move buffer to a util file, commented, also create a constants file

cmake-build-debug/.ninja_log

@@ -59,3 +59,5 @@
 7309	7612	1698284273630763380	insane_dns	ff5ae500893d0be1
 5	7368	1698284653019154297	CMakeFiles/insane_dns.dir/src/main.cpp.o	727da43cdbc82421
 7369	7621	1698284653283151767	insane_dns	ff5ae500893d0be1
+2	2997	1698338548693635693	CMakeFiles/insane_dns.dir/src/main.cpp.o	727da43cdbc82421
+2997	3087	1698338548789636298	insane_dns	ff5ae500893d0be1

cmake-build-debug/Testing/Temporary/LastTest.log

@@ -1,3 +1,3 @@
-Start testing: Oct 25 21:44 EDT
+Start testing: Oct 26 12:42 EDT
 ----------------------------------------------------------
-End testing: Oct 25 21:44 EDT
+End testing: Oct 26 12:42 EDT

include/insane_dns/constants.h

@@ -0,0 +1,30 @@
+/*
+ *  Global constants file.
+ *  Copyright (C) 2023  Brett Terpstra
+ *
+ *  This program is free software: you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License as published by
+ *  the Free Software Foundation, either version 3 of the License, or
+ *  (at your option) any later version.
+ *
+ *  This program is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License
+ *  along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+#ifndef INSANE_DNS_CONSTANTS_H
+#define INSANE_DNS_CONSTANTS_H
+
+/*
+ * --------------------------------------------
+ *          | Magic Number Constants |
+ * --------------------------------------------
+ */
+/** DNS header data offset. This is the first byte that isn't a header value (should be question label length octet) */
+static constexpr size_t DNS_HEADER_END = 12;
+
+#endif //INSANE_DNS_CONSTANTS_H

include/insane_dns/util.h

@@ -0,0 +1,112 @@
+/*
+ *  BLT Memory Util for parsing DNS packets.
+ *  This software is unlikely to become part of BLT main but is provided under the BLT license (GPL 3).
+ *  Copyright (C) 2023  Brett Terpstra
+ *
+ *  This program is free software: you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License as published by
+ *  the Free Software Foundation, either version 3 of the License, or
+ *  (at your option) any later version.
+ *
+ *  This program is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License
+ *  along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+#ifndef INSANE_DNS_UTIL_H
+#define INSANE_DNS_UTIL_H
+
+#include <insane_dns/constants.h>
+
+namespace blt
+{
+    
+    /**
+     * Basic parser for processing strings of bytes received from UDP sockets. This class provides a simple interface for efficiently copying the
+     * big endian bytes from the network into the little endian bytes required by x86 processors. The class also provides basic safety guarantees
+     * in that the program will halt execution if reading the bytes would overflow the internal buffer.
+     */
+    class byte_reader
+    {
+        private:
+            unsigned char* _data;
+            const size_t _size;
+            mutable size_t _current_byte = DNS_HEADER_END;
+        public:
+            explicit byte_reader(unsigned char* data, size_t size): _data(data), _size(size)
+            {}
+            
+            /**
+             * Read the next byte in the data stream then increment the internal counter by 1
+             * @return the next byte in the array
+             */
+            inline unsigned char& next() const
+            {
+                BLT_ASSERT(_current_byte < _size);
+                return _data[_current_byte++];
+            }
+            
+            /**
+             * Reads data into the provided template parameter, reordering the byte into the correct little endian format
+             * @tparam T type to read (deduction is automatic)
+             * @param t variable reference to read into
+             */
+            template<typename T>
+            inline void to(T& t) const
+            {
+                BLT_ASSERT(_current_byte + sizeof(T) <= _size);
+                // I hate little endian. I hate dealing with converting between endianness
+                // it is very easy to do it very slowly
+                // So I made BLT provide a simple interface to convert between bytes dependent on the platform
+                // for small integral types (16, 32, and 64) it will compile to 3 instructions using compiler intrinsics.
+                // Larger POD types are supported but will use std::reverse and therefore be slow.
+                blt::mem::fromBytes(&_data[_current_byte], t);
+                skip(sizeof(T));
+            }
+            
+            /**
+             * Copy from the internal data buffer, advancing the internal stream, into the provided unsigned char array. *No reordering is done*
+             * @param out character array to write to
+             * @param size number of bytes to copy
+             */
+            inline void copy(unsigned char*& out, size_t size) const
+            {
+                BLT_ASSERT(_current_byte + size < _size);
+                std::memcpy(out, &_data[_current_byte], size);
+                skip(size);
+            }
+            
+            /**
+             * Skip bytes in the data stream, useful for skipping sections of the DNS packet we may not care about.
+             * @param s number of bytes to skip.
+             */
+            inline void skip(size_t s = 1) const
+            {
+                _current_byte += s;
+            }
+            
+            /**
+             * @return 1 past the last byte we wrote to, otherwise known as the next byte we will be writing to.
+             */
+            inline size_t last() const
+            {
+                return _current_byte;
+            }
+            
+            /**
+             * @return a pointer to a location in the internal buffer starting at last()
+             */
+            inline unsigned char* from()
+            {
+                BLT_ASSERT(_current_byte < _size);
+                return &_data[_current_byte];
+            }
+    };
+
+}
+
+#endif //INSANE_DNS_UTIL_H

src/main.cpp

@@ -17,37 +17,63 @@
 #include <type_traits>
 #include <unordered_set>
 #include "ip.h"
+#include "insane_dns/util.h"
 
