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Fix incorrect scaling of weight 0 SRV records

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Loosely based on patch by Nico.
This commit is contained in:
Viktor Dukhovni
2016-12-12 17:51:08 -05:00
parent a7f8732d79
commit 32f8564296
1 changed files with 30 additions and 20 deletions
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38
lib/roken/resolve.c
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@@ -660,10 +660,13 @@ rk_dns_srv_order(struct rk_dns_reply *r)
headp = &r->head;
for (ss = srvs; ss < srvs + num_srv; ) {
int sum, zeros, rnd, count;
int sum, zeros, rnd, count; /* zeros -> weight scaling */
struct rk_resource_record **ee, **tt;
/* find the last record with the same priority and count the
sum of all weights */
/*
* find the last record with the same priority and count the sum of all
* weights
*/
for (sum = 0, zeros = 0, tt = ss; tt < srvs + num_srv; tt++) {
assert(*tt != NULL);
if((*tt)->u.srv->priority != (*ss)->u.srv->priority)
@@ -672,34 +675,41 @@ rk_dns_srv_order(struct rk_dns_reply *r)
if ((*tt)->u.srv->weight == 0)
zeros++;
}
/* With no zeros, add 0 and scale * 1 */
sum += zeros ? zeros : zeros++;
/* make sure scale (`zeros') is > 0 then scale out */
sum += zeros ? 1 : zeros++;
sum *= zeros;
ee = tt;
/* ss is now the first record of this priority and ee is the
first of the next */
/*
* ss is now the first record of this priority and ee is the first of
* the next or the first past the end of srvs
*/
while (ss < ee) {
rnd = rk_random() % sum + 1;
for(count = 0, tt = ss; ; tt++) {
for (count = 0, tt = ss; tt < ee; tt++) {
if (*tt == NULL)
continue;
count += (*tt)->u.srv->weight * zeros;
continue; /* this one's already been picked */
if ((*tt)->u.srv->weight == 0)
count++;
else
count += (*tt)->u.srv->weight * zeros;
if (count >= rnd)
break;
}
assert(tt < ee);
/* insert the selected record at the tail (of the head) of
the list */
/* push the selected record */
(*tt)->next = *headp;
*headp = *tt;
headp = &(*tt)->next;
sum -= (*tt)->u.srv->weight * zeros;
/*
* reduce the sum so the next iteration is sure to reach the random
* total after examining all the remaining records.
*/
if ((*tt)->u.srv->weight == 0)
sum--;
else
sum -= (*tt)->u.srv->weight * zeros;
*tt = NULL;
while (ss < ee && *ss == NULL)
ss++;