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net_sched: sfq: always randomize hash perturbation

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SFQ q->perturbation is used in sfq_hash() as an input to Jenkins hash.

We currently randomize this 32bit value only if a perturbation timer is
setup.

Its much better to always initialize it to defeat attackers, or else
they can predict very well what kind of packets they have to forge to
hit a particular flow.

Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Eric Dumazet 2012-01-04 06:23:01 +00:00 committed by David S. Miller
parent bd16a6cce2
commit 02a9098ede
1 changed files with 6 additions and 6 deletions
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12
net/sched/sch_sfq.c
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@ -591,12 +591,12 @@ static int sfq_init(struct Qdisc *sch, struct nlattr *opt)
q->cur_depth = 0;
q->tail = NULL;
q->divisor = SFQ_DEFAULT_HASH_DIVISOR;
if (opt == NULL) {
q->quantum = psched_mtu(qdisc_dev(sch));
q->scaled_quantum = SFQ_ALLOT_SIZE(q->quantum);
q->perturb_period = 0;
q->perturbation = net_random();
} else {
q->quantum = psched_mtu(qdisc_dev(sch));
q->scaled_quantum = SFQ_ALLOT_SIZE(q->quantum);
q->perturb_period = 0;
q->perturbation = net_random();
if (opt) {
int err = sfq_change(sch, opt);
if (err)
return err;