[systemd-devel] [PATCH 1/2] Ignore IPv6 link-local addresses

[Zbigniew Jędrzejewski-Szmek]

On Mon, Feb 04, 2013 at 03:56:25PM +0100, Eelco Dolstra wrote:
> Returning IPv6 link-local addresses is a bad idea, because they only
> work if an application connects specifically over the corresponding
> interface.
Isn't this a responsibility of the application to deal with that?

> So you get errors like:
> 
>   $ curl -6 http://my-machine/
>   curl: (7) Failed to connect to fe80::d6be:d9ff:fe1b:8477: Invalid argument
$ hostnamectl set-hostname bupkis-tmp
$ curl -6v bupkis-tmp
* About to connect() to bupkis-tmp port 80 (#0)
*   Trying fe80::a60:6eff:fe00:6241...
* Connection refused
* couldn't connect to host
* Closing connection #0
curl: (7) couldn't connect to host

So here everything is working as expected (I don't have an http server).

Zbyszek

> To prevent this, this patch filters out link-local addresses.  So if
> you don't have a routable IPv6 address, nss-myhostname will fall back
> to returning ::1.
> ---
>  src/nss-myhostname/netlink.c | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/src/nss-myhostname/netlink.c b/src/nss-myhostname/netlink.c
> index 53c3b50..621ca1d 100644
> --- a/src/nss-myhostname/netlink.c
> +++ b/src/nss-myhostname/netlink.c
> @@ -155,6 +155,10 @@ int ifconf_acquire_addresses(struct address **_list, unsigned *_n_list) {
>                              ifaddrmsg->ifa_scope == RT_SCOPE_NOWHERE)
>                                  continue;
>  
> +                        if (ifaddrmsg->ifa_family == AF_INET6 &&
> +                            ifaddrmsg->ifa_scope == RT_SCOPE_LINK)
> +                                continue;
> +
>                          if (ifaddrmsg->ifa_flags & IFA_F_DEPRECATED)
>                                  continue;
>  
> -- 
> 1.8.1
> 
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