Log SERVFAIL from usptream servers.

If we're doing DNSSEC validation and fail because the upstream
reply to our query is SERVFAIL, log this as the reason in
validation result line.

This will make maintainers lives easier when they get reports
of "wrong" validation failure, which is sometimes an upstream problem.

src/cache.c

@@ -2250,6 +2250,7 @@ static char *edestr(int ede)
     case EDE_UNS_NS3_ITER:                return "unsupported NSEC3 iterations value";
     case EDE_UNABLE_POLICY:               return "uanble to conform to policy";
     case EDE_SYNTHESIZED:                 return "synthesized";
+    case EDE_US_SERVFAIL:                 return "upstream returned SERVFAIL";
     default:                              return "unknown";
     }
 }

src/dns-protocol.h

@@ -86,6 +86,7 @@
 #define EDNS0_OPTION_UMBRELLA       20292 /* Cisco Umbrella temporary assignment */
 
 /* RFC-8914 extended errors, negative values are our definitions */
+#define EDE_US_SERVFAIL    -2  /* SERVFAIL from usptream */
 #define EDE_UNSET          -1  /* No extended DNS error available */
 #define EDE_OTHER           0  /* Other */
 #define EDE_USUPDNSKEY      1  /* Unsupported DNSKEY algo */

src/dnsmasq.h

@@ -778,6 +778,7 @@ struct dyndir {
 #define DNSSEC_FAIL_NSEC3_ITERS 0x0200 /* too many iterations in NSEC3 */
 #define DNSSEC_FAIL_BADPACKET   0x0400 /* bad packet */
 #define DNSSEC_FAIL_WORK        0x0800 /* too much crypto */
+#define DNSSEC_FAIL_UPSTREAM    0x1000 /* SERVFAIL from UPSTREAM */
 
 #define STAT_ISEQUAL(a, b)  (((a) & 0xffff0000) == (b))
 

src/dnssec.c

@@ -1993,8 +1993,11 @@ int dnssec_validate_reply(time_t now, struct dns_header *header, size_t plen, ch
   
   if (neganswer)
     *neganswer = 0;
+
+  if (RCODE(header) == SERVFAIL)
+    return STAT_BOGUS | DNSSEC_FAIL_UPSTREAM;
   
-  if (RCODE(header) == SERVFAIL || ntohs(header->qdcount) != 1)
+  if (ntohs(header->qdcount) != 1)
     return STAT_BOGUS;
   
   if (RCODE(header) != NXDOMAIN && RCODE(header) != NOERROR)
@@ -2365,8 +2368,9 @@ int errflags_to_ede(int status)
   /* We can end up with more than one flag set for some errors,
      so this encodes a rough priority so the (eg) No sig is reported
      before no-unexpired-sig. */
-
-  if (status & DNSSEC_FAIL_NYV)
+  if (status & DNSSEC_FAIL_UPSTREAM)
+    return EDE_US_SERVFAIL;
+  else if (status & DNSSEC_FAIL_NYV)
     return EDE_SIG_NYV;
   else if (status & DNSSEC_FAIL_EXP)
     return EDE_SIG_EXP;

src/forward.c

@@ -1399,6 +1399,9 @@ void return_reply(time_t now, struct frec *forward, struct dns_header *header, s
       
 	  a.log.ede = ede;
 	  log_query(F_SECSTAT, domain, &a, result, 0);
+
+	  if (ede == EDE_US_SERVFAIL)
+	    ede = EDE_DNSSEC_BOGUS;
 	}
     }
   
@@ -2665,6 +2668,8 @@ unsigned char *tcp_request(int confd, time_t now,
 			      
 			      a.log.ede = ede;
 			      log_query(F_SECSTAT, domain, &a, result, 0);
+			      if (ede == EDE_US_SERVFAIL)
+				ede = EDE_DNSSEC_BOGUS;
 			      
 			      if ((daemon->limit[LIMIT_CRYPTO] - validatecount) > (int)daemon->metrics[METRIC_CRYPTO_HWM])
 				daemon->metrics[METRIC_CRYPTO_HWM] = daemon->limit[LIMIT_CRYPTO] - validatecount;