On Wed, Jun 27, 2018 at 07:26:05AM -0600, Arnd Bergmann wrote:

The nes infiniband driver uses current_kernel_time() to get a nanosecond
granunarity timestamp to initialize its tcp sequence counters. This is
one of only a few remaining users of that deprecated function, so we
should try to get rid of it.

Aside from using a deprecated API, there are several problems I see here:

- Using a CLOCK_REALTIME based time source makes it predictable in
  case the time base is synchronized.
- Using a coarse timestamp means it only gets updated once per jiffie,
  making it even more predictable in order to avoid having to access
  the hardware clock source
- The upper 2 bits are always zero because the nanoseconds are at most
  999999999.

For the Linux TCP implementation, we use secure_tcp_seq(), which appears
to be appropriate here as well, and solves all the above problems.

i40iw uses a variant of the same code, so I do that same thing there
for ipv4. Unlike nes, i40e also supports ipv6, which needs to call
secure_tcpv6_seq instead.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
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v2: use secure_tcpv6_seq for IPv6 support as suggested by Shiraz Saleem.
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Looks good.

Acked-by: Shiraz Saleem <redacted>