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>
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#include <linux/types.h>
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#include "dccp.h"
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enum dccp_feat_type {
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FEAT_AT_RX = 1, /* located at RX side of half-connection */
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FEAT_AT_TX = 2, /* located at TX side of half-connection */
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FEAT_SP = 4, /* server-priority reconciliation (6.3.1) */
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FEAT_NN = 8, /* non-negotiable reconciliation (6.3.2) */
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FEAT_UNKNOWN = 0xFF /* not understood or invalid feature */
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};
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enum dccp_feat_state {
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FEAT_DEFAULT = 0, /* using default values from 6.4 */
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FEAT_INITIALISING, /* feature is being initialised */
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FEAT_CHANGING, /* Change sent but not confirmed yet */
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FEAT_UNSTABLE, /* local modification in state CHANGING */
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FEAT_STABLE /* both ends (think they) agree */
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};
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/**
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* dccp_feat_val - Container for SP or NN feature values
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* @nn: single NN value
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* @sp.vec: single SP value plus optional preference list
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* @sp.len: length of @sp.vec in bytes
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*/
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typedef union {
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u64 nn;
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struct {
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u8 *vec;
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u8 len;
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} sp;
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} dccp_feat_val;
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/**
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* struct feat_entry - Data structure to perform feature negotiation
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* @val: feature's current value (SP features may have preference list)
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* @state: feature's current state
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* @feat_num: one of %dccp_feature_numbers
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* @needs_mandatory: whether Mandatory options should be sent
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* @needs_confirm: whether to send a Confirm instead of a Change
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* @empty_confirm: whether to send an empty Confirm (depends on @needs_confirm)
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* @is_local: feature location (1) or feature-remote (0)
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* @node: list pointers, entries arranged in FIFO order
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*/
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struct dccp_feat_entry {
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dccp_feat_val val;
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enum dccp_feat_state state:8;
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u8 feat_num;
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bool needs_mandatory,
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needs_confirm,
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empty_confirm,
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is_local;
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struct list_head node;
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};
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static inline u8 dccp_feat_genopt(struct dccp_feat_entry *entry)
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{
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if (entry->needs_confirm)
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return entry->is_local ? DCCPO_CONFIRM_L : DCCPO_CONFIRM_R;
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return entry->is_local ? DCCPO_CHANGE_L : DCCPO_CHANGE_R;
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}
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#ifdef CONFIG_IP_DCCP_DEBUG
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extern const char *dccp_feat_typename(const u8 type);
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extern const char *dccp_feat_name(const u8 feat);
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