IPv4/v6 socket problem on BSD

Christophe Prevotaux c.prevotaux at hexanet.fr
Mon Jul 29 00:00:02 EST 2002

NetBSD has the same problem

On Sun, 28 Jul 2002 17:36:07 +0000 (UTC)
naddy at mips.inka.de (Christian Weisgerber) wrote:

> Currently, if IPv6-enabled rsync is run as --daemon, it will perform
> a wildcard bind(2) on an AF_INET6 socket and expect that IPv4 traffic
> will be forwarded to the v6 socket (IPv4 mapped address, RFC2553).
> This has never worked on OpenBSD which disallows IPv4 mapped addresses
> for security reasons.  On FreeBSD 5.0-CURRENT, where the behavior
> is subject to configuration, the default was switched to "disable"
> a few days ago.  According to their man page, NetBSD share this.
> Server processes that are to deal with IPv4 and IPv6 traffic will
> have to bind to two sockets, one for each protocol family.  Servers
> that fail to do so and rely on the old IPv4 mapped addresses will
> end up handling IPv6 only.
> Symptoms on typical IPv6-enabled but only IPv4-connected hosts are
> that the daemon appears to be running fine but can't be reached.
> netstat -a will show a protocol type of tcp6 instead of the expected
> tcp46.
> Workarounds for IPv4-only users include specifying an appropriate
> --address or building rsync with --disable-ipv6.
> Currently, rsync in daemon mode is only designed to read from a single
> socket.  Extending this to two sockets will require a bit of reworking,
> e.g. introducing a select(2) loop.  This also suggests extending
> --address to accept multiple addresses (or allow multiple --address
> arguments).  Altogether that's a bit more than I feel confident to
> tackle...
> -- 
> Christian "naddy" Weisgerber                          naddy at mips.inka.de
> -- 
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Christophe Prevotaux      Email: c.prevotaux at hexanet.fr
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