DNS: add Extended DNS Error EDNS0 Option

https://www.rfc-editor.org/rfc/rfc8914.html

The patch was also cross-checked with Wireshark:
```
Option: Extended DNS Error
    Option Code: Extended DNS Error (15)
    Option Length: 45
    Option Data: 000670726f6f66206f66206e6f6e2d6578697374656e6365206f66206578616d706c652e…
    Info Code: DNSSEC Bogus (6)
    Extra Text: proof of non-existence of example.com. NSEC

```

scapy/layers/dns.py

@@ -370,7 +370,8 @@ def i2m(self, pkt, s):
 # RFC 2671 - Extension Mechanisms for DNS (EDNS0)
 
 edns0types = {0: "Reserved", 1: "LLQ", 2: "UL", 3: "NSID", 4: "Reserved",
-              5: "PING", 8: "edns-client-subnet", 10: "COOKIE"}
+              5: "PING", 8: "edns-client-subnet", 10: "COOKIE",
+              15: "Extended DNS Error"}
 
 
 class EDNS0TLV(Packet):
@@ -394,6 +395,8 @@ def dispatch_hook(cls, _pkt=None, *args, **kargs):
         edns0type = struct.unpack("!H", _pkt[:2])[0]
         if edns0type == 8:
             return EDNS0ClientSubnet
+        if edns0type == 15:
+            return EDNS0ExtendedDNSError
         return EDNS0TLV
 
 
@@ -491,6 +494,54 @@ class EDNS0ClientSubnet(Packet):
                                       length_from=lambda p: p.source_plen))]
 
 
+# RFC 8914 - Extended DNS Errors
+
+# https://www.iana.org/assignments/dns-parameters/dns-parameters.xhtml#extended-dns-error-codes
+extended_dns_error_codes = {
+    0: "Other",
+    1: "Unsupported DNSKEY Algorithm",
+    2: "Unsupported DS Digest Type",
+    3: "Stale Answer",
+    4: "Forged Answer",
+    5: "DNSSEC Indeterminate",
+    6: "DNSSEC Bogus",
+    7: "Signature Expired",
+    8: "Signature Not Yet Valid",
+    9: "DNSKEY Missing",
+    10: "RRSIGs Missing",
+    11: "No Zone Key Bit Set",
+    12: "NSEC Missing",
+    13: "Cached Error",
+    14: "Not Ready",
+    15: "Blocked",
+    16: "Censored",
+    17: "Filtered",
+    18: "Prohibited",
+    19: "Stale NXDOMAIN Answer",
+    20: "Not Authoritative",
+    21: "Not Supported",
+    22: "No Reachable Authority",
+    23: "Network Error",
+    24: "Invalid Data",
+    25: "Signature Expired before Valid",
+    26: "Too Early",
+    27: "Unsupported NSEC3 Iterations Value",
+    28: "Unable to conform to policy",
+    29: "Synthesized",
+}
+
+
+# https://www.rfc-editor.org/rfc/rfc8914.html
+class EDNS0ExtendedDNSError(Packet):
+    name = "DNS EDNS0 Extended DNS Error"
+    fields_desc = [ShortEnumField("optcode", 15, edns0types),
+                   FieldLenField("optlen", None, length_of="extra_text", fmt="!H",
+                                 adjust=lambda pkt, x: x + 2),
+                   ShortEnumField("info_code", 0, extended_dns_error_codes),
+                   StrLenField("extra_text", "",
+                               length_from=lambda pkt: pkt.optlen - 2)]
+
+
 # RFC 4034 - Resource Records for the DNS Security Extensions
 
 

test/scapy/layers/dns_edns0.uts

@@ -96,3 +96,26 @@ assert raw(d) == raw_d
 
 d = DNSRROPT(raw_d)
 assert EDNS0ClientSubnet in d.rdata[0] and d.rdata[0].family == 2 and d.rdata[0].address == "2001:db8::"
+
+
++ EDNS0 - Extended DNS Error
+
+= Basic instantiation & dissection
+
+b = b'\x00\x0f\x00\x02\x00\x00'
+
+p = EDNS0ExtendedDNSError()
+assert raw(p) == b
+
+p = EDNS0ExtendedDNSError(b)
+assert p.optcode == 15 and p.optlen == 2 and p.info_code == 0 and p.extra_text == b''
+
+b = raw(EDNS0ExtendedDNSError(info_code="DNSSEC Bogus", extra_text="proof of non-existence of example.com. NSEC"))
+
+p = EDNS0ExtendedDNSError(b)
+assert p.info_code == 6 and p.optlen == 45 and p.extra_text == b'proof of non-existence of example.com. NSEC'
+
+rropt = DNSRROPT(b'\x00\x00)\x04\xd0\x00\x00\x00\x00\x001\x00\x0f\x00-\x00\x06proof of non-existence of example.com. NSEC')
+assert len(rropt.rdata) == 1
+p = rropt.rdata[0]
+assert p.info_code == 6 and p.optlen == 45 and p.extra_text == b'proof of non-existence of example.com. NSEC'