Merge tag 'v2.6.38' of git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux-2.6

[mv-sheeva.git] / net / dccp / qpolicy.c

diff --git a/net/dccp/qpolicy.c b/net/dccp/qpolicy.c
new file mode 100644 (file)
index 0000000..63c30bf
--- /dev/null
+++ b/net/dccp/qpolicy.c
@@ -0,0 +1,137 @@
+/*
+ *  net/dccp/qpolicy.c
+ *
+ *  Policy-based packet dequeueing interface for DCCP.
+ *
+ *  Copyright (c) 2008 Tomasz Grobelny <tomasz@grobelny.oswiecenia.net>
+ *
+ *  This program is free software; you can redistribute it and/or
+ *  modify it under the terms of the GNU General Public License v2
+ *  as published by the Free Software Foundation.
+ */
+#include "dccp.h"
+
+/*
+ *     Simple Dequeueing Policy:
+ *     If tx_qlen is different from 0, enqueue up to tx_qlen elements.
+ */
+static void qpolicy_simple_push(struct sock *sk, struct sk_buff *skb)
+{
+       skb_queue_tail(&sk->sk_write_queue, skb);
+}
+
+static bool qpolicy_simple_full(struct sock *sk)
+{
+       return dccp_sk(sk)->dccps_tx_qlen &&
+              sk->sk_write_queue.qlen >= dccp_sk(sk)->dccps_tx_qlen;
+}
+
+static struct sk_buff *qpolicy_simple_top(struct sock *sk)
+{
+       return skb_peek(&sk->sk_write_queue);
+}
+
+/*
+ *     Priority-based Dequeueing Policy:
+ *     If tx_qlen is different from 0 and the queue has reached its upper bound
+ *     of tx_qlen elements, replace older packets lowest-priority-first.
+ */
+static struct sk_buff *qpolicy_prio_best_skb(struct sock *sk)
+{
+       struct sk_buff *skb, *best = NULL;
+
+       skb_queue_walk(&sk->sk_write_queue, skb)
+               if (best == NULL || skb->priority > best->priority)
+                       best = skb;
+       return best;
+}
+
+static struct sk_buff *qpolicy_prio_worst_skb(struct sock *sk)
+{
+       struct sk_buff *skb, *worst = NULL;
+
+       skb_queue_walk(&sk->sk_write_queue, skb)
+               if (worst == NULL || skb->priority < worst->priority)
+                       worst = skb;
+       return worst;
+}
+
+static bool qpolicy_prio_full(struct sock *sk)
+{
+       if (qpolicy_simple_full(sk))
+               dccp_qpolicy_drop(sk, qpolicy_prio_worst_skb(sk));
+       return false;
+}
+
+/**
+ * struct dccp_qpolicy_operations  -  TX Packet Dequeueing Interface
+ * @push: add a new @skb to the write queue
+ * @full: indicates that no more packets will be admitted
+ * @top:  peeks at whatever the queueing policy defines as its `top'
+ */
+static struct dccp_qpolicy_operations {
+       void            (*push) (struct sock *sk, struct sk_buff *skb);
+       bool            (*full) (struct sock *sk);
+       struct sk_buff* (*top)  (struct sock *sk);
+       __be32          params;
+
+} qpol_table[DCCPQ_POLICY_MAX] = {
+       [DCCPQ_POLICY_SIMPLE] = {
+               .push   = qpolicy_simple_push,
+               .full   = qpolicy_simple_full,
+               .top    = qpolicy_simple_top,
+               .params = 0,
+       },
+       [DCCPQ_POLICY_PRIO] = {
+               .push   = qpolicy_simple_push,
+               .full   = qpolicy_prio_full,
+               .top    = qpolicy_prio_best_skb,
+               .params = DCCP_SCM_PRIORITY,
+       },
+};
+
+/*
+ *     Externally visible interface
+ */
+void dccp_qpolicy_push(struct sock *sk, struct sk_buff *skb)
+{
+       qpol_table[dccp_sk(sk)->dccps_qpolicy].push(sk, skb);
+}
+
+bool dccp_qpolicy_full(struct sock *sk)
+{
+       return qpol_table[dccp_sk(sk)->dccps_qpolicy].full(sk);
+}
+
+void dccp_qpolicy_drop(struct sock *sk, struct sk_buff *skb)
+{
+       if (skb != NULL) {
+               skb_unlink(skb, &sk->sk_write_queue);
+               kfree_skb(skb);
+       }
+}
+
+struct sk_buff *dccp_qpolicy_top(struct sock *sk)
+{
+       return qpol_table[dccp_sk(sk)->dccps_qpolicy].top(sk);
+}
+
+struct sk_buff *dccp_qpolicy_pop(struct sock *sk)
+{
+       struct sk_buff *skb = dccp_qpolicy_top(sk);
+
+       if (skb != NULL) {
+               /* Clear any skb fields that we used internally */
+               skb->priority = 0;
+               skb_unlink(skb, &sk->sk_write_queue);
+       }
+       return skb;
+}
+
+bool dccp_qpolicy_param_ok(struct sock *sk, __be32 param)
+{
+       /* check if exactly one bit is set */
+       if (!param || (param & (param - 1)))
+               return false;
+       return (qpol_table[dccp_sk(sk)->dccps_qpolicy].params & param) == param;
+}