dns: adding support for edns0 size customisation via envoy filters

[kishor7007]

Implementation for #40696

Currently dns response size is 1232 on UDP support as per c-ares lib(https://github.com/c-ares/c-ares/blob/main/src/lib/ares_private.h#L133) on EDNS0. we can provide the option via envoy filters to customise the size as per end user needs like 4096, etc.
[optional Relevant Links:]

Any extra documentation required to understand the issue.
https://datatracker.ietf.org/doc/html/rfc6891

Sample Service Entry for testing:

apiVersion: networking.istio.io/v1beta1
kind: ServiceEntry
metadata:
  name: external-svc-https
spec:
  hosts:
  - example.com
  location: MESH_EXTERNAL
  ports:
  - number: 443
    name: https
    protocol: TLS
  resolution: DNS

Sample Envoy filter tested with:

apiVersion: networking.istio.io/v1alpha3
kind: EnvoyFilter
metadata:
  name: dns-edns0-config
  namespace: istio-system
spec:
  configPatches:
  - applyTo: CLUSTER
    patch:
      operation: MERGE
      value:
        typed_dns_resolver_config:
          name: envoy.network.dns_resolver.cares
          typed_config:
            "@type": type.googleapis.com/envoy.extensions.network.dns_resolver.cares.v3.CaresDnsResolverConfig
            edns0_max_payload_size: 4096

Test Results:
============Before applying the envoy filter (UDP truncate, TCP retry)==================

Aug 19, 2025 11:41:01.806071736 UTC 1268 sll:ethertype:ip:udp:dns 17 192.168.1.101,192.168.1.102,192.168.1.103,192.168.1.104,192.168.1.105,192.168.1.106,192.168.1.107,192.168.1.108,192.168.1.109,192.168.1.110,192.168.1.111,192.168.1.112,192.168.1.113,192.168.1.114,192.168.2.195,192.168.2.196,192.168.2.197,192.168.2.198,192.168.2.199,192.168.2.200,192.168.2.201,192.168.2.202,192.168.3.101,192.168.3.102,192.168.3.103,192.168.3.104,192.168.3.105,192.168.3.106,192.168.3.107,192.168.3.108,192.168.3.109,192.168.3.110,192.168.3.111,192.168.3.112,192.168.3.113,192.168.3.114,192.168.3.195,192.168.3.196,192.168.3.197,192.168.3.198,192.168.3.199,192.168.3.200,192.168.4.101,192.168.4.102,192.168.4.103,192.168.4.104,192.168.4.105,192.168.4.106,192.168.4.107,192.168.4.108,192.168.4.109,192.168.4.110,192.168.4.111,192.168.4.112,192.168.4.113,192.168.4.114,192.168.4.195,192.168.5.101,192.168.5.102,192.168.5.103,192.168.5.104,192.168.5.105,192.168.5.106,192.168.5.107,192.168.5.108,192.168.5.109,192.168.5.110,192.168.5.111,192.168.5.112,192.168.5.113,192.168.5.114,192.168.5.195,192.168.6.101,192.168.6.102

Aug 19, 2025 11:41:01.806637942 UTC 2459 sll:ethertype:ip:tcp:dns 6 192.168.1.101,192.168.1.102,192.168.1.103,192.168.1.104,192.168.1.105,192.168.1.106,192.168.1.107,192.168.1.108,192.168.1.109,192.168.1.110,192.168.1.111,192.168.1.112,192.168.1.113,192.168.1.114,192.168.2.195,192.168.2.196,192.168.2.197,192.168.2.198,192.168.2.199,192.168.2.200,192.168.2.201,192.168.2.202,192.168.3.101,192.168.3.102,192.168.3.103,192.168.3.104,192.168.3.105,192.168.3.106,192.168.3.107,192.168.3.108,192.168.3.109,192.168.3.110,192.168.3.111,192.168.3.112,192.168.3.113,192.168.3.114,192.168.3.195,192.168.3.196,192.168.3.197,192.168.3.198,192.168.3.199,192.168.3.200,192.168.4.101,192.168.4.102,192.168.4.103,192.168.4.104,192.168.4.105,192.168.4.106,192.168.4.107,192.168.4.108,192.168.4.109,192.168.4.110,192.168.4.111,192.168.4.112,192.168.4.113,192.168.4.114,192.168.4.195,192.168.5.101,192.168.5.102,192.168.5.103,192.168.5.104,192.168.5.105,192.168.5.106,192.168.5.107,192.168.5.108,192.168.5.109,192.168.5.110,192.168.5.111,192.168.5.112,192.168.5.113,192.168.5.114,192.168.5.195,192.168.6.101,192.168.6.102,192.168.6.103,192.168.6.104,192.168.6.105,192.168.6.106,192.168.6.107,192.168.6.108,192.168.6.109,192.168.6.110,192.168.6.111,192.168.6.112,192.168.6.113,192.168.6.114,192.168.6.195

               =============After applying the envoy filter(whole response in UDP)=============

Aug 19, 2025 11:39:45.315502503 UTC 1476 sll:ethertype:ip:udp:dns 17 192.168.1.101,192.168.1.102,192.168.1.103,192.168.1.104,192.168.1.105,192.168.1.106,192.168.1.107,192.168.1.108,192.168.1.109,192.168.1.110,192.168.1.111,192.168.1.112,192.168.1.113,192.168.1.114,192.168.2.195,192.168.2.196,192.168.2.197,192.168.2.198,192.168.2.199,192.168.2.200,192.168.2.201,192.168.2.202,192.168.3.101,192.168.3.102,192.168.3.103,192.168.3.104,192.168.3.105,192.168.3.106,192.168.3.107,192.168.3.108,192.168.3.109,192.168.3.110,192.168.3.111,192.168.3.112,192.168.3.113,192.168.3.114,192.168.3.195,192.168.3.196,192.168.3.197,192.168.3.198,192.168.3.199,192.168.3.200,192.168.4.101,192.168.4.102,192.168.4.103,192.168.4.104,192.168.4.105,192.168.4.106,192.168.4.107,192.168.4.108,192.168.4.109,192.168.4.110,192.168.4.111,192.168.4.112,192.168.4.113,192.168.4.114,192.168.4.195,192.168.5.101,192.168.5.102,192.168.5.103,192.168.5.104,192.168.5.105,192.168.5.106,192.168.5.107,192.168.5.108,192.168.5.109,192.168.5.110,192.168.5.111,192.168.5.112,192.168.5.113,192.168.5.114,192.168.5.195,192.168.6.101,192.168.6.102,192.168.6.103,192.168.6.104,192.168.6.105,192.168.6.106,192.168.6.107,192.168.6.108,192.168.6.109,192.168.6.110,192.168.6.111,192.168.6.112,192.168.6.113,192.168.6.114,192.168.6.195

[repokitteh-read-only]

CC @envoyproxy/api-shepherds: Your approval is needed for changes made to (api/envoy/|docs/root/api-docs/).
envoyproxy/api-shepherds assignee is @markdroth
CC @envoyproxy/api-watchers: FYI only for changes made to (api/envoy/|docs/root/api-docs/).

🐱

Caused by: #40776 was opened by kishor7007.

see: more, trace.

[markdroth]

/lgtm api

[kishor7007]

@markdroth , @yanavlasov ,
If you get a chance, could you please review?

[markdroth]

/lgtm api

[kishor7007]

@yanavlasov, gentle reminder