CVE-2026-43036 net: use skb_header_pointer() for TCPv4 GSO frag_off check

In the Linux kernel, the following vulnerability has been resolved: net: use skbheaderpointer for TCPv4 GSO fragoff check Syzbot reported a KMSAN uninit-value warning in gsofeaturescheck called from netifskbfeatures 1. gsofeaturescheck reads iph-fragoff to decide whether to clear mangleidfeatures...