Pointer type of _arp in __skb_flow_dissect()

[Nicolas Iooss]

Hello,

Linux 4.11-rc4 contains the following code in function
__skb_flow_dissect(), file net/core/flow_dissector.c:

        const struct arphdr *arp;
        struct arphdr *_arp;

        arp = __skb_header_pointer(skb, nhoff, sizeof(_arp), data,
                                   hlen, &_arp);


Here _arp and arp are both pointers to arphdr structures. In other calls
to __skb_header_pointer(), the buffer argument (_arp here) would have
been a struct instead of a pointer. What makes ARP packets different in
__skb_flow_dissect()?

Thanks,
Nicolas

PS: the code which I am curious about seems to have been introduced in
4.11-rc1 with commit 55733350e5e8 ("flow disector: ARP support")