| Message ID | 1474030076-24809-1-git-send-email-mmanning@brocade.com |
|---|---|
| State | Rejected, archived |
| Delegated to: | David Miller |
| Headers | show |
On Fri, 2016-09-16 at 13:47 +0100, Mike Manning wrote: > Disabling forwarding per interface via sysctl continues to allow > forwarding. This is contrary to the sysctl documentation stating that > the forwarding sysctl is per interface, whereas currently it is only > the sysctl for all interfaces that has an effect on forwarding. The > solution is to drop any received packets instead of forwarding them > if the ingress device has a per-device forwarding sysctl that is unset. Some archaeological research might be needed because Documentation/networking/ip-sysctl.txt states : IPv4 and IPv6 work differently here; e.g. netfilter must be used to control which interfaces may forward packets and which not. If this netfilter requirement is obsolete, then your patch would need to change the doc as well. Hannes can probably comment on this ? Thanks.
On 16.09.2016 15:39, Eric Dumazet wrote: > On Fri, 2016-09-16 at 13:47 +0100, Mike Manning wrote: >> Disabling forwarding per interface via sysctl continues to allow >> forwarding. This is contrary to the sysctl documentation stating that >> the forwarding sysctl is per interface, whereas currently it is only >> the sysctl for all interfaces that has an effect on forwarding. The >> solution is to drop any received packets instead of forwarding them >> if the ingress device has a per-device forwarding sysctl that is unset. > > Some archaeological research might be needed because > Documentation/networking/ip-sysctl.txt states : > > IPv4 and IPv6 work differently here; e.g. netfilter must be used > to control which interfaces may forward packets and which not. > > If this netfilter requirement is obsolete, then your patch would need to > change the doc as well. > > Hannes can probably comment on this ? Yep, thanks. This commit breaks a very common setup: people globally enabled forwarding but disabled the forwarding knob on one special interface to allow this interface to participate in auto configuration from their provider while still forwarding packets over this interface. I fear this is so common that this would be a uapi violation. Thanks, Hannes
On 09/16/2016 04:46 PM, Hannes Frederic Sowa wrote: > On 16.09.2016 15:39, Eric Dumazet wrote: >> On Fri, 2016-09-16 at 13:47 +0100, Mike Manning wrote: >>> Disabling forwarding per interface via sysctl continues to allow >>> forwarding. This is contrary to the sysctl documentation stating that >>> the forwarding sysctl is per interface, whereas currently it is only >>> the sysctl for all interfaces that has an effect on forwarding. The >>> solution is to drop any received packets instead of forwarding them >>> if the ingress device has a per-device forwarding sysctl that is unset. >> >> Some archaeological research might be needed because >> Documentation/networking/ip-sysctl.txt states : >> >> IPv4 and IPv6 work differently here; e.g. netfilter must be used >> to control which interfaces may forward packets and which not. >> >> If this netfilter requirement is obsolete, then your patch would need to >> change the doc as well. >> >> Hannes can probably comment on this ? > > Yep, thanks. > > This commit breaks a very common setup: people globally enabled > forwarding but disabled the forwarding knob on one special interface to > allow this interface to participate in auto configuration from their > provider while still forwarding packets over this interface. > > I fear this is so common that this would be a uapi violation. > > Thanks, > Hannes > > Thanks for the use-case, I request to withdraw this patch then. So configuring an interface on a router to be in host mode is not actually disabling forwarding in the kernel, it is merely to allow SLAAC. Using ip6tables for the purpose of disabling forwarding on an interface if one wants an interface in host mode seems a heavyweight solution to work around this. If anyone has any better suggestions, please let me know.
diff --git a/net/ipv6/ip6_output.c b/net/ipv6/ip6_output.c index 1dfc402..37cd1d0 100644 --- a/net/ipv6/ip6_output.c +++ b/net/ipv6/ip6_output.c @@ -380,11 +380,15 @@ int ip6_forward(struct sk_buff *skb) struct ipv6hdr *hdr = ipv6_hdr(skb); struct inet6_skb_parm *opt = IP6CB(skb); struct net *net = dev_net(dst->dev); + struct inet6_dev *idev = __in6_dev_get(skb->dev); u32 mtu; if (net->ipv6.devconf_all->forwarding == 0) goto error; + if (idev && !idev->cnf.forwarding) + goto error; + if (skb->pkt_type != PACKET_HOST) goto drop;
Disabling forwarding per interface via sysctl continues to allow forwarding. This is contrary to the sysctl documentation stating that the forwarding sysctl is per interface, whereas currently it is only the sysctl for all interfaces that has an effect on forwarding. The solution is to drop any received packets instead of forwarding them if the ingress device has a per-device forwarding sysctl that is unset. Signed-off-by: Mike Manning <mmanning@brocade.com> --- net/ipv6/ip6_output.c | 4 ++++ 1 file changed, 4 insertions(+)