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Accept wildcards in mqtt subscription prefix #1497

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Accept wildcards in mqtt subscription prefix #1497

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e9446b2
Accept wildcards in mqtt subscription prefix
cvdenzen Aug 16, 2021
45cb263
Accept wildcards in mqtt subscription prefix
cvdenzen Aug 18, 2021
b36c846
Accept wildcards in mqtt subscription prefix
cvdenzen Aug 18, 2021
aeb62d2
Merge remote-tracking branch 'origin/carl' into carl
cvdenzen Aug 22, 2021
4a8bb44
Merge remote-tracking branch 'origin/carl' into carl
cvdenzen Aug 22, 2021
75e131b
Merge remote-tracking branch 'origin/carl' into carl
cvdenzen Aug 22, 2021
23eb210
Merge remote-tracking branch 'origin/carl' into carl
cvdenzen Aug 22, 2021
305992b
Merge branch 'carl' of https://github.com/cvdenzen/MySensors into carl
cvdenzen Aug 22, 2021
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Merge branch 'development' into carl
cvdenzen Mar 24, 2024
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Makefile.inc under version control
cvdenzen Mar 24, 2024
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24 changes: 20 additions & 4 deletions core/MyProtocol.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -111,14 +111,30 @@ bool protocolMQTT2MyMessage(MyMessage &message, char *topic, uint8_t *payload,
const unsigned int length)
{
char *str, *p;
uint8_t index = 0;
int8_t index = -1;
message.setSender(GATEWAY_ADDRESS);
message.setLast(GATEWAY_ADDRESS);
message.setEcho(false);
for (str = strtok_r(topic + strlen(MY_MQTT_SUBSCRIBE_TOPIC_PREFIX) + 1, "/", &p);

// The subscription prefix can contain wildcards, but only the + wildcard.
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@Yveaux Yveaux Aug 22, 2021 •
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Why is only the single-level + wildcard supported?
If we add support for wildcards, users will expect to be able to use multi-level # wildcards too.
If you parse right-to-left for the mysensors message field you could support any wildcard.

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The MQTT multi-level wildcard (#) is only allowed at the end of the topic. Because the prefix is always followed by other levels it cannot contain the # wildcard, although "my" code wouldn't complain about it.

The code only checks the number of / characters.
The syntactical check is left to the MQTT broker. That was already the case and I think that is right. I have browsed the MySensors code and checked all code where the PREFIX is used and none of needed a change.

// e.g. subscription prefix "+/mysensors", actual prefix "foo/mysensors"
// To fetch only the part after the mqtt prefix, discard as many
// mqtt levels (between / characters) as in the subscription prefix.
// Make a copy of the subscribe prefix because strtok is allowed to change the string.
char subscribeTopicPrefix[strlen(MY_MQTT_SUBSCRIBE_TOPIC_PREFIX) + 1];
strcpy(subscribeTopicPrefix,MY_MQTT_SUBSCRIBE_TOPIC_PREFIX);
char *strPrefix, *savePointerPrefix;
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What's the increase in ram/flash for this change?

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The savepointer (4 bytes?) is stored on stack I guess.
The increase in ram (stack use?) for the copy of the prefix string will be the length of the prefix plus 1.
The default value for the prefix is mygateway1-in, length is 13, so it will use 14 bytes on the stack. Your comment made me think about this memory usage. Actually I think malloc/free would be safer. Or maybe choose in runtime between stack and malloc depending on the prefix length? The length of the string is known at compile time, but I don't think that will help. I am not an expert in this subject.

Flash use? Is that the code length? The answer is: I don't know.

I compiled and ran it only on a raspberry pi 2, not on an Arduino.

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In core/MyGatewayTransportMQTTClient.cpp, method reconnectMQTT, there is also a local variable inTopic with a length of the prefix plus 10. So I think it is acceptable to have it as a stack variable.

for (str = strtok_r(topic, "/", &p),
strPrefix = strtok_r(subscribeTopicPrefix,"/", &savePointerPrefix);
str && index < 5;
str = strtok_r(NULL, "/", &p), index++
str = strtok_r(NULL, "/", &p),
strPrefix = strtok_r(NULL, "/", &savePointerPrefix)
) {
// Increment index (init value is -1) if we have consumed the mqtt subscription prefix
if (!strPrefix) {
index++;
}
//GATEWAY_DEBUG(PSTR("GWT:TPS:Index=%d, mqttstr=%s, prefixtoken=%s\n"), index, str,strPrefix);
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Remove dead code

switch (index) {
case 0:
// Node id
Expand Down Expand Up @@ -163,5 +179,5 @@ bool protocolMQTT2MyMessage(MyMessage &message, char *topic, uint8_t *payload,
}
}
// Return true if input valid
return (index == 5);
return (index == 4);
}