don't add padding for optimal packet size

libi2pd/ECIESX25519AEADRatchetSession.cpp

@@ -712,11 +712,15 @@ namespace garlic
 		}
 		uint8_t paddingSize = 0;
 		if (payloadLen)
+		{	
+			// don't create padding if we are close to optimal size
+			if (first || payloadLen + 19 <= ECIESX25519_OPTIMAL_PAYLOAD_SIZE || payloadLen > ECIESX25519_OPTIMAL_PAYLOAD_SIZE)
 			{	
 				RAND_bytes (&paddingSize, 1);
 				paddingSize &= 0x0F; paddingSize++; // 1 - 16
 				payloadLen += paddingSize + 3;   
 			}	
+		}	
         std::vector<uint8_t> v(payloadLen);
         size_t offset = 0;
         // DateTime

libi2pd/ECIESX25519AEADRatchetSession.h

@@ -26,6 +26,9 @@ namespace garlic
 	const int ECIESX25519_MAX_NUM_GENERATED_TAGS = 160;
 	const int ECIESX25519_NSR_NUM_GENERATED_TAGS = 12;
 	
+	const size_t ECIESX25519_OPTIMAL_PAYLOAD_SIZE = 1912;  // 1912 = 1956 /* to fit 2 tunnel messages */ 
+	// - 16 /* I2NP header */ - 16 /* poly hash */ - 8 /* tag */ - 4 /* garlic length */
+	
 	class ECIESX25519AEADRatchetSession;
     class RatchetTagSet
     {