Hello!

It looks like the proposed fix at
858898e348eb300a94b74115328ee39191829bda is causing other issues:

$ guix describe
Generation 27	Feb 17 2021 09:39:49	(current)
  guix 861ba52
    repository URL: https://git.savannah.gnu.org/git/guix.git
    branch: master
    commit: 861ba5258399360a8f4c4e7cd08958f46d2c2b1e

$ strace guix refresh libgcrypt
....
read(15, "220-Welcome hacker!\r\n220-.\r\n220-"..., 4096) = 701
write(15, "USER anonymous\r\n", 16)     = 16
read(15, "331 Send e-mail address as passw"..., 4096) = 38
write(15, "PASS guix@example.com\r\n", 23) = 23
read(15, "230 User logged in, proceed.\r\n", 4096) = 30
brk(0x1534000)                          = 0x1534000
write(15, "CWD /\r\n", 7)               = 7
read(15, "250 Directory change successful."..., 4096) = 34
write(15, "CWD gcrypt\r\n", 12)         = 12
read(15, "250-This directory is used as FT"..., 4096) = 1106
write(15, "CWD libgcrypt\r\n", 15)      = 15
read(15, "250-This is the stable version o"..., 4096) = 135
write(15, "EPSV\r\n", 6)                = 6
read(15, 
... hangs ...

Should we explicitly check if we are over an IPv6 connection instead?
Is that possible?

Léo