When fragmenting IPv4 packet, the data offset should be calculated through
the IHL field in IP header rather than using sizeof(struct rte_ipv4_hdr).
Fixes: 4c38e5532a07 ("ip_frag: refactor IPv4 fragmentation into a proper library")
Cc: stable@dpdk.org
Signed-off-by: Pu Xu <583493798@qq.com>
Acked-by: Konstantin Ananyev <konstantin.ananyev@intel.com>