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[/] [or1k/] [trunk/] [linux/] [linux-2.4/] [net/] [sched/] [sch_sfq.c] - Blame information for rev 1275

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/*
 * net/sched/sch_sfq.c  Stochastic Fairness Queueing discipline.
 *
 *              This program is free software; you can redistribute it and/or
 *              modify it under the terms of the GNU General Public License
 *              as published by the Free Software Foundation; either version
 *              2 of the License, or (at your option) any later version.
 *
 * Authors:     Alexey Kuznetsov, <kuznet@ms2.inr.ac.ru>
 */
 
#include <linux/config.h>
#include <linux/module.h>
#include <asm/uaccess.h>
#include <asm/system.h>
#include <asm/bitops.h>
#include <linux/types.h>
#include <linux/kernel.h>
#include <linux/sched.h>
#include <linux/string.h>
#include <linux/mm.h>
#include <linux/socket.h>
#include <linux/sockios.h>
#include <linux/in.h>
#include <linux/errno.h>
#include <linux/interrupt.h>
#include <linux/if_ether.h>
#include <linux/inet.h>
#include <linux/netdevice.h>
#include <linux/etherdevice.h>
#include <linux/notifier.h>
#include <linux/init.h>
#include <net/ip.h>
#include <linux/ipv6.h>
#include <net/route.h>
#include <linux/skbuff.h>
#include <net/sock.h>
#include <net/pkt_sched.h>
 
 
/*      Stochastic Fairness Queuing algorithm.
        =======================================
 
        Source:
        Paul E. McKenney "Stochastic Fairness Queuing",
        IEEE INFOCOMM'90 Proceedings, San Francisco, 1990.
 
        Paul E. McKenney "Stochastic Fairness Queuing",
        "Interworking: Research and Experience", v.2, 1991, p.113-131.
 
 
        See also:
        M. Shreedhar and George Varghese "Efficient Fair
        Queuing using Deficit Round Robin", Proc. SIGCOMM 95.
 
 
        This is not the thing that is usually called (W)FQ nowadays.
        It does not use any timestamp mechanism, but instead
        processes queues in round-robin order.
 
        ADVANTAGE:
 
        - It is very cheap. Both CPU and memory requirements are minimal.
 
        DRAWBACKS:
 
        - "Stochastic" -> It is not 100% fair.
        When hash collisions occur, several flows are considered as one.
 
        - "Round-robin" -> It introduces larger delays than virtual clock
        based schemes, and should not be used for isolating interactive
        traffic from non-interactive. It means, that this scheduler
        should be used as leaf of CBQ or P3, which put interactive traffic
        to higher priority band.
 
        We still need true WFQ for top level CSZ, but using WFQ
        for the best effort traffic is absolutely pointless:
        SFQ is superior for this purpose.
 
        IMPLEMENTATION:
        This implementation limits maximal queue length to 128;
        maximal mtu to 2^15-1; number of hash buckets to 1024.
        The only goal of this restrictions was that all data
        fit into one 4K page :-). Struct sfq_sched_data is
        organized in anti-cache manner: all the data for a bucket
        are scattered over different locations. This is not good,
        but it allowed me to put it into 4K.
 
        It is easy to increase these values, but not in flight.  */
 
#define SFQ_DEPTH               128
#define SFQ_HASH_DIVISOR        1024
 
/* This type should contain at least SFQ_DEPTH*2 values */
typedef unsigned char sfq_index;
 
struct sfq_head
{
        sfq_index       next;
        sfq_index       prev;
};
 
struct sfq_sched_data
{
/* Parameters */
        int             perturb_period;
        unsigned        quantum;        /* Allotment per round: MUST BE >= MTU */
        int             limit;
 
/* Variables */
        struct timer_list perturb_timer;
        int             perturbation;
        sfq_index       tail;           /* Index of current slot in round */
        sfq_index       max_depth;      /* Maximal depth */
 
        sfq_index       ht[SFQ_HASH_DIVISOR];   /* Hash table */
        sfq_index       next[SFQ_DEPTH];        /* Active slots link */
        short           allot[SFQ_DEPTH];       /* Current allotment per slot */
        unsigned short  hash[SFQ_DEPTH];        /* Hash value indexed by slots */
        struct sk_buff_head     qs[SFQ_DEPTH];          /* Slot queue */
        struct sfq_head dep[SFQ_DEPTH*2];       /* Linked list of slots, indexed by depth */
};
 
static __inline__ unsigned sfq_fold_hash(struct sfq_sched_data *q, u32 h, u32 h1)
{
        int pert = q->perturbation;
 
