Re: [PATCH bpf-next v2 1/8] xdp: restructure redirect actions

On 2021-01-20 17:30, Toke Høiland-Jørgensen wrote:

Björn Töpel [off-list ref] writes:

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quoted

It can't be free'd but, ri->map can be cleared via
bpf_clear_redirect_map(). So, between the helper (setting) and the
tracepoint in xdp_do_redirect() it can be cleared (say if the XDP
program is swapped out, prior running xdp_do_redirect()).

But xdp_do_redirect() should be called on driver flush before exiting
the NAPI cycle, so how can the XDP program be swapped out?

To clarify; xdp_do_redirect() is called for each packet in the NAPI poll 
loop.

Yeah, you're right. The xdp_do_redirect() is within the RCU scope, so
the program wont be destroyed (but can be swapped though!).

Hmm, so IOW the bpf_clear_redirect_map() is not needed anymore...


Björn

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