X-Git-Url: http://ftp.safe.ca/?a=blobdiff_plain;f=net%2Fdccp%2Ffeat.c;h=8434659998548575f82687e95afc8aa65df4189f;hb=51c7d4fa2675c106a980ddcdbe308b54b5151945;hp=b859722fba72f619448f0f80c33ae5279fe0db63;hpb=86349c8d9c6892b57aff4549256ab1aa65aed0f0;p=safe%2Fjmp%2Flinux-2.6

diff --git a/net/dccp/feat.c b/net/dccp/feat.c
index b859722..8434659 100644
--- a/net/dccp/feat.c
+++ b/net/dccp/feat.c
@@ -1,8 +1,13 @@
 /*
  *  net/dccp/feat.c
  *
- *  An implementation of the DCCP protocol
- *  Andrea Bittau <a.bittau@cs.ucl.ac.uk>
+ *  Feature negotiation for the DCCP protocol (RFC 4340, section 6)
+ *
+ *  Copyright (c) 2008 The University of Aberdeen, Scotland, UK
+ *  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
  *  -----------
@@ -17,19 +22,114 @@
  *  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"
 
-#define DCCP_FEAT_SP_NOAGREE (-123)
+/*
+ * 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)
+{
+	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)
  *  +--------------------------+----+-----+----+----+---------+-----------+
@@ -49,16 +149,16 @@ static const struct {
  *  +--------------------------+----+-----+----+----+---------+-----------+
  */
 } dccp_feat_table[] = {
-	{ DCCPF_CCID,		 FEAT_AT_TX, FEAT_SP, 2 },
-	{ DCCPF_SHORT_SEQNOS,	 FEAT_AT_TX, FEAT_SP, 0 },
-	{ DCCPF_SEQUENCE_WINDOW, FEAT_AT_TX, FEAT_NN, 100 },
-	{ DCCPF_ECN_INCAPABLE,	 FEAT_AT_RX, FEAT_SP, 0 },
-	{ DCCPF_ACK_RATIO,	 FEAT_AT_TX, FEAT_NN, 2 },
-	{ DCCPF_SEND_ACK_VECTOR, FEAT_AT_RX, FEAT_SP, 0 },
-	{ DCCPF_SEND_NDP_COUNT,  FEAT_AT_TX, FEAT_SP, 0 },
-	{ DCCPF_MIN_CSUM_COVER,  FEAT_AT_RX, FEAT_SP, 0 },
-	{ DCCPF_DATA_CHECKSUM,	 FEAT_AT_RX, FEAT_SP, 0 },
-	{ DCCPF_SEND_LEV_RATE,	 FEAT_AT_RX, FEAT_SP, 0 },
+	{ 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)
 
@@ -99,6 +199,48 @@ static int dccp_feat_default_value(u8 feat_num)
 	return idx < 0 ? : dccp_feat_table[idx].default_value;
 }
 
+static int __dccp_feat_activate(struct sock *sk, const int idx,
+				const bool is_local, dccp_feat_val const *fval)
+{
+	bool rx;
+	u64 val;
+
+	if (idx < 0 || idx >= DCCP_FEAT_SUPPORTED_MAX)
+		return -1;
+	if (dccp_feat_table[idx].activation_hdlr == NULL)
+		return 0;
+
+	if (fval == NULL) {
+		val = dccp_feat_table[idx].default_value;
+	} else if (dccp_feat_table[idx].reconciliation == FEAT_SP) {
+		if (fval->sp.vec == NULL) {
+			/*
+			 * This can happen when an empty Confirm is sent
+			 * for an SP (i.e. known) feature. In this case
+			 * we would be using the default anyway.
+			 */
+			DCCP_CRIT("Feature #%d undefined: using default", idx);
+			val = dccp_feat_table[idx].default_value;
+		} else {
+			val = fval->sp.vec[0];
+		}
+	} else {
+		val = fval->nn;
+	}
+
+	/* Location is RX if this is a local-RX or remote-TX feature */
+	rx = (is_local == (dccp_feat_table[idx].rxtx == FEAT_AT_RX));
+
+	return dccp_feat_table[idx].activation_hdlr(sk, val, rx);
+}
+
+/* Test for "Req'd" feature (RFC 4340, 6.4) */
+static inline int dccp_feat_must_be_understood(u8 feat_num)
+{
+	return	feat_num == DCCPF_CCID || feat_num == DCCPF_SHORT_SEQNOS ||
+		feat_num == DCCPF_SEQUENCE_WINDOW;
+}
+
 /* copy constructor, fval must not already contain allocated memory */
 static int dccp_feat_clone_sp_val(dccp_feat_val *fval, u8 const *val, u8 len)
 {
@@ -300,6 +442,20 @@ cloning_failed:
 	return -ENOMEM;
 }
 
+/**
+ * dccp_feat_valid_nn_length  -  Enforce length constraints on NN options
+ * Length is between 0 and %DCCP_OPTVAL_MAXLEN. Used for outgoing packets only,
+ * incoming options are accepted as long as their values are valid.
+ */
+static u8 dccp_feat_valid_nn_length(u8 feat_num)
+{
+	if (feat_num == DCCPF_ACK_RATIO)	/* RFC 4340, 11.3 and 6.6.8 */
+		return 2;
+	if (feat_num == DCCPF_SEQUENCE_WINDOW)	/* RFC 4340, 7.5.2 and 6.5  */
+		return 6;
+	return 0;
+}
+
 static u8 dccp_feat_is_valid_nn_val(u8 feat_num, u64 val)
 {
 	switch (feat_num) {
@@ -342,6 +498,57 @@ static u8 dccp_feat_sp_list_ok(u8 feat_num, u8 const *sp_list, u8 sp_len)
 }
 
