samples/bpf: Add xdp_sample_pkts example
Add an example program showing how to sample packets from XDP using the perf event buffer. The example userspace program just prints the ethernet header for every packet sampled. Reviewed-by: Jakub Kicinski <jakub.kicinski@netronome.com> Signed-off-by: Toke Høiland-Jørgensen <toke@toke.dk> Acked-by: Song Liu <songliubraving@fb.com> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
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@ -52,6 +52,7 @@ hostprogs-y += xdp_adjust_tail
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hostprogs-y += xdpsock
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hostprogs-y += xdp_fwd
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hostprogs-y += task_fd_query
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hostprogs-y += xdp_sample_pkts
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# Libbpf dependencies
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LIBBPF = $(TOOLS_PATH)/lib/bpf/libbpf.a
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@ -107,6 +108,7 @@ xdp_adjust_tail-objs := xdp_adjust_tail_user.o
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xdpsock-objs := bpf_load.o xdpsock_user.o
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xdp_fwd-objs := bpf_load.o xdp_fwd_user.o
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task_fd_query-objs := bpf_load.o task_fd_query_user.o $(TRACE_HELPERS)
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xdp_sample_pkts-objs := xdp_sample_pkts_user.o $(TRACE_HELPERS)
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# Tell kbuild to always build the programs
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always := $(hostprogs-y)
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@ -163,6 +165,7 @@ always += xdp_adjust_tail_kern.o
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always += xdpsock_kern.o
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always += xdp_fwd_kern.o
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always += task_fd_query_kern.o
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always += xdp_sample_pkts_kern.o
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HOSTCFLAGS += -I$(objtree)/usr/include
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HOSTCFLAGS += -I$(srctree)/tools/lib/
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@ -179,6 +182,7 @@ HOSTCFLAGS_spintest_user.o += -I$(srctree)/tools/lib/bpf/
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HOSTCFLAGS_trace_event_user.o += -I$(srctree)/tools/lib/bpf/
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HOSTCFLAGS_sampleip_user.o += -I$(srctree)/tools/lib/bpf/
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HOSTCFLAGS_task_fd_query_user.o += -I$(srctree)/tools/lib/bpf/
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HOSTCFLAGS_xdp_sample_pkts_user.o += -I$(srctree)/tools/lib/bpf/
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HOST_LOADLIBES += $(LIBBPF) -lelf
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HOSTLOADLIBES_tracex4 += -lrt
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66
samples/bpf/xdp_sample_pkts_kern.c
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66
samples/bpf/xdp_sample_pkts_kern.c
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@ -0,0 +1,66 @@
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// SPDX-License-Identifier: GPL-2.0
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#include <linux/ptrace.h>
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#include <linux/version.h>
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#include <uapi/linux/bpf.h>
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#include "bpf_helpers.h"
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#define SAMPLE_SIZE 64ul
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#define MAX_CPUS 128
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#define bpf_printk(fmt, ...) \
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({ \
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char ____fmt[] = fmt; \
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bpf_trace_printk(____fmt, sizeof(____fmt), \
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##__VA_ARGS__); \
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})
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struct bpf_map_def SEC("maps") my_map = {
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.type = BPF_MAP_TYPE_PERF_EVENT_ARRAY,
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.key_size = sizeof(int),
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.value_size = sizeof(u32),
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.max_entries = MAX_CPUS,
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};
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SEC("xdp_sample")
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int xdp_sample_prog(struct xdp_md *ctx)
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{
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void *data_end = (void *)(long)ctx->data_end;
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void *data = (void *)(long)ctx->data;
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/* Metadata will be in the perf event before the packet data. */
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struct S {
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u16 cookie;
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u16 pkt_len;
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} __packed metadata;
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if (data < data_end) {
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/* The XDP perf_event_output handler will use the upper 32 bits
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* of the flags argument as a number of bytes to include of the
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* packet payload in the event data. If the size is too big, the
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* call to bpf_perf_event_output will fail and return -EFAULT.
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*
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* See bpf_xdp_event_output in net/core/filter.c.
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*
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* The BPF_F_CURRENT_CPU flag means that the event output fd
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* will be indexed by the CPU number in the event map.