        /* Have we any rotation primitives? If not, WHY? */
        h ^= (h1<<pert) ^ (h1>>(0x1F - pert));
        h ^= h>>10;
        return h & 0x3FF;
}
 
static unsigned sfq_hash(struct sfq_sched_data *q, struct sk_buff *skb)
{
        u32 h, h2;
 
        switch (skb->protocol) {
        case __constant_htons(ETH_P_IP):
        {
                struct iphdr *iph = skb->nh.iph;
                h = iph->daddr;
                h2 = iph->saddr^iph->protocol;
                if (!(iph->frag_off&htons(IP_MF|IP_OFFSET)) &&
                    (iph->protocol == IPPROTO_TCP ||
                     iph->protocol == IPPROTO_UDP ||
                     iph->protocol == IPPROTO_ESP))
                        h2 ^= *(((u32*)iph) + iph->ihl);
                break;
        }
        case __constant_htons(ETH_P_IPV6):
        {
                struct ipv6hdr *iph = skb->nh.ipv6h;
                h = iph->daddr.s6_addr32[3];
                h2 = iph->saddr.s6_addr32[3]^iph->nexthdr;
                if (iph->nexthdr == IPPROTO_TCP ||
                    iph->nexthdr == IPPROTO_UDP ||
                    iph->nexthdr == IPPROTO_ESP)
                        h2 ^= *(u32*)&iph[1];
                break;
        }
        default:
                h = (u32)(unsigned long)skb->dst^skb->protocol;
                h2 = (u32)(unsigned long)skb->sk;
        }
        return sfq_fold_hash(q, h, h2);
}
 
extern __inline__ void sfq_link(struct sfq_sched_data *q, sfq_index x)
{
        sfq_index p, n;
        int d = q->qs[x].qlen + SFQ_DEPTH;
 
        p = d;
        n = q->dep[d].next;
        q->dep[x].next = n;
        q->dep[x].prev = p;
        q->dep[p].next = q->dep[n].prev = x;
}
 
extern __inline__ void sfq_dec(struct sfq_sched_data *q, sfq_index x)
{
        sfq_index p, n;
 
        n = q->dep[x].next;
        p = q->dep[x].prev;
        q->dep[p].next = n;
        q->dep[n].prev = p;
 
        if (n == p && q->max_depth == q->qs[x].qlen + 1)
                q->max_depth--;
 
        sfq_link(q, x);
}
 
extern __inline__ void sfq_inc(struct sfq_sched_data *q, sfq_index x)
{
        sfq_index p, n;
        int d;
 
        n = q->dep[x].next;
        p = q->dep[x].prev;
        q->dep[p].next = n;
        q->dep[n].prev = p;
        d = q->qs[x].qlen;
        if (q->max_depth < d)
                q->max_depth = d;
 
        sfq_link(q, x);
}
 
static unsigned int sfq_drop(struct Qdisc *sch)
{
        struct sfq_sched_data *q = (struct sfq_sched_data *)sch->data;
        sfq_index d = q->max_depth;
        struct sk_buff *skb;
        unsigned int len;
 
        /* Queue is full! Find the longest slot and
           drop a packet from it */
 
        if (d > 1) {
                sfq_index x = q->dep[d+SFQ_DEPTH].next;
                skb = q->qs[x].prev;
                len = skb->len;
                __skb_unlink(skb, &q->qs[x]);
                kfree_skb(skb);
                sfq_dec(q, x);
                sch->q.qlen--;
                sch->stats.drops++;
                return len;
        }
 
        if (d == 1) {
                /* It is difficult to believe, but ALL THE SLOTS HAVE LENGTH 1. */
                d = q->next[q->tail];
                q->next[q->tail] = q->next[d];
                q->allot[q->next[d]] += q->quantum;
                skb = q->qs[d].prev;
                len = skb->len;
                __skb_unlink(skb, &q->qs[d]);
                kfree_skb(skb);
                sfq_dec(q, d);
                sch->q.qlen--;
                q->ht[q->hash[d]] = SFQ_DEPTH;
                sch->stats.drops++;
                return len;
        }
 
        return 0;
}
 
static int
sfq_enqueue(struct sk_buff *skb, struct Qdisc* sch)
{
        struct sfq_sched_data *q = (struct sfq_sched_data *)sch->data;
        unsigned hash = sfq_hash(q, skb);
        sfq_index x;
 
