Re: Recv failure error under censorship conditions

From: Henrik Holst via curl-library <curl-library_at_cool.haxx.se>
Date: Thu, 15 Jul 2021 15:10:28 +0200

just fyi this is how the same request looks from here in Europe (added -v
to show more verbose):

henrik_at_ubuntu:~/utveckling/other/mdf_client$ curl -Iv google.com
* Trying 172.217.20.46:80...
* TCP_NODELAY set
* Connected to google.com (172.217.20.46) port 80 (#0)
> HEAD / HTTP/1.1
> Host: google.com
> User-Agent: curl/7.68.0
> Accept: */*
>
* Mark bundle as not supporting multiuse
< HTTP/1.1 301 Moved Permanently
HTTP/1.1 301 Moved Permanently
< Location: http://www.google.com/
Location: http://www.google.com/
< Content-Type: text/html; charset=UTF-8
Content-Type: text/html; charset=UTF-8
< Date: Thu, 15 Jul 2021 13:08:31 GMT
Date: Thu, 15 Jul 2021 13:08:31 GMT
< Expires: Sat, 14 Aug 2021 13:08:31 GMT
Expires: Sat, 14 Aug 2021 13:08:31 GMT
< Cache-Control: public, max-age=2592000
Cache-Control: public, max-age=2592000
< Server: gws
Server: gws
< Content-Length: 219
Content-Length: 219
< X-XSS-Protection: 0
X-XSS-Protection: 0
< X-Frame-Options: SAMEORIGIN
X-Frame-Options: SAMEORIGIN

<
* Connection #0 to host google.com left intact

/HH


Den tors 15 juli 2021 kl 15:07 skrev Henrik Holst <
henrik.holst_at_millistream.com>:

> As your own research shows they are most definitely filtering based on
> user-agent. Probably done in order to filter out access from various mobile
> phone apps.
>
> There could of course be other types of filters as well but your example
> clearly demonstrates the presence of a user-agent filter for web browsing.
> I assume that https is blocked completely?
>
> /HH
>
> Den tors 15 juli 2021 kl 15:00 skrev Gealber Morales via curl-library <
> curl-library_at_cool.haxx.se>:
>
>> Hello there
>>
>> Before I start to describe the technical problem that I have I should
>> clarify that I don't think this is a problem of cURL, but is related to it,
>> and maybe you know the reason of the error. In case is not related to cURL,
>> you could tell me I would understand. Ok, let me describe the problem that
>> I'm facing, first I live in Cuba. Due to the events of July 11, the
>> government limited the usage of mobile data to zero, literally zero. Until
>> yesterday, that they enable it again, but with a lot of restrictions, for
>> example you couldn't access any social network without a VPN. Now in some
>> way this seems to be affecting the use of cURL, and it would be nice to
>> know what could be some possible cause of this. Before these limitations, I
>> could use cURL without any problem, so again is not a cURL problem, but I
>> found it interesting what is happening. Behavior that is happening right
>> now, when I try to make a `HEAD` request to google or any other website,
>> I've tried with literally 7 websites, I get this message:
>>
>> ```
>> curl -I google.com
>> curl: (56) Recv failure: Conexión reinicializada por la máquina remota
>> ```
>> The curious thing is that I can access google from the browser, and I
>> tried another thing, I made the same request changing the `User-Agent` to
>> simulate the request of a browser:
>>
>> ```
>> curl -I -H "User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64)
>> AppleWebKit/537.36 (KHTML, like Gecko) Chrome/74.0.3729.169 Safari/537.36"
>> google.com
>>
>> HTTP/1.1 301 Moved Permanently
>> Location: http://www.google.com/
>> Content-Type: text/html; charset=UTF-8
>> BFCache-Opt-In: unload
>> Date: Thu, 15 Jul 2021 12:49:40 GMT
>> Expires: Sat, 14 Aug 2021 12:49:40 GMT
>> Cache-Control: public, max-age=2592000
>> Server: gws
>> Content-Length: 219
>> X-XSS-Protection: 0
>> X-Frame-Options: SAMEORIGIN
>> ```
>> In this case, I get the expected response, which is a redirection.
>>
>> I imagine that they are blocking or making some filtering by `User-Agent`
>> but not sure if it could be other reason, maybe you have an idea of what
>> could be happening.
>>
>> Thanks in advance, and sorry if this is offtopic but I found it curious
>> and is related to cURL in some way.
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Received on 2021-07-15