svn commit: r315653 - in head: lib/libstand sys/boot/common sys/boot/i386/libi386

[Ian Lepore]

On Tue, 2017-03-21 at 15:35 +0300, Slawa Olhovchenkov wrote:
> On Mon, Mar 20, 2017 at 10:20:17PM +0000, Toomas Soome wrote:
> 
> > 
> > Author: tsoome
> > Date: Mon Mar 20 22:20:17 2017
> > New Revision: 315653
> > URL: https://svnweb.freebsd.org/changeset/base/315653
> > 
> > Log:
> >   loader: verify the value from dhcp.interface-mtu and use snprintf
> > to set mtu
> >   
> >   Since the uset can set dhcp.interface-mtu, we need to try to
> > validate the
> >   value. So we verify if the conversion to int is successful and we
> > will not
> >   allow to set value greater than max IPv4 packet size.
> >   
> > +				    tmp > USHRT_MAX) {
> > +					printf("%s: bad value:
> > \"%s\", "
> > +					    "ignoring\n",
> > +					    "dhcp.interface-mtu",
> > val);
> ===
> USHRT_MAX	Maximum value for an object of type unsigned short
> int
> 65535 (216-1) or greater*
> 
> * the actual value depends on the particular system and library
> implementation, but shall reflect the limits of these types in the
> target platform.
> ===
> 
> I mean IF_MAXMTU more correct.
> 

The context here is libstand; because it is standalone by design, the
code doesn't have access to IF_MAXMTU or other kernel/userland
constants.  There is also no question that a short is 16 bits or that
USHRT_MAX will be anything other than 65535 in that environment.  If
some platform did appear that had a different-sized short by default,
we would add whatever flags are necessary to force it back to 16 bits
in src/share/mk/bsd.stand.mk.

-- Ian