        x = q->ht[hash];
        if (x == SFQ_DEPTH) {
                q->ht[hash] = x = q->dep[SFQ_DEPTH].next;
                q->hash[x] = hash;
        }
        __skb_queue_tail(&q->qs[x], skb);
        sfq_inc(q, x);
        if (q->qs[x].qlen == 1) {               /* The flow is new */
                if (q->tail == SFQ_DEPTH) {     /* It is the first flow */
                        q->tail = x;
                        q->next[x] = x;
                        q->allot[x] = q->quantum;
                } else {
                        q->next[x] = q->next[q->tail];
                        q->next[q->tail] = x;
                        q->tail = x;
                }
        }
        if (++sch->q.qlen < q->limit-1) {
                sch->stats.bytes += skb->len;
                sch->stats.packets++;
                return 0;
        }
 
        sfq_drop(sch);
        return NET_XMIT_CN;
}
 
static int
sfq_requeue(struct sk_buff *skb, struct Qdisc* sch)
{
        struct sfq_sched_data *q = (struct sfq_sched_data *)sch->data;
        unsigned hash = sfq_hash(q, skb);
        sfq_index x;
 
        x = q->ht[hash];
        if (x == SFQ_DEPTH) {
                q->ht[hash] = x = q->dep[SFQ_DEPTH].next;
                q->hash[x] = hash;
        }
        __skb_queue_head(&q->qs[x], skb);
        sfq_inc(q, x);
        if (q->qs[x].qlen == 1) {               /* The flow is new */
                if (q->tail == SFQ_DEPTH) {     /* It is the first flow */
                        q->tail = x;
                        q->next[x] = x;
                        q->allot[x] = q->quantum;
                } else {
                        q->next[x] = q->next[q->tail];
                        q->next[q->tail] = x;
                        q->tail = x;
                }
        }
        if (++sch->q.qlen < q->limit - 1)
                return 0;
 
        sch->stats.drops++;
        sfq_drop(sch);
        return NET_XMIT_CN;
}
 
 
 
 
static struct sk_buff *
sfq_dequeue(struct Qdisc* sch)
{
        struct sfq_sched_data *q = (struct sfq_sched_data *)sch->data;
        struct sk_buff *skb;
        sfq_index a, old_a;
 
        /* No active slots */
        if (q->tail == SFQ_DEPTH)
                return NULL;
 
        a = old_a = q->next[q->tail];
 
        /* Grab packet */
        skb = __skb_dequeue(&q->qs[a]);
        sfq_dec(q, a);
        sch->q.qlen--;
 
        /* Is the slot empty? */
        if (q->qs[a].qlen == 0) {
                q->ht[q->hash[a]] = SFQ_DEPTH;
                a = q->next[a];
                if (a == old_a) {
                        q->tail = SFQ_DEPTH;
                        return skb;
                }
                q->next[q->tail] = a;
                q->allot[a] += q->quantum;
        } else if ((q->allot[a] -= skb->len) <= 0) {
                q->tail = a;
                a = q->next[a];
                q->allot[a] += q->quantum;
        }
        return skb;
}
 
static void
sfq_reset(struct Qdisc* sch)
{
        struct sk_buff *skb;
 
        while ((skb = sfq_dequeue(sch)) != NULL)
                kfree_skb(skb);
}
 
static void sfq_perturbation(unsigned long arg)
{
        struct Qdisc *sch = (struct Qdisc*)arg;
        struct sfq_sched_data *q = (struct sfq_sched_data *)sch->data;
 
        q->perturbation = net_random()&0x1F;
        q->perturb_timer.expires = jiffies + q->perturb_period;
 
        if (q->perturb_period) {
                q->perturb_timer.expires = jiffies + q->perturb_period;
                add_timer(&q->perturb_timer);
        }
}
 
static int sfq_change(struct Qdisc *sch, struct rtattr *opt)
{
        struct sfq_sched_data *q = (struct sfq_sched_data *)sch->data;
        struct tc_sfq_qopt *ctl = RTA_DATA(opt);
 
        if (opt->rta_len < RTA_LENGTH(sizeof(*ctl)))
                return -EINVAL;
 
        sch_tree_lock(sch);
        q->quantum = ctl->quantum ? : psched_mtu(sch->dev);
        q->perturb_period = ctl->perturb_period*HZ;
        if (ctl->limit)
                q->limit = min_t(u32, ctl->limit, SFQ_DEPTH);
 
        while (sch->q.qlen >= q->limit-1)
                sfq_drop(sch);
 
        del_timer(&q->perturb_timer);
        if (q->perturb_period) {
                q->perturb_timer.expires = jiffies + q->perturb_period;
                add_timer(&q->perturb_timer);
        }
        sch_tree_unlock(sch);
        return 0;
}
 
