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authorTomasz Grobelny <tomasz@grobelny.oswiecenia.net>2010-12-04 13:38:01 +0100
committerGerrit Renker <gerrit@erg.abdn.ac.uk>2010-12-07 13:47:12 +0100
commit871a2c16c21b988688b4ab1a78eadd969765c0a3 (patch)
tree34ffb3be1402747ef3b7fdb754fb99778bd45728 /net/dccp/qpolicy.c
parentcfa969e385a23e4c85f50e0ed5de25a2e18bf9d4 (diff)
downloadlinux-871a2c16c21b988688b4ab1a78eadd969765c0a3.tar.gz
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>
Diffstat (limited to 'net/dccp/qpolicy.c')
-rw-r--r--net/dccp/qpolicy.c126
1 files changed, 126 insertions, 0 deletions
diff --git a/net/dccp/qpolicy.c b/net/dccp/qpolicy.c
new file mode 100644
index 00000000000..4b0fd6b11f6
--- /dev/null
+++ b/net/dccp/qpolicy.c
@@ -0,0 +1,126 @@
+/*
+ * 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);
+
+} qpol_table[DCCPQ_POLICY_MAX] = {
+ [DCCPQ_POLICY_SIMPLE] = {
+ .push = qpolicy_simple_push,
+ .full = qpolicy_simple_full,
+ .top = qpolicy_simple_top,
+ },
+ [DCCPQ_POLICY_PRIO] = {
+ .push = qpolicy_simple_push,
+ .full = qpolicy_prio_full,
+ .top = qpolicy_prio_best_skb,
+ },
+};
+
+/*
+ * 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;
+}