Re: [PATCH] [v3] infiniband: i40iw, nes: don't use wall time for TCP sequence numbers

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.

Acked-by: Shiraz Saleem <redacted>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
---
v2: use secure_tcpv6_seq for IPv6 support as suggested by Shiraz Saleem.
v3: add a soft IPv6 dependency to prevent a link error with CONFIG_IPV6=m,
    this now forces i40iw to be a module as well, add an IS_ENABLED()
    check to avoid calling it when IPV6 is completely disabled.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
---
 drivers/infiniband/hw/i40iw/Kconfig    |  1 +
 drivers/infiniband/hw/i40iw/i40iw_cm.c | 26 +++++++++++++++++++++-----
 drivers/infiniband/hw/nes/nes_cm.c     |  8 +++++---
 net/core/secure_seq.c                  |  1 +
 4 files changed, 28 insertions(+), 8 deletions(-)

diff --git a/drivers/infiniband/hw/i40iw/Kconfig b/drivers/infiniband/hw/i40iw/Kconfig
index 2962979c06e9..d867ef1ac72a 100644
--- a/drivers/infiniband/hw/i40iw/Kconfig
+++ b/drivers/infiniband/hw/i40iw/Kconfig

@@ -1,6 +1,7 @@
 config INFINIBAND_I40IW
 	tristate "Intel(R) Ethernet X722 iWARP Driver"
 	depends on INET && I40E
+	depends on IPV6 || !IPV6
 	depends on PCI
 	select GENERIC_ALLOCATOR
 	---help---