dccp: Policy-based packet dequeueing infrastructure

This patch adds a generic infrastructure for policy-based dequeueing of 
TX packets and provides two policies:
 * a simple FIFO policy (which is the default) and
 * a priority based policy (set via socket options).
Both policies honour the tx_qlen sysctl for the maximum size of the write
queue (can be overridden via socket options). 

The priority policy uses skb->priority internally to assign an u32 priority
identifier, using the same ranking as SO_PRIORITY. The skb->priority field
is set to 0 when the packet leaves DCCP. The priority is supplied as ancillary
data using cmsg(3), the patch also provides the requisite parsing routines.

Signed-off-by: Tomasz Grobelny <tomasz@grobelny.oswiecenia.net>
Signed-off-by: Gerrit Renker <gerrit@erg.abdn.ac.uk>

1 files changed, 12 insertions, 0 deletions

diff --git a/net/dccp/dccp.h b/net/dccp/dccp.h
index 74c90cd27677..ce2dd6f6f34d 100644
--- a/net/dccp/dccp.h
+++ b/net/dccp/dccp.h
@@ -234,6 +234,18 @@ extern void dccp_reqsk_send_ack(struct sock *sk, struct sk_buff *skb,
 extern void dccp_send_sync(struct sock *sk, const u64 seq,
                            const enum dccp_pkt_type pkt_type);
 
+/*
+ * TX Packet Dequeueing Interface
+ */
+extern void             dccp_qpolicy_push(struct sock *sk, struct sk_buff *skb);
+extern bool             dccp_qpolicy_full(struct sock *sk);
+extern void             dccp_qpolicy_drop(struct sock *sk, struct sk_buff *skb);
+extern struct sk_buff   *dccp_qpolicy_top(struct sock *sk);
+extern struct sk_buff   *dccp_qpolicy_pop(struct sock *sk);
+
+/*
+ * TX Packet Output and TX Timers
+ */
 extern void dccp_write_xmit(struct sock *sk);
 extern void dccp_write_space(struct sock *sk);
 extern void dccp_flush_write_queue(struct sock *sk, long *time_budget);