[Sbcl-devel] GET-HOST-BY-NAME: addrinfo-flags with AI_ADDRCONFIG by default

[Tito L. <tit...@gm...>]

Hi,

getaddrinfo() in GNU C library assumes ai_flags with a value of
(AI_V4MAPPED | AI_ADDRCONFIG) if the argument `hints' is NULL

[POSIX specifies different defaults, see NOTES in `man getaddrinfo']

AI_ADDRCONFIG means: "Use configuration of this host to choose
returned address type.."

I have accidentally noticed that problem by running a dhcpcd
client daemon

    sh> dhcpcd eth0

but without a physical connection to talk with a DHCP server.
Then I have tried to start a local Swank server but the required port
number is ignored, because addrinfo-family after getaddrinfo() is
always AF_INET6 in this case and SWANK/SBCL::RESOLVE-HOSTNAME
considers the first HOST-ENT returned from GET-HOST-BY-NAME (for IPv4
addresses):

  ;; slime/swank/sbcl.lisp
  (defun resolve-hostname (name)
    (car (sb-bsd-sockets:host-ent-addresses
          (sb-bsd-sockets:get-host-by-name name))))

so the result is NIL and the specified port number is ignored during
socket-bind.

A solution is to alloc a struct addrinfo for the argument `hints' of
getaddrinfo(), set ai_family to AF_UNSPEC and the other slots (flags,
socktype and protocol should be enough) to zero.

I have attached a git-diff because I don't have a good log message
at moment.