feat(network): add support for forward guest localhost DNS for unikraft

[alimx07]

Description

This PR will add support for localhost semantics added in #793 for unikraft unikernels. This will be done by modifying the CMD line defined here:

u.configureUnikraftArgs(data.Rootfs.Type, data.Net.IP, data.Net.Gateway, data.Net.Mask, data.Net.DNSServer)

as the new DNSServer will be either:

• the Default 8.8.8.8
• The Custom one defined in internal/constants/network_constants (e.g. 192.168.100.100)

The exact of this happens is defined in #793 but as breif, we detect if we have localhost resolvers ,then rewrite them to point to our Custom resolver, where we apply TC rules to intercept traffic and redirect it according to our rules

Related issues

• Continue feat: forward guest DNS to Docker's embedded resolver #793

How was this tested?

LLM usage

Checklist

• I have read the contribution guide.
• The linter passes locally (make lint).
• The e2e tests of at least one tool pass locally (make test_ctr, make test_nerdctl, make test_docker, make test_crictl).
• If LLMs were used: I have read the llm policy.

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[cmainas]

Hello @alimx07 , this looks good, We can merge it directly.

[cmainas]

However, please complete the PR description correctly.

[cmainas]

Hello @alimx07 ,

let;s make this as a standalone PR and fix the hardcoded value of unikraft's DNS configuration. What we need is to simply read the /etc/resolv/conf file find the dns server and set DNSServer respectively. See #979 (comment) for more context.

[alimx07]

Hello @alimx07 ,

let;s make this as a standalone PR and fix the hardcoded value of unikraft's DNS configuration. What we need is to simply read the /etc/resolv/conf file find the dns server and set DNSServer respectively. See #979 (comment) for more context.

Hi @cmainas , I tried to make it minimal, it does the required functionality but even that we still need the docker PR for docker case and TC rules.

[cmainas]

Thank you @alimx07 ,

this PR fixes an existing bug for k8s deployments so it has priority over the docker case.

A few changes for the CI, so we can merge:

• sign-off and squash your commits
• add yourself in https://github.com/urunc-dev/urunc/blob/main/.github/contributors.yaml
• mark this as ready for review. You can can mark the sidecar test PR as draft
• the test will never succeed. I have created a new image harbor.nbfc.io/nubificus/urunc/dns-test-qemu-unikraft-initrd:latest . The expected output should be github.com OK. I have also added these comments in the respective lines.

[cmainas]

Replace with harbor.nbfc.io/nubificus/urunc/dns-test-qemu-unikraft-initrd:latest

[cmainas]

Replace with github.com OK

[cmainas]

Hello @alimx07 ,

thank you for the rebase, but the it does not build. Also, now we need to take into account libcontainer and move the DNS server discovery in the "urunc create" process, since "urunc monitor" in libcontainer does not have a view of the host rootfs.

[cmainas]

We need to move this to InitisalSetup so it can also take effect in libcontainer. The monitorSpec struct can be updated to store the value of DNS so it can be then read from the urunc reexec and urunc monitor processes.

[alimx07]

Hi @cmainas, sorry, I have been a bit busy these days. If others are blocked, feel free to assign someone else to continue with this PR. Otherwise, I’ll look into it over the weekend.