 /**
+ * dccp_feat_insert_opts  -  Generate FN options from current list state
+ * @skb: next sk_buff to be sent to the peer
+ * @dp: for client during handshake and general negotiation
+ * @dreq: used by the server only (all Changes/Confirms in LISTEN/RESPOND)
+ */
+int dccp_feat_insert_opts(struct dccp_sock *dp, struct dccp_request_sock *dreq,
+			  struct sk_buff *skb)
+{
+	struct list_head *fn = dreq ? &dreq->dreq_featneg : &dp->dccps_featneg;
+	struct dccp_feat_entry *pos, *next;
+	u8 opt, type, len, *ptr, nn_in_nbo[DCCP_OPTVAL_MAXLEN];
+	bool rpt;
+
+	/* put entries into @skb in the order they appear in the list */
+	list_for_each_entry_safe_reverse(pos, next, fn, node) {
+		opt  = dccp_feat_genopt(pos);
+		type = dccp_feat_type(pos->feat_num);
+		rpt  = false;
+
+		if (pos->empty_confirm) {
+			len = 0;
+			ptr = NULL;
+		} else {
+			if (type == FEAT_SP) {
+				len = pos->val.sp.len;
+				ptr = pos->val.sp.vec;
+				rpt = pos->needs_confirm;
+			} else if (type == FEAT_NN) {
+				len = dccp_feat_valid_nn_length(pos->feat_num);
+				ptr = nn_in_nbo;
+				dccp_encode_value_var(pos->val.nn, ptr, len);
+			} else {
+				DCCP_BUG("unknown feature %u", pos->feat_num);
+				return -1;
+			}
+		}
+
+		if (dccp_insert_fn_opt(skb, opt, pos->feat_num, ptr, len, rpt))
+			return -1;
+		if (pos->needs_mandatory && dccp_insert_option_mandatory(skb))
+			return -1;
+		/*
+		 * Enter CHANGING after transmitting the Change option (6.6.2).
+		 */
+		if (pos->state == FEAT_INITIALISING)
+			pos->state = FEAT_CHANGING;
+	}
+	return 0;
+}
+
+/**
  * __feat_register_nn  -  Register new NN value on socket
  * @fn: feature-negotiation list to register with
  * @feat: an NN feature from %dccp_feature_numbers
@@ -383,577 +590,671 @@ static int __feat_register_sp(struct list_head *fn, u8 feat, u8 is_local,
 	    !dccp_feat_sp_list_ok(feat, sp_val, sp_len))
 		return -EINVAL;
 
+	/* Avoid negotiating alien CCIDs by only advertising supported ones */
+	if (feat == DCCPF_CCID && !ccid_support_check(sp_val, sp_len))
+		return -EOPNOTSUPP;
+
 	if (dccp_feat_clone_sp_val(&fval, sp_val, sp_len))
 		return -ENOMEM;
 
 	return dccp_feat_push_change(fn, feat, is_local, mandatory, &fval);
 }
 
-int dccp_feat_change(struct dccp_minisock *dmsk, u8 type, u8 feature,
-		     u8 *val, u8 len, gfp_t gfp)
-{
-	struct dccp_opt_pend *opt;
-
-	dccp_feat_debug(type, feature, *val);
-
-	if (len > 3) {
-		DCCP_WARN("invalid length %d\n", len);
+/**
+ * dccp_feat_register_sp  -  Register requests to change SP feature values
+ * @sk: client or listening socket
+ * @feat: one of %dccp_feature_numbers
+ * @is_local: whether the local (1) or remote (0) @feat is meant
+ * @list: array of preferred values, in descending order of preference
+ * @len: length of @list in bytes
+ */
+int dccp_feat_register_sp(struct sock *sk, u8 feat, u8 is_local,
+			  u8 const *list, u8 len)
+{	 /* any changes must be registered before establishing the connection */
+	if (sk->sk_state != DCCP_CLOSED)
+		return -EISCONN;
+	if (dccp_feat_type(feat) != FEAT_SP)
 		return -EINVAL;
-	}
-	/* XXX add further sanity checks */
-
-	/* check if that feature is already being negotiated */
-	list_for_each_entry(opt, &dmsk->dccpms_pending, dccpop_node) {
-		/* ok we found a negotiation for this option already */
-		if (opt->dccpop_feat == feature && opt->dccpop_type == type) {
-			dccp_pr_debug("Replacing old\n");
-			/* replace */
-			BUG_ON(opt->dccpop_val == NULL);
-			kfree(opt->dccpop_val);
-			opt->dccpop_val	 = val;
-			opt->dccpop_len	 = len;
-			opt->dccpop_conf = 0;
-			return 0;
-		}
-	}
-
-	/* negotiation for a new feature */
-	opt = kmalloc(sizeof(*opt), gfp);
-	if (opt == NULL)
-		return -ENOMEM;
-
-	opt->dccpop_type = type;
-	opt->dccpop_feat = feature;
-	opt->dccpop_len	 = len;
-	opt->dccpop_val	 = val;
-	opt->dccpop_conf = 0;
-	opt->dccpop_sc	 = NULL;
-
-	BUG_ON(opt->dccpop_val == NULL);
-
-	list_add_tail(&opt->dccpop_node, &dmsk->dccpms_pending);
-	return 0;
+	return __feat_register_sp(&dccp_sk(sk)->dccps_featneg, feat, is_local,
+				  0, list, len);
 }
 
-EXPORT_SYMBOL_GPL(dccp_feat_change);
-
-static int dccp_feat_update_ccid(struct sock *sk, u8 type, u8 new_ccid_nr)
+/* Analogous to dccp_feat_register_sp(), but for non-negotiable values */
+int dccp_feat_register_nn(struct sock *sk, u8 feat, u64 val)
 {
-	struct dccp_sock *dp = dccp_sk(sk);
-	struct dccp_minisock *dmsk = dccp_msk(sk);
-	/* figure out if we are changing our CCID or the peer's */
-	const int rx = type == DCCPO_CHANGE_R;
-	const u8 ccid_nr = rx ? dmsk->dccpms_rx_ccid : dmsk->dccpms_tx_ccid;
-	struct ccid *new_ccid;
-
-	/* Check if nothing is being changed. */
-	if (ccid_nr == new_ccid_nr)
-		return 0;
-
-	new_ccid = ccid_new(new_ccid_nr, sk, rx, GFP_ATOMIC);
-	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;
-		dmsk->dccpms_rx_ccid = new_ccid_nr;
-	} else {
-		ccid_hc_tx_delete(dp->dccps_hc_tx_ccid, sk);
-		dp->dccps_hc_tx_ccid = new_ccid;
-		dmsk->dccpms_tx_ccid = new_ccid_nr;
-	}
-
-	return 0;
+	/* any changes must be registered before establishing the connection */
+	if (sk->sk_state != DCCP_CLOSED)
+		return -EISCONN;
+	if (dccp_feat_type(feat) != FEAT_NN)
+		return -EINVAL;
+	return __feat_register_nn(&dccp_sk(sk)->dccps_featneg, feat, 0, val);
 }
 
