Add IP::fragment_offset and IP::flags

include/tins/ip.h

@@ -68,6 +68,15 @@ namespace Tins {
          */
         typedef IPv4Address address_type;
 
+        /**
+         * Type used to represent the different IP flags.
+         */
+        enum Flags {
+            FLAG_RESERVED = 4,
+            DONT_FRAGMENT = 2,
+            MORE_FRAGMENTS = 1
+        };
+
         /**
          * \brief Enum indicating the option's class.
          *
@@ -292,10 +301,36 @@ namespace Tins {
 
         /**
          * \brief Getter for the fragment offset field.
+         * 
+         * This method is deprecated. Use IP::fragment_offset and IP::flags.
          *
+         * \deprecated
          * \return The fragment offset for this IP PDU.
+         * \sa IP::fragment_offset
+         * \sa IP::flags
          */
-        uint16_t frag_off() const { return Endian::be_to_host(_ip.frag_off); }
+        TINS_DEPRECATED(uint16_t frag_off() const) { return Endian::be_to_host(_ip.frag_off); }
+
+        /**
+         * \brief Getter for the fragment offset field.
+         * 
+         * This will return the fragment offset field, as present in the packet, 
+         * which indicates the offset of this fragment in blocks of 8 bytes. 
+         * 
+         * \return The fragment offset, measured in units of 8 byte blocks 
+         */
+        small_uint<13> fragment_offset() const { 
+            return Endian::be_to_host(_ip.frag_off) & 0x1fff;
+        }
+
+        /**
+         * \brief Getter for the flags field.
+         *
+         * \return The IP flags field
+         */
+        Flags flags() const {
+            return static_cast<Flags>((_ip.frag_off & 0xe0) >> 5); 
+        }
 
         /**
          * \brief Getter for the time to live field.
@@ -362,9 +397,32 @@ namespace Tins {
         /**
          * \brief Setter for the fragment offset field.
          *
+         * This method is deprecated. Use IP::fragment_offset and IP::flags.
+         *
+         * \deprecated
          * \param new_frag_off The new fragment offset.
+         * \sa IP::fragment_offset
+         * \sa IP::flags
          */
-        void frag_off(uint16_t new_frag_off);
+        TINS_DEPRECATED(void frag_off(uint16_t new_frag_off));
+        
+        /**
+         * \brief Setter for the fragment offset field.
+         *
+         * The value provided is measured in units of 8 byte blocks. This means that
+         * if you want this packet to have a fragment offset of <i>X</i>, 
+         * you need to provide <i>X / 8</i> as the argument to this method.
+         *  
+         * \param new_frag_off The new fragment offset, measured in units of 8 byte blocks.
+         */
+        void fragment_offset(small_uint<13> new_frag_off);
+
+        /**
+         * \brief Setter for the flags field.
+         * 
+         * \param new_flags The new IP flags field value.
+         */
+        void flags(Flags new_flags);
 
         /**
          * \brief Setter for the time to live field.

src/ip.cpp

@@ -157,9 +157,7 @@ void IP::init_ip_fields() {
 }
 
 bool IP::is_fragmented() const {
-    // It's 0 if offset == 0 && more_frag == 0
-    // It's 0x4000 if dont_fragment = 1
-    return frag_off() != 0 && frag_off() != 0x4000;
+    return flags() == IP::MORE_FRAGMENTS || fragment_offset() != 0;
 }
 
 /* Setters */
@@ -180,6 +178,14 @@ void IP::frag_off(uint16_t new_frag_off) {
     _ip.frag_off = Endian::host_to_be(new_frag_off);
 }
 
+void IP::fragment_offset(small_uint<13> new_frag_off) {
+    _ip.frag_off = (_ip.frag_off & 0xe0) | Endian::host_to_be<uint16_t>(new_frag_off);
+}
+
+void IP::flags(Flags new_flags) {
+    _ip.frag_off = (_ip.frag_off & 0xff1f) | (new_flags << 5);
+}
+
 void IP::ttl(uint8_t new_ttl) {
     _ip.ttl = new_ttl;
 }

src/ip_reassembler.cpp

@@ -52,7 +52,7 @@ void IPv4Stream::add_fragment(IP *ip) {
         return;
     fragments.insert(it, IPv4Fragment(ip->inner_pdu(), offset));
     received_size += ip->inner_pdu()->size();
-    if(!extract_more_frag(ip)) {
+    if(ip->flags() != IP::MORE_FRAGMENTS) {
         total_size = offset + ip->inner_pdu()->size();
         received_end = true;
     }
@@ -83,12 +83,9 @@ PDU *IPv4Stream::allocate_pdu() const {
 }
 
 uint16_t IPv4Stream::extract_offset(const IP *ip) {
-    return (ip->frag_off() & 0x1fff) * 8;
+    return ip->fragment_offset() * 8;
 }
 
-bool IPv4Stream::extract_more_frag(const IP *ip) {
-    return (ip->frag_off() & 0x2000) != 0;
-}
 } // namespace Internals
 
 IPv4Reassembler::IPv4Reassembler(overlapping_technique technique)