Hi Arnd, On Thu, 14 Jul 2016 13:39:13 +0200, Arnd Bergmann <a...@arndb.de> wrote :
> On Wednesday, July 13, 2016 7:38:25 PM CEST Deepa Dinamani wrote: > > On Wed, Jul 13, 2016 at 1:40 PM, Deepa Dinamani <deepa.ker...@gmail.com> > > wrote: > > [...] > [...] > > > > > > Another way of handling this would be to use the flags in sendmsg/recvmsg. > > > Since cmsg is sent using these calls, at the time of call, > > > sendmsg/recvmsg can > > > indicate whether 64 bit time_t or 32 bit time_t is used. > > > This will eliminate the need for new options and kernel need not depend on > > > __USE_TIME_BITS64. > > Good point, I had forgotten how we discussed that a while ago. > > [...] > [...] > > > > > > But, if we are not using optlen here, then probably just using new > > > numbers for > > > timestamps also makes sense. > > > > Forgot to note one more thing here. > > Since we are already using struct sizes for ioctls, shouldn't this be > > similar. > > So optlen should also be okay? > > Just as in the example Arnd pointed out above: > > > > /* Set and get port timeout (struct timeval's) */ > > #define PPGETTIME _IOR(PP_IOCTL, 0x95, struct timeval) > > #define PPSETTIME _IOW(PP_IOCTL, 0x96, struct timeval) > > I've added the netdev list and David Miller to Cc here, it seems > either way would work, and I don't have a strong preference. > > a) add a flag to recvmsg() that glibc always passes when called > using __USE_TIME_BITS64 to handle reading the timestamps, and > rely on the optlen value for SO_RCVTIMEO/SO_SNTTIMEO to > decide how to interpret the data > > b) handle all five sockopts using conditional option numbers > and don't rely on the recvmsg() flag or optlen. > > Using either a) or b) is probably better than a combination of > them, so I've not listed that as another alternative. > > To work around the header inclusion order problem we discussed > earlier for approach b), I suppose we can do this using > something like > > > #define SO_RCVTIMEO_TIME32 21 > #define SO_RCVTIMEO_TIME64 53 > > #define SO_RCVTIMEO (__USE_TIME_BITS==64 ? SO_RCVTIMEO_TIME64 : > SO_RCVTIMEO_TIME32) > > where __USE_TIME_BITS is a macro defined by the libc. We cannot easily > check for whether a macro is defined in a conditional expression, > but I think the above should work, as long as we don't need use the > value from assembler code. > > Arnd Seems like there was no reply on the netdev or libc-alpha lists or from David. I personally am not fond of relying on length to determine which variant of an argument we are dealing with, therefore I prefer option b over option a and will update the design doc accordingly. Cordialement, Albert ARIBAUD 3ADEV
