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dccp: Initialisation framework for feature negotiation

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

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

Signed-off-by: Gerrit Renker <gerrit@erg.abdn.ac.uk>
Acked-by: Ian McDonald <ian.mcdonald@jandi.co.nz>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Gerrit Renker
2009-01-16 23:36:30 +00:00
committed by David S. Miller
parent 5cda9364f1
commit f90f92eed7
3 changed files with 57 additions and 29 deletions
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65
net/dccp/feat.c
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@@ -1115,23 +1115,70 @@ 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;
INIT_LIST_HEAD(&dmsk->dccpms_pending); /* XXX no longer used */
INIT_LIST_HEAD(&dmsk->dccpms_conf); /* XXX no longer used */
/* Non-negotiable (NN) features */
rc = __feat_register_nn(fn, DCCPF_SEQUENCE_WINDOW, 0,
sysctl_dccp_feat_sequence_window);
if (rc)
return rc;
/* Ack ratio */
rc = __feat_register_nn(&dp->dccps_featneg, DCCPF_ACK_RATIO, 0,
dp->dccps_l_ack_ratio);
/* Server-priority (SP) features */
/* 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;
/*
* 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;
}
EXPORT_SYMBOL_GPL(dccp_feat_init);
int dccp_feat_activate_values(struct sock *sk, struct list_head *fn_list)
{
struct dccp_sock *dp = dccp_sk(sk);