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Generic SRV records checker for happyDomain.

For each SRV record attached to an svcs.UnknownSRV service, the checker
resolves every target and probes reachability:

  - DNS resolution (A/AAAA), CNAME detection (RFC 2782 violation),
    null-target detection (RFC 2782 "service explicitly unavailable")
  - TCP connect to target:port for _tcp SRVs
  - UDP probe for _udp SRVs, using ICMP port-unreachable detection

The checker also publishes TLS endpoints (host, port, SNI) for every
SRV target hitting a well-known direct-TLS port (443, 465, 636, 853,
993, 995, 5061, 5223, …) via the EndpointDiscoverer SDK interface, so
a downstream TLS checker can pick them up.

The HTML report groups records as cards and surfaces the most common
failure scenarios (DNS failure, CNAME target, TCP unreachable,
null-target) at the top with remediation guidance.
This commit is contained in:
nemunaire 2026-04-19 10:28:39 +07:00
commit 7e50f404a1
27 changed files with 2389 additions and 0 deletions
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39
checker/rules_redundancy.go Normal file
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package checker
import (
"context"
"fmt"
sdk "git.happydns.org/checker-sdk-go/checker"
)
type ruleRedundancy struct{}
func RuleRedundancy() sdk.CheckRule { return &ruleRedundancy{} }
func (ruleRedundancy) Name() string { return "srv_redundancy" }
func (ruleRedundancy) Description() string {
return "At least two distinct SRV targets exist (avoids single point of failure)."
}
func (ruleRedundancy) Evaluate(ctx context.Context, obs sdk.ObservationGetter, _ sdk.CheckerOptions) []sdk.CheckState {
d, cs := getData(ctx, obs)
if cs != nil {
return []sdk.CheckState{*cs}
}
targets := map[string]bool{}
for _, r := range d.Records {
if r.IsNullTarget {
continue
}
targets[r.Target] = true
}
if len(targets) >= 2 {
return []sdk.CheckState{{Status: sdk.StatusOK, Code: "srv_redundant",
Message: fmt.Sprintf("%d distinct targets.", len(targets))}}
}
if len(targets) == 1 {
return []sdk.CheckState{{Status: sdk.StatusInfo, Code: "srv_single_target",
Message: "Single SRV target: no redundancy at DNS level."}}
}
return []sdk.CheckState{{Status: sdk.StatusUnknown, Code: "srv_no_targets_redundancy",
Message: "No usable SRV targets."}}
}