xref: /kernel/linux/linux-6.6/net/dccp/qpolicy.c (revision 62306a36) 
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 */
15static void qpolicy_simple_push(struct sock *sk, struct sk_buff *skb)
16{
17	skb_queue_tail(&sk->sk_write_queue, skb);
18}
19
20static 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
26static 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 */
36static 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
46static 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
56static 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 * @params: parameter passed to policy operation
69 */
70struct dccp_qpolicy_operations {
71	void		(*push)	(struct sock *sk, struct sk_buff *skb);
72	bool		(*full) (struct sock *sk);
73	struct sk_buff*	(*top)  (struct sock *sk);
74	__be32		params;
75};
76
77static struct dccp_qpolicy_operations qpol_table[DCCPQ_POLICY_MAX] = {
78	[DCCPQ_POLICY_SIMPLE] = {
79		.push   = qpolicy_simple_push,
80		.full   = qpolicy_simple_full,
81		.top    = qpolicy_simple_top,
82		.params = 0,
83	},
84	[DCCPQ_POLICY_PRIO] = {
85		.push   = qpolicy_simple_push,
86		.full   = qpolicy_prio_full,
87		.top    = qpolicy_prio_best_skb,
88		.params = DCCP_SCM_PRIORITY,
89	},
90};
91
92/*
93 *	Externally visible interface
94 */
95void dccp_qpolicy_push(struct sock *sk, struct sk_buff *skb)
96{
97	qpol_table[dccp_sk(sk)->dccps_qpolicy].push(sk, skb);
98}
99
100bool dccp_qpolicy_full(struct sock *sk)
101{
102	return qpol_table[dccp_sk(sk)->dccps_qpolicy].full(sk);
103}
104
105void dccp_qpolicy_drop(struct sock *sk, struct sk_buff *skb)
106{
107	if (skb != NULL) {
108		skb_unlink(skb, &sk->sk_write_queue);
109		kfree_skb(skb);
110	}
111}
112
113struct sk_buff *dccp_qpolicy_top(struct sock *sk)
114{
115	return qpol_table[dccp_sk(sk)->dccps_qpolicy].top(sk);
116}
117
118struct sk_buff *dccp_qpolicy_pop(struct sock *sk)
119{
120	struct sk_buff *skb = dccp_qpolicy_top(sk);
121
122	if (skb != NULL) {
123		/* Clear any skb fields that we used internally */
124		skb->priority = 0;
125		skb_unlink(skb, &sk->sk_write_queue);
126	}
127	return skb;
128}
129
130bool dccp_qpolicy_param_ok(struct sock *sk, __be32 param)
131{
132	/* check if exactly one bit is set */
133	if (!param || (param & (param - 1)))
134		return false;
135	return (qpol_table[dccp_sk(sk)->dccps_qpolicy].params & param) == param;
136}
137