[ upstream commit f25d8b9 ]

When Cilium is used in chaining mode with portmap, the hostPort is
translated using iptables DNAT as inserted by the portmap plugin.  When
this happens all within a node, we can preserve the source identity for
the reply traffic for correct visibility. The traffic will be allowed
anyway based on the connection tracking state.

To work with clang-7 and avoid the pattern where the ctx is read into
a register and then incremented then finally a value assigned to it,

  r1 = %[ctx]
  r1 += 8
  ...
  *(u32)(r1 +=8) = %[mark]

We wrote the code block in asm which is not the same as master branch
which was able to use C code due to use of clang-11. We attempted to
update the branch to clang-10 but that created a separate set of issue
that was causing more code churn than we wanted.

Updates: #9784

Signed-off-by: Thomas Graf <thomas@cilium.io>
Signed-off-by: John Fastabend <john.fastabend@gmail.com>

[ upstream commit 9499596 ]

Requires the following tests to pass:
```
NAME                                                     READY   STATUS    RESTARTS   AGE
echo-a-5f555bbc8b-9cxv9                                  1/1     Running   0          41s
echo-b-659766fb56-zw2wl                                  1/1     Running   0          41s
echo-b-host-65d7db76d8-5wmhm                             1/1     Running   0          41s
host-to-b-multi-node-clusterip-c7557d4f8-gv6ws           1/1     Running   0          41s
host-to-b-multi-node-headless-5dfcdf9b76-9hcqn           1/1     Running   0          41s
pod-to-a-6cf58894b7-mqg67                                1/1     Running   0          40s
pod-to-a-allowed-cnp-5898f7d8c9-bdfxz                    1/1     Running   0          41s
pod-to-a-external-1111-5779fb7cb9-tgdlh                  1/1     Running   0          39s
pod-to-a-l3-denied-cnp-74b9566cc7-zjhhh                  1/1     Running   0          41s
pod-to-b-intra-node-77b485d996-xfv45                     1/1     Running   0          40s
pod-to-b-intra-node-hostport-6c55bf8459-vddt2            1/1     Running   0          40s
pod-to-b-multi-node-clusterip-75f5c78f68-2lk8x           1/1     Running   0          40s
pod-to-b-multi-node-headless-5df88f9bd4-f5jlt            1/1     Running   0          40s
pod-to-b-multi-node-hostport-d7c8d659f-4xqpt             1/1     Running   0          39s
pod-to-external-fqdn-allow-google-cnp-74466b4c6f-dxvlq   1/1     Running   0          39s
```

Signed-off-by: Thomas Graf <thomas@cilium.io>
Signed-off-by: John Fastabend <john.fastabend@gmail.com>