-static int dccp_feat_update(struct sock *sk, u8 type, u8 feat, u8 val)
+/*
+ *	Tracking features whose value depend on the choice of CCID
+ *
+ * This is designed with an extension in mind so that a list walk could be done
+ * before activating any features. However, the existing framework was found to
+ * work satisfactorily up until now, the automatic verification is left open.
+ * When adding new CCIDs, add a corresponding dependency table here.
+ */
+static const struct ccid_dependency *dccp_feat_ccid_deps(u8 ccid, bool is_local)
 {
-	dccp_feat_debug(type, feat, val);
-
-	switch (feat) {
-	case DCCPF_CCID:
-		return dccp_feat_update_ccid(sk, type, val);
+	static const struct ccid_dependency ccid2_dependencies[2][2] = {
+		/*
+		 * CCID2 mandates Ack Vectors (RFC 4341, 4.): as CCID is a TX
+		 * feature and Send Ack Vector is an RX feature, `is_local'
+		 * needs to be reversed.
+		 */
+		{	/* Dependencies of the receiver-side (remote) CCID2 */
+			{
+				.dependent_feat	= DCCPF_SEND_ACK_VECTOR,
+				.is_local	= true,
+				.is_mandatory	= true,
+				.val		= 1
+			},
+			{ 0, 0, 0, 0 }
+		},
+		{	/* Dependencies of the sender-side (local) CCID2 */
+			{
+				.dependent_feat	= DCCPF_SEND_ACK_VECTOR,
+				.is_local	= false,
+				.is_mandatory	= true,
+				.val		= 1
+			},
+			{ 0, 0, 0, 0 }
+		}
+	};
+	static const struct ccid_dependency ccid3_dependencies[2][5] = {
+		{	/*
+			 * Dependencies of the receiver-side CCID3
+			 */
+			{	/* locally disable Ack Vectors */
+				.dependent_feat	= DCCPF_SEND_ACK_VECTOR,
+				.is_local	= true,
+				.is_mandatory	= false,
+				.val		= 0
+			},
+			{	/* see below why Send Loss Event Rate is on */
+				.dependent_feat	= DCCPF_SEND_LEV_RATE,
+				.is_local	= true,
+				.is_mandatory	= true,
+				.val		= 1
+			},
+			{	/* NDP Count is needed as per RFC 4342, 6.1.1 */
+				.dependent_feat	= DCCPF_SEND_NDP_COUNT,
+				.is_local	= false,
+				.is_mandatory	= true,
+				.val		= 1
+			},
+			{ 0, 0, 0, 0 },
+		},
+		{	/*
+			 * CCID3 at the TX side: we request that the HC-receiver
+			 * will not send Ack Vectors (they will be ignored, so
+			 * Mandatory is not set); we enable Send Loss Event Rate
+			 * (Mandatory since the implementation does not support
+			 * the Loss Intervals option of RFC 4342, 8.6).
+			 * The last two options are for peer's information only.
+			*/
+			{
+				.dependent_feat	= DCCPF_SEND_ACK_VECTOR,
+				.is_local	= false,
+				.is_mandatory	= false,
+				.val		= 0
+			},
+			{
+				.dependent_feat	= DCCPF_SEND_LEV_RATE,
+				.is_local	= false,
+				.is_mandatory	= true,
+				.val		= 1
+			},
+			{	/* this CCID does not support Ack Ratio */
+				.dependent_feat	= DCCPF_ACK_RATIO,
+				.is_local	= true,
+				.is_mandatory	= false,
+				.val		= 0
+			},
+			{	/* tell receiver we are sending NDP counts */
+				.dependent_feat	= DCCPF_SEND_NDP_COUNT,
+				.is_local	= true,
+				.is_mandatory	= false,
+				.val		= 1
+			},
+			{ 0, 0, 0, 0 }
+		}
+	};
+	switch (ccid) {
+	case DCCPC_CCID2:
+		return ccid2_dependencies[is_local];
+	case DCCPC_CCID3:
+		return ccid3_dependencies[is_local];
 	default:
-		dccp_pr_debug("UNIMPLEMENTED: %s(%d, ...)\n",
-			      dccp_feat_typename(type), feat);
-		break;
+		return NULL;
 	}
-	return 0;
 }
 
-static int dccp_feat_reconcile(struct sock *sk, struct dccp_opt_pend *opt,
-			       u8 *rpref, u8 rlen)
+/**
+ * dccp_feat_propagate_ccid - Resolve dependencies of features on choice of CCID
+ * @fn: feature-negotiation list to update
+ * @id: CCID number to track
+ * @is_local: whether TX CCID (1) or RX CCID (0) is meant
+ * This function needs to be called after registering all other features.
+ */
+static int dccp_feat_propagate_ccid(struct list_head *fn, u8 id, bool is_local)
 {
-	struct dccp_sock *dp = dccp_sk(sk);
-	u8 *spref, slen, *res = NULL;
-	int i, j, rc, agree = 1;
+	const struct ccid_dependency *table = dccp_feat_ccid_deps(id, is_local);
+	int i, rc = (table == NULL);
+
+	for (i = 0; rc == 0 && table[i].dependent_feat != DCCPF_RESERVED; i++)
+		if (dccp_feat_type(table[i].dependent_feat) == FEAT_SP)
+			rc = __feat_register_sp(fn, table[i].dependent_feat,
+						    table[i].is_local,
+						    table[i].is_mandatory,
+						    &table[i].val, 1);
+		else
+			rc = __feat_register_nn(fn, table[i].dependent_feat,
+						    table[i].is_mandatory,
+						    table[i].val);
+	return rc;
+}
 
-	BUG_ON(rpref == NULL);
+/**
+ * dccp_feat_finalise_settings  -  Finalise settings before starting negotiation
+ * @dp: client or listening socket (settings will be inherited)
+ * This is called after all registrations (socket initialisation, sysctls, and
+ * sockopt calls), and before sending the first packet containing Change options
+ * (ie. client-Request or server-Response), to ensure internal consistency.
+ */
+int dccp_feat_finalise_settings(struct dccp_sock *dp)
+{
+	struct list_head *fn = &dp->dccps_featneg;
+	struct dccp_feat_entry *entry;
+	int i = 2, ccids[2] = { -1, -1 };
 
