> On 4 Mar 2019, at 12:44, Toke Høiland-Jørgensen <t...@redhat.com> wrote:
>
> Kevin Darbyshire-Bryant <ke...@darbyshire-bryant.me.uk> writes:
>
>>> On 4 Mar 2019, at 11:17, Toke Høiland-Jørgensen <t...@redhat.com> wrote:
>>>
>>> Kevin Darbyshire-Bryant <ke...@darbyshire-bryant.me.uk> writes:
>>>
>>>>> On 4 Mar 2019, at 08:39, Pete Heist <p...@heistp.net> wrote:
>>>>>
>>>>>
>>>>>> On Mar 3, 2019, at 12:52 PM, Kevin Darbyshire-Bryant
>>>>>> <ke...@darbyshire-bryant.me.uk> wrote:
>>>>>>
>>>>>> The very bad idea:
>>>>>>
>>>>>> And it’s bad ‘cos it’s sort of incompatible with the existing fwmark
>>>>>> implementation as described above. So an awful lot of our
>>>>>> shenanigans above is due to DSCP not traversing the internet
>>>>>> particularly well. The solution above abstracts DSCP into ’tins’
>>>>>> which we put into fwmarks. Another approach would be to put the DSCP
>>>>>> *into* the fwmark. CAKE could (optionally) copy the FWMARK contained
>>>>>> DSCP into the diffserv field onto the actual packets. Voila DSCP
>>>>>> traversal across ’tinternet with tin/bandwidth allocation in our
>>>>>> local domain preserved.
>>>>>
>>>>> If I understand it right, another use case for this “very bad idea”
>>>>> is preserving DSCP locally while traversing upstream WiFi links as
>>>>> besteffort, which avoids airtime efficiency problems that can occur
>>>>> with 802.11e (WMM). In cases where the router config can’t be changed
>>>>> (802.11e is mandatory after all) I’ve used IPIP tunnels for this, as
>>>>> it hides DSCP from the WiFi stack while preserving the values through
>>>>> the tunnel, but this would be easier. Neat… :)
>>>>
>>>> Everyone has understood the intent & maybe the implementation
>>>> correctly. 2 patches attached, one for cake, one for tc.
>>>>
>>>> They are naively coded and some of it undoes Toke’s recent tidying up
>>>> (sorry!)
>>>
>>> Heh. First comment: Don't do that ;)
>>
>> I did say naively coded.
>>
>>>
>>> A few more below.
>>>
>>>> 012C ACB2 28C6 C53E 9775 9123 B3A2 389B 9DE2 334A
>>>> diff --git a/pkt_sched.h b/pkt_sched.h
>>>> index a2f570c..d1f288d 100644
>>>> --- a/pkt_sched.h
>>>> +++ b/pkt_sched.h
>>>> @@ -879,6 +879,7 @@ enum {
>>>> TCA_CAKE_ACK_FILTER,
>>>> TCA_CAKE_SPLIT_GSO,
>>>> TCA_CAKE_FWMARK,
>>>> + TCA_CAKE_ICING,
>>>> __TCA_CAKE_MAX
>>>> };
>>>> #define TCA_CAKE_MAX (__TCA_CAKE_MAX - 1)
>>>> diff --git a/sch_cake.c b/sch_cake.c
>>>> index 733b897..5aca0f3 100644
>>>> --- a/sch_cake.c
>>>> +++ b/sch_cake.c
>>>> @@ -270,7 +270,8 @@ enum {
>>>> CAKE_FLAG_INGRESS = BIT(2),
>>>> CAKE_FLAG_WASH = BIT(3),
>>>> CAKE_FLAG_SPLIT_GSO = BIT(4),
>>>> - CAKE_FLAG_FWMARK = BIT(5)
>>>> + CAKE_FLAG_FWMARK = BIT(5),
>>>> + CAKE_FLAG_ICING = BIT(6)
>>>
>>> This implies that icing and fwmark can be enabled completely
>>> independently of each other. Are you sure about the semantics for that?
>>
>> No, I’m not. I sent the patches so others could see my lunacy in action and
>> hopefully improve it.
>>
>> The actual operation links FWMARK, INGRESS & ICING in a variety of
>> combinations.
>
> Right, so obviously this needs to be thought through…
Yes. Volunteers with thoughts & ideally code sought.
>
>>>> };
>>>>
>>>> /* COBALT operates the Codel and BLUE algorithms in parallel, in order to
>>>> @@ -333,7 +334,7 @@ static const u8 diffserv8[] = {
>>>> };
>>>>
>>>> static const u8 diffserv4[] = {
>>>> - 0, 2, 0, 0, 2, 0, 0, 0,
>>>> + 0, 1, 0, 0, 2, 0, 0, 0,
>>>> 1, 0, 0, 0, 0, 0, 0, 0,
>>>> 2, 0, 2, 0, 2, 0, 2, 0,
>>>> 2, 0, 2, 0, 2, 0, 2, 0,
>>>> @@ -344,7 +345,7 @@ static const u8 diffserv4[] = {
>>>> };
>>>>
>>>> static const u8 diffserv3[] = {
>>>> - 0, 0, 0, 0, 2, 0, 0, 0,
>>>> + 0, 1, 0, 0, 2, 0, 0, 0,
>>>
>>> Why are you messing with the diffserv mappings in this patch?
