File-copy from v4.4.100
This is the result of 'cp' from a linux-stable tree with the 'v4.4.100'
tag checked out (commit 26d6298789e695c9f627ce49a7bbd2286405798a) on
git://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
Please refer to that tree for all history prior to this point.
Change-Id: I8a9ee2aea93cd29c52c847d0ce33091a73ae6afe
diff --git a/net/dccp/qpolicy.c b/net/dccp/qpolicy.c
new file mode 100644
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;
+}