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Fix hostname resolution for proxied connections #913

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Fix hostname resolution for proxied connections #913

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f162017
Fix hostname resolution for proxied connections
bartosz822 May 15, 2023
465b0e6
Do not use `InetSocketAddress.createUnresolved` for uris already cont…
bartosz822 May 15, 2023
8d9679d
Add unit test
bartosz822 Oct 31, 2025
45da71d
Add enableInetAddressCreateUnresolved option
bartosz822 Nov 5, 2025
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4 changes: 3 additions & 1 deletion src/main/java/io/nats/client/impl/SocketDataPort.java
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Original file line number Diff line number Diff line change
Expand Up @@ -74,7 +74,9 @@ public void connect(@NonNull NatsConnection conn, @NonNull NatsUri nuri, long ti
socket = connectToFastestIp(options, host, port, (int) timeout);
} else {
socket = createSocket(options);
socket.connect(new InetSocketAddress(host, port), (int) timeout);
InetSocketAddress inetSocketAddress = (options.isNoResolveHostnames() && !nuri.hostIsIpAddress()) ?
InetSocketAddress.createUnresolved(host, port) : new InetSocketAddress(host, port);
socket.connect(inetSocketAddress, (int) timeout);
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@scottf scottf Oct 30, 2025

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Also, resolution is supposed to be done before it gets here. Look in the NatsConnection line 540 and work backward. Also look in NatsServerPool, where it does resolveHostToIps.
Resolution does not belong here, it belongs further back up the call chain.

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@bartosz822 bartosz822 Oct 31, 2025

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I agree that the resolution probably belongs further back up the call chain. However the problem is that even if it didn't happen earlier, the default constructor of InetSocketAddress will perform it.

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@scottf scottf Oct 31, 2025

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Would it be correct to say that this is only an issue in some cases AND only when a proxy is provided?

Why can't the proxy be expected to do this work?

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@bartosz822 bartosz822 Oct 31, 2025

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Yes it is an issue only in some cases, it only really is an issue if a proxy is doing whitelisting based on domain names, which is a common use-case in secure/enterprise environments.

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@scottf scottf Oct 31, 2025

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So the question remains, why can't this be part of the Option.proxy's responsibility? If it can be, we can simply add documentation to that effect.

I'm suspicious how common this really is in secure/enterprise environments. Enterprises are the most common users of this client, it's been around for 7 years, and this is the first time I'm hearing about the issue.

At a minimum we need an opt in solution to ensure backward compatibility, like isEnableInetAddressCreateUnresolved or something like that.

if (options.isEnableFastFallback()) {
    socket = connectToFastestIp(options, host, port, (int) timeout);
} 
else {
    InetSocketAddress inetSocketAddress;
    if (options.isEnableInetAddressUnresolved() && !nuri.hostIsIpAddress()) {
        inetSocketAddress = InetSocketAddress.createUnresolved(host, port);
    }
    else {
        inetSocketAddress = new InetSocketAddress(host, port);
    }
    socket.connect(inetSocketAddress, (int) timeout);
}

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@scottf scottf Nov 5, 2025

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@bartosz822 bump

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@bartosz822 bartosz822 Nov 5, 2025

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Added the suggested option.

I don't understand how it could be part of the Option.proxy responsibility? What do you mean by that?

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@scottf scottf Nov 5, 2025

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The proxy seems to have some flexibility. You test has a proxy implementation. It seems like code could just go in there. But at least there is a backward compatible way now, so I think that's fine.

}

if (options.getSocketReadTimeoutMillis() > 0) {
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