dccp: support for the exchange of NN options in established state 1/2
In contrast to static feature negotiation at the begin of a connection, this
patch introduces support for exchange of dynamically changing options.
Such an update/exchange is necessary in at least two cases:
* CCID-2's Ack Ratio (RFC 4341, 6.1.2) which changes during the connection;
* Sequence Window values that, as per RFC 4340, 7.5.2, should be sent "as
the connection progresses".
Both are non-negotiable (NN) features, which means that no new capabilities
are negotiated, but rather that changes in known parameters are brought
up-to-date at either end.
Thse characteristics are reflected by the implementation:
* only NN options can be exchanged after connection setup;
* an ack is scheduled directly after activation to speed up the update;
* CCIDs may request changes to an NN feature even if a negotiation for that
feature is already underway: this is required by CCID-2, where changes in
cwnd necessitate Ack Ratio changes, such that the previous Ack Ratio (which
is still being negotiated) would cause irrecoverable RTO timeouts (thanks
to work by Samuel Jero).
Signed-off-by: Gerrit Renker <gerrit@erg.abdn.ac.uk>
Signed-off-by: Samuel Jero <sj323707@ohio.edu>
Acked-by: Ian McDonald <ian.mcdonald@jandi.co.uk>
diff --git a/net/dccp/dccp.h b/net/dccp/dccp.h
index 5fdb072..583490a 100644
--- a/net/dccp/dccp.h
+++ b/net/dccp/dccp.h
@@ -474,6 +474,7 @@
return dccp_ackvec_pending(sk) || inet_csk_ack_scheduled(sk);
}
+extern int dccp_feat_signal_nn_change(struct sock *sk, u8 feat, u64 nn_val);
extern int dccp_feat_finalise_settings(struct dccp_sock *dp);
extern int dccp_feat_server_ccid_dependencies(struct dccp_request_sock *dreq);
extern int dccp_feat_insert_opts(struct dccp_sock*, struct dccp_request_sock*,