No ipv4 fallback when ipv6 connection does not work

[mruprich]

When fetching something with wget2 that is only reachable via IPv4, by default wget tries IPv6 and then fails. I think that it would be good to have an IPv4 fallback similar to what wget1 used to have.

Example:

# wget2 -t1 http://www.spinics.net/lists/linux-mm/attachments//gtarazbJaHPaAT.gtar
Failed to send 252 bytes (hostname='www.spinics.net', ip=2604:9a00:2010:a03b:4::114, errno=113)

                          [Files: 0  Bytes: 0  [0 B/s] Redirects: 0  Todo: 0  Errors: 0         ]

Same example with wget1:

# wget -t1 http://www.spinics.net/lists/linux-mm/attachments//gtarazbJaHPaAT.gtar
--2024-06-26 10:01:51--  http://www.spinics.net/lists/linux-mm/attachments//gtarazbJaHPaAT.gtar
Resolving www.spinics.net (www.spinics.net)... 2604:9a00:2010:a03b:4::114, 207.244.127.203
Connecting to www.spinics.net (www.spinics.net)|2604:9a00:2010:a03b:4::114|:80... failed: No route to host.
Connecting to www.spinics.net (www.spinics.net)|207.244.127.203|:80... connected.
HTTP request sent, awaiting response... 301 Moved Permanently
Location: https://www.spinics.net/lists/linux-mm/attachments//gtarazbJaHPaAT.gtar [following]
--2024-06-26 10:01:51--  https://www.spinics.net/lists/linux-mm/attachments//gtarazbJaHPaAT.gtar
Connecting to www.spinics.net (www.spinics.net)|207.244.127.203|:443... connected.
HTTP request sent, awaiting response... 200 OK
Length: 19817 (19K) [application/x-gtar]
Saving to: ‘gtarazbJaHPaAT.gtar’

gtarazbJaHPaAT.gtar           100%[================================================>]  19.35K  --.-KB/s    in 0.008s  

2024-06-26 10:01:51 (2.37 MB/s) - ‘gtarazbJaHPaAT.gtar’ saved [19817/19817]

Also the output of that in wget2 could be a bit more detailed. errno=113 does not really say much about what the problem is.