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([2601:282:803:7700:d897:9718:2ec7:8952]) by smtp.googlemail.com with ESMTPSA id p10sm18397441qtu.14.2020.04.17.14.29.22 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 17 Apr 2020 14:29:24 -0700 (PDT) Subject: Re: [PATCH RFC-v5 bpf-next 09/12] dev: Support xdp in the Tx path for xdp_frames To: Jesper Dangaard Brouer , David Ahern Cc: netdev@vger.kernel.org, davem@davemloft.net, kuba@kernel.org, prashantbhole.linux@gmail.com, jasowang@redhat.com, toke@redhat.com, toshiaki.makita1@gmail.com, daniel@iogearbox.net, john.fastabend@gmail.com, ast@kernel.org, kafai@fb.com, songliubraving@fb.com, yhs@fb.com, andriin@fb.com, David Ahern References: <20200413171801.54406-1-dsahern@kernel.org> <20200413171801.54406-10-dsahern@kernel.org> <20200417103055.51a25b2d@carbon> From: David Ahern Message-ID: <4bd9f68f-ca64-66a5-d05b-567032e2a48d@gmail.com> Date: Fri, 17 Apr 2020 15:29:19 -0600 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:68.0) Gecko/20100101 Thunderbird/68.7.0 MIME-Version: 1.0 In-Reply-To: <20200417103055.51a25b2d@carbon> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On 4/17/20 2:30 AM, Jesper Dangaard Brouer wrote: >> diff --git a/net/core/dev.c b/net/core/dev.c >> index 1bbaeb8842ed..f23dc6043329 100644 >> --- a/net/core/dev.c >> +++ b/net/core/dev.c >> @@ -4720,6 +4720,76 @@ u32 do_xdp_egress_skb(struct net_device *dev, struct sk_buff *skb) >> } >> EXPORT_SYMBOL_GPL(do_xdp_egress_skb); >> >> +static u32 __xdp_egress_frame(struct net_device *dev, >> + struct bpf_prog *xdp_prog, >> + struct xdp_frame *xdp_frame, >> + struct xdp_txq_info *txq) >> +{ >> + struct xdp_buff xdp; >> + u32 act; >> + >> + xdp.data_hard_start = xdp_frame->data - xdp_frame->headroom; > > You also need: minus sizeof(*xdp_frame). Updated. thanks. > > The BPF-helper xdp_adjust_head will not allow BPF-prog to access the > memory area that is used for xdp_frame, thus it still is safe. > > >> + xdp.data = xdp_frame->data; >> + xdp.data_end = xdp.data + xdp_frame->len; >> + xdp_set_data_meta_invalid(&xdp); >> + xdp.txq = txq; > > I think this will be the 3rd place we convert xdp-frame to xdp_buff, > perhaps we should introduce a helper function call. > >> + act = bpf_prog_run_xdp(xdp_prog, &xdp); >> + act = handle_xdp_egress_act(act, dev, xdp_prog); >> + >> + /* if not dropping frame, readjust pointers in case >> + * program made changes to the buffer >> + */ >> + if (act != XDP_DROP) { >> + int headroom = xdp.data - xdp.data_hard_start; >> + int metasize = xdp.data - xdp.data_meta; >> + >> + metasize = metasize > 0 ? metasize : 0; >> + if (unlikely((headroom - metasize) < sizeof(*xdp_frame))) >> + return XDP_DROP; >> + >> + xdp_frame = xdp.data_hard_start; > > Is this needed? removed. > >> + xdp_frame->data = xdp.data; >> + xdp_frame->len = xdp.data_end - xdp.data; >> + xdp_frame->headroom = headroom - sizeof(*xdp_frame); >> + xdp_frame->metasize = metasize; >> + /* xdp_frame->mem is unchanged */ > > This looks very similar to convert_to_xdp_frame. yes, except the rxq references since rxq is not set. > Maybe we need an central update_xdp_frame(xdp_buff) call? > > > Untested code-up: > sure, that should work.