Move padding constants to their own namespace.

PowerDNS · Jan 6, 2025 · 2751ed0 · 2751ed0
1 parent a6b8e45
commit 2751ed0
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Showing 4 changed files with 13 additions and 19 deletions.
diff --git a/pdns/dnspacket.cc b/pdns/dnspacket.cc
@@ -391,13 +391,12 @@ void DNSPacket::wrapup(bool throwsOnTruncation)
 
       if (d_ednspadding) {
         size_t remaining = d_tcp ? 65535 : getMaxReplyLen();
-        const size_t blockSize = 468; // RFC8467 4.1
         // Note that optsize already contains the size of the EDNS0 padding
         // option header.
-        size_t modulo = (pw.size() + optsize) % blockSize;
+        size_t modulo = (pw.size() + optsize) % rfc8467::serverPaddingBlockSize;
         size_t padSize = 0;
         if (modulo > 0) {
-          padSize = std::min(blockSize - modulo, remaining);
+          padSize = std::min(rfc8467::serverPaddingBlockSize - modulo, remaining);
         }
         opts.emplace_back(EDNSOptionCode::PADDING, makeEDNSPaddingOptString(padSize));
       }

diff --git a/pdns/ednspadding.hh b/pdns/ednspadding.hh
@@ -24,3 +24,9 @@
 #include <string>
 
 std::string makeEDNSPaddingOptString(size_t bytes);
+
+namespace rfc8467 {
+  // Constants from RFC8467 4.1 "Recommended Strategy: Block-Length Padding"
+  const size_t clientPaddingBlockSize = 128;
+  const size_t serverPaddingBlockSize = 468;
+}
diff --git a/pdns/recursordist/lwres.cc b/pdns/recursordist/lwres.cc
@@ -373,15 +373,11 @@ static void addPadding(const DNSPacketWriter& pw, size_t bufsize, DNSPacketWrite
   const size_t currentSize = pw.getSizeWithOpts(opts);
   if (currentSize < (bufsize - 4)) {
     const size_t remaining = bufsize - (currentSize + 4);
-    /* from rfc8467, "4.1.  Recommended Strategy: Block-Length Padding":
-       Clients SHOULD pad queries to the closest multiple of 128 octets.
-       Note we are in the client role here.
-    */
-    const size_t blockSize = 128;
-    const size_t modulo = (currentSize + 4) % blockSize;
+    // Note we are in the client role here.
+    const size_t modulo = (currentSize + 4) % rfc8467::clientPaddingBlockSize;
     size_t padSize = 0;
     if (modulo > 0) {
-      padSize = std::min(blockSize - modulo, remaining);
+      padSize = std::min(rfc8467::clientPaddingBlockSize - modulo, remaining);
     }
     opts.emplace_back(EDNSOptionCode::PADDING, makeEDNSPaddingOptString(padSize));
   }

diff --git a/pdns/recursordist/pdns_recursor.cc b/pdns/recursordist/pdns_recursor.cc
@@ -1623,17 +1623,10 @@ void startDoResolve(void* arg) // NOLINT(readability-function-cognitive-complexi
 
       if (currentSize < (maxSize - 4)) {
         size_t remaining = maxSize - (currentSize + 4);
-        /* from rfc8467, "4.1.  Recommended Strategy: Block-Length Padding":
-           If a server receives a query that includes the EDNS(0) "Padding"
-           option, it MUST pad the corresponding response (see Section 4 of
-           RFC 7830) and SHOULD pad the corresponding response to a
-           multiple of 468 octets (see below).
-        */
-        const size_t blockSize = 468;
-        size_t modulo = (currentSize + 4) % blockSize;
+        size_t modulo = (currentSize + 4) % rfc8467::serverPaddingBlockSize;
         size_t padSize = 0;
         if (modulo > 0) {
-          padSize = std::min(blockSize - modulo, remaining);
+          padSize = std::min(rfc8467::serverPaddingBlockSize - modulo, remaining);
         }
         returnedEdnsOptions.emplace_back(EDNSOptionCode::PADDING, makeEDNSPaddingOptString(padSize));
       }