-	/* check if we are the black sheep */
-	if (dp->dccps_role == DCCP_ROLE_CLIENT) {
-		spref = rpref;
-		slen  = rlen;
-		rpref = opt->dccpop_val;
-		rlen  = opt->dccpop_len;
-	} else {
-		spref = opt->dccpop_val;
-		slen  = opt->dccpop_len;
-	}
 	/*
-	 * Now we have server preference list in spref and client preference in
-	 * rpref
+	 * Propagating CCIDs:
+	 * 1) not useful to propagate CCID settings if this host advertises more
+	 *    than one CCID: the choice of CCID  may still change - if this is
+	 *    the client, or if this is the server and the client sends
+	 *    singleton CCID values.
+	 * 2) since is that propagate_ccid changes the list, we defer changing
+	 *    the sorted list until after the traversal.
 	 */
-	BUG_ON(spref == NULL);
-	BUG_ON(rpref == NULL);
-
-	/* FIXME sanity check vals */
-
-	/* Are values in any order?  XXX Lame "algorithm" here */
-	for (i = 0; i < slen; i++) {
-		for (j = 0; j < rlen; j++) {
-			if (spref[i] == rpref[j]) {
-				res = &spref[i];
-				break;
-			}
-		}
-		if (res)
-			break;
-	}
-
-	/* we didn't agree on anything */
-	if (res == NULL) {
-		/* confirm previous value */
-		switch (opt->dccpop_feat) {
-		case DCCPF_CCID:
-			/* XXX did i get this right? =P */
-			if (opt->dccpop_type == DCCPO_CHANGE_L)
-				res = &dccp_msk(sk)->dccpms_tx_ccid;
-			else
-				res = &dccp_msk(sk)->dccpms_rx_ccid;
-			break;
-
-		default:
-			DCCP_BUG("Fell through, feat=%d", opt->dccpop_feat);
-			/* XXX implement res */
-			return -EFAULT;
-		}
-
-		dccp_pr_debug("Don't agree... reconfirming %d\n", *res);
-		agree = 0; /* this is used for mandatory options... */
-	}
-
-	/* need to put result and our preference list */
-	rlen = 1 + opt->dccpop_len;
-	rpref = kmalloc(rlen, GFP_ATOMIC);
-	if (rpref == NULL)
-		return -ENOMEM;
-
-	*rpref = *res;
-	memcpy(&rpref[1], opt->dccpop_val, opt->dccpop_len);
-
-	/* put it in the "confirm queue" */
-	if (opt->dccpop_sc == NULL) {
-		opt->dccpop_sc = kmalloc(sizeof(*opt->dccpop_sc), GFP_ATOMIC);
-		if (opt->dccpop_sc == NULL) {
-			kfree(rpref);
-			return -ENOMEM;
-		}
-	} else {
-		/* recycle the confirm slot */
-		BUG_ON(opt->dccpop_sc->dccpoc_val == NULL);
-		kfree(opt->dccpop_sc->dccpoc_val);
-		dccp_pr_debug("recycling confirm slot\n");
-	}
-	memset(opt->dccpop_sc, 0, sizeof(*opt->dccpop_sc));
+	list_for_each_entry(entry, fn, node)
+		if (entry->feat_num == DCCPF_CCID && entry->val.sp.len == 1)
+			ccids[entry->is_local] = entry->val.sp.vec[0];
+	while (i--)
+		if (ccids[i] > 0 && dccp_feat_propagate_ccid(fn, ccids[i], i))
+			return -1;
+	return 0;
+}
 
-	opt->dccpop_sc->dccpoc_val = rpref;
-	opt->dccpop_sc->dccpoc_len = rlen;
+/**
+ * dccp_feat_server_ccid_dependencies  -  Resolve CCID-dependent features
+ * It is the server which resolves the dependencies once the CCID has been
+ * fully negotiated. If no CCID has been negotiated, it uses the default CCID.
+ */
+int dccp_feat_server_ccid_dependencies(struct dccp_request_sock *dreq)
+{
+	struct list_head *fn = &dreq->dreq_featneg;
+	struct dccp_feat_entry *entry;
+	u8 is_local, ccid;
 
-	/* update the option on our side [we are about to send the confirm] */
-	rc = dccp_feat_update(sk, opt->dccpop_type, opt->dccpop_feat, *res);
-	if (rc) {
-		kfree(opt->dccpop_sc->dccpoc_val);
-		kfree(opt->dccpop_sc);
-		opt->dccpop_sc = NULL;
-		return rc;
-	}
+	for (is_local = 0; is_local <= 1; is_local++) {
+		entry = dccp_feat_list_lookup(fn, DCCPF_CCID, is_local);
 
-	dccp_pr_debug("Will confirm %d\n", *rpref);
+		if (entry != NULL && !entry->empty_confirm)
+			ccid = entry->val.sp.vec[0];
+		else
+			ccid = dccp_feat_default_value(DCCPF_CCID);
 
-	/* say we want to change to X but we just got a confirm X, suppress our
-	 * change
-	 */
-	if (!opt->dccpop_conf) {
-		if (*opt->dccpop_val == *res)
-			opt->dccpop_conf = 1;
-		dccp_pr_debug("won't ask for change of same feature\n");
+		if (dccp_feat_propagate_ccid(fn, ccid, is_local))
+			return -1;
 	}
-
-	return agree ? 0 : DCCP_FEAT_SP_NOAGREE; /* used for mandatory opts */
+	return 0;
 }
 
-static int dccp_feat_sp(struct sock *sk, u8 type, u8 feature, u8 *val, u8 len)
+/* Select the first entry in @servlist that also occurs in @clilist (6.3.1) */
+static int dccp_feat_preflist_match(u8 *servlist, u8 slen, u8 *clilist, u8 clen)
 {
-	struct dccp_minisock *dmsk = dccp_msk(sk);
-	struct dccp_opt_pend *opt;
-	int rc = 1;
-	u8 t;
+	u8 c, s;
 
-	/*
-	 * We received a CHANGE.  We gotta match it against our own preference
-	 * list.  If we got a CHANGE_R it means it's a change for us, so we need
-	 * to compare our CHANGE_L list.
-	 */
-	if (type == DCCPO_CHANGE_L)
-		t = DCCPO_CHANGE_R;
-	else
-		t = DCCPO_CHANGE_L;
+	for (s = 0; s < slen; s++)
+		for (c = 0; c < clen; c++)
+			if (servlist[s] == clilist[c])
+				return servlist[s];
+	return -1;
+}
 
-	/* find our preference list for this feature */
-	list_for_each_entry(opt, &dmsk->dccpms_pending, dccpop_node) {
-		if (opt->dccpop_type != t || opt->dccpop_feat != feature)
-			continue;
+/**
+ * dccp_feat_prefer  -  Move preferred entry to the start of array
+ * Reorder the @array_len elements in @array so that @preferred_value comes
+ * first. Returns >0 to indicate that @preferred_value does occur in @array.
+ */
+static u8 dccp_feat_prefer(u8 preferred_value, u8 *array, u8 array_len)
+{
+	u8 i, does_occur = 0;
 
-		/* find the winner from the two preference lists */
-		rc = dccp_feat_reconcile(sk, opt, val, len);
-		break;
+	if (array != NULL) {
+		for (i = 0; i < array_len; i++)
+			if (array[i] == preferred_value) {
+				array[i] = array[0];
+				does_occur++;
+			}
+		if (does_occur)
+			array[0] = preferred_value;
 	}
-
-	/* We didn't deal with the change.  This can happen if we have no
-	 * preference list for the feature.  In fact, it just shouldn't
-	 * happen---if we understand a feature, we should have a preference list
-	 * with at least the default value.
-	 */
-	BUG_ON(rc == 1);
-
-	return rc;
+	return does_occur;
 }
 
-static int dccp_feat_nn(struct sock *sk, u8 type, u8 feature, u8 *val, u8 len)
+/**
+ * dccp_feat_reconcile  -  Reconcile SP preference lists
+ *  @fval: SP list to reconcile into
+ *  @arr: received SP preference list
+ *  @len: length of @arr in bytes
+ *  @is_server: whether this side is the server (and @fv is the server's list)
+ *  @reorder: whether to reorder the list in @fv after reconciling with @arr
+ * When successful, > 0 is returned and the reconciled list is in @fval.
+ * A value of 0 means that negotiation failed (no shared entry).
+ */
+static int dccp_feat_reconcile(dccp_feat_val *fv, u8 *arr, u8 len,
+			       bool is_server, bool reorder)
 {
-	struct dccp_opt_pend *opt;
-	struct dccp_minisock *dmsk = dccp_msk(sk);
-	u8 *copy;
 	int rc;
 
