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[93.144.71.136]) by smtp.gmail.com with ESMTPSA id v2-20020adf8b42000000b001edc38024c9sm7746241wra.65.2022.03.18.12.54.52 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 18 Mar 2022 12:54:53 -0700 (PDT) Date: Fri, 18 Mar 2022 20:54:51 +0100 From: Lorenzo Bianconi To: Jakub Kicinski Cc: Lorenzo Bianconi , bpf@vger.kernel.org, netdev@vger.kernel.org, davem@davemloft.net, ast@kernel.org, daniel@iogearbox.net, brouer@redhat.com, pabeni@redhat.com, toke@redhat.com, andrii@kernel.org, nbd@nbd.name Subject: Re: [PATCH bpf-next] net: xdp: introduce XDP_PACKET_HEADROOM_MIN for veth and generic-xdp Message-ID: References: <039064e87f19f93e0d0347fc8e5c692c789774e6.1647630686.git.lorenzo@kernel.org> <20220318123323.75973f84@kicinski-fedora-pc1c0hjn.dhcp.thefacebook.com> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha512; protocol="application/pgp-signature"; boundary="FFVkPaJuvWVg7EHv" Content-Disposition: inline In-Reply-To: <20220318123323.75973f84@kicinski-fedora-pc1c0hjn.dhcp.thefacebook.com> Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org --FFVkPaJuvWVg7EHv Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Mar 18, Jakub Kicinski wrote: > On Fri, 18 Mar 2022 20:19:29 +0100 Lorenzo Bianconi wrote: > > diff --git a/net/core/dev.c b/net/core/dev.c > > index ba69ddf85af6..92d560e648ab 100644 > > --- a/net/core/dev.c > > +++ b/net/core/dev.c > > @@ -4737,7 +4737,7 @@ static u32 netif_receive_generic_xdp(struct sk_bu= ff *skb, > > * native XDP provides, thus we need to do it here as well. > > */ > > if (skb_cloned(skb) || skb_is_nonlinear(skb) || > > - skb_headroom(skb) < XDP_PACKET_HEADROOM) { > > + skb_headroom(skb) < XDP_PACKET_HEADROOM_MIN) { > > int hroom =3D XDP_PACKET_HEADROOM - skb_headroom(skb); > > int troom =3D skb->tail + skb->data_len - skb->end; > > =20 >=20 > IIUC the initial purpose of SKB mode was to be able to test or > experiment with XDP "until drivers add support". If that's still > the case the semantics of XDP SKB should be as close to ideal > XDP implementation as possible. XDP in skb-mode is useful if we want to perform a XDP_REDIRECT from an ethernet driver into a wlan device since mac80211 requires a skb. >=20 > We had a knob for specifying needed headroom, is that thing not=20 > working / not a potentially cleaner direction? >=20 which one do you mean? I guess it would be useful :) Regards, Lorenzo --FFVkPaJuvWVg7EHv Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iHUEABYKAB0WIQTquNwa3Txd3rGGn7Y6cBh0uS2trAUCYjTjigAKCRA6cBh0uS2t rHSSAP0TtIh/ZoQVXXyM6GkB50TGUvEhWtaJK6HgwovSiW+RIwEAzzqFjoppHLL6 L5RDhQHu91NDTBcXqIML6fNBQYv2SQg= =+Mhf -----END PGP SIGNATURE----- --FFVkPaJuvWVg7EHv--