CL 548795 mistakenly changed one of the //sys declaration to "// sys"
while resolving a merge conflict.

For golang/go#64710

Change-Id: I029b461fd3ca7b76f3bd23b3343f7e63c4bb09f3
Reviewed-on: https://go-review.googlesource.com/c/sys/+/688857
Reviewed-by: Keith Randall <khr@golang.org>
Reviewed-by: Tobias Klauser <tobias.klauser@gmail.com>
Reviewed-by: Keith Randall <khr@google.com>
Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>

Change-Id: I8b05b5cea86d41423dac9fd96a5000a6daa1e8c3
Reviewed-on: https://go-review.googlesource.com/c/sys/+/690816
Reviewed-by: Tobias Klauser <tobias.klauser@gmail.com>
Reviewed-by: Mark Freeman <mark@golang.org>
Auto-Submit: Tobias Klauser <tobias.klauser@gmail.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Michael Knyszek <mknyszek@google.com>

The following constants were missing for nft conntrack:

- NFT_CT_SRC_IP
- NFT_CT_DST_IP
- NFT_CT_SRC_IP6
- NFT_CT_DST_IP6
- NFT_CT_ID

https://git.netfilter.org/libnftnl/tree/include/linux/netfilter/nf_tables.h?id=7a7722ee336fac14690851f6c84965582a741601#n1173

Change-Id: I2f9bd12c1ab8569ee019310c040b46b214f65b76
GitHub-Last-Rev: 8fac63b
GitHub-Pull-Request: #257
Reviewed-on: https://go-review.googlesource.com/c/sys/+/689922
Reviewed-by: Michael Knyszek <mknyszek@google.com>
Reviewed-by: Tobias Klauser <tobias.klauser@gmail.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Mark Freeman <mark@golang.org>

As discussed later in golang/go#64710, these checks are unnecessary.

For golang/go#64710

Change-Id: I8693af81cc543b886732922eb5cd64e07ed4b7a8
Reviewed-on: https://go-review.googlesource.com/c/sys/+/688858
Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>
Reviewed-by: Mark Freeman <mark@golang.org>
Reviewed-by: Tobias Klauser <tobias.klauser@gmail.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Auto-Submit: Tobias Klauser <tobias.klauser@gmail.com>

Change-Id: Id0b60b5bbc33c48e49ba655babf0856878960e29
Reviewed-on: https://go-review.googlesource.com/c/sys/+/693215
Auto-Submit: Tobias Klauser <tobias.klauser@gmail.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Michael Knyszek <mknyszek@google.com>
Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>