Subject: Re: [RFC ipsec-next v2 2/8] iptfs: uapi: ip: add ip_tfs_*_hdr packet formats

From: Christian Hopps <[email-masked]>
Date: Mon, 20 Nov 2023 15:18:49 -0500

Sabrina Dubroca <[email-masked]> writes:

> 2023-11-12, 22:52:13 -0500, Christian Hopps wrote:
>> From: Christian Hopps <[email-masked]>
>>
>> Add the on-wire basic and congestion-control IP-TFS packet headers.
>>
>> Signed-off-by: Christian Hopps <[email-masked]>
>> ---
>>  include/uapi/linux/ip.h | 17 +++++++++++++++++
>>  1 file changed, 17 insertions(+)
>>
>> diff --git a/include/uapi/linux/ip.h b/include/uapi/linux/ip.h
>> index 283dec7e3645..cc83878ecf08 100644
>> --- a/include/uapi/linux/ip.h
>> +++ b/include/uapi/linux/ip.h
>> @@ -137,6 +137,23 @@ struct ip_beet_phdr {
>>  	__u8 reserved;
>>  };
>>
>> +struct ip_iptfs_hdr {
>> +	__u8 subtype;		/* 0*: basic, 1: CC */
>> +	__u8 flags;
>> +	__be16 block_offset;
>> +};
>> +
>> +struct ip_iptfs_cc_hdr {
>> +	__u8 subtype;		/* 0: basic, 1*: CC */
>> +	__u8 flags;
>> +	__be16 block_offset;
>> +	__be32 loss_rate;
>> +	__u8 rtt_and_adelay1[4];
>> +	__u8 adelay2_and_xdelay[4];
>
> Given how the fields are split, wouldn't it be more convenient to have
> a single __be64, rather than reading some bits from multiple __u8?

This is a good point, I carried this over from an earlier implementation, let me give it some though but probably change it.

>> +	__be32 tval;
>> +	__be32 techo;
>> +};

> I don't think these need to be part of uapi. Can we move them to
> include/net/iptfs.h (or possibly net/xfrm/xfrm_iptfs.c)? It would also
> make more sense to have them near the definitions for
> IPTFS_SUBTYPE_*. And it would be easier to change how we split and
> name fields for kernel consumption if we're not stuck with whatever we
> put in uapi.

The other ipsec modes headers were added here, so I was simply following along. I don't mind moving things but would like to understand why iptfs would be different from the other modes, for example, `struct ip_comp_hdr` and `struct ip_beet_phdr` appears in this file.

Thanks!
Chris.