>>
>> This is a combination patch of Dave’s new LE coding and the
>> fwmark/dscp mangling.
>
> Ah. Well let's keep that separate from this patch/discussion…
Done
>
>>>
>>>> 1, 0, 0, 0, 0, 0, 0, 0,
>>>> 0, 0, 0, 0, 0, 0, 0, 0,
>>>> 0, 0, 0, 0, 0, 0, 0, 0,
>>>> @@ -1618,7 +1619,24 @@ static unsigned int cake_drop(struct Qdisc *sch,
>>>> struct sk_buff **to_free)
>>>> return idx + (tin << 16);
>>>> }
>>>>
>>>> -static u8 cake_handle_diffserv(struct sk_buff *skb, u16 wash)
>>>> +void cake_update_diffserv(struct sk_buff *skb, u8 dscp)
>>>> +{
>>>> + switch (skb->protocol) {
>>>> + case htons(ETH_P_IP):
>>>> + if ((ipv4_get_dsfield(ip_hdr(skb)) & ~INET_ECN_MASK) != dscp)
>>>> + ipv4_change_dsfield(ip_hdr(skb), INET_ECN_MASK, dscp);
>>>> + break;
>>>> + case htons(ETH_P_IPV6):
>>>> + if ((ipv6_get_dsfield(ipv6_hdr(skb)) & ~INET_ECN_MASK) != dscp)
>>>> + ipv6_change_dsfield(ipv6_hdr(skb), INET_ECN_MASK, dscp);
>>>> + break;
>>>> + default:
>>>> + break;
>>>> + }
>>>> +
>>>> +}
>>>
>>> So washing is just a special case of this (wash is
>>> cake_update_diffserv(skb,0)). So you shouldn't need to add another
>>> function, just augment the existing handling code.
>>
>> Erm, that’s exactly what I’ve done.
>
> Ah, right; I guess it's just the reverting of the cleanup patch that is
> the issue, then :)
With the reverting of the cleaning reverted - if that makes any sense.
And I have major twitchiness at the result.
>
>>>> +static u8 cake_handle_diffserv(struct sk_buff *skb, bool wash)
>>>> {
>>>> u8 dscp;
>>>>
>>>> @@ -1644,37 +1662,70 @@ static u8 cake_handle_diffserv(struct sk_buff
>>>> *skb, u16 wash)
>>>> }
>>>> }
>>>>
>>>> +#if IS_REACHABLE(CONFIG_NF_CONNTRACK)
>>>
>>> Save an ifdef below by moving the ifdef inside the function definition.
>>>
>>>> +void cake_update_ct_mark(struct sk_buff *skb, u8 dscp)
>>>> +{
>>>> + enum ip_conntrack_info ctinfo;
>>>> + struct nf_conn *ct;
>>>> +
>>>> + ct = nf_ct_get(skb, &ctinfo);
>>>> + if (!ct)
>>>> + return;
>>>> +
>>>> + ct->mark &= 0x80ffffff;
>>>> + ct->mark |= (0x40 | dscp) << 24;
>>>
>>> Right, so we *might* have an argument that putting the *tin* into the
>>> fwmark is CAKE's business, but copying over the dscp mark is not
>>> something a qdisc should be doing…
>>
>> Why ever not? It’s not the DSCP, it’s a lookup value into the cake
>> priority table, it just happens to look like the DSCP ;-)
>
> If it quacks like a duck…
I honestly don’t know where to go from here. I’m clearly trying to do
something that the kernel doesn’t want to do.
>
>>
>>>> + nf_conntrack_event_cache(IPCT_MARK, ct);
>>>> +}
>>>> +#endif
>>>
>>> Also, are you sure this will work in all permutations of conntrack being
>>> a module vs not etc? (we had to jump through quite some hoops to get the
>>> conntrack hooks to work last time; this is probably my biggest worry here).
>>
>> No, I have absolutely no clue here at all.
>
> Well, another issue that needs fixing, then…
Again bright-eyed & bushy tailed volunteers sought!
>
> -Toke
v2 addressing some of the comments attached. Is it best to keep the in
progress patches here or should they be github PRs ?
Cheers,
Kevin D-B
012C ACB2 28C6 C53E 9775 9123 B3A2 389B 9DE2 334A
v2-0001-Copy-dscp-to-fwmark.patch
Description: v2-0001-Copy-dscp-to-fwmark.patch
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