Re: git: eb8dcdeac22d - main - jail: network epoch protection for IP address lists

On 26 Dec 2021, at 19:14, Gleb Smirnoff <glebius@freebsd.org> wrote:
> 
>  Jessica,
> 
> On Sun, Dec 26, 2021 at 07:07:06PM +0000, Jessica Clarke wrote:
> J> > +struct prison_ip {
> J> > +	struct epoch_context ctx;
> J> > +	uint32_t	ips;
> J> > +#ifdef FUTURE_C
> J> > +	union {
> J> > +		struct in_addr pr_ip4[];
> J> > +		struct in6_addr pr_ip6[];
> J> > +	};
> J> > +#else /* No future C :( */
> J> > +#define	PR_IP(pip, i)	((const char *)((pip) + 1) + pr_families[af].size * (i))
> J> > +#define	PR_IPD(pip, i)	((char *)((pip) + 1) + pr_families[af].size * (i))
> J> > +#endif
> J> > +};
> J> 
> J> You can make this work with a prison_ip base and prison_ipv[46] derived
> J> structs.
> J> 
> J> As it stands this is quite gross, you’re assuming things about
> J> alignment, and don’t even have a flexible char[] at the end to
> J> represent the extra data.
> 
> Will adding char [] to the end be sufficient to guarantee proper alignment?

No.

> Using prison_ipv[46] derived structs won't work as most functions are now
> made protocol independent.

Why not? Just cast from prison_ip * to prison_ipv4 * when known/needed?

Jess