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 Changing non-negotiable (NN) values is supported in state OPEN/PARTOPEN.
 *  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 <linux/slab.h>
#include "ccid.h"
#include "feat.h"

/* feature-specific sysctls - initialised to the defaults from RFC 4340, 6.4 */
unsigned long	sysctl_dccp_sequence_window __read_mostly = 100;
int		sysctl_dccp_rx_ccid	    __read_mostly = 2,
		sysctl_dccp_tx_ccid	    __read_mostly = 2;

/*
 * 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);

	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)
{
	struct dccp_sock *dp = dccp_sk(sk);

	if (rx) {
		dp->dccps_r_seq_win = seq_win;
		/* propagate changes to update SWL/SWH */
		dccp_update_gsr(sk, dp->dccps_gsr);
	} else {
		dp->dccps_l_seq_win = seq_win;
		/* propagate changes to update AWL */
		dccp_update_gss(sk, dp->dccps_gss);
	}
	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_sk(sk)->dccps_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.
 */
static int dccp_hdlr_min_cscov(struct sock *sk, u64 cscov, bool rx)
{
	struct dccp_sock *dp = dccp_sk(sk);

	if (rx)
		dp->dccps_pcrlen = cscov;
	else {
		if (dp->dccps_pcslen == 0)
			dp->dccps_pcslen = cscov;
		else if (cscov > dp->dccps_pcslen)
			DCCP_WARN("CsCov %u too small, peer requires >= %u\n",
				  dp->dccps_pcslen, (u8)cscov);
	}
	return 0;
}

static const struct {
	u8			feat_num;		/* DCCPF_xxx */
	enum dccp_feat_type	rxtx;			/* RX or TX  */
	enum dccp_feat_type	reconciliation;		/* SP or NN  */
	u8			default_value;		/* as in 6.4 */
	int (*activation_hdlr)(struct sock *sk, u64 val, bool rx);
/*
 *    Lookup table for location and type of features (from RFC 4340/4342)
 *  +--------------------------+----+-----+----+----+---------+-----------+
 *  | Feature                  | Location | Reconc. | Initial |  Section  |
 *  |                          | RX | TX  | SP | NN |  Value  | Reference |
 *  +--------------------------+----+-----+----+----+---------+-----------+
 *  | DCCPF_CCID               |    |  X  | X  |    |   2     | 10        |
 *  | DCCPF_SHORT_SEQNOS       |    |  X  | X  |    |   0     |  7.6.1    |
 *  | DCCPF_SEQUENCE_WINDOW    |    |  X  |    | X  | 100     |  7.5.2    |
 *  | DCCPF_ECN_INCAPABLE      | X  |     | X  |    |   0     | 12.1      |
 *  | DCCPF_ACK_RATIO          |    |  X  |    | X  |   2     | 11.3      |
 *  | DCCPF_SEND_ACK_VECTOR    | X  |     | X  |    |   0     | 11.5      |
 *  | DCCPF_SEND_NDP_COUNT     |    |  X  | X  |    |   0     |  7.7.2    |
 *  | DCCPF_MIN_CSUM_COVER     | X  |     | X  |    |   0     |  9.2.1    |
 *  | DCCPF_DATA_CHECKSUM      | X  |     | X  |    |   0     |  9.3.1    |
 *  | DCCPF_SEND_LEV_RATE      | X  |     | X  |    |   0     | 4342/8.4  |
 *  +--------------------------+----+-----+----+----+---------+-----------+
 */
} dccp_feat_table[] = {
	{ DCCPF_CCID,		 FEAT_AT_TX, FEAT_SP, 2,   dccp_hdlr_ccid     },
	{ DCCPF_SHORT_SEQNOS,	 FEAT_AT_TX, FEAT_SP, 0,   NULL },
	{ DCCPF_SEQUENCE_WINDOW, FEAT_AT_TX, FEAT_NN, 100, dccp_hdlr_seq_win  },
	{ DCCPF_ECN_INCAPABLE,	 FEAT_AT_RX, FEAT_SP, 0,   NULL },
	{ DCCPF_ACK_RATIO,	 FEAT_AT_TX, FEAT_NN, 2,   dccp_hdlr_ack_ratio},
	{ DCCPF_SEND_ACK_VECTOR, FEAT_AT_RX, FEAT_SP, 0,   dccp_hdlr_ackvec   },
	{ DCCPF_SEND_NDP_COUNT,  FEAT_AT_TX, FEAT_SP, 0,   dccp_hdlr_ndp      },
	{ DCCPF_MIN_CSUM_COVER,  FEAT_AT_RX, FEAT_SP, 0,   dccp_hdlr_min_cscov},
	{ DCCPF_DATA_CHECKSUM,	 FEAT_AT_RX, FEAT_SP, 0,   NULL },
	{ DCCPF_SEND_LEV_RATE,	 FEAT_AT_RX, FEAT_SP, 0,   NULL },
};
#define DCCP_FEAT_SUPPORTED_MAX		ARRAY_SIZE(dccp_feat_table)

/**
 * dccp_feat_index  -  Hash function to map feature number into array position
 * Returns consecutive array index or -1 if the feature is not understood.
 */
static int dccp_feat_index(u8 feat_num)
{
	/* The first 9 entries are occupied by the types from RFC 4340, 6.4 */
	if (feat_num > DCCPF_RESERVED &