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[79.176.0.156]) by smtp.gmail.com with ESMTPSA id n189sm1778796wme.33.2020.01.23.00.23.24 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 23 Jan 2020 00:23:26 -0800 (PST) Date: Thu, 23 Jan 2020 03:23:22 -0500 From: "Michael S. Tsirkin" To: David Ahern Cc: netdev@vger.kernel.org, prashantbhole.linux@gmail.com, jasowang@redhat.com, davem@davemloft.net, jakub.kicinski@netronome.com, jbrouer@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, dsahern@gmail.com Subject: Re: [PATCH bpf-next 10/12] tun: run XDP program in tx path Message-ID: <20200123032154-mutt-send-email-mst@kernel.org> References: <20200123014210.38412-1-dsahern@kernel.org> <20200123014210.38412-11-dsahern@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200123014210.38412-11-dsahern@kernel.org> Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On Wed, Jan 22, 2020 at 06:42:08PM -0700, David Ahern wrote: > From: Prashant Bhole > > Run the XDP program as soon as packet is removed from the ptr > ring. Since this is XDP in tx path, the traditional handling of > XDP actions XDP_TX/REDIRECT isn't valid. For this reason we call > do_xdp_generic_core instead of do_xdp_generic. do_xdp_generic_core > just runs the program and leaves the action handling to us. > > Signed-off-by: Prashant Bhole > --- > drivers/net/tun.c | 153 +++++++++++++++++++++++++++++++++++++++++++++- > 1 file changed, 150 insertions(+), 3 deletions(-) > > diff --git a/drivers/net/tun.c b/drivers/net/tun.c > index b6bac773f2a0..71bcd4ec2571 100644 > --- a/drivers/net/tun.c > +++ b/drivers/net/tun.c > @@ -130,6 +130,7 @@ struct tap_filter { > /* MAX_TAP_QUEUES 256 is chosen to allow rx/tx queues to be equal > * to max number of VCPUs in guest. */ > #define MAX_TAP_QUEUES 256 > +#define MAX_TAP_BATCH 64 > #define MAX_TAP_FLOWS 4096 > > #define TUN_FLOW_EXPIRE (3 * HZ) > @@ -175,6 +176,7 @@ struct tun_file { > struct tun_struct *detached; > struct ptr_ring tx_ring; > struct xdp_rxq_info xdp_rxq; > + void *pkt_ptrs[MAX_TAP_BATCH]; > }; > > struct tun_page { > @@ -2140,6 +2142,107 @@ static ssize_t tun_put_user(struct tun_struct *tun, > return total; > } > > +static struct sk_buff *tun_prepare_xdp_skb(struct sk_buff *skb) > +{ > + struct sk_buff *nskb; > + > + if (skb_shared(skb) || skb_cloned(skb)) { > + nskb = skb_copy(skb, GFP_ATOMIC); > + consume_skb(skb); > + return nskb; > + } > + > + return skb; > +} > + > +static u32 tun_do_xdp_tx_generic(struct tun_struct *tun, > + struct sk_buff *skb) > +{ > + struct bpf_prog *xdp_prog; > + struct xdp_buff xdp; > + u32 act = XDP_PASS; > + > + xdp_prog = rcu_dereference(tun->xdp_egress_prog); > + if (xdp_prog) { > + skb = tun_prepare_xdp_skb(skb); > + if (!skb) { > + act = XDP_DROP; > + kfree_skb(skb); > + goto drop; > + } > + > + act = do_xdp_generic_core(skb, &xdp, xdp_prog); > + switch (act) { > + case XDP_TX: > + /* Rx path generic XDP will be called in this path > + */ > + local_bh_disable(); > + netif_receive_skb(skb); > + local_bh_enable(); > + break; > + case XDP_PASS: > + break; > + case XDP_REDIRECT: > + /* Since we are not handling this case yet, let's free > + * skb here. In case of XDP_DROP/XDP_ABORTED, the