[Cake] diffserv based on firewall mark
moeller0 at gmx.de
Wed Oct 12 05:10:30 EDT 2016
> On Oct 12, 2016, at 10:11 , ching lu <lsching17 at gmail.com> wrote:
> For egress, setting DSCP field should work.
> iptables -> wan egress -> cake
> But is it possible to set DSCP to 0x0 after cake's classification? i
> do not know how ISP handle non-zero DSCP, there seems to be no
> standard for this.
Interestingly cake, at some point in the past offered exactly that functionality, but it got removed due to added complexity with very little practical applicability (and a potential layering violation, but one could equally argue that the current layering is partly sub-optimal/wrong and hence violating it to better reflect reality might be acceptable). But current cake does not offer this. If you are willing to daisy-chain two routers, you could run cake on the respective egress interfaces connecting both routers, and do the DSCP cleaning on the outer router’s egress interface toward the internet…
> For ingress, DSCP field may not be set by network peer at all, and i
> have multiple LAN interfaces
> AFAIK, the order is "wan ingress -> ifb egress -> cake -> iptables"
> The trick of setting DSCP by iptables do not work because cake comes first
Hence Jonathan’s recommendation to make sure that cake follows iptables, by setting it up on egress interfaces only…
> On Wed, Oct 12, 2016 at 3:26 PM, Jonathan Morton <chromatix99 at gmail.com> wrote:
>>> On 12 Oct, 2016, at 08:52, ching lu <lsching17 at gmail.com> wrote:
>>> I deprioritize bittorrent traffic by marking related connections in
>>> iptables (e.g. detect by port number) and route them to corresponding
>>> HTB class and qdisc.
>>> How can i archive the same goal using the cake qdisc?
>> Modify your iptables rules to set the DSCP rather than a kernel-internal mark. You probably want "-j DSCP —set-dscp-class CS1”, as CS1 is the “bulk low priority” code. Cake’s default Diffserv mode will pick that up appropriately.
>> You also need to make sure Cake sees your packets *after* they’ve been through the firewall, which generally means attaching it to the egress port in each direction, not the ingress port. You’ve probably already done this, if you’re happy with your HTB setup.
>> If you have multiple LAN interfaces (eg, both Ethernet and wifi), you should loop the inbound traffic through a common IFB device (and attach Cake to that instead of the physical interfaces) to simplify configuration.
>> - Jonathan Morton
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