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7cf245a37e
Fix all files in samples/bpf to include libbpf header files with the bpf/
prefix, to be consistent with external users of the library. Also ensure
that all includes of exported libbpf header files (those that are exported
on 'make install' of the library) use bracketed includes instead of quoted.
To make sure no new files are introduced that doesn't include the bpf/
prefix in its include, remove tools/lib/bpf from the include path entirely,
and use tools/lib instead.
Fixes: 6910d7d386 ("selftests/bpf: Ensure bpf_helper_defs.h are taken from selftests dir")
Signed-off-by: Toke Høiland-Jørgensen <toke@redhat.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Jesper Dangaard Brouer <brouer@redhat.com>
Acked-by: Andrii Nakryiko <andriin@fb.com>
Link: https://lore.kernel.org/bpf/157952560911.1683545.8795966751309534150.stgit@toke.dk
105 lines
3 KiB
C
105 lines
3 KiB
C
/* SPDX-License-Identifier: GPL-2.0
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* Copyright (c) 2018 Jesper Dangaard Brouer, Red Hat Inc.
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*
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* Example howto transfer info from XDP to SKB, e.g. skb->mark
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* -----------------------------------------------------------
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* This uses the XDP data_meta infrastructure, and is a cooperation
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* between two bpf-programs (1) XDP and (2) clsact at TC-ingress hook.
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*
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* Notice: This example does not use the BPF C-loader (bpf_load.c),
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* but instead rely on the iproute2 TC tool for loading BPF-objects.
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*/
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#include <uapi/linux/bpf.h>
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#include <uapi/linux/pkt_cls.h>
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#include <bpf/bpf_helpers.h>
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/*
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* This struct is stored in the XDP 'data_meta' area, which is located
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* just in-front-of the raw packet payload data. The meaning is
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* specific to these two BPF programs that use it as a communication
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* channel. XDP adjust/increase the area via a bpf-helper, and TC use
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* boundary checks to see if data have been provided.
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*
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* The struct must be 4 byte aligned, which here is enforced by the
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* struct __attribute__((aligned(4))).
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*/
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struct meta_info {
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__u32 mark;
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} __attribute__((aligned(4)));
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SEC("xdp_mark")
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int _xdp_mark(struct xdp_md *ctx)
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{
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struct meta_info *meta;
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void *data, *data_end;
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int ret;
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/* Reserve space in-front of data pointer for our meta info.
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* (Notice drivers not supporting data_meta will fail here!)
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*/
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ret = bpf_xdp_adjust_meta(ctx, -(int)sizeof(*meta));
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if (ret < 0)
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return XDP_ABORTED;
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/* Notice: Kernel-side verifier requires that loading of
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* ctx->data MUST happen _after_ helper bpf_xdp_adjust_meta(),
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* as pkt-data pointers are invalidated. Helpers that require
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* this are determined/marked by bpf_helper_changes_pkt_data()
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*/
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data = (void *)(unsigned long)ctx->data;
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/* Check data_meta have room for meta_info struct */
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meta = (void *)(unsigned long)ctx->data_meta;
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if (meta + 1 > data)
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return XDP_ABORTED;
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meta->mark = 42;
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return XDP_PASS;
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}
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SEC("tc_mark")
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int _tc_mark(struct __sk_buff *ctx)
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{
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void *data = (void *)(unsigned long)ctx->data;
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void *data_end = (void *)(unsigned long)ctx->data_end;
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void *data_meta = (void *)(unsigned long)ctx->data_meta;
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struct meta_info *meta = data_meta;
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/* Check XDP gave us some data_meta */
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if (meta + 1 > data) {
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ctx->mark = 41;
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/* Skip "accept" if no data_meta is avail */
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return TC_ACT_OK;
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}
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/* Hint: See func tc_cls_act_is_valid_access() for BPF_WRITE access */
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ctx->mark = meta->mark; /* Transfer XDP-mark to SKB-mark */
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return TC_ACT_OK;
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}
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/* Manually attaching these programs:
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export DEV=ixgbe2
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export FILE=xdp2skb_meta_kern.o
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# via TC command
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tc qdisc del dev $DEV clsact 2> /dev/null
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tc qdisc add dev $DEV clsact
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tc filter add dev $DEV ingress prio 1 handle 1 bpf da obj $FILE sec tc_mark
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tc filter show dev $DEV ingress
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# XDP via IP command:
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ip link set dev $DEV xdp off
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ip link set dev $DEV xdp obj $FILE sec xdp_mark
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# Use iptable to "see" if SKBs are marked
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iptables -I INPUT -p icmp -m mark --mark 41 # == 0x29
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iptables -I INPUT -p icmp -m mark --mark 42 # == 0x2a
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# Hint: catch XDP_ABORTED errors via
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perf record -e xdp:*
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perf script
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*/
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