On Sat, Aug 06, 2016 at 01:36:26AM +0300, Vadim Kochan wrote:
> On Wed, Aug 03, 2016 at 04:27:14PM +0200, Tobias Klauser wrote:
> > On 2016-07-26 at 21:35:10 +0200, Vadim Kochan <vadi...@gmail.com> wrote:
> > > Extended 'struct packet_dyn' with proto fields which has
> > > dynamically changing values at runtime.
> > >
> > > Implement incrementing of proto field at runtime with min & max
> > > parameters, by default if the 'min' parameter is not specified
> > > then original value is used. For fields which len is greater
> > > than 4 - last 4 bytes are incremented as unsigned int value.
> > >
> > > Added 'field_changed' callback for proto header which
> > > may be used for check if csum updating is needed. This callback
> > > is called after field was changed at runtime.
> > >
> > > Added 'packet_update' callback to let proto header know
> > > when to apply final proto header changes at runtime (csum update).
> >
> > The documentation of these callbacks would also make sense where they're
> > defined.
> >
> > > Signed-off-by: Vadim Kochan <vadi...@gmail.com>
> > > ---
> > > trafgen.c | 9 ++++++
> > > trafgen_conf.h | 7 ++++
> > > trafgen_proto.c | 99
> > > +++++++++++++++++++++++++++++++++++++++++++++++++++++++++
> > > trafgen_proto.h | 26 +++++++++++++++
> > > 4 files changed, 141 insertions(+)
> > >
> > > diff --git a/trafgen.c b/trafgen.c
> > > index b76b5d7..553dfa5 100644
> > > --- a/trafgen.c
> > > +++ b/trafgen.c
> > > void proto_packet_finish(void)
> > > {
> > > struct proto_hdr **headers = ¤t_packet()->headers[0];
> > > @@ -433,3 +446,89 @@ void proto_packet_finish(void)
> > > p->packet_finish(p);
> > > }
> > > }
> > > +
> > > +static inline unsigned int field_inc(struct proto_field *field)
> > > +{
> > > + uint32_t val;
> > > +
> > > + val = field->func.val - field->func.min;
> > > + val = (val + field->func.inc) % field->func.max;
> >
> > Shouldn't this be
> >
> > val = (val + field->func.inc) % (field->func.max - field->func.min + 1)
> >
> > to be consistent with apply_counter()?
I simplified it and now it really works well:
#define max_int32(a, b)
\
({
\
int32_t _a = (int32_t) (a);
\
int32_t _b = (int32_t) (b);
\
_a - ((_a - _b) & ((_a - _b) >> (sizeof(int32_t) * 8 -
1))); \
})
static inline unsigned int field_inc(struct proto_field *field)
{
uint32_t min = field->func.min;
uint32_t max = field->func.max;
uint32_t val = field->func.val;
uint32_t inc = field->func.inc;
uint32_t next;
next = (val + inc) % (max + 1);
field->func.val = max_int32(next, min);
return val;
}
so max_int32(a,b) should be fast enough w/o branching.
>
> Sure, I tried this approach while implementing 1st version but when I
> used the following case:
>
> trafgen/trafgen -o lo -n 10 --cpu 1 '{ eth(type=0x800), fill(0xff, 10),
> dinc(5, 20, 5) }'
>
> then interval between 5 & 20 changes very differently. But in my version
> it repeats from 5 till 20 (yes here is a little difference that initial
> value is incremented immideately). Also semantic of proto dinc is
> dinc(step, min, max), and I will change it to looks like low-level one -
> dinc(min, max, step).
>
> >
> > Also, I think you should probably get rid of as many pointer
> > dereferences as possible in these runtime functions, i.e. store max and
> > min in temporary variables.
>
> OK, makes sense.
>
> >
> > > + field->func.val = val + field->func.min;
> > > +
> > > + return field->func.val;
> > > +}
> > > +
> > > +static void field_inc_func(struct proto_field *field)
> > > +{
> > > + if (field->len == 1) {
> > > + uint8_t val;
> > > +
> > > + val = field_inc(field);
> > > + proto_field_set_u8(field->hdr, field->id, val);
> >
> > Assignment on declaration please. Or even better:
> >
> > proto_field_set_u8(field->hdr, field->id, field_inc(field));
>
> OK
>
> >
> > > + } else if (field->len == 2) {
> > > + uint16_t val;
> > > +
> > > + val = field_inc(field);
> > > + proto_field_set_be16(field->hdr, field->id, val);
> >
> > Same.
