On 2021-11-20 21:16 +01, Otto Moerbeek <o...@drijf.net> wrote:
> On Sat, Nov 20, 2021 at 06:44:58PM +0100, Florian Obser wrote:
>
>> On 2021-11-20 18:41 +01, Florian Obser <flor...@openbsd.org> wrote:
>> > On 2021-11-20 18:19 +01, Florian Obser <flor...@openbsd.org> wrote:
>> >
>> >> +/*
>> >> + * Clear AD flag in the answer.
>> >> + */
>> >> +static void
>> >> +clear_ad(struct asr_result *ar)
>> >> +{
>> >> + struct asr_dns_header *h;
>> >> + uint16_t flags;
>> >> +
>> >> + h = (struct asr_dns_header *)ar->ar_data;
>> >> + flags = ntohs(h->flags);
>> >> + flags &= ~(AD_MASK);
>> >> + h->flags = htons(flags);
>> >> +}
>> >> +
>> >
>> > btw. is it possible that this is not alligned correctly on sparc64?
>> >
>> > should be do something like (not even compile tested)
>> >
>> > static void
>> > clear_ad(struct asr_result *ar)
>> > {
>> > struct asr_dns_header h;
>> >
>> > memmove(&h, ar->ar_data, sizeof(h));
>> > h.flags = ntohs(h.flags);
>> > h.flags &= ~(AD_MASK);
>> > h.flags = htons(h.flags);
>> > memmove(ar->ar_data, &h, sizeof(h));
>> > }
>> >
>>
>> memcpy obviously, I was distracted by the copious amount of memmove in
>> asr code...
>
> It is not needed to copy the "whole" header just to change the flags.
> You could just copy out, modify and copy back the flags field only.
>
> otoh, it's just 12 bytes, so no big deal.
right. So I have tried my patch (without the memcpy dance) on sparc64
over udp and tcp and I have also tracked this down in the code. This
should be fine as is. ar->ar_data comes directly out of malloc
(reallocarray) in ensure_ibuf() and the struct is defined thusly:
struct asr_dns_header {
uint16_t id;
uint16_t flags;
uint16_t qdcount;
uint16_t ancount;
uint16_t nscount;
uint16_t arcount;
};
>
> -Otto
>
--
I'm not entirely sure you are real.