static int sfq_init(struct Qdisc *sch, struct rtattr *opt)
{
        struct sfq_sched_data *q = (struct sfq_sched_data *)sch->data;
        int i;
 
        q->perturb_timer.data = (unsigned long)sch;
        q->perturb_timer.function = sfq_perturbation;
        init_timer(&q->perturb_timer);
 
        for (i=0; i<SFQ_HASH_DIVISOR; i++)
                q->ht[i] = SFQ_DEPTH;
        for (i=0; i<SFQ_DEPTH; i++) {
                skb_queue_head_init(&q->qs[i]);
                q->dep[i+SFQ_DEPTH].next = i+SFQ_DEPTH;
                q->dep[i+SFQ_DEPTH].prev = i+SFQ_DEPTH;
        }
        q->limit = SFQ_DEPTH;
        q->max_depth = 0;
        q->tail = SFQ_DEPTH;
        if (opt == NULL) {
                q->quantum = psched_mtu(sch->dev);
                q->perturb_period = 0;
        } else {
                int err = sfq_change(sch, opt);
                if (err)
                        return err;
        }
        for (i=0; i<SFQ_DEPTH; i++)
                sfq_link(q, i);
        MOD_INC_USE_COUNT;
        return 0;
}
 
static void sfq_destroy(struct Qdisc *sch)
{
        struct sfq_sched_data *q = (struct sfq_sched_data *)sch->data;
        del_timer(&q->perturb_timer);
        MOD_DEC_USE_COUNT;
}
 
static int sfq_dump(struct Qdisc *sch, struct sk_buff *skb)
{
        struct sfq_sched_data *q = (struct sfq_sched_data *)sch->data;
        unsigned char    *b = skb->tail;
        struct tc_sfq_qopt opt;
 
        opt.quantum = q->quantum;
        opt.perturb_period = q->perturb_period/HZ;
 
        opt.limit = q->limit;
        opt.divisor = SFQ_HASH_DIVISOR;
        opt.flows = q->limit;
 
        RTA_PUT(skb, TCA_OPTIONS, sizeof(opt), &opt);
 
        return skb->len;
 
rtattr_failure:
        skb_trim(skb, b - skb->data);
        return -1;
}
 
struct Qdisc_ops sfq_qdisc_ops =
{
        NULL,
        NULL,
        "sfq",
        sizeof(struct sfq_sched_data),
 
        sfq_enqueue,
        sfq_dequeue,
        sfq_requeue,
        sfq_drop,
 
        sfq_init,
        sfq_reset,
        sfq_destroy,
        NULL, /* sfq_change */
 
        sfq_dump,
};
 
#ifdef MODULE
int init_module(void)
{
        return register_qdisc(&sfq_qdisc_ops);
}
 
void cleanup_module(void)
{
        unregister_qdisc(&sfq_qdisc_ops);
}
#endif
MODULE_LICENSE("GPL");

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[/] [or1k/] [trunk/] [linux/] [linux-2.4/] [net/] [sched/] [sch_sfq.c] - Blame information for rev 1275

