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| author | Gerrit Renker <gerrit@erg.abdn.ac.uk> | 2009-02-27 22:38:28 +0000 |
|---|---|---|
| committer | David S. Miller <davem@davemloft.net> | 2009-03-02 03:07:23 -0800 |
| commit | 361a5c1dd0bd7bb2b90e7fe9127b366d3566522e (patch) | |
| tree | 440150dfa03f976d4ef6d3062744f2185373820d /net/dccp/ackvec.h | |
| parent | 9ce01461028d595a6f1cd724fbd7a0dd70464fe4 (diff) | |
| download | linux-361a5c1dd0bd7bb2b90e7fe9127b366d3566522e.tar.gz linux-361a5c1dd0bd7bb2b90e7fe9127b366d3566522e.tar.bz2 linux-361a5c1dd0bd7bb2b90e7fe9127b366d3566522e.zip | |
dccp: Minimise header option overhead in setting the MPS
This patch resolves a long-standing FIXME to dynamically update the Maximum
Packet Size depending on actual options usage.
It uses the flags set by the feature-negotiation infrastructure to compute
the required header option size.
Most options are fixed-size, a notable exception are Ack Vectors (required
currently only by CCID-2). These can have any length between 3 and 1020
bytes. As a result of testing, 16 bytes (2 bytes for type/length plus 14 Ack
Vector cells) have been found to be sufficient for loss-free situations.
There are currently no CCID-specific header options which may appear on data
packets, thus it is not necessary to define a corresponding CCID field as
suggested in the old comment.
Further changes:
----------------
Adjusted the type of 'cur_mps' to match the unsigned return type of the
function.
Signed-off-by: Gerrit Renker <gerrit@erg.abdn.ac.uk>
Acked-by: Ian McDonald <ian.mcdonald@jandi.co.nz>
Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net/dccp/ackvec.h')
| -rw-r--r-- | net/dccp/ackvec.h | 3 |
1 files changed, 3 insertions, 0 deletions
diff --git a/net/dccp/ackvec.h b/net/dccp/ackvec.h index 45f95e55f873..7ea557b7c6b1 100644 --- a/net/dccp/ackvec.h +++ b/net/dccp/ackvec.h @@ -20,6 +20,9 @@ /* We can spread an ack vector across multiple options */ #define DCCP_MAX_ACKVEC_LEN (DCCP_SINGLE_OPT_MAXLEN * 2) +/* Estimated minimum average Ack Vector length - used for updating MPS */ +#define DCCPAV_MIN_OPTLEN 16 + #define DCCP_ACKVEC_STATE_RECEIVED 0 #define DCCP_ACKVEC_STATE_ECN_MARKED (1 << 6) #define DCCP_ACKVEC_STATE_NOT_RECEIVED (3 << 6) |