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 | */ |
15 | static void qpolicy_simple_push(struct sock *sk, struct sk_buff *skb) |
16 | { |
17 | skb_queue_tail(list: &sk->sk_write_queue, newsk: skb); |
18 | } |
19 | |
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 | |
26 | static struct sk_buff *qpolicy_simple_top(struct sock *sk) |
27 | { |
28 | return skb_peek(list_: &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 | */ |
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 | |
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 | |
56 | static bool qpolicy_prio_full(struct sock *sk) |
57 | { |
58 | if (qpolicy_simple_full(sk)) |
59 | dccp_qpolicy_drop(sk, skb: 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 | */ |
70 | struct 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 | |
77 | static 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 | */ |
95 | void dccp_qpolicy_push(struct sock *sk, struct sk_buff *skb) |
96 | { |
97 | qpol_table[dccp_sk(sk)->dccps_qpolicy].push(sk, skb); |
98 | } |
99 | |
100 | bool dccp_qpolicy_full(struct sock *sk) |
101 | { |
102 | return qpol_table[dccp_sk(sk)->dccps_qpolicy].full(sk); |
103 | } |
104 | |
105 | void dccp_qpolicy_drop(struct sock *sk, struct sk_buff *skb) |
106 | { |
107 | if (skb != NULL) { |
108 | skb_unlink(skb, list: &sk->sk_write_queue); |
109 | kfree_skb(skb); |
110 | } |
111 | } |
112 | |
113 | struct sk_buff *dccp_qpolicy_top(struct sock *sk) |
114 | { |
115 | return qpol_table[dccp_sk(sk)->dccps_qpolicy].top(sk); |
116 | } |
117 | |
118 | struct 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, list: &sk->sk_write_queue); |
126 | } |
127 | return skb; |
128 | } |
129 | |
130 | bool 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 | |