netdev - Re: [PATCH bpf-next 1/2] bpf: add CHECKSUM

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Date: Wed, 22 May 2024 22:21:53 +0100
From: Vadim Fedorenko <vadim.fedorenko@...ux.dev>
To: Simon Horman <horms@...nel.org>
Cc: Martin KaFai Lau <martin.lau@...ux.dev>,
 Andrii Nakryiko <andrii@...nel.org>, Alexei Starovoitov <ast@...nel.org>,
 Mykola Lysenko <mykolal@...com>, Jakub Kicinski <kuba@...nel.org>,
 bpf@...r.kernel.org, netdev@...r.kernel.org
Subject: Re: [PATCH bpf-next 1/2] bpf: add CHECKSUM_COMPLETE to bpf test progs

On 22/05/2024 19:32, Simon Horman wrote:
> On Wed, May 22, 2024 at 07:57:10AM -0700, Vadim Fedorenko wrote:
>> Add special flag to validate that TC BPF program properly updates
>> checksum information in skb.
>>
>> Signed-off-by: Vadim Fedorenko <vadfed@...a.com>
> 
> ...
> 
>> diff --git a/net/bpf/test_run.c b/net/bpf/test_run.c
>> index f6aad4ed2ab2..841552785c65 100644
>> --- a/net/bpf/test_run.c
>> +++ b/net/bpf/test_run.c
>> @@ -974,10 +974,13 @@ int bpf_prog_test_run_skb(struct bpf_prog *prog, const union bpf_attr *kattr,
>>   	int hh_len = ETH_HLEN;
>>   	struct sk_buff *skb;
>>   	struct sock *sk;
>> +	__wsum csum;
>> +	__sum16 sum;
> 
> Hi Vadim,
> 
> sum seems to be is unused in this function.
> And, fwiiw, the scope of csum looks like it could be reduced.

Ah, leftover from previous iteration, thanks for catching it!
Ok, I'll move csum to the "if" block in v2.

>>   	void *data;
>>   	int ret;
>>   
>> -	if (kattr->test.flags || kattr->test.cpu || kattr->test.batch_size)
>> +	if ((kattr->test.flags & ~BPF_F_TEST_SKB_CHECKSUM_COMPLETE) ||
>> +	    kattr->test.cpu || kattr->test.batch_size)
>>   		return -EINVAL;
>>   
>>   	data = bpf_test_init(kattr, kattr->test.data_size_in,
>> @@ -1025,6 +1028,12 @@ int bpf_prog_test_run_skb(struct bpf_prog *prog, const union bpf_attr *kattr,
>>   
>>   	skb_reserve(skb, NET_SKB_PAD + NET_IP_ALIGN);
>>   	__skb_put(skb, size);
>> +
>> +	if (kattr->test.flags & BPF_F_TEST_SKB_CHECKSUM_COMPLETE) {
>> +		skb->csum = skb_checksum(skb, 0, skb->len, 0);
>> +		skb->ip_summed = CHECKSUM_COMPLETE;
>> +	}
>> +
>>   	if (ctx && ctx->ifindex > 1) {
>>   		dev = dev_get_by_index(net, ctx->ifindex);
>>   		if (!dev) {
>> @@ -1079,6 +1088,14 @@ int bpf_prog_test_run_skb(struct bpf_prog *prog, const union bpf_attr *kattr,
>>   	}
>>   	convert_skb_to___skb(skb, ctx);
>>   
>> +	if (kattr->test.flags & BPF_F_TEST_SKB_CHECKSUM_COMPLETE) {
>> +		csum = skb_checksum(skb, 0, skb->len, 0);
>> +		if (skb->csum != csum) {
>> +			ret = -EINVAL;
>> +			goto out;
>> +		}
>> +	}
>> +
>>   	size = skb->len;
>>   	/* bpf program can never convert linear skb to non-linear */
>>   	if (WARN_ON_ONCE(skb_is_nonlinear(skb)))
> 
> ...