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authorGerrit Renker <gerrit@erg.abdn.ac.uk>2008-11-04 23:38:20 -0800
committerDavid S. Miller <davem@davemloft.net>2008-11-04 23:38:20 -0800
commitbd012f2e7be9f69a47d240ded0fa491967d9827c (patch)
tree940cc895a7da7a065847cf604cddfab097e385cc /net/dccp
parentd5f642384e9da75393160350f75bbb9a527f7c58 (diff)
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dccp: Basic data structure for feature negotiation
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). Thanks to Arnaldo, who contributed the streamlined layout of the entry struct. Signed-off-by: Gerrit Renker <gerrit@erg.abdn.ac.uk> Acked-by: Arnaldo Carvalho de Melo <acme@redhat.com> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net/dccp')
-rw-r--r--net/dccp/feat.h61
1 files changed, 61 insertions, 0 deletions
diff --git a/net/dccp/feat.h b/net/dccp/feat.h
index e272222..56df82c 100644
--- a/net/dccp/feat.h
+++ b/net/dccp/feat.h
@@ -14,6 +14,67 @@
#include <linux/types.h>
#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
+ * @val: feature's current value (SP features may have preference list)
+ * @state: feature's current state
+ * @feat_num: one of %dccp_feature_numbers
+ * @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 {
+ dccp_feat_val val;
+ enum dccp_feat_state state:8;
+ u8 feat_num;
+
+ bool needs_mandatory,
+ needs_confirm,
+ empty_confirm,
+ is_local;
+
+ 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);