On 8 Jul 2021, at 22:18, Ilya Maximets wrote:
> On 5/17/21 3:20 PM, Eelco Chaudron wrote:
>> When OVs installs the flower rule, it only checks for the OK from the
>> kernel. It does not check if the rule requested matches the one
>> actually programmed. This change will add this check and warns the
>> user if this is not the case.
>>
>> Signed-off-by: Eelco Chaudron <echau...@redhat.com>
>> ---
>> lib/tc.c | 59 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
>> 1 file changed, 59 insertions(+)
>>
>> diff --git a/lib/tc.c b/lib/tc.c
>> index a27cca2cc..e134f6a06 100644
>> --- a/lib/tc.c
>> +++ b/lib/tc.c
>> @@ -2979,6 +2979,50 @@ nl_msg_put_flower_options(struct ofpbuf *request,
>> struct tc_flower *flower)
>> return 0;
>> }
>>
>> +static bool
>> +cmp_tc_flower_match_action(const struct tc_flower *a,
>> + const struct tc_flower *b)
>> +{
>> + if (memcmp(&a->mask, &b->mask, sizeof a->mask)) {
>> + VLOG_DBG_RL(&error_rl, "tc flower compare failed mask compare");
>> + return false;
>> + }
>> +
>> + /* We can not memcmp() the key as some keys might be set while the mask
>> + * is not.*/
>> +
>> + for (int i = 0; i < sizeof a->key; i++) {
>> + uint8_t mask = ((uint8_t *)&a->mask)[i];
>> + uint8_t key_a = ((uint8_t *)&a->key)[i] & mask;
>> + uint8_t key_b = ((uint8_t *)&b->key)[i] & mask;
>> +
>> + if (key_a != key_b) {
>> + VLOG_DBG_RL(&error_rl, "tc flower compare failed key compare at
>> "
>> + "%d", i);
>> + return false;
>> + }
>> + }
>> +
>> + /* Compare the actions. */
>> + const struct tc_action *action_a = a->actions;
>> + const struct tc_action *action_b = b->actions;
>> +
>> + if (a->action_count != b->action_count) {
>> + VLOG_DBG_RL(&error_rl, "tc flower compare failed action length
>> check");
>> + return false;
>> + }
>> +
>> + for (int i = 0; i < a->action_count; i++, action_a++, action_b++) {
>> + if (memcmp(action_a, action_b, sizeof *action_a)) {
>> + VLOG_DBG_RL(&error_rl, "tc flower compare failed action compare
>> "
>> + "for %d", i);
>> + return false;
>> + }
>> + }
>> +
>> + return true;
>> +}
>> +
>> int
>> tc_replace_flower(struct tcf_id *id, struct tc_flower *flower)
>> {
>> @@ -3010,6 +3054,21 @@ tc_replace_flower(struct tcf_id *id, struct tc_flower
>> *flower)
>>
>> id->prio = tc_get_major(tc->tcm_info);
>> id->handle = tc->tcm_handle;
>> +
>> + if (id->prio != TC_RESERVED_PRIORITY_POLICE) {
>> + struct tc_flower flower_out;
>> + struct tcf_id id_out;
>> + int ret;
>> +
>> + ret = parse_netlink_to_tc_flower(reply, &id_out, &flower_out,
>> + false);
>> +
>> + if (ret || !cmp_tc_flower_match_action(flower, &flower_out)) {
>> + VLOG_WARN_RL(&error_rl, "Kernel flower acknowledgment does "
>> + "not match request!\n Set dpif_netlink to dbg
>> to "
>> + "see which rule caused this error.");
>
> So we're only printing the warning and not reverting the change
> and not returning an error, right? So, OVS will continue to
> work with the incorrect rule installed?
> I think, we should revert the incorrect change and return the
> error, so the flow could be installed to the OVS kernel datapath,
> but maybe this is a task for a separate change.
>
> What do you think?
The goal was to make sure we do not break anything, in case there is an
existing kernel bug. As unfortunately, we are missing a good set of TC unit
tests.
With the "warning only" option, we can backport this. And if in the field we do
not see any (false) reports, a follow-up patch can do as you suggested.
//Eelco
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