-	/* NN features must be Change L (sec. 6.3.2) */
-	if (type != DCCPO_CHANGE_L) {
-		dccp_pr_debug("received %s for NN feature %d\n",
-				dccp_feat_typename(type), feature);
-		return -EFAULT;
-	}
-
-	/* XXX sanity check opt val */
-
-	/* copy option so we can confirm it */
-	opt = kzalloc(sizeof(*opt), GFP_ATOMIC);
-	if (opt == NULL)
-		return -ENOMEM;
-
-	copy = kmemdup(val, len, GFP_ATOMIC);
-	if (copy == NULL) {
-		kfree(opt);
-		return -ENOMEM;
+	if (!fv->sp.vec || !arr) {
+		DCCP_CRIT("NULL feature value or array");
+		return 0;
 	}
 
-	opt->dccpop_type = DCCPO_CONFIRM_R; /* NN can only confirm R */
-	opt->dccpop_feat = feature;
-	opt->dccpop_val	 = copy;
-	opt->dccpop_len	 = len;
+	if (is_server)
+		rc = dccp_feat_preflist_match(fv->sp.vec, fv->sp.len, arr, len);
+	else
+		rc = dccp_feat_preflist_match(arr, len, fv->sp.vec, fv->sp.len);
 
-	/* change feature */
-	rc = dccp_feat_update(sk, type, feature, *val);
-	if (rc) {
-		kfree(opt->dccpop_val);
-		kfree(opt);
+	if (!reorder)
 		return rc;
-	}
-
-	dccp_feat_debug(type, feature, *copy);
-
-	list_add_tail(&opt->dccpop_node, &dmsk->dccpms_conf);
+	if (rc < 0)
+		return 0;
 
-	return 0;
+	/*
+	 * Reorder list: used for activating features and in dccp_insert_fn_opt.
+	 */
+	return dccp_feat_prefer(rc, fv->sp.vec, fv->sp.len);
 }
 
-static void dccp_feat_empty_confirm(struct dccp_minisock *dmsk,
-				    u8 type, u8 feature)
+/**
+ * dccp_feat_change_recv  -  Process incoming ChangeL/R options
+ * @fn: feature-negotiation list to update
+ * @is_mandatory: whether the Change was preceded by a Mandatory option
+ * @opt: %DCCPO_CHANGE_L or %DCCPO_CHANGE_R
+ * @feat: one of %dccp_feature_numbers
+ * @val: NN value or SP value/preference list
+ * @len: length of @val in bytes
+ * @server: whether this node is the server (1) or the client (0)
+ */
+static u8 dccp_feat_change_recv(struct list_head *fn, u8 is_mandatory, u8 opt,
+				u8 feat, u8 *val, u8 len, const bool server)
 {
-	/* XXX check if other confirms for that are queued and recycle slot */
-	struct dccp_opt_pend *opt = kzalloc(sizeof(*opt), GFP_ATOMIC);
-
-	if (opt == NULL) {
-		/* XXX what do we do?  Ignoring should be fine.  It's a change
-		 * after all =P
-		 */
-		return;
-	}
-
-	switch (type) {
-	case DCCPO_CHANGE_L:
-		opt->dccpop_type = DCCPO_CONFIRM_R;
-		break;
-	case DCCPO_CHANGE_R:
-		opt->dccpop_type = DCCPO_CONFIRM_L;
-		break;
-	default:
-		DCCP_WARN("invalid type %d\n", type);
-		kfree(opt);
-		return;
-	}
-	opt->dccpop_feat = feature;
-	opt->dccpop_val	 = NULL;
-	opt->dccpop_len	 = 0;
-
-	/* change feature */
-	dccp_pr_debug("Empty %s(%d)\n", dccp_feat_typename(type), feature);
+	u8 defval, type = dccp_feat_type(feat);
+	const bool local = (opt == DCCPO_CHANGE_R);
+	struct dccp_feat_entry *entry;
+	dccp_feat_val fval;
 
-	list_add_tail(&opt->dccpop_node, &dmsk->dccpms_conf);
-}
+	if (len == 0 || type == FEAT_UNKNOWN)		/* 6.1 and 6.6.8 */
+		goto unknown_feature_or_value;
 
-static void dccp_feat_flush_confirm(struct sock *sk)
-{
-	struct dccp_minisock *dmsk = dccp_msk(sk);
-	/* Check if there is anything to confirm in the first place */
-	int yes = !list_empty(&dmsk->dccpms_conf);
+	/*
+	 *	Negotiation of NN features: Change R is invalid, so there is no
+	 *	simultaneous negotiation; hence we do not look up in the list.
+	 */
+	if (type == FEAT_NN) {
+		if (local || len > sizeof(fval.nn))
+			goto unknown_feature_or_value;
 
-	if (!yes) {
-		struct dccp_opt_pend *opt;
+		/* 6.3.2: "The feature remote MUST accept any valid value..." */
+		fval.nn = dccp_decode_value_var(val, len);
+		if (!dccp_feat_is_valid_nn_val(feat, fval.nn))
+			goto unknown_feature_or_value;
 
-		list_for_each_entry(opt, &dmsk->dccpms_pending, dccpop_node) {
-			if (opt->dccpop_conf) {
-				yes = 1;
-				break;
-			}
-		}
+		return dccp_feat_push_confirm(fn, feat, local, &fval);
 	}
 
-	if (!yes)
-		return;
+	/*
+	 *	Unidirectional/simultaneous negotiation of SP features (6.3.1)
+	 */
+	entry = dccp_feat_list_lookup(fn, feat, local);
+	if (entry == NULL) {
+		/*
+		 * No particular preferences have been registered. We deal with
+		 * this situation by assuming that all valid values are equally
+		 * acceptable, and apply the following checks:
+		 * - if the peer's list is a singleton, we accept a valid value;
+		 * - if we are the server, we first try to see if the peer (the
+		 *   client) advertises the default value. If yes, we use it,
+		 *   otherwise we accept the preferred value;
+		 * - else if we are the client, we use the first list element.
+		 */
+		if (dccp_feat_clone_sp_val(&fval, val, 1))
+			return DCCP_RESET_CODE_TOO_BUSY;
+
+		if (len > 1 && server) {
+			defval = dccp_feat_default_value(feat);
+			if (dccp_feat_preflist_match(&defval, 1, val, len) > -1)
+				fval.sp.vec[0] = defval;
+		} else if (!dccp_feat_is_valid_sp_val(feat, fval.sp.vec[0])) {
+			kfree(fval.sp.vec);
+			goto unknown_feature_or_value;
+		}
 
