+// IdenticalResourceRecord returns true if two resources records have
+// the same name, type, class, and identical rdata (InterfaceID and TTL may differ)
+
+// IdenticalSameNameRecord is the same, except it skips the expensive SameDomainName() check,
+// which is at its most expensive and least useful in cases where we know in advance that the names match
+
+// Note: The dominant use of IdenticalResourceRecord is from ProcessQuery(), handling known-answer lists. In this case
+// it's common to have a whole bunch or records with exactly the same name (e.g. "_http._tcp.local") but different RDATA.
+// The SameDomainName() check is expensive when the names match, and in this case *all* the names match, so we
+// used to waste a lot of CPU time verifying that the names match, only then to find that the RDATA is different.
+// We observed mDNSResponder spending 30% of its total CPU time on this single task alone.
+// By swapping the checks so that we check the RDATA first, we can quickly detect when it's different
+// (99% of the time) and then bail out before we waste time on the expensive SameDomainName() check.
+
+#define IdenticalResourceRecord(r1,r2) ( \
+ (r1)->rrtype == (r2)->rrtype && \
+ (r1)->rrclass == (r2)->rrclass && \
+ (r1)->namehash == (r2)->namehash && \
+ (r1)->rdlength == (r2)->rdlength && \
+ (r1)->rdatahash == (r2)->rdatahash && \
+ SameRDataBody((r1), &(r2)->rdata->u) && \
+ SameDomainName((r1)->name, (r2)->name))
+
+#define IdenticalSameNameRecord(r1,r2) ( \
+ (r1)->rrtype == (r2)->rrtype && \
+ (r1)->rrclass == (r2)->rrclass && \
+ (r1)->rdlength == (r2)->rdlength && \
+ (r1)->rdatahash == (r2)->rdatahash && \
+ SameRDataBody((r1), &(r2)->rdata->u))
+
+// A given RRType answers a QuestionType if RRType is CNAME, or types match, or QuestionType is ANY,
+// or the RRType is NSEC and positively asserts the nonexistence of the type being requested
+#define RRTypeAnswersQuestionType(R,T) ((R)->rrtype == kDNSType_CNAME || (R)->rrtype == (T) || (T) == kDNSQType_ANY || RRAssertsNonexistence((R),(T)))
+#define RRAssertsNonexistence(R,T) ((R)->rrtype == kDNSType_NSEC && (T) < kDNSQType_ANY && !((R)->rdata->u.nsec.bitmap[(T)>>3] & (128 >> ((T)&7))))
+
+extern mDNSu32 RDataHashValue(const ResourceRecord *const rr);
+extern mDNSBool SameRDataBody(const ResourceRecord *const r1, const RDataBody *const r2);
+extern mDNSBool SameNameRecordAnswersQuestion(const ResourceRecord *const rr, const DNSQuestion *const q);
projects / apple / mdnsresponder.git / blobdiff