dccp ccid-2: Separate option parsing from CCID processing

This patch replaces an almost identical replication of code: large parts
of dccp_parse_options() re-appeared as ccid2_ackvector() in ccid2.c.

Apart from the duplication, this caused two more problems:
 1. CCIDs should not need to be concerned with parsing header options;
 2. one can not assume that Ack Vectors appear as a contiguous area within an
    skb, it is legal to insert other options and/or padding in between. The
    current code would throw an error and stop reading in such a case.

The patch provides a new data structure and associated list housekeeping.

Only small changes were necessary to integrate with CCID-2: data structure
initialisation, adapt list traversal routine, and add call to the provided
cleanup routine.

The latter also lead to fixing the following BUG: CCID-2 so far ignored
Ack Vectors on all packets other than Ack/DataAck, which is incorrect,
since Ack Vectors can be present on any packet that has an Ack field.

Details:
--------
 * received Ack Vectors are parsed by dccp_parse_options() alone, which passes
   the result on to the CCID-specific routine ccid_hc_tx_parse_options();
 * CCIDs interested in using/decoding Ack Vector information will add code
   to fetch parsed Ack Vectors via this interface;
 * a data structure, `struct dccp_ackvec_parsed' is provided as interface;
 * this structure arranges Ack Vectors of the same skb into a FIFO order;
 * a doubly-linked list is used to keep the required FIFO code small.

Signed-off-by: Gerrit Renker <gerrit@erg.abdn.ac.uk>

1 files changed, 2 insertions, 0 deletions

diff --git a/net/dccp/ccids/ccid2.h b/net/dccp/ccids/ccid2.h
index d781580..907deed 100644
--- a/net/dccp/ccids/ccid2.h
+++ b/net/dccp/ccids/ccid2.h
@@ -47,6 +47,7 @@ struct ccid2_seq {
  * @lastrtt: time RTT was last measured
  * @rpseq: last consecutive seqno
  * @rpdupack: dupacks since rpseq
+ * @av_chunks: list of Ack Vectors received on current skb
  */
 struct ccid2_hc_tx_sock {
 	u32			cwnd;
@@ -66,6 +67,7 @@ struct ccid2_hc_tx_sock {
 	int			rpdupack;
 	unsigned long		last_cong;
 	u64			high_ack;
+	struct list_head	av_chunks;
 };
 
 struct ccid2_hc_rx_sock {