Protocol not available (92) - Should this work in ubuntu?

I'm trying to use this in linux ubuntu to get the SO_ORIGINAL_DST from a tcp socket that is redirect via iptables.

Looking at some working golang code:

```go
const SO_ORIGINAL_DST = 80

...

addr, err := syscall.GetsockoptIPv6Mreq(int(clientConnFile.Fd()), syscall.IPPROTO_IP, SO_ORIGINAL_DST)
log.Debugf("getOriginalDst(): SO_ORIGINAL_DST=%+v\n", addr)
if err != nil {
log.Infof("GETORIGINALDST|%v->?->FAILEDTOBEDETERMINED|ERR: getsocketopt(SO_ORIGINAL_DST) failed: %v", srcipport, err)
return
}
```

It would appear that IPPROTO_IP = 0 and SO_ORIGINAL_DST = 80.

I would have expected (although I'm sure I'm completely missing something) the following code to work:

```javascript
const net = require('net');
const {getsockopt, setsockopt} = require('.');

const SOL_SOCKET = 1;

const server = net.createServer((c) => {
console.log(getsockopt(c, SOL_SOCKET, 80))
});
server.listen(8080, () => {
console.log('server bound');
});
```

But it returns:

```bash
/root/tproxy/node-sockopt/index.js:17
return _getsockopt(fd(socket), level, flagName)
^

TypeError: getsockopt failed: Protocol not available (92)
at getsockopt (/root/tproxy/node-sockopt/index.js:17:9)
at Socket. (/root/tproxy/node-sockopt/test.js:19:22)
at Socket.onListening (dgram.js:225:10)
at Socket.emit (events.js:315:20)
at startListening (dgram.js:150:10)
at dgram.js:345:7
at processTicksAndRejections (internal/process/task_queues.js:85:21)
```

It looks like my combination of 1 and 80 is either incorrect, or I'm using this completely wrong.

