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Date: Wed, 3 Aug 2016 10:01:54 -0700
From: Tom Herbert <tom@...bertland.com>
To: Brenden Blanco <bblanco@...mgrid.com>
Cc: "David S. Miller" <davem@...emloft.net>,
Linux Kernel Network Developers <netdev@...r.kernel.org>,
Jamal Hadi Salim <jhs@...atatu.com>,
Saeed Mahameed <saeedm@....mellanox.co.il>,
Martin KaFai Lau <kafai@...com>,
Jesper Dangaard Brouer <brouer@...hat.com>,
Ari Saha <as754m@....com>,
Alexei Starovoitov <alexei.starovoitov@...il.com>,
Or Gerlitz <gerlitz.or@...il.com>,
john fastabend <john.fastabend@...il.com>,
Hannes Frederic Sowa <hannes@...essinduktion.org>,
Thomas Graf <tgraf@...g.ch>,
Daniel Borkmann <daniel@...earbox.net>,
Tariq Toukan <ttoukan.linux@...il.com>,
Aaron Yue <haoxuany@...com>
Subject: Re: [PATCH v10 12/12] bpf: add sample for xdp forwarding and rewrite
On Tue, Jul 19, 2016 at 12:16 PM, Brenden Blanco <bblanco@...mgrid.com> wrote:
> Add a sample that rewrites and forwards packets out on the same
> interface. Observed single core forwarding performance of ~10Mpps.
>
> Since the mlx4 driver under test recycles every single packet page, the
> perf output shows almost exclusively just the ring management and bpf
> program work. Slowdowns are likely occurring due to cache misses.
>
> Signed-off-by: Brenden Blanco <bblanco@...mgrid.com>
> ---
> samples/bpf/Makefile | 5 +++
> samples/bpf/xdp2_kern.c | 114 ++++++++++++++++++++++++++++++++++++++++++++++++
> 2 files changed, 119 insertions(+)
> create mode 100644 samples/bpf/xdp2_kern.c
>
> diff --git a/samples/bpf/Makefile b/samples/bpf/Makefile
> index 0e4ab3a..d2d2b35 100644
> --- a/samples/bpf/Makefile
> +++ b/samples/bpf/Makefile
> @@ -22,6 +22,7 @@ hostprogs-y += map_perf_test
> hostprogs-y += test_overhead
> hostprogs-y += test_cgrp2_array_pin
> hostprogs-y += xdp1
> +hostprogs-y += xdp2
>
> test_verifier-objs := test_verifier.o libbpf.o
> test_maps-objs := test_maps.o libbpf.o
> @@ -44,6 +45,8 @@ map_perf_test-objs := bpf_load.o libbpf.o map_perf_test_user.o
> test_overhead-objs := bpf_load.o libbpf.o test_overhead_user.o
> test_cgrp2_array_pin-objs := libbpf.o test_cgrp2_array_pin.o
> xdp1-objs := bpf_load.o libbpf.o xdp1_user.o
> +# reuse xdp1 source intentionally
> +xdp2-objs := bpf_load.o libbpf.o xdp1_user.o
>
> # Tell kbuild to always build the programs
> always := $(hostprogs-y)
> @@ -67,6 +70,7 @@ always += test_overhead_kprobe_kern.o
> always += parse_varlen.o parse_simple.o parse_ldabs.o
> always += test_cgrp2_tc_kern.o
> always += xdp1_kern.o
> +always += xdp2_kern.o
>
> HOSTCFLAGS += -I$(objtree)/usr/include
>
> @@ -88,6 +92,7 @@ HOSTLOADLIBES_spintest += -lelf
> HOSTLOADLIBES_map_perf_test += -lelf -lrt
> HOSTLOADLIBES_test_overhead += -lelf -lrt
> HOSTLOADLIBES_xdp1 += -lelf
> +HOSTLOADLIBES_xdp2 += -lelf
>
> # Allows pointing LLC/CLANG to a LLVM backend with bpf support, redefine on cmdline:
> # make samples/bpf/ LLC=~/git/llvm/build/bin/llc CLANG=~/git/llvm/build/bin/clang
> diff --git a/samples/bpf/xdp2_kern.c b/samples/bpf/xdp2_kern.c
> new file mode 100644
> index 0000000..38fe7e1
> --- /dev/null
> +++ b/samples/bpf/xdp2_kern.c
> @@ -0,0 +1,114 @@
> +/* Copyright (c) 2016 PLUMgrid
> + *
> + * This program is free software; you can redistribute it and/or
> + * modify it under the terms of version 2 of the GNU General Public
> + * License as published by the Free Software Foundation.