-/**
+/*
  * ----------------------------
  *          | CONFIG |
  * ----------------------------
  */
-// should we strictly match results? ie block *wikipedia.org* or just wikipedia.org?
+/** should we strictly match results? ie block `*wikipedia.org*` or just `wikipedia.org`? */
 static constexpr bool STRICT_MATCHING = false;
-// true -> only match A records ; false -> match any named record (configure with NON_STRICT_REPLACE_ALL)
-static constexpr bool STRICT_FILTERING = false;
-// true -> match all records ; false -> match only records we might want to replace (A, AAAA, CNAME)
-static constexpr bool NON_STRICT_REPLACE_ALL = true;
 
-// DNS server to use for forwarding to / resolving DNS requests
+/** DNS server to use for forwarding to / resolving DNS requests */
 static inline constexpr std::string DNS_SERVER_IP()
 {
     return "8.8.8.8";
 }
 
-// replacement IP address. Make sure this is a 4 octet string seperated by .
+/** replacement IP address. Make sure this is a 4 octet string seperated by `.` */
 static inline constexpr IPAddress REPLACEMENT_IP()
 {
     return {"139.57.100.6"};
 }
 
+/**
+ * List of disallowed domains.
+ * Note: if you are using STRICT_MATCHING=false it will not match to the root domain.
+ * Eg it will match `*en.wikipedia.org*` NOT `*wikipedia.org*`
+ */
 static const std::unordered_set<std::string> DISALLOWED_DOMAINS{
         "en.wikipedia.org",
         "tpgc.me",
         "zombo.com"
 };
 
+/*
+ * -----------------------------------
+ *          | Do Not Change |
+ * -----------------------------------
+ */
+// these features were planned but not added because I realized you guys won't care or give extra marks which broke my obsession with it
+// so uhh don't change em otherwise the code will break :3
+
+/** true -> only match A records ; false -> match any named record (configure with NON_STRICT_REPLACE_ALL) */
+static constexpr bool STRICT_FILTERING = true;
+/** true -> match all records ; false -> match only records we might want to replace (A, AAAA, CNAME) */
+static constexpr bool NON_STRICT_REPLACE_ALL = true;
+
+// was going to add TCP and ad blocking support
+// that also isn't going to happen now.
+/** list of web address to download the ad block lists from */
+static constexpr std::vector<std::string> BLOCK_LISTS{};
+/** true -> block ad DNS requests ; false -> do nothing */
+static constexpr bool BLOCK_ADS = false;
+/** true -> send back the REPLACEMENT_IP() ; false -> send back a fail state in the DNS request. */
+static constexpr bool REDIRECT_ADS = true;
+
+// 5F826B
+
 // DNS data contains:
 // 2 bytes for transaction id
 // 2 bytes for flags
@@ -71,57 +97,6 @@ static const std::unordered_set<std::string> DISALLOWED_DOMAINS{
 // 2 byte for length of data
 // (lengthy) byte for data
 
-class byte_reader
-{
-    private:
-        unsigned char* data;
-        mutable size_t current_byte = 0;
-    public:
-        explicit byte_reader(unsigned char* data): data(data)
-        {
-            reset();
-        }
-        
-        inline void reset() const
-        {
-            // magic number for end of header
-            current_byte = 12;
-        }
-        
-        inline unsigned char& next() const
-        {
-            return data[current_byte++];
-        }
-        
-        template<typename T>
-        inline void to(T& t) const
-        {
-            blt::mem::fromBytes(&data[current_byte], t);
-            skip(sizeof(T));
-        }
-        
-        inline void copy(unsigned char*& out, size_t size) const
-        {
-            std::memcpy(out, &data[current_byte], size);
-            current_byte += size;
-        }
-        
-        inline void skip(size_t s = 1) const
-        {
-            current_byte += s;
-        }
-        
-        inline size_t last() const
-        {
-            return current_byte;
-        }
-        
-        inline unsigned char* from()
-        {
-            return &data[current_byte];
-        }
-};
-
 class send_buffer;
 
 class question
@@ -376,7 +351,7 @@ int main()
             uint16_t num_of_answers;
             blt::mem::fromBytes(&mod_recv_buf[6], num_of_answers);
             
-            byte_reader reader2(mod_recv_buf.data());
+            byte_reader reader2(mod_recv_buf.data(), mod_recv_buf.size());
             
             BLT_INFO("Bytes answered %d with %d answers", out_bytes, num_of_answers);