skb > + * was already freed in do_xdp_generic_core() > + */ > + kfree_skb(skb); > + /* fall through */ > + default: > + bpf_warn_invalid_xdp_action(act); > + /* fall through */ > + case XDP_ABORTED: > + trace_xdp_exception(tun->dev, xdp_prog, act); > + /* fall through */ > + case XDP_DROP: > + goto drop; > + } > + } > + > + return act; > +drop: > + this_cpu_inc(tun->pcpu_stats->tx_dropped); > + return act; > +} > + > +static u32 tun_do_xdp_tx(struct tun_struct *tun, struct tun_file *tfile, > + struct xdp_frame *frame) > +{ > + struct bpf_prog *xdp_prog; > + struct xdp_buff xdp; > + u32 act = XDP_PASS; > + > + xdp_prog = rcu_dereference(tun->xdp_egress_prog); > + if (xdp_prog) { > + xdp.data_hard_start = frame->data - frame->headroom; > + xdp.data = frame->data; > + xdp.data_end = xdp.data + frame->len; > + xdp.data_meta = xdp.data - frame->metasize; > + > + act = bpf_prog_run_xdp(xdp_prog, &xdp); > + switch (act) { > + case XDP_PASS: > + break; > + case XDP_TX: > + /* fall through */ > + case XDP_REDIRECT: > + /* fall through */ > + default: > + bpf_warn_invalid_xdp_action(act); > + /* fall through */ > + case XDP_ABORTED: > + trace_xdp_exception(tun->dev, xdp_prog, act); > + /* fall through */ > + case XDP_DROP: > + xdp_return_frame_rx_napi(frame); > + break; > + } > + } > + > + return act; > +} > + > static void *tun_ring_recv(struct tun_file *tfile, int noblock, int *err) > { > DECLARE_WAITQUEUE(wait, current); > @@ -2557,6 +2660,52 @@ static int tun_sendmsg(struct socket *sock, struct msghdr *m, size_t total_len) > return ret; > } > > +static int tun_consume_packets(struct tun_file *tfile, void **ptr_array, int n) > +{ > + void **pkts = tfile->pkt_ptrs; > + struct xdp_frame *frame; > + struct tun_struct *tun; > + int i, num_ptrs; > + int pkt_cnt = 0; > + void *ptr; > + u32 act; > + int batchsz; > + > + if (unlikely(!tfile)) > + return 0; > + > + rcu_read_lock(); > + tun = rcu_dereference(tfile->tun); > + if (unlikely(!tun)) { > + rcu_read_unlock(); > + return 0; > + } > + > + while (n) { > + batchsz = (n > MAX_TAP_BATCH) ? MAX_TAP_BATCH : n; > + n -= batchsz; > + num_ptrs = ptr_ring_consume_batched(&tfile->tx_ring, pkts, > + batchsz); > + if (!num_ptrs) > + break; Can't we avoid looping over the packets in the current case where there are no xdp programs at all? > + for (i = 0; i < num_ptrs; i++) { > + ptr = pkts[i]; > + if (tun_is_xdp_frame(ptr)) { > + frame = tun_ptr_to_xdp(ptr); > + act = tun_do_xdp_tx(tun, tfile, frame); > + } else { > + act = tun_do_xdp_tx_generic(tun, ptr); > + } > + > + if (act == XDP_PASS) > + ptr_array[pkt_cnt++] = ptr; > + } > + } > + > + rcu_read_unlock(); > + return pkt_cnt; > +} > + > static int tun_recvmsg(struct socket *sock, struct msghdr *m, size_t total_len, > int flags) > { > @@ -2577,9 +2726,7 @@ static int tun_recvmsg(struct socket *sock, struct msghdr *m, size_t total_len, > ptr = ctl->ptr; > break; > case TUN_MSG_CONSUME_PKTS: > - ret = ptr_ring_consume_batched(&tfile->tx_ring, > - ctl->ptr, > - ctl->num); > + ret = tun_consume_packets(tfile, ctl->ptr, ctl->num); > goto out; > case TUN_MSG_UNCONSUME_PKTS: > ptr_ring_unconsume(&tfile->tx_ring, ctl->ptr, > -- > 2.21.1 (Apple Git-122.3)