Support for showing internet connectivity through proxy servers

[icyflame]

Currently, if I run this from the CLI, and am behind a HTTP/HTTPS proxy, then, it returns offline. Although, I can access internet through the browser, and using the HTTP protocol from the CLI. (I have exported the http_proxy and https_proxy ENV variables)

[silverwind]

That would mean both the DNS and handshake check fail, which is strange. I assume your DNS is proxied too. Could you post the output of dig (no argument) and nc -v google.com 80? Maybe that gives any clue.

[icyflame]

I am sorry, currently, I am not in that environment. I will post the required output when I get back. (Will be a while or that to happen)

What do you mean by:

DNS is proxied too

[silverwind]

I mean something is intercepting DNS packets and answering on behalf of the real targeted DNS servers.

[sindresorhus]

ping @icyflame

[icyflame]

@sindresorhus Still not back in the environment with proxy servers, will post the required output once I am back.
(Around July 2nd week, closing this issue till then)

[sindresorhus]

Ok, make sure you try the latest release when you do. We've done some improvements.

[silverwind]

I played a bit with my router set to intercepting dns, and surprisingly it didn't alter the packet (source address was still the original one). Maybe your proxy was altering the dns transaction id. I removed that check now because it wasn't really helpful, and we should have a new version pretty momentarily, maybe you can give that one a try.

Still puzzles me why the second check (TCP handshake on port 80) failed for you though.

[icyflame]

The problem still exists. These are the requested outputs :-

$ dig

; <<>> DiG 9.9.5-3ubuntu0.1-Ubuntu <<>>
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: FORMERR, id: 1325
;; flags: qr rd ra; QUERY: 0, ANSWER: 0, AUTHORITY: 0, ADDITIONAL: 0

;; WARNING: EDNS query returned status FORMERR - retry with '+noedns'

;; Query time: 1 msec
;; SERVER: 127.0.1.1#53(127.0.1.1)
;; WHEN: Wed Jul 22 15:18:47 IST 2015
;; MSG SIZE  rcvd: 12

$ nc -v www.google.com 80
nc: connect to www.google.com port 80 (tcp) failed: Connection refused
nc: connect to www.google.com port 80 (tcp) failed: Network is unreachable

---

/ @silverwind @sindresorhus

[silverwind]

Interesting. Could you also post dig +noedns? Also, do you know what software that proxy is running?

[icyflame]

$ dig +noedns

; <<>> DiG 9.9.5-3ubuntu0.1-Ubuntu <<>> +noedns
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 23140
;; flags: qr rd ra; QUERY: 1, ANSWER: 13, AUTHORITY: 0, ADDITIONAL: 14

;; QUESTION SECTION:
;.              IN  NS

;; ANSWER SECTION:
.           355677  IN  NS  f.root-servers.net.
.           355677  IN  NS  j.root-servers.net.
.           355677  IN  NS  a.root-servers.net.
.           355677  IN  NS  l.root-servers.net.
.           355677  IN  NS  h.root-servers.net.
.           355677  IN  NS  m.root-servers.net.
.           355677  IN  NS  i.root-servers.net.
.           355677  IN  NS  g.root-servers.net.
.           355677  IN  NS  d.root-servers.net.
.           355677  IN  NS  e.root-servers.net.
.           355677  IN  NS  c.root-servers.net.
.           355677  IN  NS  k.root-servers.net.
.           355677  IN  NS  b.root-servers.net.

;; ADDITIONAL SECTION:
a.root-servers.net. 528457  IN  A   198.41.0.4
b.root-servers.net. 14695   IN  A   192.228.79.201
b.root-servers.net. 14695   IN  AAAA    2001:500:84::b
c.root-servers.net. 14695   IN  A   192.33.4.12
c.root-servers.net. 14695   IN  AAAA    2001:500:2::c
d.root-servers.net. 14695   IN  A   199.7.91.13
d.root-servers.net. 14695   IN  AAAA    2001:500:2d::d
e.root-servers.net. 14695   IN  A   192.203.230.10
f.root-servers.net. 254493  IN  A   192.5.5.241
f.root-servers.net. 14695   IN  AAAA    2001:500:2f::f
g.root-servers.net. 269281  IN  A   192.112.36.4
h.root-servers.net. 269281  IN  A   128.63.2.53
h.root-servers.net. 14695   IN  AAAA    2001:500:1::803f:235
i.root-servers.net. 14695   IN  A   192.36.148.17

;; Query time: 1 msec
;; SERVER: 127.0.1.1#53(127.0.1.1)
;; WHEN: Wed Jul 22 15:48:44 IST 2015
;; MSG SIZE  rcvd: 512

No, I am sorry, I don't have any idea as to what software the proxy is running.

[silverwind]

Thanks, that should suffice. I'll have to read up on EDNS now :)

[kokarn]

Any progress on this? Running in to the same problem.

[icyflame]

No, not really.

cc @silverwind and @sindresorhus

[kokarn]

It seems like #22 might be related and a sound workaround. Would love to test.

[icyflame]

@kokarn Why a "sound workaround"? I just tried to dig a couple of name servers (including google's 8.8.8.8 / ns1) and it didn't work.

[kokarn]

As far as I understand that would make online-detection actually work as intended, eg give us online if online even behind a proxy.

Seems to work through our proxy at least.

[silverwind]

Moving this topic to sindresorhus/is-reachable#7.