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, 28 insertions, 0 deletions

diff --git a/net/dccp/ackvec.c b/net/dccp/ackvec.c
index 66b8a51300c0..41819848bdda 100644
--- a/net/dccp/ackvec.c
+++ b/net/dccp/ackvec.c
@@ -343,6 +343,34 @@ free_records:
         }
 }
 
+/*
+ *      Routines to keep track of Ack Vectors received in an skb
+ */
+int dccp_ackvec_parsed_add(struct list_head *head, u8 *vec, u8 len, u8 nonce)
+{
+        struct dccp_ackvec_parsed *new = kmalloc(sizeof(*new), GFP_ATOMIC);
+
+        if (new == NULL)
+                return -ENOBUFS;
+        new->vec   = vec;
+        new->len   = len;
+        new->nonce = nonce;
+
+        list_add_tail(&new->node, head);
+        return 0;
+}
+EXPORT_SYMBOL_GPL(dccp_ackvec_parsed_add);
+
+void dccp_ackvec_parsed_cleanup(struct list_head *parsed_chunks)
+{
+        struct dccp_ackvec_parsed *cur, *next;
+
+        list_for_each_entry_safe(cur, next, parsed_chunks, node)
+                kfree(cur);
+        INIT_LIST_HEAD(parsed_chunks);
+}
+EXPORT_SYMBOL_GPL(dccp_ackvec_parsed_cleanup);
+
 int __init dccp_ackvec_init(void)
 {
         dccp_ackvec_slab = kmem_cache_create("dccp_ackvec",