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, 3 insertions, 4 deletions

diff --git a/net/dccp/output.c b/net/dccp/output.c
index b1eaf7bcfb11..2532797a8009 100644
--- a/net/dccp/output.c
+++ b/net/dccp/output.c
@@ -241,7 +241,7 @@ static void dccp_xmit_packet(struct sock *sk)
 {
         int err, len;
         struct dccp_sock *dp = dccp_sk(sk);
-        struct sk_buff *skb = skb_dequeue(&sk->sk_write_queue);
+        struct sk_buff *skb = dccp_qpolicy_pop(sk);
 
         if (unlikely(skb == NULL))
                 return;
@@ -344,7 +344,7 @@ void dccp_write_xmit(struct sock *sk)
         struct dccp_sock *dp = dccp_sk(sk);
         struct sk_buff *skb;
 
-        while ((skb = skb_peek(&sk->sk_write_queue))) {
+        while ((skb = dccp_qpolicy_top(sk))) {
                 int rc = ccid_hc_tx_send_packet(dp->dccps_hc_tx_ccid, sk, skb);
 
                 switch (ccid_packet_dequeue_eval(rc)) {
@@ -358,8 +358,7 @@ void dccp_write_xmit(struct sock *sk)
                         dccp_xmit_packet(sk);
                         break;
                 case CCID_PACKET_ERR:
-                        skb_dequeue(&sk->sk_write_queue);
-                        kfree_skb(skb);
+                        dccp_qpolicy_drop(sk, skb);
                         dccp_pr_debug("packet discarded due to err=%d\n", rc);
                 }
         }