Line No.	Rev	Author	Line
1	1275	phoenix	`/*`
2			`* net/sched/sch_sfq.c Stochastic Fairness Queueing discipline.`
3			`*`
4			`* This program is free software; you can redistribute it and/or`
5			`* modify it under the terms of the GNU General Public License`
6			`* as published by the Free Software Foundation; either version`
7			`* 2 of the License, or (at your option) any later version.`
8			`*`
9			`* Authors: Alexey Kuznetsov, <kuznet@ms2.inr.ac.ru>`
10			`*/`
11
12			`#include <linux/config.h>`
13			`#include <linux/module.h>`
14			`#include <asm/uaccess.h>`
15			`#include <asm/system.h>`
16			`#include <asm/bitops.h>`
17			`#include <linux/types.h>`
18			`#include <linux/kernel.h>`
19			`#include <linux/sched.h>`
20			`#include <linux/string.h>`
21			`#include <linux/mm.h>`
22			`#include <linux/socket.h>`
23			`#include <linux/sockios.h>`
24			`#include <linux/in.h>`
25			`#include <linux/errno.h>`
26			`#include <linux/interrupt.h>`
27			`#include <linux/if_ether.h>`
28			`#include <linux/inet.h>`
29			`#include <linux/netdevice.h>`
30			`#include <linux/etherdevice.h>`
31			`#include <linux/notifier.h>`
32			`#include <linux/init.h>`
33			`#include <net/ip.h>`
34			`#include <linux/ipv6.h>`
35			`#include <net/route.h>`
36			`#include <linux/skbuff.h>`
37			`#include <net/sock.h>`
38			`#include <net/pkt_sched.h>`
39
40
41			`/* Stochastic Fairness Queuing algorithm.`
42			`=======================================`
43
44			`Source:`
45			`Paul E. McKenney "Stochastic Fairness Queuing",`
46			`IEEE INFOCOMM'90 Proceedings, San Francisco, 1990.`
47
48			`Paul E. McKenney "Stochastic Fairness Queuing",`
49			`"Interworking: Research and Experience", v.2, 1991, p.113-131.`
50
51
52			`See also:`
53			`M. Shreedhar and George Varghese "Efficient Fair`
54			`Queuing using Deficit Round Robin", Proc. SIGCOMM 95.`
55
56
57			`This is not the thing that is usually called (W)FQ nowadays.`
58			`It does not use any timestamp mechanism, but instead`
59			`processes queues in round-robin order.`
60
61			`ADVANTAGE:`
62
63			`- It is very cheap. Both CPU and memory requirements are minimal.`
64
65			`DRAWBACKS:`
66
67			`- "Stochastic" -> It is not 100% fair.`
68			`When hash collisions occur, several flows are considered as one.`
69
70			`- "Round-robin" -> It introduces larger delays than virtual clock`
71			`based schemes, and should not be used for isolating interactive`
72			`traffic from non-interactive. It means, that this scheduler`
73			`should be used as leaf of CBQ or P3, which put interactive traffic`
74			`to higher priority band.`
75
76			`We still need true WFQ for top level CSZ, but using WFQ`
77			`for the best effort traffic is absolutely pointless:`
78			`SFQ is superior for this purpose.`
79
80			`IMPLEMENTATION:`
81			`This implementation limits maximal queue length to 128;`
82			`maximal mtu to 2^15-1; number of hash buckets to 1024.`
83			`The only goal of this restrictions was that all data`
84			`fit into one 4K page :-). Struct sfq_sched_data is`
85			`organized in anti-cache manner: all the data for a bucket`
86			`are scattered over different locations. This is not good,`
87			`but it allowed me to put it into 4K.`
88
89			`It is easy to increase these values, but not in flight. */`
90
91			`#define SFQ_DEPTH 128`
92			`#define SFQ_HASH_DIVISOR 1024`
93
94			`/* This type should contain at least SFQ_DEPTH2 values /`
95			`typedef unsigned char sfq_index;`
96
97			`struct sfq_head`
98			`{`
99			`sfq_index next;`
100			`sfq_index prev;`
101			`};`
102
103			`struct sfq_sched_data`
104			`{`
105			`/* Parameters */`
106			`int perturb_period;`