> OK
>
> >
> > > + } else if (field->len == 4) {
> > > + uint32_t val;
> > > +
> > > + val = field_inc(field);
> > > + proto_field_set_be32(field->hdr, field->id, val);
> >
> > Same.
> OK
>
> >
> > > + } else if (field->len > 4) {
> > > + uint8_t *bytes = __proto_field_get_bytes(field);
> > > + uint32_t val;
> > > +
> > > + bytes += field->len - 4;
> > > + val = field_inc(field);
> > > +
> > > + *(uint32_t *)bytes = bswap_32(val);
> >
> > This part looks really odd. Did you actually verify it produces the
> > correct result on both big/little endian and for various field lengths?
> >
> > To be honest I don't see much use for counters going beyond UINT32_T_MAX
> > (or maybe UINT64_T_MAX, which should be handled as a separate case if
> > then). Or do you know of a protocol with sequence numbers (or similar) >
> > 64 bit for which this would really be useful?
>
> Hm, may be it looks & sounds odd but I use it for incrementing MAC & IPv6
> addresses (the last 4 bytes, it might be improved to 8 bytes for x64
> arch). In the future I think to extend syntax to allow specify interval
> of incrementing like:
>
> ipv4(saddr[0:3]=dinc())
>
> or may be you have better idea, but I dont wanna extend dinc() for this.
Also I think may be in case of MAC/IPv6 (field->len > 4) - use index of the
current
incremented byte and when it is reached 0xFF - pick the next one. But if
you OK with current approach (but I am not sure you do) - I will change it in
future patches.
>
> >
> > > + }
> > > +}
> > > +
> > > +void proto_field_func_add(struct proto_hdr *hdr, uint32_t fid,
> > > + struct proto_field_func *func)
> > > +{
> > > + struct proto_field *field = proto_field_by_id(hdr, fid);
> > > +
> > > + bug_on(!func);
> > > +
> > > + memcpy(&field->func, func, sizeof(*func));
> > > +
> > > + if (func->type & PROTO_FIELD_FUNC_INC) {
> > > + if (field->len == 1)
> > > + field->func.val = proto_field_get_u8(hdr, fid);
> > > + else if (field->len == 2)
> > > + field->func.val = proto_field_get_u16(hdr, fid);
> > > + else if (field->len == 4)
> > > + field->func.val = proto_field_get_u32(hdr, fid);
> > > + else if (field->len > 4) {
> > > + uint8_t *bytes = __proto_field_get_bytes(field);
> > > +
> > > + bytes += field->len - 4;
> > > + field->func.val = bswap_32(*(uint32_t *)bytes);
> > > + }
> > > +
> > > + if (field->func.max) {
> > > + field->func.max = (field->func.max - field->func.min +
> > > + field->func.inc) ?:
> > > + 1;
> >
> > To me it is not entirely obvious why you do this here (I assume it has
> > something to do with reducing calculations at runtime?). In any case
> > this needs an explanatory comment.
I removed this.
>
> Fuf, sorry, I can't say why I did so, probably I was fighting with
> circular increment problem, anyway I can't say exactly why, need to look
> closer.
>
> >
> > > + } else {
> > > + field->func.max = (uint32_t)~0;
> > > + }
> > > +
> > > + if (func->type & PROTO_FIELD_FUNC_MIN)
> > > + field->func.val = field->func.min;
OK, I removed this.
> >
> > Why does this need an own condition? Don't we expect to start
> > incrementing from the min value in any case?
> >
> I was thinking about to keep existing field value if MIN was not
> specified. For example of MAC/IPv6 address was used, then I increment
> existing bytes array. Probably it looks ugly, not sure how to simplify it.
>
> > > +
> > > + field->func.update_field = field_inc_func;
> > > + }
> > > +}
> > > +
>
> Thanks for comments,
> Vadim Kochan
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