On 2026/10/06 17:01, Theo de Raadt wrote:
> Stuart Lamble <[email protected]> wrote:
>
> > On Wed, Oct 7, 2026, at 09:25, Theo de Raadt wrote:
> > > warning: rand() may return deterministic values, is that what
> > > you want?
> > >
> > > In this day and age, wow.
> >
> > It also comes out when compiling Kea. I haven’t had the time to look into
> > it and figure out if it’s a concern.
>
> The existance of rand() in a binary is always a concern, unless it has been
> reviewed and declared OK. It is almost never OK. Using it is never required,
> those days are gone.
>
> I think you are saying it backwards. If it exists in a binary, it is bad and
> wrong.
>
This is only in a benchmark tool (perfdhcp), not part of the main
program. Predictability is not really a concern there afaik.
Looks like modulo bias though.
/// \brief Returns random relay address.
///
/// \return single string containing relay address.
std::string getRandRelayAddr() { return relay_addr_list_[rand() %
relay_addr_list_.size()]; }
/// \brief Returns random packet from the storage.
///
/// This function picks random packet from the storage and returns
/// it. It is way slower than the @c getNext function because it has to
/// iterate over all existing entries from the beginning of the storage
/// to the random packet's position. Therefore, care should be taken
/// when using this function to access elements when storage is large.
///
/// \return random packet from the storage.
PacketPtr getRandom() {
if (empty()) {
return (PacketPtr());
}
current_pointer_ = storage_.begin();
if (size() > 1) {
std::advance(current_pointer_, rand() % (size() - 1));
}
PacketPtr packet = *current_pointer_;
current_pointer_ = storage_.erase(current_pointer_);
return (packet);
}
