Re: [Cerowrt-devel] https://tools.ietf.org/html/draft-ietf-tsvwg-le-phb-06 is in last call

[Jonathan Morton <chromatix99@gmail.com>]

> On 3 Feb, 2019, at 8:39 pm, Dave Taht <dave.taht@gmail.com> wrote:
> 
> it's 000001 which I guess is:
> 
> diff --git a/sch_cake.c b/sch_cake.c
> index 3a26db0..67263b3 100644
> --- a/sch_cake.c
> +++ b/sch_cake.c
> @@ -343,7 +343,7 @@ static const u8 diffserv4[] = {
> };
> 
> static const u8 diffserv3[] = {
> -       0, 0, 0, 0, 2, 0, 0, 0,
> +       0, 1, 0, 0, 2, 0, 0, 0,
>        1, 0, 0, 0, 0, 0, 0, 0,
>        0, 0, 0, 0, 0, 0, 0, 0,
>        0, 0, 0, 0, 0, 0, 0, 0,
> 
> (or is that reversed? my big endian/little endian chops scuks, and
> nobody modified the gen_cake_const tool to match what cake expects
> now)

That looks correct to me, though it should also be added to the other Diffserv modes including a bulk tin.  Fields in TCP/IP are all laid out in "network order" which is most-significant bit/byte first, the same way you'd *normally* write a number down.

The TOS field can sometimes be confusing because the DSCP field is the upper 6 bits and the ECN field the lower 2, and the BSD Sockets API gives you the while byte to work with while DSCPs are quoted as just their own 6 bits.  So you have to shift the latter left two bits before applying them to the former.

 - Jonathan Morton