-	/* OK there is something to confirm... */
-	/* XXX check if packet is in flight?  Send delayed ack?? */
-	if (sk->sk_state == DCCP_OPEN)
-		dccp_send_ack(sk);
-}
+		/* Treat unsupported CCIDs like invalid values */
+		if (feat == DCCPF_CCID && !ccid_support_check(fval.sp.vec, 1)) {
+			kfree(fval.sp.vec);
+			goto not_valid_or_not_known;
+		}
 
-int dccp_feat_change_recv(struct sock *sk, u8 type, u8 feature, u8 *val, u8 len)
-{
-	int rc;
+		return dccp_feat_push_confirm(fn, feat, local, &fval);
 
-	/* Ignore Change requests other than during connection setup */
-	if (sk->sk_state != DCCP_LISTEN && sk->sk_state != DCCP_REQUESTING)
+	} else if (entry->state == FEAT_UNSTABLE) {	/* 6.6.2 */
 		return 0;
-	dccp_feat_debug(type, feature, *val);
-
-	/* figure out if it's SP or NN feature */
-	switch (feature) {
-	/* deal with SP features */
-	case DCCPF_CCID:
-		rc = dccp_feat_sp(sk, type, feature, val, len);
-		break;
-
-	/* deal with NN features */
-	case DCCPF_ACK_RATIO:
-		rc = dccp_feat_nn(sk, type, feature, val, len);
-		break;
-
-	/* XXX implement other features */
-	default:
-		dccp_pr_debug("UNIMPLEMENTED: not handling %s(%d, ...)\n",
-			      dccp_feat_typename(type), feature);
-		rc = -EFAULT;
-		break;
 	}
 
-	/* check if there were problems changing features */
-	if (rc) {
-		/* If we don't agree on SP, we sent a confirm for old value.
-		 * However we propagate rc to caller in case option was
-		 * mandatory
+	if (dccp_feat_reconcile(&entry->val, val, len, server, true)) {
+		entry->empty_confirm = 0;
+	} else if (is_mandatory) {
+		return DCCP_RESET_CODE_MANDATORY_ERROR;
+	} else if (entry->state == FEAT_INITIALISING) {
+		/*
+		 * Failed simultaneous negotiation (server only): try to `save'
+		 * the connection by checking whether entry contains the default
+		 * value for @feat. If yes, send an empty Confirm to signal that
+		 * the received Change was not understood - which implies using
+		 * the default value.
+		 * If this also fails, we use Reset as the last resort.
 		 */
-		if (rc != DCCP_FEAT_SP_NOAGREE)
-			dccp_feat_empty_confirm(dccp_msk(sk), type, feature);
+		WARN_ON(!server);
+		defval = dccp_feat_default_value(feat);
+		if (!dccp_feat_reconcile(&entry->val, &defval, 1, server, true))
+			return DCCP_RESET_CODE_OPTION_ERROR;
+		entry->empty_confirm = 1;
 	}
+	entry->needs_confirm   = 1;
+	entry->needs_mandatory = 0;
+	entry->state	       = FEAT_STABLE;
+	return 0;
 
-	/* generate the confirm [if required] */
-	dccp_feat_flush_confirm(sk);
+unknown_feature_or_value:
+	if (!is_mandatory)
+		return dccp_push_empty_confirm(fn, feat, local);
 
-	return rc;
+not_valid_or_not_known:
+	return is_mandatory ? DCCP_RESET_CODE_MANDATORY_ERROR
+			    : DCCP_RESET_CODE_OPTION_ERROR;
 }
 
-EXPORT_SYMBOL_GPL(dccp_feat_change_recv);
-
-int dccp_feat_confirm_recv(struct sock *sk, u8 type, u8 feature,
-			   u8 *val, u8 len)
+/**
+ * dccp_feat_confirm_recv  -  Process received Confirm options
+ * @fn: feature-negotiation list to update
+ * @is_mandatory: whether @opt was preceded by a Mandatory option
+ * @opt: %DCCPO_CONFIRM_L or %DCCPO_CONFIRM_R
+ * @feat: one of %dccp_feature_numbers
+ * @val: NN value or SP value/preference list
+ * @len: length of @val in bytes
+ * @server: whether this node is server (1) or client (0)
+ */
+static u8 dccp_feat_confirm_recv(struct list_head *fn, u8 is_mandatory, u8 opt,
+				 u8 feat, u8 *val, u8 len, const bool server)
 {
-	u8 t;
-	struct dccp_opt_pend *opt;
-	struct dccp_minisock *dmsk = dccp_msk(sk);
-	int found = 0;
-	int all_confirmed = 1;
+	u8 *plist, plen, type = dccp_feat_type(feat);
+	const bool local = (opt == DCCPO_CONFIRM_R);
+	struct dccp_feat_entry *entry = dccp_feat_list_lookup(fn, feat, local);
+
+	if (entry == NULL) {	/* nothing queued: ignore or handle error */
+		if (is_mandatory && type == FEAT_UNKNOWN)
+			return DCCP_RESET_CODE_MANDATORY_ERROR;
 
-	/* Ignore Confirm options other than during connection setup */
-	if (sk->sk_state != DCCP_LISTEN && sk->sk_state != DCCP_REQUESTING)
+		if (!local && type == FEAT_NN)		/* 6.3.2 */
+			goto confirmation_failed;
 		return 0;
-	dccp_feat_debug(type, feature, *val);
+	}
 
-	/* locate our change request */
-	switch (type) {
-	case DCCPO_CONFIRM_L: t = DCCPO_CHANGE_R; break;
-	case DCCPO_CONFIRM_R: t = DCCPO_CHANGE_L; break;
-	default:	      DCCP_WARN("invalid type %d\n", type);
-			      return 1;
+	if (entry->state != FEAT_CHANGING)		/* 6.6.2 */
+		return 0;
 
+	if (len == 0) {
+		if (dccp_feat_must_be_understood(feat))	/* 6.6.7 */
+			goto confirmation_failed;
+		/*
+		 * Empty Confirm during connection setup: this means reverting
+		 * to the `old' value, which in this case is the default. Since
+		 * we handle default values automatically when no other values
+		 * have been set, we revert to the old value by removing this
+		 * entry from the list.
+		 */
+		dccp_feat_list_pop(entry);
+		return 0;
 	}
-	/* XXX sanity check feature value */
-
-	list_for_each_entry(opt, &dmsk->dccpms_pending, dccpop_node) {
-		if (!opt->dccpop_conf && opt->dccpop_type == t &&
-		    opt->dccpop_feat == feature) {
-			found = 1;
-			dccp_pr_debug("feature %d found\n", opt->dccpop_feat);
 
-			/* XXX do sanity check */
+	if (type == FEAT_NN) {
+		if (len > sizeof(entry->val.nn))
+			goto confirmation_failed;
 
