net: IP4 Packet checksum is now big endian, checksum getter for TCP packet

Author: AndreasAakesson

api/net/ip4/packet_ip4.hpp

@@ -86,7 +86,7 @@ namespace net {
 
     /** Get the IP header checksum field as-is */
     uint16_t ip_checksum() const noexcept
-    { return ntohs(ip_header().check); }
+    { return ip_header().check; }
 
     /** Get source address */
     const ip4::Addr& ip_src() const noexcept
@@ -171,7 +171,7 @@ namespace net {
 
     /** Set IP header checksum field directly */
     void set_ip_checksum(uint16_t sum) noexcept
-    { ip_header().check = ntohs(sum); }
+    { ip_header().check = sum; }
 
     /** Calculate and set IP header checksum field */
     void set_ip_checksum() noexcept {

api/net/tcp/packet.hpp

@@ -84,6 +84,9 @@ class Packet : public PacketIP4 {
   inline uint16_t win() const
   { return ntohs(tcp_header().window_size); }
 
+  uint16_t tcp_checksum() const noexcept
+  { return tcp_header().checksum; }
+
   inline Socket source() const
   { return Socket{ip_src(), src_port()}; }