nw_path_enumerate_gateways gives me no love

Question

Created Feb ’21

Replies 3

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Participants 2

This doesn't enumerate even though I do have a gateway.
Did anybody have any luck with this function? Its neighbor

Code Block nw_path_enumerate_interfaces()

works fine, connection is also fine.

Code Block auto path = nw_connection_copy_current_path(connection);
nw_path_enumerate_gateways(path, ^bool(nw_endpoint_t gateway) {
	os_log_info(oslog, "Gateway!");
	return true;
}

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Answer 1

DTS Engineer OP

Apple

Feb ’21

Accepted Answer

I’d completely forgotten about the gateways property. Nice catch!

Anyway, I tried this out and I saw some very strange behaviour. For example, when I open a TCP connection I see the gateways property populated when the connection is in the .preparing state and then depopulated when it gets into the .ready state. This last bit is definitely a bug, one that I filed for myself (r. 74269834).

Anyway, I do see the gateways property populated during the .preparing state, which might be enough for your needs. Do you also see that? If not, how are you testing it? I’m testing on an iPhone running iOS 14.4 on Wi-Fi with a TCP connection to example.com.

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Quinn “The Eskimo!” @ Developer Technical Support @ Apple
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0

Answer 2

hardloafz OP

Feb ’21

Nice!
Same thing on Big Sur - "preparing" has it, "ready" and after no more.
It also works in path_changed_handler block - kind of makes sense, I can stash it away there.
In my case this is a UDP connection, so this can be done without actually sending any packets.
Thank you, Quinn!

1

Answer 3

hardloafz OP

Feb ’21

Still spotty though, in case of a route pointing at VPN interface doesn't ever return anything. I'd expect it to work like

Code Block  route -n get <IP>

So gateway output points at your next hop.

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