Merge tag 'modules-for-v5.5' of git://git.kernel.org/pub/scm/linux/kernel/git/jeyu...
[linux-2.6-microblaze.git] / net / dccp / qpolicy.c
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(&sk->sk_write_queue, 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(&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, 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  */
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
98 bool dccp_qpolicy_full(struct sock *sk)
99 {
100         return qpol_table[dccp_sk(sk)->dccps_qpolicy].full(sk);
101 }
102
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
111 struct sk_buff *dccp_qpolicy_top(struct sock *sk)
112 {
113         return qpol_table[dccp_sk(sk)->dccps_qpolicy].top(sk);
114 }
115
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
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 }