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Strip OPT from response when client lacked EDNS0; add tests; show EDE in capture

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This commit is contained in:
Viktor Liu
2026-05-06 10:31:03 +02:00
parent e394818b9f
commit bea54ef6aa
3 changed files with 145 additions and 4 deletions
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29
util/capture/text.go
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@@ -10,6 +10,7 @@ import (
"github.com/google/gopacket"
"github.com/google/gopacket/layers"
"github.com/miekg/dns"
)
// TextWriter writes human-readable one-line-per-packet summaries.
@@ -594,7 +595,8 @@ func formatDNSResponse(d *layers.DNS, rd string, plen int) string {
arCount := d.ARCount
if d.ResponseCode != layers.DNSResponseCodeNoErr {
return fmt.Sprintf("%04x %d/%d/%d %s (%d)", d.ID, anCount, nsCount, arCount, d.ResponseCode, plen)
ede := formatEDE(d)
return fmt.Sprintf("%04x %d/%d/%d %s%s (%d)", d.ID, anCount, nsCount, arCount, d.ResponseCode, ede, plen)
}
if anCount > 0 && len(d.Answers) > 0 {
@@ -607,6 +609,31 @@ func formatDNSResponse(d *layers.DNS, rd string, plen int) string {
return fmt.Sprintf("%04x %d/%d/%d (%d)", d.ID, anCount, nsCount, arCount, plen)
}
// dnsOPTCodeEDE is the EDNS0 option code for Extended DNS Errors (RFC 8914).
const dnsOPTCodeEDE layers.DNSOptionCode = layers.DNSOptionCode(dns.EDNS0EDE)
// formatEDE returns " EDE=Name" for the first Extended DNS Error option
// found in the response, or empty string if none is present.
func formatEDE(d *layers.DNS) string {
for _, rr := range d.Additionals {
if rr.Type != layers.DNSTypeOPT {
continue
}
for _, opt := range rr.OPT {
if opt.Code != dnsOPTCodeEDE || len(opt.Data) < 2 {
continue
}
info := binary.BigEndian.Uint16(opt.Data[:2])
name, ok := dns.ExtendedErrorCodeToString[info]
if !ok {
name = fmt.Sprintf("%d", info)
}
return " EDE=" + name
}
}
return ""
}
func shortRData(rr *layers.DNSResourceRecord) string {
switch rr.Type {
case layers.DNSTypeA, layers.DNSTypeAAAA: