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[IPV6]: Fix race in route selection. 

We eliminated rt6_dflt_lock (to protect default router pointer)
at 2.6.17-rc1, and introduced rt6_select() for general router selection.
The function is called in the context of rt6_lock read-lock held,
but this means, we have some race conditions when we do round-robin.

Signed-off-by; YOSHIFUJI Hideaki <yoshfuji@linux-ipv6.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
YOSHIFUJI Hideaki 2006-04-28 15:59:15 -07:00 committed by David S. Miller
parent e959d8121f
commit c302e6d54e
1 changed files with 4 additions and 1 deletions
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5
net/ipv6/route.c
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@ -317,7 +317,7 @@ static struct rt6_info *rt6_select(struct rt6_info **head, int oif,
__FUNCTION__, head, head ? *head : NULL, oif); __FUNCTION__, head, head ? *head : NULL, oif);
for (rt = rt0, metric = rt0->rt6i_metric; for (rt = rt0, metric = rt0->rt6i_metric;
rt && rt->rt6i_metric == metric; rt && rt->rt6i_metric == metric && (!last || rt != rt0);
rt = rt->u.next) { rt = rt->u.next) {
int m; int m;
@ -343,9 +343,12 @@ static struct rt6_info *rt6_select(struct rt6_info **head, int oif,
(strict & RT6_SELECT_F_REACHABLE) && (strict & RT6_SELECT_F_REACHABLE) &&
last && last != rt0) { last && last != rt0) {
/* no entries matched; do round-robin */ /* no entries matched; do round-robin */
static spinlock_t lock = SPIN_LOCK_UNLOCKED;
spin_lock(&lock);
*head = rt0->u.next; *head = rt0->u.next;
rt0->u.next = last->u.next; rt0->u.next = last->u.next;
last->u.next = rt0; last->u.next = rt0;
spin_unlock(&lock);
} }
RT6_TRACE("%s() => %p, score=%d\n", RT6_TRACE("%s() => %p, score=%d\n",