Daniel Borkmann
c2002f9837
Commit17bedab272("bpf: xdp: Allow head adjustment in XDP prog") added the xdp_adjust_head bit to the BPF prog in order to tell drivers that the program that is to be attached requires support for the XDP bpf_xdp_adjust_head() helper such that drivers not supporting this helper can reject the program. There are also drivers that do support the helper, but need to check for xdp_adjust_head bit in order to move packet metadata prepended by the firmware away for making headroom. For these cases, the current check for xdp_adjust_head bit is insufficient since there can be cases where the program itself does not use the bpf_xdp_adjust_head() helper, but tail calls into another program that uses bpf_xdp_adjust_head(). As such, the xdp_adjust_head bit is still set to 0. Since the first program has no control over which program it calls into, we need to assume that bpf_xdp_adjust_head() helper is used upon tail calls. Thus, for the very same reasons in cb_access, set the xdp_adjust_head bit to 1 when the main program uses tail calls. Fixes:17bedab272("bpf: xdp: Allow head adjustment in XDP prog") Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> Acked-by: Alexei Starovoitov <ast@kernel.org> Cc: Martin KaFai Lau <kafai@fb.com> Signed-off-by: David S. Miller <davem@davemloft.net>
Linux kernel ============ This file was moved to Documentation/admin-guide/README.rst Please notice that there are several guides for kernel developers and users. These guides can be rendered in a number of formats, like HTML and PDF. In order to build the documentation, use ``make htmldocs`` or ``make pdfdocs``. There are various text files in the Documentation/ subdirectory, several of them using the Restructured Text markup notation. See Documentation/00-INDEX for a list of what is contained in each file. Please read the Documentation/process/changes.rst file, as it contains the requirements for building and running the kernel, and information about the problems which may result by upgrading your kernel.