->dccps_hc_tx_ccid = new_ccid;
	}
	return 0;
}

static int dccp_hdlr_seq_win(struct sock *sk, u64 seq_win, bool rx)
{
	if (!rx)
		dccp_msk(sk)->dccpms_sequence_window = seq_win;
	return 0;
}

static int dccp_hdlr_ack_ratio(struct sock *sk, u64 ratio, bool rx)
{
	if (rx)
		dccp_sk(sk)->dccps_r_ack_ratio = ratio;
	else
		dccp_sk(sk)->dccps_l_ack_ratio = ratio;
	return 0;
}

static int dccp_hdlr_ackvec(struct sock *sk, u64 enable, bool rx)
{
	struct dccp_sock *dp = dccp_sk(sk);

	if (rx) {
		if (enable && dp->dccps_hc_rx_ackvec == NULL) {
			dp->dccps_hc_rx_ackvec = dccp_ackvec_alloc(gfp_any());
			if (dp->dccps_hc_rx_ackvec == NULL)
				return -ENOMEM;
		} else if (!enable) {
			dccp_ackvec_free(dp->dccps_hc_rx_ackvec);
			dp->dccps_hc_rx_ackvec = NULL;
		}
	}
	return 0;
}

static int dccp_hdlr_ndp(struct sock *sk, u64 enable, bool rx)
{
	if (!rx)
		dccp_msk(sk)->dccpms_send_ndp_count = (enable > 0);
	return 0;
}

/*
 * Minimum Checksum Coverage is located at the RX side (9.2.1). This means that
 * `rx' holds when the sending peer informs about his partial coverage via a
 * ChangeR() option. In the other case, we are the sender and the receiver
 * announces its coverage via ChangeL() options. The policy here is to honour
 * such communication by enabling the corresponding partial coverage - but only
 * if it has not been set manually before; the warning here means that all
 * packets will be dropped.