> + */
> +#define KBUILD_MODNAME "foo"
> +#include <uapi/linux/bpf.h>
> +#include <linux/in.h>
> +#include <linux/if_ether.h>
> +#include <linux/if_packet.h>
> +#include <linux/if_vlan.h>
> +#include <linux/ip.h>
> +#include <linux/ipv6.h>
> +#include "bpf_helpers.h"
> +
> +struct bpf_map_def SEC("maps") dropcnt = {
> + .type = BPF_MAP_TYPE_PERCPU_ARRAY,
> + .key_size = sizeof(u32),
> + .value_size = sizeof(long),
> + .max_entries = 256,
> +};
> +
> +static void swap_src_dst_mac(void *data)
> +{
> + unsigned short *p = data;
> + unsigned short dst[3];
> +
> + dst[0] = p[0];
> + dst[1] = p[1];
> + dst[2] = p[2];
> + p[0] = p[3];
> + p[1] = p[4];
> + p[2] = p[5];
> + p[3] = dst[0];
> + p[4] = dst[1];
> + p[5] = dst[2];
> +}
> +
> +static int parse_ipv4(void *data, u64 nh_off, void *data_end)
> +{
> + struct iphdr *iph = data + nh_off;
> +
> + if (iph + 1 > data_end)
> + return 0;
> + return iph->protocol;
> +}
> +
> +static int parse_ipv6(void *data, u64 nh_off, void *data_end)
> +{
> + struct ipv6hdr *ip6h = data + nh_off;
> +
> + if (ip6h + 1 > data_end)
> + return 0;
> + return ip6h->nexthdr;
> +}
> +
> +SEC("xdp1")
> +int xdp_prog1(struct xdp_md *ctx)
> +{
> + void *data_end = (void *)(long)ctx->data_end;
> + void *data = (void *)(long)ctx->data;
Brendan,
It seems that the cast to long here is done because data_end and data
are u32s in xdp_md. So the effect is that we are upcasting a
thirty-bit integer into a sixty-four bit pointer (in fact without the
cast we see compiler warnings). I don't understand how this can be
correct. Can you shed some light on this?
Thanks,
Tom
> + struct ethhdr *eth = data;
> + int rc = XDP_DROP;
> + long *value;
> + u16 h_proto;
> + u64 nh_off;
> + u32 index;
> +
> + nh_off = sizeof(*eth);
> + if (data + nh_off > data_end)
> + return rc;
> +
> + h_proto = eth->h_proto;
> +
> + if (h_proto == htons(ETH_P_8021Q) || h_proto == htons(ETH_P_8021AD)) {
> + struct vlan_hdr *vhdr;
> +
> + vhdr = data + nh_off;
> + nh_off += sizeof(struct vlan_hdr);
> + if (data + nh_off > data_end)
> + return rc;
> + h_proto = vhdr->h_vlan_encapsulated_proto;
> + }
> + if (h_proto == htons(ETH_P_8021Q) || h_proto == htons(ETH_P_8021AD)) {
> + struct vlan_hdr *vhdr;
> +
> + vhdr = data + nh_off;
> + nh_off += sizeof(struct vlan_hdr);
> + if (data + nh_off > data_end)
> + return rc;
> + h_proto = vhdr->h_vlan_encapsulated_proto;
> + }
> +
> + if (h_proto == htons(ETH_P_IP))
> + index = parse_ipv4(data, nh_off, data_end);
> + else if (h_proto == htons(ETH_P_IPV6))
> + index = parse_ipv6(data, nh_off, data_end);
> + else
> + index = 0;
> +
> + value = bpf_map_lookup_elem(&dropcnt, &index);
> + if (value)
> + *value += 1;
> +
> + if (index == 17) {
> + swap_src_dst_mac(data);
> + rc = XDP_TX;
> + }
> +
> + return rc;
> +}
> +
> +char _license[] SEC("license") = "GPL";
> --
> 2.8.2
>
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