-			opt->dccpop_conf = 1;
+		if (entry->val.nn == dccp_decode_value_var(val, len))
+			goto confirmation_succeeded;
 
-			/* We got a confirmation---change the option */
-			dccp_feat_update(sk, opt->dccpop_type,
-					 opt->dccpop_feat, *val);
+		DCCP_WARN("Bogus Confirm for non-existing value\n");
+		goto confirmation_failed;
+	}
 
-			/* XXX check the return value of dccp_feat_update */
-			break;
-		}
+	/*
+	 * Parsing SP Confirms: the first element of @val is the preferred
+	 * SP value which the peer confirms, the remainder depends on @len.
+	 * Note that only the confirmed value need to be a valid SP value.
+	 */
+	if (!dccp_feat_is_valid_sp_val(feat, *val))
+		goto confirmation_failed;
+
+	if (len == 1) {		/* peer didn't supply a preference list */
+		plist = val;
+		plen  = len;
+	} else {		/* preferred value + preference list */
+		plist = val + 1;
+		plen  = len - 1;
+	}
 
-		if (!opt->dccpop_conf)
-			all_confirmed = 0;
+	/* Check whether the peer got the reconciliation right (6.6.8) */
+	if (dccp_feat_reconcile(&entry->val, plist, plen, server, 0) != *val) {
+		DCCP_WARN("Confirm selected the wrong value %u\n", *val);
+		return DCCP_RESET_CODE_OPTION_ERROR;
 	}
+	entry->val.sp.vec[0] = *val;
 
-	if (!found)
-		dccp_pr_debug("%s(%d, ...) never requested\n",
-			      dccp_feat_typename(type), feature);
+confirmation_succeeded:
+	entry->state = FEAT_STABLE;
 	return 0;
-}
 
-EXPORT_SYMBOL_GPL(dccp_feat_confirm_recv);
+confirmation_failed:
+	DCCP_WARN("Confirmation failed\n");
+	return is_mandatory ? DCCP_RESET_CODE_MANDATORY_ERROR
+			    : DCCP_RESET_CODE_OPTION_ERROR;
+}
 
-void dccp_feat_clean(struct dccp_minisock *dmsk)
+/**
+ * dccp_feat_parse_options  -  Process Feature-Negotiation Options
+ * @sk: for general use and used by the client during connection setup
+ * @dreq: used by the server during connection setup
+ * @mandatory: whether @opt was preceded by a Mandatory option
+ * @opt: %DCCPO_CHANGE_L | %DCCPO_CHANGE_R | %DCCPO_CONFIRM_L | %DCCPO_CONFIRM_R
+ * @feat: one of %dccp_feature_numbers
+ * @val: value contents of @opt
+ * @len: length of @val in bytes
+ * Returns 0 on success, a Reset code for ending the connection otherwise.
+ */
+int dccp_feat_parse_options(struct sock *sk, struct dccp_request_sock *dreq,
+			    u8 mandatory, u8 opt, u8 feat, u8 *val, u8 len)
 {
-	struct dccp_opt_pend *opt, *next;
-
-	list_for_each_entry_safe(opt, next, &dmsk->dccpms_pending,
-				 dccpop_node) {
-		BUG_ON(opt->dccpop_val == NULL);
-		kfree(opt->dccpop_val);
+	struct dccp_sock *dp = dccp_sk(sk);
+	struct list_head *fn = dreq ? &dreq->dreq_featneg : &dp->dccps_featneg;
+	bool server = false;
 
-		if (opt->dccpop_sc != NULL) {
-			BUG_ON(opt->dccpop_sc->dccpoc_val == NULL);
-			kfree(opt->dccpop_sc->dccpoc_val);
-			kfree(opt->dccpop_sc);
+	switch (sk->sk_state) {
+	/*
+	 *	Negotiation during connection setup
+	 */
+	case DCCP_LISTEN:
+		server = true;			/* fall through */
+	case DCCP_REQUESTING:
+		switch (opt) {
+		case DCCPO_CHANGE_L:
+		case DCCPO_CHANGE_R:
+			return dccp_feat_change_recv(fn, mandatory, opt, feat,
+						     val, len, server);
+		case DCCPO_CONFIRM_R:
+		case DCCPO_CONFIRM_L:
+			return dccp_feat_confirm_recv(fn, mandatory, opt, feat,
+						      val, len, server);
 		}
-
-		kfree(opt);
-	}
-	INIT_LIST_HEAD(&dmsk->dccpms_pending);
-
-	list_for_each_entry_safe(opt, next, &dmsk->dccpms_conf, dccpop_node) {
-		BUG_ON(opt == NULL);
-		if (opt->dccpop_val != NULL)
-			kfree(opt->dccpop_val);
-		kfree(opt);
 	}
-	INIT_LIST_HEAD(&dmsk->dccpms_conf);
+	return 0;	/* ignore FN options in all other states */
 }
 
-EXPORT_SYMBOL_GPL(dccp_feat_clean);
-
-/* this is to be called only when a listening sock creates its child.  It is
- * assumed by the function---the confirm is not duplicated, but rather it is
- * "passed on".
+/**
+ * dccp_feat_init  -  Seed feature negotiation with host-specific defaults
+ * This initialises global defaults, depending on the value of the sysctls.
+ * These can later be overridden by registering changes via setsockopt calls.
+ * The last link in the chain is finalise_settings, to make sure that between
+ * here and the start of actual feature negotiation no inconsistencies enter.
+ *
+ * All features not appearing below use either defaults or are otherwise
+ * later adjusted through dccp_feat_finalise_settings().
  */
-int dccp_feat_clone(struct sock *oldsk, struct sock *newsk)
+int dccp_feat_init(struct sock *sk)
 {
-	struct dccp_minisock *olddmsk = dccp_msk(oldsk);
-	struct dccp_minisock *newdmsk = dccp_msk(newsk);
-	struct dccp_opt_pend *opt;
-	int rc = 0;
+	struct list_head *fn = &dccp_sk(sk)->dccps_featneg;
+	u8 on = 1, off = 0;
+	int rc;
+	struct {
+		u8 *val;
+		u8 len;
+	} tx, rx;
+
+	/* Non-negotiable (NN) features */
+	rc = __feat_register_nn(fn, DCCPF_SEQUENCE_WINDOW, 0,
+				    sysctl_dccp_feat_sequence_window);
+	if (rc)
+		return rc;
 
-	INIT_LIST_HEAD(&newdmsk->dccpms_pending);
-	INIT_LIST_HEAD(&newdmsk->dccpms_conf);
+	/* Server-priority (SP) features */
 
-	list_for_each_entry(opt, &olddmsk->dccpms_pending, dccpop_node) {
-		struct dccp_opt_pend *newopt;
-		/* copy the value of the option */
-		u8 *val = kmemdup(opt->dccpop_val, opt->dccpop_len, GFP_ATOMIC);
+	/* Advertise that short seqnos are not supported (7.6.1) */
+	rc = __feat_register_sp(fn, DCCPF_SHORT_SEQNOS, true, true, &off, 1);
+	if (rc)
+		return rc;
 