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*/
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u64 flags = BPF_F_CURRENT_CPU;
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u16 sample_size;
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int ret;
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metadata.cookie = 0xdead;
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metadata.pkt_len = (u16)(data_end - data);
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sample_size = min(metadata.pkt_len, SAMPLE_SIZE);
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flags |= (u64)sample_size << 32;
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ret = bpf_perf_event_output(ctx, &my_map, flags,
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&metadata, sizeof(metadata));
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if (ret)
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bpf_printk("perf_event_output failed: %d\n", ret);
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}
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return XDP_PASS;
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}
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char _license[] SEC("license") = "GPL";
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u32 _version SEC("version") = LINUX_VERSION_CODE;
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169
samples/bpf/xdp_sample_pkts_user.c
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169
samples/bpf/xdp_sample_pkts_user.c
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@ -0,0 +1,169 @@
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// SPDX-License-Identifier: GPL-2.0
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#include <stdio.h>
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#include <stdlib.h>
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#include <string.h>
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#include <linux/perf_event.h>
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#include <linux/bpf.h>
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#include <net/if.h>
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#include <errno.h>
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#include <assert.h>
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#include <sys/sysinfo.h>
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#include <sys/ioctl.h>
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#include <signal.h>
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#include <libbpf.h>
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#include <bpf/bpf.h>
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#include "perf-sys.h"
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#include "trace_helpers.h"
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#define MAX_CPUS 128
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static int pmu_fds[MAX_CPUS], if_idx;
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static struct perf_event_mmap_page *headers[MAX_CPUS];
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static char *if_name;
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static int do_attach(int idx, int fd, const char *name)
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{
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int err;
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err = bpf_set_link_xdp_fd(idx, fd, 0);
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if (err < 0)
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printf("ERROR: failed to attach program to %s\n", name);
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return err;
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}
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static int do_detach(int idx, const char *name)
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{
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int err;
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err = bpf_set_link_xdp_fd(idx, -1, 0);
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if (err < 0)
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printf("ERROR: failed to detach program from %s\n", name);
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return err;
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}
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#define SAMPLE_SIZE 64
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static int print_bpf_output(void *data, int size)
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{
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struct {
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__u16 cookie;
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__u16 pkt_len;
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__u8 pkt_data[SAMPLE_SIZE];
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} __packed *e = data;
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int i;
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if (e->cookie != 0xdead) {
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printf("BUG cookie %x sized %d\n",
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e->cookie, size);
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return LIBBPF_PERF_EVENT_ERROR;
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}
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printf("Pkt len: %-5d bytes. Ethernet hdr: ", e->pkt_len);
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for (i = 0; i < 14 && i < e->pkt_len; i++)
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printf("%02x ", e->pkt_data[i]);
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printf("\n");
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return LIBBPF_PERF_EVENT_CONT;
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}
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static void test_bpf_perf_event(int map_fd, int num)
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{
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struct perf_event_attr attr = {
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.sample_type = PERF_SAMPLE_RAW,
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.type = PERF_TYPE_SOFTWARE,
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.config = PERF_COUNT_SW_BPF_OUTPUT,
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.wakeup_events = 1, /* get an fd notification for every event */
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};
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int i;
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for (i = 0; i < num; i++) {
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int key = i;
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pmu_fds[i] = sys_perf_event_open(&attr, -1/*pid*/, i/*cpu*/,
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-1/*group_fd*/, 0);
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assert(pmu_fds[i] >= 0);
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assert(bpf_map_update_elem(map_fd, &key,
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&pmu_fds[i], BPF_ANY) == 0);
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ioctl(pmu_fds[i], PERF_EVENT_IOC_ENABLE, 0);
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}
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}
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static void sig_handler(int signo)
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{
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do_detach(if_idx, if_name);
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exit(0);
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}
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int main(int argc, char **argv)
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{
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struct bpf_prog_load_attr prog_load_attr = {
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.prog_type = BPF_PROG_TYPE_XDP,
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};
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struct bpf_object *obj;
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struct bpf_map *map;
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int prog_fd, map_fd;
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char filename[256];
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int ret, err, i;
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int numcpus;
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if (argc < 2) {
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printf("Usage: %s <ifname>\n", argv[0]);
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return 1;
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}
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numcpus = get_nprocs();
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if (numcpus > MAX_CPUS)
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numcpus = MAX_CPUS;
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snprintf(filename, sizeof(filename), "%s_kern.o", argv[0]);
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prog_load_attr.file = filename;
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if (bpf_prog_load_xattr(&prog_load_attr, &obj, &prog_fd))
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return 1;
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if (!prog_fd) {
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printf("load_bpf_file: %s\n", strerror(errno));
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return 1;
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}
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map = bpf_map__next(NULL, obj);
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if (!map) {
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printf("finding a map in obj file failed\n");
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return 1;
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}
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map_fd = bpf_map__fd(map);
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if_idx = if_nametoindex(argv[1]);
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if (!if_idx)
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if_idx = strtoul(argv[1], NULL, 0);
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if (!if_idx) {
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fprintf(stderr, "Invalid ifname\n");
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return 1;
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}
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if_name = argv[1];
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err = do_attach(if_idx, prog_fd, argv[1]);
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if (err)
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return err;
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if (signal(SIGINT, sig_handler) ||
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signal(SIGHUP, sig_handler) ||
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signal(SIGTERM, sig_handler)) {
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perror("signal");
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return 1;
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}
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test_bpf_perf_event(map_fd, numcpus);
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for (i = 0; i < numcpus; i++)
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if (perf_event_mmap_header(pmu_fds[i], &headers[i]) < 0)
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return 1;
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ret = perf_event_poller_multi(pmu_fds, headers, numcpus,
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print_bpf_output);
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kill(0, SIGINT);
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return ret;
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}
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