Next I ran a couple of loops to try every possibility I could think of. But I can't see 80 working for any level + flagName combination.

```javascript
for (let x = 0; x < 100; x++ ) {
for (let y = 0; y < 100; y++ ) {
try {
console.log({x,y}, getsockopt(c, x, y))
} catch (error) {
}
}
}
```

```text
{ x: 0, y: 1 } 0
{ x: 0, y: 2 } 64
{ x: 0, y: 3 } 0
{ x: 0, y: 4 } 74898496
{ x: 0, y: 6 } 0
{ x: 0, y: 7 } 0
{ x: 0, y: 8 } 0
{ x: 0, y: 9 } 0
{ x: 0, y: 10 } 1
{ x: 0, y: 11 } 0
{ x: 0, y: 12 } 0
{ x: 0, y: 13 } 0
{ x: 0, y: 14 } 1500
{ x: 0, y: 15 } 0
{ x: 0, y: 18 } 0
{ x: 0, y: 19 } 0
{ x: 0, y: 20 } 0
{ x: 0, y: 21 } 0
{ x: 0, y: 22 } 0
{ x: 0, y: 23 } 0
{ x: 0, y: 24 } 0
{ x: 0, y: 25 } 0
{ x: 0, y: 32 } 0
{ x: 0, y: 33 } 64
{ x: 0, y: 34 } 1
{ x: 0, y: 49 } 0
{ x: 0, y: 50 } 0
{ x: 1, y: 1 } 0
{ x: 1, y: 2 } 1
{ x: 1, y: 3 } 1
{ x: 1, y: 4 } 0
{ x: 1, y: 5 } 0
{ x: 1, y: 6 } 0
{ x: 1, y: 7 } 130560
{ x: 1, y: 8 } 131072
{ x: 1, y: 9 } 0
{ x: 1, y: 10 } 0
{ x: 1, y: 11 } 0
{ x: 1, y: 12 } 0
{ x: 1, y: 13 } 0
{ x: 1, y: 14 } 0
{ x: 1, y: 15 } 0
{ x: 1, y: 16 } 0
{ x: 1, y: 17 } 0
{ x: 1, y: 18 } 1
{ x: 1, y: 19 } 1
{ x: 1, y: 20 } 0
{ x: 1, y: 21 } 0
{ x: 1, y: 25 } 0
{ x: 1, y: 26 } 75578616
{ x: 1, y: 28 } 1020264458
{ x: 1, y: 29 } 0
{ x: 1, y: 30 } 0
{ x: 1, y: 34 } 0
{ x: 1, y: 35 } 0
{ x: 1, y: 36 } 0
{ x: 1, y: 37 } 0
{ x: 1, y: 38 } 6
{ x: 1, y: 39 } 10
{ x: 1, y: 40 } 0
{ x: 1, y: 41 } 0
{ x: 1, y: 43 } 0
{ x: 1, y: 44 } 0
{ x: 1, y: 45 } 0
{ x: 1, y: 46 } 0
{ x: 1, y: 47 } -1
{ x: 1, y: 48 } 64
{ x: 1, y: 49 } 0
{ x: 1, y: 55 } 2304
{ x: 1, y: 56 } 0
{ x: 1, y: 60 } 0
{ x: 6, y: 1 } 0
{ x: 6, y: 2 } 1448
{ x: 6, y: 3 } 0
{ x: 6, y: 4 } 7200
{ x: 6, y: 5 } 75
{ x: 6, y: 6 } 9
{ x: 6, y: 7 } 6
{ x: 6, y: 8 } 60
{ x: 6, y: 9 } 0
{ x: 6, y: 10 } 64076
{ x: 6, y: 11 } 1
{ x: 6, y: 12 } 1
{ x: 6, y: 13 } 7496290
{ x: 6, y: 16 } 0
{ x: 6, y: 17 } 0
{ x: 6, y: 18 } 0
{ x: 6, y: 19 } 0
{ x: 6, y: 23 } 0
{ x: 6, y: 24 } -1560222177
{ x: 6, y: 25 } 0
{ x: 6, y: 26 } 0
{ x: 6, y: 27 } 0
{ x: 6, y: 28 } -1645237088
{ x: 6, y: 30 } 0
{ x: 6, y: 31 } -1645237088
{ x: 6, y: 33 } 0
{ x: 6, y: 34 } 0
{ x: 41, y: 1 } 10
{ x: 41, y: 2 } 0
{ x: 41, y: 3 } 0
{ x: 41, y: 4 } 0
{ x: 41, y: 5 } 0
{ x: 41, y: 6 } -1645237088
{ x: 41, y: 8 } 0
{ x: 41, y: 11 } 0
{ x: 41, y: 16 } 64
{ x: 41, y: 17 } 4
{ x: 41, y: 18 } 64
{ x: 41, y: 19 } 1
{ x: 41, y: 23 } 1
{ x: 41, y: 24 } 1500
{ x: 41, y: 25 } 0
{ x: 41, y: 26 } 0
{ x: 41, y: 33 } 0
{ x: 41, y: 49 } 0
{ x: 41, y: 51 } 0
{ x: 41, y: 53 } 0
{ x: 41, y: 54 } -1645237088
{ x: 41, y: 55 } -1645237088
{ x: 41, y: 56 } 0
{ x: 41, y: 57 } -1645237088
{ x: 41, y: 58 } 0
{ x: 41, y: 59 } -1645237088
{ x: 41, y: 60 } 0
{ x: 41, y: 62 } 0
{ x: 41, y: 66 } 0
{ x: 41, y: 67 } 0
{ x: 41, y: 70 } 1
{ x: 41, y: 72 } 1280
{ x: 41, y: 73 } 0
{ x: 41, y: 74 } 0
{ x: 41, y: 75 } 0
{ x: 41, y: 76 } 0
{ x: 41, y: 77 } 0
{ x: 41, y: 78 } 0
```

Could you please point me in the right direction?

Start with index.js at the getsockopt wrapper and test.js at the server callback shown in the stack trace. Reproduce the Ubuntu failure using the reported socket and option values, then compare the JavaScript call with the Go example; done means identifying the supported invocation or documenting why this option is unavailable.

Written by the indexing model from the issue text.