-		if (val == NULL)
-			goto out_clean;
+	/* RFC 4340 12.1: "If a DCCP is not ECN capable, ..." */
+	rc = __feat_register_sp(fn, DCCPF_ECN_INCAPABLE, true, true, &on, 1);
+	if (rc)
+		return rc;
 
-		newopt = kmemdup(opt, sizeof(*newopt), GFP_ATOMIC);
-		if (newopt == NULL) {
-			kfree(val);
-			goto out_clean;
-		}
+	/*
+	 * We advertise the available list of CCIDs and reorder according to
+	 * preferences, to avoid failure resulting from negotiating different
+	 * singleton values (which always leads to failure).
+	 * These settings can still (later) be overridden via sockopts.
+	 */
+	if (ccid_get_builtin_ccids(&tx.val, &tx.len) ||
+	    ccid_get_builtin_ccids(&rx.val, &rx.len))
+		return -ENOBUFS;
 
-		/* insert the option */
-		newopt->dccpop_val = val;
-		list_add_tail(&newopt->dccpop_node, &newdmsk->dccpms_pending);
+	/* Pre-load all CCID modules that are going to be advertised */
+	rc = -EUNATCH;
+	if (ccid_request_modules(tx.val, tx.len))
+		goto free_ccid_lists;
 
-		/* XXX what happens with backlogs and multiple connections at
-		 * once...
-		 */
-		/* the master socket no longer needs to worry about confirms */
-		opt->dccpop_sc = NULL; /* it's not a memleak---new socket has it */
+	if (!dccp_feat_prefer(sysctl_dccp_feat_tx_ccid, tx.val, tx.len) ||
+	    !dccp_feat_prefer(sysctl_dccp_feat_rx_ccid, rx.val, rx.len))
+		goto free_ccid_lists;
 
-		/* reset state for a new socket */
-		opt->dccpop_conf = 0;
-	}
+	rc = __feat_register_sp(fn, DCCPF_CCID, true, false, tx.val, tx.len);
+	if (rc)
+		goto free_ccid_lists;
 
-	/* XXX not doing anything about the conf queue */
+	rc = __feat_register_sp(fn, DCCPF_CCID, false, false, rx.val, rx.len);
 
-out:
+free_ccid_lists:
+	kfree(tx.val);
+	kfree(rx.val);
 	return rc;
-
-out_clean:
-	dccp_feat_clean(newdmsk);
-	rc = -ENOMEM;
-	goto out;
 }
 
-EXPORT_SYMBOL_GPL(dccp_feat_clone);
-
-int dccp_feat_init(struct sock *sk)
+int dccp_feat_activate_values(struct sock *sk, struct list_head *fn_list)
 {
 	struct dccp_sock *dp = dccp_sk(sk);
-	struct dccp_minisock *dmsk = dccp_msk(sk);
-	int rc;
+	struct dccp_feat_entry *cur, *next;
+	int idx;
+	dccp_feat_val *fvals[DCCP_FEAT_SUPPORTED_MAX][2] = {
+		 [0 ... DCCP_FEAT_SUPPORTED_MAX-1] = { NULL, NULL }
+	};
 
-	INIT_LIST_HEAD(&dmsk->dccpms_pending);	/* XXX no longer used */
-	INIT_LIST_HEAD(&dmsk->dccpms_conf);	/* XXX no longer used */
+	list_for_each_entry(cur, fn_list, node) {
+		/*
+		 * An empty Confirm means that either an unknown feature type
+		 * or an invalid value was present. In the first case there is
+		 * nothing to activate, in the other the default value is used.
+		 */
+		if (cur->empty_confirm)
+			continue;
 
-	/* CCID L */
-	rc = __feat_register_sp(&dp->dccps_featneg, DCCPF_CCID, 1, 0,
-				&dmsk->dccpms_tx_ccid, 1);
-	if (rc)
-		goto out;
+		idx = dccp_feat_index(cur->feat_num);
+		if (idx < 0) {
+			DCCP_BUG("Unknown feature %u", cur->feat_num);
+			goto activation_failed;
+		}
+		if (cur->state != FEAT_STABLE) {
+			DCCP_CRIT("Negotiation of %s %u failed in state %u",
+				  cur->is_local ? "local" : "remote",
+				  cur->feat_num, cur->state);
+			goto activation_failed;
+		}
+		fvals[idx][cur->is_local] = &cur->val;
+	}
 
-	/* CCID R */
-	rc = __feat_register_sp(&dp->dccps_featneg, DCCPF_CCID, 0, 0,
-				&dmsk->dccpms_rx_ccid, 1);
-	if (rc)
-		goto out;
+	/*
+	 * Activate in decreasing order of index, so that the CCIDs are always
+	 * activated as the last feature. This avoids the case where a CCID
+	 * relies on the initialisation of one or more features that it depends
+	 * on (e.g. Send NDP Count, Send Ack Vector, and Ack Ratio features).
+	 */
+	for (idx = DCCP_FEAT_SUPPORTED_MAX; --idx >= 0;)
+		if (__dccp_feat_activate(sk, idx, 0, fvals[idx][0]) ||
+		    __dccp_feat_activate(sk, idx, 1, fvals[idx][1])) {
+			DCCP_CRIT("Could not activate %d", idx);
+			goto activation_failed;
+		}
 
-	/* Ack ratio */
-	rc = __feat_register_nn(&dp->dccps_featneg, DCCPF_ACK_RATIO, 0,
-				dmsk->dccpms_ack_ratio);
-out:
-	return rc;
-}
+	/* Clean up Change options which have been confirmed already */
+	list_for_each_entry_safe(cur, next, fn_list, node)
+		if (!cur->needs_confirm)
+			dccp_feat_list_pop(cur);
+
+	dccp_pr_debug("Activation OK\n");
+	return 0;
 
-EXPORT_SYMBOL_GPL(dccp_feat_init);
+activation_failed:
+	/*
+	 * We clean up everything that may have been allocated, since
+	 * it is difficult to track at which stage negotiation failed.
+	 * This is ok, since all allocation functions below are robust
+	 * against NULL arguments.
+	 */
+	ccid_hc_rx_delete(dp->dccps_hc_rx_ccid, sk);
+	ccid_hc_tx_delete(dp->dccps_hc_tx_ccid, sk);
+	dp->dccps_hc_rx_ccid = dp->dccps_hc_tx_ccid = NULL;
+	dccp_ackvec_free(dp->dccps_hc_rx_ackvec);
+	dp->dccps_hc_rx_ackvec = NULL;
+	return -1;
+}
 
 #ifdef CONFIG_IP_DCCP_DEBUG
 const char *dccp_feat_typename(const u8 type)