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fix enforcement of tcp-clients (v1)

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tcp-clients settings could be exceeded in some cases by
creating more and more active TCP clients that are over
the set quota limit, which in the end could lead to a
DoS attack by e.g. exhaustion of file descriptors.

If TCP client we're closing went over the quota (so it's
not attached to a quota) mark it as mortal - so that it
will be destroyed and not set up to listen for new
connections - unless it's the last client for a specific
interface.

(cherry picked from commit eafcff07c25bdbe038ae1e4b6660602a080b9395)
This commit is contained in:
Witold Kręcicki
2019-01-03 14:17:43 +01:00
committed by Evan Hunt
parent 94ba15ea38
commit 9e7617cc84
1 changed files with 12 additions and 1 deletions
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13
lib/ns/client.c
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@@ -441,8 +441,19 @@ exit_check(ns_client_t *client) {
isc_socket_detach(&client->tcpsocket);
}
if (client->tcpquota != NULL)
if (client->tcpquota != NULL) {
isc_quota_detach(&client->tcpquota);
} else {
/*
* We went over quota with this client, we don't
* want to restart listening unless this is the
* last client on this interface, which is
* checked later.
*/
if (TCP_CLIENT(client)) {
client->mortal = true;
}
}
if (client->timerset) {
(void)isc_timer_reset(client->timer,