1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3 * net/dccp/qpolicy.c
4 *
5 * Policy-based packet dequeueing interface for DCCP.
6 *
7 * Copyright (c) 2008 Tomasz Grobelny <tomasz@grobelny.oswiecenia.net>
8 */
9 #include "dccp.h"
10
11 /*
12 * Simple Dequeueing Policy:
13 * If tx_qlen is different from 0, enqueue up to tx_qlen elements.
14 */
qpolicy_simple_push(struct sock * sk,struct sk_buff * skb)15 static void qpolicy_simple_push(struct sock *sk, struct sk_buff *skb)
16 {
17 skb_queue_tail(&sk->sk_write_queue, skb);
18 }
19
qpolicy_simple_full(struct sock * sk)20 static bool qpolicy_simple_full(struct sock *sk)
21 {
22 return dccp_sk(sk)->dccps_tx_qlen &&
23 sk->sk_write_queue.qlen >= dccp_sk(sk)->dccps_tx_qlen;
24 }
25
qpolicy_simple_top(struct sock * sk)26 static struct sk_buff *qpolicy_simple_top(struct sock *sk)
27 {
28 return skb_peek(&sk->sk_write_queue);
29 }
30
31 /*
32 * Priority-based Dequeueing Policy:
33 * If tx_qlen is different from 0 and the queue has reached its upper bound
34 * of tx_qlen elements, replace older packets lowest-priority-first.
35 */
qpolicy_prio_best_skb(struct sock * sk)36 static struct sk_buff *qpolicy_prio_best_skb(struct sock *sk)
37 {
38 struct sk_buff *skb, *best = NULL;
39
40 skb_queue_walk(&sk->sk_write_queue, skb)
41 if (best == NULL || skb->priority > best->priority)
42 best = skb;
43 return best;
44 }
45
qpolicy_prio_worst_skb(struct sock * sk)46 static struct sk_buff *qpolicy_prio_worst_skb(struct sock *sk)
47 {
48 struct sk_buff *skb, *worst = NULL;
49
50 skb_queue_walk(&sk->sk_write_queue, skb)
51 if (worst == NULL || skb->priority < worst->priority)
52 worst = skb;
53 return worst;
54 }
55
qpolicy_prio_full(struct sock * sk)56 static bool qpolicy_prio_full(struct sock *sk)
57 {
58 if (qpolicy_simple_full(sk))
59 dccp_qpolicy_drop(sk, qpolicy_prio_worst_skb(sk));
60 return false;
61 }
62
63 /**
64 * struct dccp_qpolicy_operations - TX Packet Dequeueing Interface
65 * @push: add a new @skb to the write queue
66 * @full: indicates that no more packets will be admitted
67 * @top: peeks at whatever the queueing policy defines as its `top'
68 */
69 static struct dccp_qpolicy_operations {
70 void (*push) (struct sock *sk, struct sk_buff *skb);
71 bool (*full) (struct sock *sk);
72 struct sk_buff* (*top) (struct sock *sk);
73 __be32 params;
74
75 } qpol_table[DCCPQ_POLICY_MAX] = {
76 [DCCPQ_POLICY_SIMPLE] = {
77 .push = qpolicy_simple_push,
78 .full = qpolicy_simple_full,
79 .top = qpolicy_simple_top,
80 .params = 0,
81 },
82 [DCCPQ_POLICY_PRIO] = {
83 .push = qpolicy_simple_push,
84 .full = qpolicy_prio_full,
85 .top = qpolicy_prio_best_skb,
86 .params = DCCP_SCM_PRIORITY,
87 },
88 };
89
90 /*
91 * Externally visible interface
92 */
dccp_qpolicy_push(struct sock * sk,struct sk_buff * skb)93 void dccp_qpolicy_push(struct sock *sk, struct sk_buff *skb)
94 {
95 qpol_table[dccp_sk(sk)->dccps_qpolicy].push(sk, skb);
96 }
97
dccp_qpolicy_full(struct sock * sk)98 bool dccp_qpolicy_full(struct sock *sk)
99 {
100 return qpol_table[dccp_sk(sk)->dccps_qpolicy].full(sk);
101 }
102
dccp_qpolicy_drop(struct sock * sk,struct sk_buff * skb)103 void dccp_qpolicy_drop(struct sock *sk, struct sk_buff *skb)
104 {
105 if (skb != NULL) {
106 skb_unlink(skb, &sk->sk_write_queue);
107 kfree_skb(skb);
108 }
109 }
110
dccp_qpolicy_top(struct sock * sk)111 struct sk_buff *dccp_qpolicy_top(struct sock *sk)
112 {
113 return qpol_table[dccp_sk(sk)->dccps_qpolicy].top(sk);
114 }
115
dccp_qpolicy_pop(struct sock * sk)116 struct sk_buff *dccp_qpolicy_pop(struct sock *sk)
117 {
118 struct sk_buff *skb = dccp_qpolicy_top(sk);
119
120 if (skb != NULL) {
121 /* Clear any skb fields that we used internally */
122 skb->priority = 0;
123 skb_unlink(skb, &sk->sk_write_queue);
124 }
125 return skb;
126 }
127
dccp_qpolicy_param_ok(struct sock * sk,__be32 param)128 bool dccp_qpolicy_param_ok(struct sock *sk, __be32 param)
129 {
130 /* check if exactly one bit is set */
131 if (!param || (param & (param - 1)))
132 return false;
133 return (qpol_table[dccp_sk(sk)->dccps_qpolicy].params & param) == param;
134 }
135
