This patch prepares for the new and extended feature-negotiation routines.
The following feature-negotiation data structures are provided:

	* a container for the various (SP or NN) values,

	* symbolic state names to track feature states,

	* an entry struct which holds all current information together,

	* elementary functions to fill in and process these structures.
Entry structs are arranged as FIFO for the following reason: RFC 4340 specifies

that if multiple options of the same type are present, they are processed in the

order of their appearance in the packet; which means that this order needs to be

preserved in the local data structure (the later insertion code also respects

this order).
The struct list_head has been chosen for the following reasons: the most

frequent operations are

 * add new entry at tail (when receiving Change or setting socket options);

 * delete entry (when Confirm has been received);

 * deep copy of entire list (cloning from listening socket onto request socket).
The NN value has been set to 64 bit, which is a currently sufficient upper limit

(Sequence Window feature has 48 bit).
Signed-off-by: Gerrit Renker

Acked-by: Ian McDonald

---

 net/dccp/feat.c |   14 ++++++++++++

 net/dccp/feat.h |   60 +++++++++++++++++++++++++++++++++++++++++++++++++++++++

 2 files changed, 74 insertions(+), 0 deletions(-)
--- a/net/dccp/feat.c

+++ b/net/dccp/feat.c

@@ -23,6 +23,20 @@
 #define DCCP_FEAT_SP_NOAGREE (-123)
+/* 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)

+{

+	fval->sp.len = len;

+	if (fval->sp.len > 0) {

+		fval->sp.vec = kmemdup(val, len, gfp_any());

+		if (fval->sp.vec == NULL) {

+			fval->sp.len = 0;

+			return -ENOBUFS;

+		}

+	}

+	return 0;

+}

+

 int dccp_feat_change(struct dccp_minisock *dmsk, u8 type, u8 feature,

 		     u8 *val, u8 len, gfp_t gfp)

 {

--- a/net/dccp/feat.h

+++ b/net/dccp/feat.h

@@ -14,6 +14,66 @@

 #include

 #include "dccp.h"
+enum dccp_feat_type {

+	FEAT_AT_RX   = 1,	/* located at RX side of half-connection  */

+	FEAT_AT_TX   = 2,	/* located at TX side of half-connection  */

+	FEAT_SP      = 4,	/* server-priority reconciliation (6.3.1) */

+	FEAT_NN	     = 8,	/* non-negotiable reconciliation (6.3.2)  */

+	FEAT_UNKNOWN = 0xFF	/* not understood or invalid feature	  */

+};

+

+enum dccp_feat_state {

+	FEAT_DEFAULT = 0,	/* using default values from 6.4 */

+	FEAT_INITIALISING,	/* feature is being initialised  */

+	FEAT_CHANGING,		/* Change sent but not confirmed yet */

+	FEAT_UNSTABLE,		/* local modification in state CHANGING */

+	FEAT_STABLE		/* both ends (think they) agree */

+};

+

+/**

+ * dccp_feat_val  -  Container for SP or NN feature values

+ * @nn:     single NN value

+ * @sp.vec: single SP value plus optional preference list

+ * @sp.len: length of @sp.vec in bytes

+ */

+typedef union {

+	u64 nn;

+	struct {

+		u8	*vec;

+		u8	len;

+	}   sp;

+} dccp_feat_val;

+

+/**

+ * struct feat_entry  -  Data structure to perform feature negotiation

+ * @feat_num: one of %dccp_feature_numbers

+ * @val: feature's current value (SP features may have preference list)

+ * @state: feature's current state

+ * @needs_mandatory: whether Mandatory options should be sent

+ * @needs_confirm: whether to send a Confirm instead of a Change

+ * @empty_confirm: whether to send an empty Confirm (depends on @needs_confirm)

+ * @is_local: feature location (1) or feature-remote (0)

+ * @node: list pointers, entries arranged in FIFO order

+ */

+struct dccp_feat_entry {

+	u8                      feat_num;

+	dccp_feat_val           val;

+	enum dccp_feat_state    state:8;

+	bool			needs_mandatory:1,

+				needs_confirm:1,

+				empty_confirm:1,

+				is_local:1;

+

+	struct list_head	node;

+};

+

+static inline u8 dccp_feat_genopt(struct dccp_feat_entry *entry)

+{

+	if (entry->needs_confirm)

+		return entry->is_local ? DCCPO_CONFIRM_L : DCCPO_CONFIRM_R;

+	return entry->is_local ? DCCPO_CHANGE_L : DCCPO_CHANGE_R;

+}

+

 #ifdef CONFIG_IP_DCCP_DEBUG

 extern const char *dccp_feat_typename(const u8 type);

 extern const char *dccp_feat_name(const u8 feat);

--

1.6.0.rc2
--

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