107			`unsigned quantum; /* Allotment per round: MUST BE >= MTU */`
108			`int limit;`
109
110			`/* Variables */`
111			`struct timer_list perturb_timer;`
112			`int perturbation;`
113			`sfq_index tail; /* Index of current slot in round */`
114			`sfq_index max_depth; /* Maximal depth */`
115
116			`sfq_index ht[SFQ_HASH_DIVISOR]; /* Hash table */`
117			`sfq_index next[SFQ_DEPTH]; /* Active slots link */`
118			`short allot[SFQ_DEPTH]; /* Current allotment per slot */`
119			`unsigned short hash[SFQ_DEPTH]; /* Hash value indexed by slots */`
120			`struct sk_buff_head qs[SFQ_DEPTH]; /* Slot queue */`
121			`struct sfq_head dep[SFQ_DEPTH2]; / Linked list of slots, indexed by depth */`
122			`};`
123
124			`static __inline__ unsigned sfq_fold_hash(struct sfq_sched_data *q, u32 h, u32 h1)`
125			`{`
126			`int pert = q->perturbation;`
127
128			`/* Have we any rotation primitives? If not, WHY? */`
129			`h ^= (h1<<pert) ^ (h1>>(0x1F - pert));`
130			`h ^= h>>10;`
131			`return h & 0x3FF;`
132			`}`
133
134			`static unsigned sfq_hash(struct sfq_sched_data q, struct sk_buff skb)`
135			`{`
136			`u32 h, h2;`
137
138			`switch (skb->protocol) {`
139			`case __constant_htons(ETH_P_IP):`
140			`{`
141			`struct iphdr *iph = skb->nh.iph;`
142			`h = iph->daddr;`
143			`h2 = iph->saddr^iph->protocol;`
144			`if (!(iph->frag_off&htons(IP_MF\|IP_OFFSET)) &&`
145			`(iph->protocol == IPPROTO_TCP \|\|`
146			`iph->protocol == IPPROTO_UDP \|\|`
147			`iph->protocol == IPPROTO_ESP))`
148			`h2 ^= (((u32)iph) + iph->ihl);`
149			`break;`
150			`}`
151			`case __constant_htons(ETH_P_IPV6):`
152			`{`
153			`struct ipv6hdr *iph = skb->nh.ipv6h;`
154			`h = iph->daddr.s6_addr32[3];`
155			`h2 = iph->saddr.s6_addr32[3]^iph->nexthdr;`
156			`if (iph->nexthdr == IPPROTO_TCP \|\|`
157			`iph->nexthdr == IPPROTO_UDP \|\|`
158			`iph->nexthdr == IPPROTO_ESP)`
159			`h2 ^= (u32)&iph[1];`
160			`break;`
161			`}`
162			`default:`
163			`h = (u32)(unsigned long)skb->dst^skb->protocol;`
164			`h2 = (u32)(unsigned long)skb->sk;`
165			`}`
166			`return sfq_fold_hash(q, h, h2);`
167			`}`
168
169			`extern __inline__ void sfq_link(struct sfq_sched_data *q, sfq_index x)`
170			`{`
171			`sfq_index p, n;`
172			`int d = q->qs[x].qlen + SFQ_DEPTH;`
173
174			`p = d;`
175			`n = q->dep[d].next;`
176			`q->dep[x].next = n;`
177			`q->dep[x].prev = p;`
178			`q->dep[p].next = q->dep[n].prev = x;`
179			`}`
180
181			`extern __inline__ void sfq_dec(struct sfq_sched_data *q, sfq_index x)`
182			`{`
183			`sfq_index p, n;`
184
185			`n = q->dep[x].next;`
186			`p = q->dep[x].prev;`
187			`q->dep[p].next = n;`
188			`q->dep[n].prev = p;`
189
190			`if (n == p && q->max_depth == q->qs[x].qlen + 1)`
191			`q->max_depth--;`
192
193			`sfq_link(q, x);`
194			`}`
195
196			`extern __inline__ void sfq_inc(struct sfq_sched_data *q, sfq_index x)`
197			`{`
198			`sfq_index p, n;`
199			`int d;`
200
201			`n = q->dep[x].next;`
202			`p = q->dep[x].prev;`
203			`q->dep[p].next = n;`
204			`q->dep[n].prev = p;`
205			`d = q->qs[x].qlen;`
206			`if (q->max_depth < d)`
207			`q->max_depth = d;`
208
209			`sfq_link(q, x);`
210			`}`
211
212			`static unsigned int sfq_drop(struct Qdisc *sch)`
213			`{`
214			`struct sfq_sched_data q = (struct sfq_sched_data )sch->data;`
215			`sfq_index d = q->max_depth;`
216			`struct sk_buff *skb;`
217			`unsigned int len;`
218
219			`/* Queue is full! Find the longest slot and`
220			`drop a packet from it */`
221
222			`if (d > 1) {`
223			`sfq_index x = q->dep[d+SFQ_DEPTH].next;`
224			`skb = q->qs[x].prev;`
225			`len = skb->len;`
226			`__skb_unlink(skb, &q->qs[x]);`
227			`kfree_skb(skb);`
