[libvirt] [PATCH] qemu: Check for down limit of SLIRP prefix too

[John Ferlan]

On 02/06/2018 05:59 AM, Michal Privoznik wrote:
> https://bugzilla.redhat.com/show_bug.cgi?id=1515533
> 
> We're already checking if IPv4 prefix isn't too long. But we are
> not checking if it isn't too short. QEMU supports prefixes longer
> than 4 (including). I haven't find anything similar related to
> IPv6 in qemu sources.
> 
> Signed-off-by: Michal Privoznik <mprivozn at redhat.com>
> ---
>  src/qemu/qemu_domain.c | 6 ++++++
>  1 file changed, 6 insertions(+)
> 
> diff --git a/src/qemu/qemu_domain.c b/src/qemu/qemu_domain.c
> index df433c2f0..4fc4db68b 100644
> --- a/src/qemu/qemu_domain.c
> +++ b/src/qemu/qemu_domain.c
> @@ -3744,6 +3744,12 @@ qemuDomainDeviceDefValidateNetwork(const virDomainNetDef *net)
>                                     _("prefix too long"));
>                      return -1;
>                  }
> +
> +                if (ip->prefix < 4) {
> +                    virReportError(VIR_ERR_XML_ERROR, "%s",
> +                                   _("prefix too short"));
> +                    return -1;
> +                }

Why not just mimic what QEMU essentially does in
net/slirp.c/net_slirp_init with a:

    if (ip->prefix < 4 || ip->prefix > 27) {
        virReportError(VIR_ERR_XLM_ERROR, "%s",
                       _("invalid prefix, must be in range of 4-27"));
        return -1;
    }

Perhaps even a note in formatdomain.html.in that the supported range for
the prefix is hypervisor dependent (but I'm not requiring that).

I trust that the details can be worked out, so

Reviewed-by: John Ferlan <jferlan at redhat.com>

for the concept/code

John

>              }
>  
>              if (VIR_SOCKET_ADDR_IS_FAMILY(&ip->address, AF_INET6)) {
>