[WireGuard] WireGuard ECN Implementation

[Dave Taht]

that + 1 was clever. I think you are done... and I should go change the blog. :)

On Thu, Sep 29, 2016 at 11:59 AM, Jason A. Donenfeld <Jason at zx2c4.com> wrote:
> On Thu, Sep 29, 2016 at 8:19 PM, Dave Taht <dave.taht at gmail.com> wrote:
>> I think the correct behavior here is to only set ce on the inner
>> packet if the inner packet is marked as ecn capable.
>
> IP_ECN_set_ce already does this. It exits early if it isn't already
> ECT(1) or ECT(0):
>
> static inline int IP_ECN_set_ce(struct iphdr *iph)
> {
>        u32 check = (__force u32)iph->check;
>        u32 ecn = (iph->tos + 1) & INET_ECN_MASK;
>
>        /*
>         * After the last operation we have (in binary):
>         * INET_ECN_NOT_ECT => 01
>         * INET_ECN_ECT_1   => 10
>         * INET_ECN_ECT_0   => 11
>         * INET_ECN_CE      => 00
>         */
>        if (!(ecn & 2))
>                return !ecn;
>
>        /*
>         * The following gives us:
>         * INET_ECN_ECT_1 => check += htons(0xFFFD)
>         * INET_ECN_ECT_0 => check += htons(0xFFFE)
>         */
>        check += (__force u16)htons(0xFFFB) + (__force u16)htons(ecn);
>
>        iph->check = (__force __sum16)(check + (check>=0xFFFF));
>        iph->tos |= INET_ECN_CE;
>        return 1;
> }
>
>
>
>>
>> It looked to as tho leveraging the other newer ecn capable codebases
>> in the kernel was sane also.
>
> I tried to copy already existing code in the kernel for this. Is there
> a certain driver that you think does it particularly well that I
> should copy?



-- 
Dave Täht
Let's go make home routers and wifi faster! With better software!
http://blog.cerowrt.org