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SubjectRe: [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

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