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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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63
checker/rules_reachable.go Normal file
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package checker
import (
"context"
"fmt"
"strings"
sdk "git.happydns.org/checker-sdk-go/checker"
)
type ruleTCPReachable struct{}
func RuleTCPReachable() sdk.CheckRule { return &ruleTCPReachable{} }
func (ruleTCPReachable) Name() string { return "srv_tcp_reachable" }
func (ruleTCPReachable) Description() string {
return "Every TCP SRV target:port accepts a TCP connection."
}
func (ruleTCPReachable) Evaluate(ctx context.Context, obs sdk.ObservationGetter, _ sdk.CheckerOptions) []sdk.CheckState {
d, cs := getData(ctx, obs)
if cs != nil {
return []sdk.CheckState{*cs}
}
total, ok, failed := countProbeResults(d, protoTCP)
if total == 0 {
return []sdk.CheckState{{Status: sdk.StatusUnknown, Code: "srv_tcp_na",
Message: "No TCP targets to test."}}
}
if ok == total {
return []sdk.CheckState{{Status: sdk.StatusOK, Code: "srv_tcp_ok",
Message: fmt.Sprintf("All %d TCP target(s) reachable.", total)}}
}
if ok == 0 {
return []sdk.CheckState{{Status: sdk.StatusCrit, Code: "srv_tcp_all_down",
Message: fmt.Sprintf("All %d TCP target(s) unreachable: %s", total, strings.Join(failed, "; "))}}
}
return []sdk.CheckState{{Status: sdk.StatusWarn, Code: "srv_tcp_partial",
Message: fmt.Sprintf("%d/%d TCP target(s) unreachable: %s", total-ok, total, strings.Join(failed, "; "))}}
}
type ruleUDPReachable struct{}
func RuleUDPReachable() sdk.CheckRule { return &ruleUDPReachable{} }
func (ruleUDPReachable) Name() string { return "srv_udp_reachable" }
func (ruleUDPReachable) Description() string {
return "UDP SRV targets do not return ICMP port-unreachable."
}
func (ruleUDPReachable) Evaluate(ctx context.Context, obs sdk.ObservationGetter, _ sdk.CheckerOptions) []sdk.CheckState {
d, cs := getData(ctx, obs)
if cs != nil {
return []sdk.CheckState{*cs}
}
total, ok, failed := countProbeResults(d, protoUDP)
if total == 0 {
return []sdk.CheckState{{Status: sdk.StatusUnknown, Code: "srv_udp_na",
Message: "No UDP targets to test."}}
}
if ok == total {
return []sdk.CheckState{{Status: sdk.StatusOK, Code: "srv_udp_ok",
Message: fmt.Sprintf("All %d UDP target(s) reachable.", total)}}
}
return []sdk.CheckState{{Status: sdk.StatusWarn, Code: "srv_udp_issue",
Message: fmt.Sprintf("%d/%d UDP target(s) reported port unreachable: %s", total-ok, total, strings.Join(failed, "; "))}}
}