On Fri, Jun 30, 2017 at 2:16 PM, Y Song <ys114321@xxxxxxxxx> wrote:
> Maybe *data is not a printable character?
>
> On Fri, Jun 30, 2017 at 12:54 PM, MD I. Islam <tamim@xxxxxxxxxxx> wrote:
>> Hi
>>
>> I have following code attached to an interface:
>>
>> SEC("simple")
>> int handle_ingress(struct __sk_buff *skb)
>> {
>> unsigned char *data = (unsigned char *)(long)skb->data;
Don't you need a data_end check first?
>> char fmt[] = "%u\n";
>> bpf_trace_printk(fmt, sizeof(fmt), *data);
>> return 0;
>> }
>>
>> When packets pass through the interface, it does not print anything at
>> /sys/kernel/debug/tracing/trace_pipe. However if I do
>> bpf_trace_printk(fmt, sizeof(fmt), data), it prints the pointer. Could
>> you please advise what is wrong here?
>>
>> Many thanks
>> Tamim
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