diff options
author | Gerrit Renker <gerrit@erg.abdn.ac.uk> | 2008-11-05 07:38:20 (GMT) |
---|---|---|
committer | David S. Miller <davem@davemloft.net> | 2008-11-05 07:38:20 (GMT) |
commit | bd012f2e7be9f69a47d240ded0fa491967d9827c (patch) | |
tree | 940cc895a7da7a065847cf604cddfab097e385cc /net | |
parent | d5f642384e9da75393160350f75bbb9a527f7c58 (diff) | |
download | linux-fsl-qoriq-bd012f2e7be9f69a47d240ded0fa491967d9827c.tar.xz |
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')
-rw-r--r-- | net/dccp/feat.h | 61 |
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); |