Hi, On Mon, Jan 30, 2023 at 06:29:33PM +0100, Arne Schwabe wrote: > The undefined behaviour USAN clang checker found this. > > This fix is a bit messy but so are the original structures.
I wonder...
> + struct sockaddr_dl sdl = { 0 };
> + memcpy(&sdl, &ifr.ifr_addr, sizeof(ifr.ifr_addr));
> + memcpy(rgi->hwaddr, LLADDR(&sdl), 6);
> rgi->flags |= RGI_HWADDR_DEFINED;
... why you keep the "sockaddr_dl" intermediate - this was useful
for "we use it as a pointer", but doing two memcpy() with a huge
explanation above looks weird.
LLADDR on FreeBSD is
#define LLADDR(s) ((caddr_t)((s)->sdl_data + (s)->sdl_nlen))
(to operate on a "struct sockaddr_dl")
struct ifaddr has
struct ifaddr {
struct sockaddr *ifa_addr; /* address of interface */
struct sockaddr *ifa_dstaddr; /* other end of p-to-p link */
struct sockaddr *ifa_netmask; /* used to determine subnet */
... so the first memcpy() isn't actually copying the MAC address around,
just a bunch of pointers, and then we dereference the first of them
for the second memcpy(), using the dereferencing macro for a
"sockaddr_dl" structure.
FreeBSD also has
#define IF_LLADDR(ifp) \
LLADDR((struct sockaddr_dl *)((ifp)->if_addr->ifa_addr))
which sounds like "feed in an *ifr, out comes a pointer for the
memcpy() to rgi->addr".
I'll check the other BSDs if LL_IFADDR() is available everywhere, but
if not, we can just do the same thing (struct ifr is aligned) and
get rid of the "sdl" and the first memcpy().
(Am I overlooking something?)
gert
--
"If was one thing all people took for granted, was conviction that if you
feed honest figures into a computer, honest figures come out. Never doubted
it myself till I met a computer with a sense of humor."
Robert A. Heinlein, The Moon is a Harsh Mistress
Gert Doering - Munich, Germany g...@greenie.muc.de
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