net: bad shadowing in ipsock_posix.go; unhelpful ip.String result

[ianlancetaylor]

On tip, the file net/ipsock_posix.go has these lines

        if ip = ip.To4(); ip == nil {
            return nil, &AddrError{Err: "non-IPv4 address", Addr: ip.String()}
        }

It's pretty clear here that the ip.String stored in AddrError is using the wrong ip. This code will always set the Addr field to "<nil>".

The same error occurs a few lines down using To16.

I would send in the obvious fix, but the effect would be to change the Addr field from "<nil>" to "?", which is only barely an improvement. We probably need to fix these cases in ipsock_posix.go and also fix IP.String to produce more useful output for an unrecognized length.

[ianlancetaylor]

CC @mikioh

[hbhasker]

Would it make sense to change the name and replace it with something like

Addr: fmt.Sprintf("%v", origIP)

That will print the IP as a byte array, which is probably the right thing to do rather than have ip.String() return an invalid ip representation?

[gopherbot]

CL https://golang.org/cl/21642 mentions this issue.