Re: [Y2038] [PATCH v2 6/8] socket: Add SO_TIMESTAMP[NS]_NEW

...

Also for the other comment. The reason the conditionals were not consistent is because they were not consistent to begin with.

The only difference I see is an inversion of the test. Nesting order is the same:

    int need_software_tstamp = sock_flag(sk, SOCK_RCVTSTAMP);
    ...
    if (need_software_tstamp) {
            if (!sock_flag(sk, SOCK_RCVTSTAMPNS)) {
            } else {
            }
    }

vs

            if (sock_flag(sk, SOCK_RCVTSTAMP)) {
                    if (sock_flag(sk, SOCK_RCVTSTAMPNS)) {
                    } else {
                    }
            }

I suggest just adding something like

    if (need_software_tstamp) {

•          if (sock_uses_new_tstamp(sk) {
  

•               __sock_recv_timestamp_new(msg, sk,
  

ktime_to_timespec64(skb->tstamp));

•          } else if (!sock_flag(sk, SOCK_RCVTSTAMPNS)) {
  

•           if (!sock_flag(sk, SOCK_RCVTSTAMPNS)) {
            } else {
            }
  
  

and

            if (sock_flag(sk, SOCK_RCVTSTAMP)) {

•                  if (sock_uses_new_tstamp(sk) {
  

•                       __sock_recv_timestamp_new(msg, sk, ts);
  

•                  else if (sock_flag(sk, SOCK_RCVTSTAMPNS)) {
  

•                   if (sock_flag(sk, SOCK_RCVTSTAMPNS)) {
                    } else {
                    }
  
  

I think we can use the same helper for both the sock and tcp variant. The only intended difference between the two functions, as described in the tcp_recv_timestamp function comment, is the absence of an skb in the tcp case. That is immaterial at this level.

I will just not refactor things into a function: __sock_rescv_timestamp_new(). I will just add new conditionals for the new timestamps. When you guys refactor the other timestamp stuff like you mentioned below maybe you can move the new timestamps to a new funtcion as you see fit.

The helper functions in skbuff.h might first need to be refactored first. But I again leave this to you guys.

Note also (2) tentative helper function sock_uses_new_tstamp(const struct sock *sk) instead of testing sock_flag(sk, SOCK_TSTAMP_NEW) directly. Since the .._NEW variants are equivalent to .._OLD on 64-bit, I wonder if we can just compile out the branch. Something like

static inline bool sock_uses_new_tstamp(const struct sock *sk) {
        return (sizeof(time_t) != sizeof(__kernel_long_t)) &&
                   sock_flag(sk, SOCK_TSTAMP_NEW);
}

You could just ifdef CONFIG_64BIT if you are worried about branching. Note that SO_TIMESTAMP is by default SO_TIMESTAMP_OLD on 64 bit machines. But, I will again leave the optimization to you. I will implement in a straight forward way and you guys can deicde how you want to optimize the fast path or what should it even be.

-Deepa