Hello Glen, On Tue, 2014-10-28 at 11:26 +1030, Glen Turner wrote: > On 04/10/2014, at 2:31 AM, Dan Williams wrote: > > > On Fri, 2014-10-03 at 11:36 -0400, Chuck Anderson wrote: > >> I'm not sure if this is a kernel thing or a NetworkManager thing. Did > >> something change in how IPv6 router advertisements are handled by > >> NetworkManager in Fedora 20? > > > > I think it's a NetworkManager thing. We'll fix it. > > Hi Dan, > > I've had a lot of trouble in IPv4 with DHCP in hotel systems setting the MTU > to less than the 576 minimum (and sometimes less than the size of the IPv4 > header). I believe that this was a misguided effort to implement fair queuing. > > It might be worthwhile anticipating such issues for IPv6, roughly: > > /* IPv6 minimum link MTU specified on page 24 of RFC 2460. */ > #define IPV6_MINIMUM_MTU 1280 > > unsigned int enforce_link_mtu_bounds(unsigned int offered_link_mtu, > char *interface_name) > { > if (offered_link_mtu < IPV6_MINIMUM_MTU) { > syslog("Offered link MTU for %s is %u, increased to " IPV6_MINIMUM_MTU > "\n", > (interface_name) ? interface_name : "an interface", > offered_link_mtu); > return IPV6_MINIMUM_MTU; > } > return offered_link_mtu; > }
We now ignore bad IPv6 MTUs: src/rdisc/nm-lndp-rdisc.c: 627 if (mtu >= 1280) { 628 rdisc->mtu = mtu; 629 changed |= NM_RDISC_CONFIG_MTU; 630 } else { 631 /* All sorts of bad things would happen if we accepted this. 632 * Kernel would set it, but would flush out all IPv6 addresses away 633 * from the link, even the link-local, and we wouldn't be able to 634 * listen for further RAs that could fix the MTU. */ 635 warning ("(%s): MTU too small for IPv6 ignored: %d", rdisc->ifname, mtu); 636 } > > -glen Lubo _______________________________________________ networkmanager-list mailing list networkmanager-list@gnome.org https://mail.gnome.org/mailman/listinfo/networkmanager-list