On 2015-05-06 13:52, Christos Zoulas wrote:
In article <[email protected]>,
Paul Goyette <[email protected]> wrote:
what controls the selection of a protocol when both are available?
More specifically, if I 'ftp ftp.netbsd.org' what causes it to try ipv6 first,
and use ipv4 as a fall back?
In a way it depends on the program. A program can explicitly ask for V4
or V6 addresses, and then obviously that is the order things will be
handled. If a program calls getaddrinfo() without specifying the family,
getaddrinfo() in NetBSD prefers V6 addresses over V4 addresses. This
manifests itself by the result that getaddrinfo() returns have the IPv6
addresses appear first in the resulting list, and the IPv4 addresses
come after. A program would normally go through the list from start to
end, trying one address at a time, so then it would try IPv6 first. But
of course, a program can do things differently if it wants to...
My ipv6 connectivity is via a slow vpn (from Manila to San Jose, CA!) so I
would prefer that connections default to ipv4 unless I explicitly ask for v6.
You could just throw in "-4" to the ftp command, and you will be doing
IPv4 only...
FreeBSD has:
https://www.freebsd.org/cgi/man.cgi?query=ip6addrctl&sektion=8
I was thinking of copying it...
That could be handy. However, how does it work? Do getaddrinfo() then
somehow lookup this preference table and sort the results based on that?
Or is this somehow solved in some different way?
Johnny
--
Johnny Billquist || "I'm on a bus
|| on a psychedelic trip
email: [email protected] || Reading murder books
pdp is alive! || tryin' to stay hip" - B. Idol
