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Message-Id: <1311600996-6712-3-git-send-email-gerrit@erg.abdn.ac.uk>
Date: Mon, 25 Jul 2011 07:36:31 -0600
From: Gerrit Renker <gerrit@....abdn.ac.uk>
To: davem@...emloft.net
Cc: dccp@...r.kernel.org, netdev@...r.kernel.org
Subject: [PATCH 2/7] dccp: support for exchanging of NN options in established state 2/2
This patch adds the receiver side and the (fast-path) activation part for
dynamic changes of non-negotiable (NN) parameters in (PART)OPEN state.
Signed-off-by: Gerrit Renker <gerrit@....abdn.ac.uk>
Signed-off-by: Samuel Jero <sj323707@...o.edu>
Acked-by: Ian McDonald <ian.mcdonald@...di.co.uk>
---
net/dccp/feat.c | 116 +++++++++++++++++++++++++++++++++++++++++++++++++++++++
1 files changed, 116 insertions(+), 0 deletions(-)
--- a/net/dccp/feat.c
+++ b/net/dccp/feat.c
@@ -344,6 +344,20 @@ static int __dccp_feat_activate(struct sock *sk, const int idx,
return dccp_feat_table[idx].activation_hdlr(sk, val, rx);
}
+/**
+ * dccp_feat_activate - Activate feature value on socket
+ * @sk: fully connected DCCP socket (after handshake is complete)
+ * @feat_num: feature to activate, one of %dccp_feature_numbers
+ * @local: whether local (1) or remote (0) @feat_num is meant
+ * @fval: the value (SP or NN) to activate, or NULL to use the default value
+ * For general use this function is preferable over __dccp_feat_activate().
+ */
+static int dccp_feat_activate(struct sock *sk, u8 feat_num, bool local,
+ dccp_feat_val const *fval)
+{
+ return __dccp_feat_activate(sk, dccp_feat_index(feat_num), local, fval);
+}
+
/* Test for "Req'd" feature (RFC 4340, 6.4) */
static inline int dccp_feat_must_be_understood(u8 feat_num)
{
@@ -1252,6 +1266,100 @@ confirmation_failed:
}
/**
+ * dccp_feat_handle_nn_established - Fast-path reception of NN options
+ * @sk: socket of an established DCCP connection
+ * @mandatory: whether @opt was preceded by a Mandatory option
+ * @opt: %DCCPO_CHANGE_L | %DCCPO_CONFIRM_R (NN only)
+ * @feat: NN number, one of %dccp_feature_numbers
+ * @val: NN value
+ * @len: length of @val in bytes
+ * This function combines the functionality of change_recv/confirm_recv, with
+ * the following differences (reset codes are the same):
+ * - cleanup after receiving the Confirm;
+ * - values are directly activated after successful parsing;
+ * - deliberately restricted to NN features.
+ * The restriction to NN features is essential since SP features can have non-
+ * predictable outcomes (depending on the remote configuration), and are inter-
+ * dependent (CCIDs for instance cause further dependencies).
+ */
+static u8 dccp_feat_handle_nn_established(struct sock *sk, u8 mandatory, u8 opt,
+ u8 feat, u8 *val, u8 len)
+{
+ struct list_head *fn = &dccp_sk(sk)->dccps_featneg;
+ const bool local = (opt == DCCPO_CONFIRM_R);
+ struct dccp_feat_entry *entry;
+ u8 type = dccp_feat_type(feat);
+ dccp_feat_val fval;
+
+ dccp_feat_print_opt(opt, feat, val, len, mandatory);
+
+ /* Ignore non-mandatory unknown and non-NN features */
+ if (type == FEAT_UNKNOWN) {
+ if (local && !mandatory)
+ return 0;
+ goto fast_path_unknown;
+ } else if (type != FEAT_NN) {
+ return 0;
+ }
+
+ /*
+ * We don't accept empty Confirms, since in fast-path feature
+ * negotiation the values are enabled immediately after sending
+ * the Change option.
+ * Empty Changes on the other hand are invalid (RFC 4340, 6.1).
+ */
+ if (len == 0 || len > sizeof(fval.nn))
+ goto fast_path_unknown;
+
+ if (opt == DCCPO_CHANGE_L) {
+ fval.nn = dccp_decode_value_var(val, len);
+ if (!dccp_feat_is_valid_nn_val(feat, fval.nn))
+ goto fast_path_unknown;
+
+ if (dccp_feat_push_confirm(fn, feat, local, &fval) ||
+ dccp_feat_activate(sk, feat, local, &fval))
+ return DCCP_RESET_CODE_TOO_BUSY;
+
+ /* set the `Ack Pending' flag to piggyback a Confirm */
+ inet_csk_schedule_ack(sk);
+
+ } else if (opt == DCCPO_CONFIRM_R) {
+ entry = dccp_feat_list_lookup(fn, feat, local);
+ if (entry == NULL || entry->state != FEAT_CHANGING)
+ return 0;
+
+ fval.nn = dccp_decode_value_var(val, len);
+ /*
+ * Just ignore a value that doesn't match our current value.
+ * If the option changes twice within two RTTs, then at least
+ * one CONFIRM will be received for the old value after a
+ * new CHANGE was sent.
+ */
+ if (fval.nn != entry->val.nn)
+ return 0;
+
+ /* Only activate after receiving the Confirm option (6.6.1). */
+ dccp_feat_activate(sk, feat, local, &fval);
+
+ /* It has been confirmed - so remove the entry */
+ dccp_feat_list_pop(entry);
+
+ } else {
+ DCCP_WARN("Received illegal option %u\n", opt);
+ goto fast_path_failed;
+ }
+ return 0;
+
+fast_path_unknown:
+ if (!mandatory)
+ return dccp_push_empty_confirm(fn, feat, local);
+
+fast_path_failed:
+ return mandatory ? DCCP_RESET_CODE_MANDATORY_ERROR
+ : DCCP_RESET_CODE_OPTION_ERROR;
+}
+
+/**
* 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
@@ -1286,6 +1394,14 @@ int dccp_feat_parse_options(struct sock *sk, struct dccp_request_sock *dreq,
return dccp_feat_confirm_recv(fn, mandatory, opt, feat,
val, len, server);
}
+ break;
+ /*
+ * Support for exchanging NN options on an established connection.
+ */
+ case DCCP_OPEN:
+ case DCCP_PARTOPEN:
+ return dccp_feat_handle_nn_established(sk, mandatory, opt, feat,
+ val, len);
}
return 0; /* ignore FN options in all other states */
}
--
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