xref: /openbmc/linux/net/dccp/qpolicy.c (revision 871a2c16c21b988688b4ab1a78eadd969765c0a3) 
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  */
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 
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 
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  */
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 
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 
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 
77 } 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 	},
83 	[DCCPQ_POLICY_PRIO] = {
84 		.push = qpolicy_simple_push,
85 		.full = qpolicy_prio_full,
86 		.top  = qpolicy_prio_best_skb,
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