[Sonny_Jim]

Something odd is happening with curl.  It appears to be failing left, right and centre in my logs.  So let's take an example URL:

http://mirrors.kodi.tv/addons/krypton/pl...fanart.jpg

wget http://mirrors.kodi.tv/addons/krypton/pl...fanart.jpg
--2018-01-16 16:56:41--  http://mirrors.kodi.tv/addons/krypton/pl...fanart.jpg
Resolving mirrors.kodi.tv (mirrors.kodi.tv)... 89.16.176.16
Connecting to mirrors.kodi.tv (mirrors.kodi.tv)|89.16.176.16|:80... connected.
HTTP request sent, awaiting response... 302 Moved Temporarily
Location: http://ftp.halifax.rwth-aachen.de/xbmc/a...fanart.jpg [following]
--2018-01-16 16:56:42--  http://ftp.halifax.rwth-aachen.de/xbmc/a...fanart.jpg
Resolving ftp.halifax.rwth-aachen.de (ftp.halifax.rwth-aachen.de)... 137.226.34.46, 2a00:8a60:e012:a00::21
Connecting to ftp.halifax.rwth-aachen.de (ftp.halifax.rwth-aachen.de)|137.226.34.46|:80... connected.
HTTP request sent, awaiting response... 200 OK
Length: 465479 (455K) [image/jpeg]
Saving to: ‘fanart.jpg.1’

fanart.jpg.1                            100%[==============================================================================>] 454.57K  66.0KB/s   in 6.9s

2018-01-16 16:56:50 (66.0 KB/s) - ‘fanart.jpg.1’ saved [465479/465479]

As you can see, that works fine, now let's try it with curl (which Kodi uses extensively):

curl -Lv http://mirrors.kodi.tv/addons/krypton/pl...fanart.jpg
* Hostname was NOT found in DNS cache
*   Trying 89.16.176.16...
* Connected to mirrors.kodi.tv (89.16.176.16) port 80 (#0)
> GET /addons/krypton/plugin.video.giantbomb/fanart.jpg HTTP/1.1
> User-Agent: curl/7.38.0
> Host: mirrors.kodi.tv
> Accept: */*
>
< HTTP/1.1 302 Moved Temporarily
* Server nginx is not blacklisted
< Server: nginx
< Date: Tue, 16 Jan 2018 05:57:51 GMT
< Content-Type: text/html
< Content-Length: 154
< Connection: close
< Location: http://ftp.halifax.rwth-aachen.de/xbmc/a...fanart.jpg
< X-Frame-Options: SAMEORIGIN
<
* Closing connection 0
* Issue another request to this URL: 'http://ftp.halifax.rwth-aachen.de/xbmc/addons/krypton/plugin.video.giantbomb/fanart.jpg'
* Hostname was NOT found in DNS cache
*   Trying 137.226.34.46...
*   Trying 2a00:8a60:e012:a00::21...
* connect to 2a00:8a60:e012:a00::21 port 80 failed: Network is unreachable
* Failed to connect to ftp.halifax.rwth-aachen.de port 80: Network is unreachable
* Closing connection 1
curl: (7) Failed to connect to ftp.halifax.rwth-aachen.de port 80: Network is unreachable

Now isn't that strange?  Further investigation reveals that it only fails when ipv6 is used, if I force curl to use --ipv4 it works fine.  So as a cheap and dirty fix I disabled ipv6 by adding 'ipv6.disable=1' to /boot/cmdline.txt and rebooted.  Hey presto, curl starts working again.

The distro I am using is Retropie, but from what I gather the mainline distro has turned on ipv6 by default.

[Minklet]

Did you ever find a proper solution for this? I get the same error, but even with forcing ipv4 I get 'Not Found' for upgrades eg

http://mirrors.kodi.tv/addons/krypton/pl...0.2.zip.md

[wsnipex]

looks like your curl is trying to use ipv6: connect to 2a00:8a60:e012:a00::21 port 80 failed: Network is unreachable