In the IP header, Flags + Fragment Offset is a 16-bit field.
Use ntohs() instead of ntohl(), otherwise the Flags/Fragment Offset values may not display correctly.
Before (DF set)
Vr HL TOS Len ID Flg off TTL Pro cks Src Dst 4 5 00 0054 0001 0 0000 40 01 b6a4 192.0.2.1 192.0.2.2
After (DF set)
Vr HL TOS Len ID Flg off TTL Pro cks Src Dst 4 5 00 0054 0001 2 0000 40 01 b6a4 192.0.2.1 192.0.2.2