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ofproto-dpif-trace: Fix infinite recirculation tracing.

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Trace attempts to process all the recirculations.  However, if there
is a recirculation loop, i.e. if every recirculation generates another
recirculation, this process will never stop.  It will grind until the
trace fills the system memory.

A simple reproducer:

  make sandbox
  ovs-vsctl add-br br0
  ovs-vsctl add-port br0 p1
  ovs-ofctl add-flow br0 "table=0,in_port=p1,ip,actions=ct(table=0)"
  ovs-appctl ofproto/trace br0 in_port=p1,ip

Limit the number of recirculations trace is processing with a fairly
arbitrary number - 4096 (loosely based on the resubmit limit, but
they are not actually related).

Not adding a test for this since it's only for a trace, but also
because the test may lead to OOM event in a system if the test fails,
which is not nice.

Fixes: e6bc8e7493 ("ofproto/trace: Add support for tracing conntrack recirculation")
Reported-by: Jaime Caamaño Ruiz <jcaamano@redhat.com>
Acked-by: Simon Horman <horms@ovn.org>
Signed-off-by: Ilya Maximets <i.maximets@ovn.org>
This commit is contained in:
Ilya Maximets
2024-02-22 16:06:32 +01:00
parent 99c86c6c46
commit 6fc215de30
1 changed files with 18 additions and 0 deletions
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18
ofproto/ofproto-dpif-trace.c
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@@ -845,17 +845,35 @@ ofproto_trace(struct ofproto_dpif *ofproto, const struct flow *flow,
bool names)
{
struct ovs_list recirc_queue = OVS_LIST_INITIALIZER(&recirc_queue);
int recirculations = 0;
ofproto_trace__(ofproto, flow, packet, &recirc_queue,
ofpacts, ofpacts_len, output, names);
struct oftrace_recirc_node *recirc_node;
LIST_FOR_EACH_POP (recirc_node, node, &recirc_queue) {
if (recirculations++ > 4096) {
ds_put_cstr(output, "\n\n");
ds_put_char_multiple(output, '=', 79);
ds_put_cstr(output, "\nTrace reached the recirculation limit."
" Sopping the trace here.");
ds_put_format(output,
"\nQueued but not processed: %"PRIuSIZE
" recirculations.",
ovs_list_size(&recirc_queue) + 1);
oftrace_recirc_node_destroy(recirc_node);
break;
}
ofproto_trace_recirc_node(recirc_node, next_ct_states, output);
ofproto_trace__(ofproto, &recirc_node->flow, recirc_node->packet,
&recirc_queue, ofpacts, ofpacts_len, output,
names);
oftrace_recirc_node_destroy(recirc_node);
}
/* Destroy remaining recirculation nodes, if any. */
LIST_FOR_EACH_POP (recirc_node, node, &recirc_queue) {
oftrace_recirc_node_destroy(recirc_node);
}
}
void