1 /*
2 * net/dccp/qpolicy.c
3 *
4 * Policy-based packet dequeueing interface for DCCP.
5 *
6 * Copyright (c) 2008 Tomasz Grobelny <tomasz@grobelny.oswiecenia.net>
7 *
8 * This program is free software; you can redistribute it and/or
9 * modify it under the terms of the GNU General Public License v2
10 * as published by the Free Software Foundation.
11 */
12 #include "dccp.h"
13
14 /*
15 * Simple Dequeueing Policy:
16 * If tx_qlen is different from 0, enqueue up to tx_qlen elements.
17 */
qpolicy_simple_push(struct sock * sk,struct sk_buff * skb)18 static void qpolicy_simple_push(struct sock *sk, struct sk_buff *skb)
19 {
20 skb_queue_tail(&sk->sk_write_queue, skb);
21 }
22
qpolicy_simple_full(struct sock * sk)23 static bool qpolicy_simple_full(struct sock *sk)
24 {
25 return dccp_sk(sk)->dccps_tx_qlen &&
26 sk->sk_write_queue.qlen >= dccp_sk(sk)->dccps_tx_qlen;
27 }
28
qpolicy_simple_top(struct sock * sk)29 static struct sk_buff *qpolicy_simple_top(struct sock *sk)
30 {
31 return skb_peek(&sk->sk_write_queue);
32 }
33
34 /*
35 * Priority-based Dequeueing Policy:
36 * If tx_qlen is different from 0 and the queue has reached its upper bound
37 * of tx_qlen elements, replace older packets lowest-priority-first.
38 */
qpolicy_prio_best_skb(struct sock * sk)39 static struct sk_buff *qpolicy_prio_best_skb(struct sock *sk)
40 {
41 struct sk_buff *skb, *best = NULL;
42
43 skb_queue_walk(&sk->sk_write_queue, skb)
44 if (best == NULL || skb->priority > best->priority)
45 best = skb;
46 return best;
47 }
48
qpolicy_prio_worst_skb(struct sock * sk)49 static struct sk_buff *qpolicy_prio_worst_skb(struct sock *sk)
50 {
51 struct sk_buff *skb, *worst = NULL;
52
53 skb_queue_walk(&sk->sk_write_queue, skb)
54 if (worst == NULL || skb->priority < worst->priority)
55 worst = skb;
56 return worst;
57 }
58
qpolicy_prio_full(struct sock * sk)59 static bool qpolicy_prio_full(struct sock *sk)
60 {
61 if (qpolicy_simple_full(sk))
62 dccp_qpolicy_drop(sk, qpolicy_prio_worst_skb(sk));
63 return false;
64 }
65
66 /**
67 * struct dccp_qpolicy_operations - TX Packet Dequeueing Interface
68 * @push: add a new @skb to the write queue
69 * @full: indicates that no more packets will be admitted
70 * @top: peeks at whatever the queueing policy defines as its `top'
71 */
72 static struct dccp_qpolicy_operations {
73 void (*push) (struct sock *sk, struct sk_buff *skb);
74 bool (*full) (struct sock *sk);
75 struct sk_buff* (*top) (struct sock *sk);
76 __be32 params;
77
78 } qpol_table[DCCPQ_POLICY_MAX] = {
79 [DCCPQ_POLICY_SIMPLE] = {
80 .push = qpolicy_simple_push,
81 .full = qpolicy_simple_full,
82 .top = qpolicy_simple_top,
83 .params = 0,
84 },
85 [DCCPQ_POLICY_PRIO] = {
86 .push = qpolicy_simple_push,
87 .full = qpolicy_prio_full,
88 .top = qpolicy_prio_best_skb,
89 .params = DCCP_SCM_PRIORITY,
90 },
91 };
92
93 /*
94 * Externally visible interface
95 */
dccp_qpolicy_push(struct sock * sk,struct sk_buff * skb)96 void dccp_qpolicy_push(struct sock *sk, struct sk_buff *skb)
97 {
98 qpol_table[dccp_sk(sk)->dccps_qpolicy].push(sk, skb);
99 }
100
dccp_qpolicy_full(struct sock * sk)101 bool dccp_qpolicy_full(struct sock *sk)
102 {
103 return qpol_table[dccp_sk(sk)->dccps_qpolicy].full(sk);
104 }
105
dccp_qpolicy_drop(struct sock * sk,struct sk_buff * skb)106 void dccp_qpolicy_drop(struct sock *sk, struct sk_buff *skb)
107 {
108 if (skb != NULL) {
109 skb_unlink(skb, &sk->sk_write_queue);
110 kfree_skb(skb);
111 }
112 }
113
dccp_qpolicy_top(struct sock * sk)114 struct sk_buff *dccp_qpolicy_top(struct sock *sk)
115 {
116 return qpol_table[dccp_sk(sk)->dccps_qpolicy].top(sk);
117 }
118
dccp_qpolicy_pop(struct sock * sk)119 struct sk_buff *dccp_qpolicy_pop(struct sock *sk)
120 {
121 struct sk_buff *skb = dccp_qpolicy_top(sk);
122
123 if (skb != NULL) {
124 /* Clear any skb fields that we used internally */
125 skb->priority = 0;
126 skb_unlink(skb, &sk->sk_write_queue);
127 }
128 return skb;
129 }
130
dccp_qpolicy_param_ok(struct sock * sk,__be32 param)131 bool dccp_qpolicy_param_ok(struct sock *sk, __be32 param)
132 {
133 /* check if exactly one bit is set */
134 if (!param || (param & (param - 1)))
135 return false;
136 return (qpol_table[dccp_sk(sk)->dccps_qpolicy].params & param) == param;
137 }
138
