net: LookupPort translates negative numbers into valid port numbers on Windows without error.

[ChrisHines]

OS: Windows 7 Professional, SP1.
Go: go1.5.1 windows/amd64

The following program prints 65527 on Windows, but panics on Linux.

package main

import (
    "fmt"
    "net"
)

func main() {
    port, err := net.LookupPort("tcp", "-9")
    if err != nil {
        panic(err)
    }
    fmt.Println(port)
}

Also "-2000000000" returns 27648 and "-4294967295" or numerically smaller returns 1.

[bradfitz]

/cc @alexbrainman

I guess this is the newLookupPort path?

func newLookupPort(network, service string) (int, error) {
        acquireThread()
        defer releaseThread()
        var stype int32
        switch network {
        case "tcp4", "tcp6":
                stype = syscall.SOCK_STREAM
        case "udp4", "udp6":
                stype = syscall.SOCK_DGRAM
        }
        hints := syscall.AddrinfoW{
                Family:   syscall.AF_UNSPEC,
                Socktype: stype,
                Protocol: syscall.IPPROTO_IP,
        }
        var result *syscall.AddrinfoW
        e := syscall.GetAddrInfoW(nil, syscall.StringToUTF16Ptr(service), &hints, &result)
        if e != nil {
                return 0, &DNSError{Err: os.NewSyscallError("getaddrinfow", e).Error(), Name: network + "/" + service}
        }
        defer syscall.FreeAddrInfoW(result)
        if result == nil {
                return 0, &DNSError{Err: syscall.EINVAL.Error(), Name: network + "/" + service}
        }
        addr := unsafe.Pointer(result.Addr)
        switch result.Family {
        case syscall.AF_INET:
                a := (*syscall.RawSockaddrInet4)(addr)
                return int(syscall.Ntohs(a.Port)), nil
        case syscall.AF_INET6:
                a := (*syscall.RawSockaddrInet6)(addr)
                return int(syscall.Ntohs(a.Port)), nil
        }
        return 0, &DNSError{Err: syscall.EINVAL.Error(), Name: network + "/" + service}
}

[alexbrainman]

Let me play with this a little bit.

Alex

[alexbrainman]

@ChrisHines your program prinsts:

panic: invalid port -9

goroutine 1 [running]:
main.main()
        /root/src/t/main.go:11 +0x9b

on my windows 7 amd64 (as expected). Mind you, I use current Go tip. We also have TestLookupPort in net package that checks that net.LookupPort("tcp", "-1") fails. Can you run that test to see if it PASSes? You can add your values to the test to see what is going on. You can also debug this yourself (since it is broken for you). Just add fmt.Printf or similar everywhere in net as you descend into net.LookupPort call. Please let us know how you went. Thank you.

Alex

[ChrisHines]

@alexbrainman This issue was fixed by b50b21d.