From: Alexei Starovoitov <a...@fb.com> Date: Thu, 11 May 2017 15:53:06 -0700
> On 5/11/17 9:05 AM, David Miller wrote: >> + had_id = (dst_reg->id != 0); >> + >> /* dst_reg stays as pkt_ptr type and since some positive >> * integer value was added to the pointer, increment its 'id' >> */ >> dst_reg->id = ++env->id_gen; >> >> - /* something was added to pkt_ptr, set range and off to zero */ >> + /* something was added to pkt_ptr, set range to zero */ >> + dst_reg->aux_off = dst_reg->off; > > what about 2nd addition of a variable to pkt_ptr ? > aux_off sort-of remembers already accumulated offset in pkt_ptr, but > above line will hard assign it which doesn't seem right for the 2nd > addition. > Ex: > before first add, reg->off == 14 > after first add, aux_off = 14, off = 0 > then imm4 added, now we have reg->off=4, aux_off=14 > now we do 2nd add of variable and > reg->aux_off becomes 4 > and if we later do u64 load from the packet it will be rejected > due to (net_ip_align + 4) whereas it should have been ok > due to (net_ip_align + 14 + 4). Indeed, we have to accumulate. I was just thinking about this earlier today. Thanks for pointing this out, I'll work on a fix and write some test cases.
