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Commit 5d3dac26 authored by Gerrit Renker's avatar Gerrit Renker
Browse files

dccp: Initialisation framework for feature negotiation 



This initialises feature negotiation from two tables, which are initialised
from sysctls. 

As a novel feature, specifics of the implementation (e.g. currently short
seqnos and ECN are not supported) are advertised for robustness.

Signed-off-by: default avatarGerrit Renker <gerrit@erg.abdn.ac.uk>
Acked-by: default avatarIan McDonald <ian.mcdonald@jandi.co.nz>
parent b235dc4a

include/linux/dccp.h

+0 −19
Original line number Diff line number Diff line
@@ -369,28 +369,9 @@ static inline unsigned int dccp_hdr_len(const struct sk_buff *skb) 
  * Will be used to pass the state from dccp_request_sock to dccp_sock.

  *

  * @dccpms_sequence_window - Sequence Window Feature (section 7.5.2)

  * @dccpms_pending - List of features being negotiated

  * @dccpms_conf -

  */

struct dccp_minisock {

	__u64			dccpms_sequence_window;

	struct list_head	dccpms_pending;

	struct list_head	dccpms_conf;

};



struct dccp_opt_conf {

	__u8			*dccpoc_val;

	__u8			dccpoc_len;

};



struct dccp_opt_pend {

	struct list_head	dccpop_node;

	__u8			dccpop_type;

	__u8			dccpop_feat;

	__u8		        *dccpop_val;

	__u8			dccpop_len;

	int			dccpop_conf;

	struct dccp_opt_conf    *dccpop_sc;

};



extern void dccp_minisock_init(struct dccp_minisock *dmsk);

net/dccp/feat.c

+56 −10
Original line number Diff line number Diff line
@@ -1110,23 +1110,69 @@ int dccp_feat_parse_options(struct sock *sk, struct dccp_request_sock *dreq, 
	return 0;	/* ignore FN options in all other states */

}



/**

 * 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_init(struct sock *sk)

{

	struct dccp_sock *dp = dccp_sk(sk);

	struct dccp_minisock *dmsk = dccp_msk(sk);

	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(&dmsk->dccpms_pending);	/* XXX no longer used */

	INIT_LIST_HEAD(&dmsk->dccpms_conf);	/* XXX no longer used */

	/* Server-priority (SP) features */



	/* Ack ratio */

	rc = __feat_register_nn(&dp->dccps_featneg, DCCPF_ACK_RATIO, 0,

				dp->dccps_l_ack_ratio);

out:

	/* 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;



	/* 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;

}



EXPORT_SYMBOL_GPL(dccp_feat_init);

	/*

	 * 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;



	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;



	rc = __feat_register_sp(fn, DCCPF_CCID, true, false, tx.val, tx.len);

	if (rc)

		goto free_ccid_lists;



	rc = __feat_register_sp(fn, DCCPF_CCID, false, false, rx.val, rx.len);



free_ccid_lists:

	kfree(tx.val);

	kfree(rx.val);

	return rc;

}



int dccp_feat_activate_values(struct sock *sk, struct list_head *fn_list)

{

net/dccp/feat.h

+1 −1
Original line number Diff line number Diff line
@@ -112,13 +112,13 @@ static inline void dccp_feat_debug(const u8 type, const u8 feat, const u8 val) 
#define dccp_feat_debug(type, feat, val)

#endif /* CONFIG_IP_DCCP_DEBUG */



extern int  dccp_feat_init(struct sock *sk);

extern int  dccp_feat_register_sp(struct sock *sk, u8 feat, u8 is_local,

				  u8 const *list, u8 len);

extern int  dccp_feat_register_nn(struct sock *sk, u8 feat, u64 val);

extern int  dccp_feat_parse_options(struct sock *, struct dccp_request_sock *,

				    u8 mand, u8 opt, u8 feat, u8 *val, u8 len);

extern int  dccp_feat_clone_list(struct list_head const *, struct list_head *);

extern int  dccp_feat_init(struct sock *sk);



/*

 * Encoding variable-length options and their maximum length.