xdp: Allow bpf_xdp_adjust_tail() to grow packet size

Finally, after all drivers have a frame size, allow BPF-helper bpf_xdp_adjust_tail() to grow or extend packet size at frame tail. Remember that helper/macro xdp_data_hard_end have reserved some tailroom. Thus, this helper makes sure that the BPF-prog don't have access to this tailroom area. V2: Remove one chicken check and use WARN_ONCE for other

Jesper Dangaard Brouer committed 6 years ago

Commit c8741e21 parent d628ee42 files · +11 −4Browse files

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include/uapi/linux/bpf.h+2−2

@@ -2015,8 +2015,8 @@ union bpf_attr { · 2014 unmodified lines
2015	2015	* int bpf_xdp_adjust_tail(struct xdp_buff *xdp_md, int delta)
2016	2016	* Description
2017	2017	* Adjust (move) xdp_md\ ->data_end by delta bytes. It is
2018		− * only possible to shrink the packet as of this writing,
2019		− * therefore delta must be a negative integer.
	2018	+ * possible to both shrink and grow the packet tail.
	2019	+ * Shrink done via delta being a negative integer.
2020	2020	*
2021	2021	* A call to this helper is susceptible to change the underlying
2022	2022	* packet buffer. Therefore, at load time, all checks on pointers