228			`sfq_dec(q, x);`
229			`sch->q.qlen--;`
230			`sch->stats.drops++;`
231			`return len;`
232			`}`
233
234			`if (d == 1) {`
235			`/* It is difficult to believe, but ALL THE SLOTS HAVE LENGTH 1. */`
236			`d = q->next[q->tail];`
237			`q->next[q->tail] = q->next[d];`
238			`q->allot[q->next[d]] += q->quantum;`
239			`skb = q->qs[d].prev;`
240			`len = skb->len;`
241			`__skb_unlink(skb, &q->qs[d]);`
242			`kfree_skb(skb);`
243			`sfq_dec(q, d);`
244			`sch->q.qlen--;`
245			`q->ht[q->hash[d]] = SFQ_DEPTH;`
246			`sch->stats.drops++;`
247			`return len;`
248			`}`
249
250			`return 0;`
251			`}`
252
253			`static int`
254			`sfq_enqueue(struct sk_buff skb, struct Qdisc sch)`
255			`{`
256			`struct sfq_sched_data q = (struct sfq_sched_data )sch->data;`
257			`unsigned hash = sfq_hash(q, skb);`
258			`sfq_index x;`
259
260			`x = q->ht[hash];`
261			`if (x == SFQ_DEPTH) {`
262			`q->ht[hash] = x = q->dep[SFQ_DEPTH].next;`
263			`q->hash[x] = hash;`
264			`}`
265			`__skb_queue_tail(&q->qs[x], skb);`
266			`sfq_inc(q, x);`
267			`if (q->qs[x].qlen == 1) { /* The flow is new */`
268			`if (q->tail == SFQ_DEPTH) { /* It is the first flow */`
269			`q->tail = x;`
270			`q->next[x] = x;`
271			`q->allot[x] = q->quantum;`
272			`} else {`
273			`q->next[x] = q->next[q->tail];`
274			`q->next[q->tail] = x;`
275			`q->tail = x;`
276			`}`
277			`}`
278			`if (++sch->q.qlen < q->limit-1) {`
279			`sch->stats.bytes += skb->len;`
280			`sch->stats.packets++;`
281			`return 0;`
282			`}`
283
284			`sfq_drop(sch);`
285			`return NET_XMIT_CN;`
286			`}`
287
288			`static int`
289			`sfq_requeue(struct sk_buff skb, struct Qdisc sch)`
290			`{`
291			`struct sfq_sched_data q = (struct sfq_sched_data )sch->data;`
292			`unsigned hash = sfq_hash(q, skb);`
293			`sfq_index x;`
294
295			`x = q->ht[hash];`
296			`if (x == SFQ_DEPTH) {`
297			`q->ht[hash] = x = q->dep[SFQ_DEPTH].next;`
298			`q->hash[x] = hash;`
299			`}`
300			`__skb_queue_head(&q->qs[x], skb);`
301			`sfq_inc(q, x);`
302			`if (q->qs[x].qlen == 1) { /* The flow is new */`
303			`if (q->tail == SFQ_DEPTH) { /* It is the first flow */`
304			`q->tail = x;`
305			`q->next[x] = x;`
306			`q->allot[x] = q->quantum;`
307			`} else {`
308			`q->next[x] = q->next[q->tail];`
309			`q->next[q->tail] = x;`
310			`q->tail = x;`
311			`}`
312			`}`
313			`if (++sch->q.qlen < q->limit - 1)`
314			`return 0;`
315
316			`sch->stats.drops++;`
317			`sfq_drop(sch);`
318			`return NET_XMIT_CN;`
319			`}`
320
321
322
323
324			`static struct sk_buff *`
325			`sfq_dequeue(struct Qdisc* sch)`
326			`{`
327			`struct sfq_sched_data q = (struct sfq_sched_data )sch->data;`
328			`struct sk_buff *skb;`
329			`sfq_index a, old_a;`
330
331			`/* No active slots */`
332			`if (q->tail == SFQ_DEPTH)`
333			`return NULL;`
334
335			`a = old_a = q->next[q->tail];`
336
337			`/* Grab packet */`
338			`skb = __skb_dequeue(&q->qs[a]);`
339			`sfq_dec(q, a);`
340			`sch->q.qlen--;`
341
342			`/* Is the slot empty? */`
343			`if (q->qs[a].qlen == 0) {`
344			`q->ht[q->hash[a]] = SFQ_DEPTH;`
345			`a = q->next[a];`
346			`if (a == old_a) {`
347			`q->tail = SFQ_DEPTH;`
348			`return skb;`
349			`}`
350			`q->next[q->tail] = a;`
351			`q->allot[a] += q->quantum;`
352			`} else if ((q->allot[a] -= skb->len) <= 0) {`
353			`q->tail = a;`
354			`a = q->next[a];`
355			`q->allot[a] += q->quantum;`
356			`}`
357			`return skb;`
358			`}`
359
360			`static void`
361			`sfq_reset(struct Qdisc* sch)`
362			`{`
363			`struct sk_buff *skb;`
364
365			`while ((skb = sfq_dequeue(sch)) != NULL)`
366			`kfree_skb(skb);`
367			`}`
368
369			`static void sfq_perturbation(unsigned long arg)`
