[DCCP]: Introducing CCMPS

This introduces a CCMPS field for setting a CCID-specific upper bound on the application payload
size, as is defined in RFC 4340, section 14.

Only the TX CCID is considered in setting this limit, since the RX CCID generates comparatively
small (DCCP-Ack) feedback packets. The CCMPS field includes network and transport layer header
lengths. The only current CCMPS customer is CCID4 (via RFC 4828).

A wrapper is used to allow querying the CCMPS even at times where the CCID modules may not have
been fully negotiated yet.

In dccp_sync_mss() the variable `mss_now' has been renamed into `cur_mps', to reflect that we are
dealing with an MPS, but not an MSS.
Since the DCCP code closely follows the TCP code, the identifiers `dccp_sync_mss' and
`dccps_mss_cache' have been kept, as they have direct TCP counterparts.

Signed-off-by: Gerrit Renker <gerrit@erg.abdn.ac.uk>
Signed-off-by: Ian McDonald <ian.mcdonald@jandi.co.nz>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 2 insertions, 0 deletions

diff --git a/net/dccp/ccid.h b/net/dccp/ccid.h
index e3cdd8afc801..fdeae7b57319 100644
--- a/net/dccp/ccid.h
+++ b/net/dccp/ccid.h
@@ -27,6 +27,7 @@ struct tcp_info;
  *  struct ccid_operations  -  Interface to Congestion-Control Infrastructure
  *
  *  @ccid_id: numerical CCID ID (up to %CCID_MAX, cf. table 5 in RFC 4340, 10.)
+ *  @ccid_ccmps: the CCMPS including network/transport headers (0 when disabled)
  *  @ccid_name: alphabetical identifier string for @ccid_id
  *  @ccid_owner: module which implements/owns this CCID
  *  @ccid_hc_{r,t}x_slab: memory pool for the receiver/sender half-connection
@@ -45,6 +46,7 @@ struct tcp_info;
  */
 struct ccid_operations {
         unsigned char           ccid_id;
+        __u32                   ccid_ccmps;
         const char              *ccid_name;
         struct module           *ccid_owner;
         struct kmem_cache       *ccid_hc_rx_slab,