net: should expand IP address 1.1 to 1.0.0.1

[perpetual-hydrofoil]

nameserver 1.1 in /etc/resolv.conf not parsed

What did you do?

go get github.com/kevinburke/twilio-go

What did you see instead?

go get github.com/kevinburke/twilio-go: module github.com/kevinburke/twilio-go:
Get https://proxy.golang.org/github.com/kevinburke/twilio-go/@v/list:
dial tcp: lookup proxy.golang.org on [::1]:53: dial tcp [::1]:53:
connect: connection refused

Workaround

Change 1.1 to 1.0.0.1 or 1.1.1.1 in /etc/resolv.conf

# /etc/resolv.conf
nameserver 1.1

[davecheney]

Looking at http://man7.org/linux/man-pages/man5/resolv.conf.5.html, name server is defined to be an IPV4 or IPV6 address, nameserver 1.1 appears to be neither so I don't see how it could be used as a DNS server.

Why did you expect that Go would be able to use 1.1 as a nameserver?

[perpetual-hydrofoil]

1.1 should expand to 1.0.0.1

Examples:

Try putting nameserver 1.1 into resolv.conf and then ping something; your resolver should properly use that resolver.

Or, just ping 1.1 or traceroute 1.1, or ping 127.1. On Linux (but apparently not Mac), you can even ping 0 (which expands to 0.0.0.0)

CloudFlare's public nameservers are documented at: https://1.1/ (which should be a working link in your browser)

dig google.com @1.1
....
;; ANSWER SECTION:
google.com.     120 IN  A   172.217.6.142
....
;; SERVER: 1.0.0.1#53(1.0.0.1)

The expansion rules are covered here (part of POSIX / IEEE 1003.1).

http://man7.org/linux/man-pages/man3/inet_addr.3.html

#! /usr/bin/env python

import socket
print(socket.gethostbyname('1.1'))
# '1.0.0.1'

It appears that net does not properly expand and parse IPv4 in this format, so that might be the underlying cause here.

[ianlancetaylor]

This is part of POSIX (IEEE 1003.1).

Do you have a citation for that? I didn't think that IEEE 1003.1 talked about networking at all. Thanks.

[perpetual-hydrofoil]

package main

import (
    "fmt"
    "net"
    "os"
)

func main() {
    ip := net.ParseIP("1.1")
    if ip.To4() == nil {
        fmt.Printf("IPv4 expansion is not working.")
        os.Exit(1)
    }
}

[rhedile]

Sorry Ian, but technically he is right. Couldn't find a way to link into the relevant part of the spec. Rgds, Nigel Vickers The Open Group Base Specifications Issue 7, 2018 edition IEEE Std 1003.1™-2017 (Revision of IEEE Std 1003.1-2008) Copyright © 2001-2018 IEEE and The Open Group #include <arpa/inet.h> in_addr_t inet_addr(const char *cp); char *inet_ntoa(struct in_addr in); DESCRIPTION The inet_addr() function shall convert the string pointed to by cp, in the standard IPv4 dotted decimal notation, to an integer value suitable for use as an Internet address. The inet_ntoa() function shall convert the Internet host address specified by in to a string in the Internet standard dot notation. The inet_ntoa() function need not be thread-safe. All Internet addresses shall be returned in network order (bytes ordered from left to right). Values specified using IPv4 dotted decimal notation take one of the following forms: a.b.c.d When four parts are specified, each shall be interpreted as a byte of data and assigned, from left to right, to the four bytes of an Internet address. a.b.c When a three-part address is specified, the last part shall be interpreted as a 16-bit quantity and placed in the rightmost two bytes of the network address. This makes the three-part address format convenient for specifying Class B network addresses as "128.net.host". a.b When a two-part address is supplied, the last part shall be interpreted as a 24-bit quantity and placed in the rightmost three bytes of the network address. This makes the two-part address format convenient for specifying Class A network addresses as "net.host". a When only one part is given, the value shall be stored directly in the network address without any byte rearrangement. All numbers supplied as parts in IPv4 dotted decimal notation may be decimal, octal, or hexadecimal, as specified in the ISO C standard (that is, a leading 0x or 0X implies hexadecimal; otherwise, a leading '0' implies octal; otherwise, the number is interpreted as decimal).

…

On Tue, 28 Jan 2020 at 16:25, Ian Lance Taylor ***@***.***> wrote: This is part of POSIX (IEEE 1003.1). Do you have a citation for that? I didn't think that IEEE 1003.1 talked about networking at all. Thanks. — You are receiving this because you are subscribed to this thread. Reply to this email directly, view it on GitHub <#36822?email_source=notifications&email_token=ABAB73CP5DM7F6MOV672SZ3RABE5JA5CNFSM4KMLTTQ2YY3PNVWWK3TUL52HS4DFVREXG43VMVBW63LNMVXHJKTDN5WW2ZLOORPWSZGOEKDWG6A#issuecomment-579298168>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/ABAB73GUHRTR33H4XTS7SULRABE5JANCNFSM4KMLTTQQ> .

[ianlancetaylor]

Thanks for the pointer.

[davecheney]

Indeed, TIL!

http://1089054054/

[davecheney]

Well, that's just about all the internet I can handle today. Good evening