370			`{`
371			`struct Qdisc sch = (struct Qdisc)arg;`
372			`struct sfq_sched_data q = (struct sfq_sched_data )sch->data;`
373
374			`q->perturbation = net_random()&0x1F;`
375			`q->perturb_timer.expires = jiffies + q->perturb_period;`
376
377			`if (q->perturb_period) {`
378			`q->perturb_timer.expires = jiffies + q->perturb_period;`
379			`add_timer(&q->perturb_timer);`
380			`}`
381			`}`
382
383			`static int sfq_change(struct Qdisc sch, struct rtattr opt)`
384			`{`
385			`struct sfq_sched_data q = (struct sfq_sched_data )sch->data;`
386			`struct tc_sfq_qopt *ctl = RTA_DATA(opt);`
387
388			`if (opt->rta_len < RTA_LENGTH(sizeof(*ctl)))`
389			`return -EINVAL;`
390
391			`sch_tree_lock(sch);`
392			`q->quantum = ctl->quantum ? : psched_mtu(sch->dev);`
393			`q->perturb_period = ctl->perturb_period*HZ;`
394			`if (ctl->limit)`
395			`q->limit = min_t(u32, ctl->limit, SFQ_DEPTH);`
396
397			`while (sch->q.qlen >= q->limit-1)`
398			`sfq_drop(sch);`
399
400			`del_timer(&q->perturb_timer);`
401			`if (q->perturb_period) {`
402			`q->perturb_timer.expires = jiffies + q->perturb_period;`
403			`add_timer(&q->perturb_timer);`
404			`}`
405			`sch_tree_unlock(sch);`
406			`return 0;`
407			`}`
408
409			`static int sfq_init(struct Qdisc sch, struct rtattr opt)`
410			`{`
411			`struct sfq_sched_data q = (struct sfq_sched_data )sch->data;`
412			`int i;`
413
414			`q->perturb_timer.data = (unsigned long)sch;`
415			`q->perturb_timer.function = sfq_perturbation;`
416			`init_timer(&q->perturb_timer);`
417
418			`for (i=0; i<SFQ_HASH_DIVISOR; i++)`
419			`q->ht[i] = SFQ_DEPTH;`
420			`for (i=0; i<SFQ_DEPTH; i++) {`
421			`skb_queue_head_init(&q->qs[i]);`
422			`q->dep[i+SFQ_DEPTH].next = i+SFQ_DEPTH;`
423			`q->dep[i+SFQ_DEPTH].prev = i+SFQ_DEPTH;`
424			`}`
425			`q->limit = SFQ_DEPTH;`
426			`q->max_depth = 0;`
427			`q->tail = SFQ_DEPTH;`
428			`if (opt == NULL) {`
429			`q->quantum = psched_mtu(sch->dev);`
430			`q->perturb_period = 0;`
431			`} else {`
432			`int err = sfq_change(sch, opt);`
433			`if (err)`
434			`return err;`
435			`}`
436			`for (i=0; i<SFQ_DEPTH; i++)`
437			`sfq_link(q, i);`
438			`MOD_INC_USE_COUNT;`
439			`return 0;`
440			`}`
441
442			`static void sfq_destroy(struct Qdisc *sch)`
443			`{`
444			`struct sfq_sched_data q = (struct sfq_sched_data )sch->data;`
445			`del_timer(&q->perturb_timer);`
446			`MOD_DEC_USE_COUNT;`
447			`}`
448
449			`static int sfq_dump(struct Qdisc sch, struct sk_buff skb)`
450			`{`
451			`struct sfq_sched_data q = (struct sfq_sched_data )sch->data;`
452			`unsigned char *b = skb->tail;`
453			`struct tc_sfq_qopt opt;`
454
455			`opt.quantum = q->quantum;`
456			`opt.perturb_period = q->perturb_period/HZ;`
457
458			`opt.limit = q->limit;`
459			`opt.divisor = SFQ_HASH_DIVISOR;`
460			`opt.flows = q->limit;`
461
462			`RTA_PUT(skb, TCA_OPTIONS, sizeof(opt), &opt);`
463
464			`return skb->len;`
465
466			`rtattr_failure:`
467			`skb_trim(skb, b - skb->data);`
468			`return -1;`
469			`}`
470
471			`struct Qdisc_ops sfq_qdisc_ops =`
472			`{`
473			`NULL,`
474			`NULL,`
475			`"sfq",`
476			`sizeof(struct sfq_sched_data),`
477
478			`sfq_enqueue,`
479			`sfq_dequeue,`
480			`sfq_requeue,`
481			`sfq_drop,`
482
483			`sfq_init,`
484			`sfq_reset,`
485			`sfq_destroy,`
486			`NULL, /* sfq_change */`
487
488			`sfq_dump,`
489			`};`
490
491			`#ifdef MODULE`
492			`int init_module(void)`
493			`{`
494			`return register_qdisc(&sfq_qdisc_ops);`
495			`}`
496
497			`void cleanup_module(void)`
498			`{`
499			`unregister_qdisc(&sfq_qdisc_ops);`
500			`}`
501			`#endif`
502			`MODULE_LICENSE("GPL");`