On Mon, Jun 25, 2018 at 5:25 AM, Toke Høiland-Jørgensen <[email protected]> wrote: > 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 <[email protected]> > Signed-off-by: Toke Høiland-Jørgensen <[email protected]>
Acked-by: Song Liu <[email protected]> > --- > samples/bpf/Makefile | 4 + > samples/bpf/xdp_sample_pkts_kern.c | 66 ++++++++++++++ > samples/bpf/xdp_sample_pkts_user.c | 169 > ++++++++++++++++++++++++++++++++++++ > 3 files changed, 239 insertions(+) > create mode 100644 samples/bpf/xdp_sample_pkts_kern.c > create mode 100644 samples/bpf/xdp_sample_pkts_user.c > > diff --git a/samples/bpf/Makefile b/samples/bpf/Makefile > index 1303af10e54d..9ea2f7b64869 100644 > --- a/samples/bpf/Makefile > +++ b/samples/bpf/Makefile > @@ -52,6 +52,7 @@ hostprogs-y += xdp_adjust_tail > hostprogs-y += xdpsock > hostprogs-y += xdp_fwd > hostprogs-y += task_fd_query > +hostprogs-y += xdp_sample_pkts > > # Libbpf dependencies > LIBBPF = $(TOOLS_PATH)/lib/bpf/libbpf.a > @@ -107,6 +108,7 @@ xdp_adjust_tail-objs := xdp_adjust_tail_user.o > xdpsock-objs := bpf_load.o xdpsock_user.o > xdp_fwd-objs := bpf_load.o xdp_fwd_user.o > task_fd_query-objs := bpf_load.o task_fd_query_user.o $(TRACE_HELPERS) > +xdp_sample_pkts-objs := xdp_sample_pkts_user.o $(TRACE_HELPERS) > > # Tell kbuild to always build the programs > always := $(hostprogs-y) > @@ -163,6 +165,7 @@ always += xdp_adjust_tail_kern.o > always += xdpsock_kern.o > always += xdp_fwd_kern.o > always += task_fd_query_kern.o > +always += xdp_sample_pkts_kern.o > > HOSTCFLAGS += -I$(objtree)/usr/include > HOSTCFLAGS += -I$(srctree)/tools/lib/ > @@ -179,6 +182,7 @@ HOSTCFLAGS_spintest_user.o += -I$(srctree)/tools/lib/bpf/ > HOSTCFLAGS_trace_event_user.o += -I$(srctree)/tools/lib/bpf/ > HOSTCFLAGS_sampleip_user.o += -I$(srctree)/tools/lib/bpf/ > HOSTCFLAGS_task_fd_query_user.o += -I$(srctree)/tools/lib/bpf/ > +HOSTCFLAGS_xdp_sample_pkts_user.o += -I$(srctree)/tools/lib/bpf/ > > HOST_LOADLIBES += $(LIBBPF) -lelf > HOSTLOADLIBES_tracex4 += -lrt > diff --git a/samples/bpf/xdp_sample_pkts_kern.c > b/samples/bpf/xdp_sample_pkts_kern.c > new file mode 100644 > index 000000000000..f7ca8b850978 > --- /dev/null > +++ b/samples/bpf/xdp_sample_pkts_kern.c > @@ -0,0 +1,66 @@ > +// SPDX-License-Identifier: GPL-2.0 > +#include <linux/ptrace.h> > +#include <linux/version.h> > +#include <uapi/linux/bpf.h> > +#include "bpf_helpers.h" > + > +#define SAMPLE_SIZE 64ul > +#define MAX_CPUS 128 > + > +#define bpf_printk(fmt, ...) \ > +({ \ > + char ____fmt[] = fmt; \ > + bpf_trace_printk(____fmt, sizeof(____fmt), \ > + ##__VA_ARGS__); \ > +}) > + > +struct bpf_map_def SEC("maps") my_map = { > + .type = BPF_MAP_TYPE_PERF_EVENT_ARRAY, > + .key_size = sizeof(int), > + .value_size = sizeof(u32), > + .max_entries = MAX_CPUS, > +}; > + > +SEC("xdp_sample") > +int xdp_sample_prog(struct xdp_md *ctx) > +{ > + void *data_end = (void *)(long)ctx->data_end; > + void *data = (void *)(long)ctx->data; > + > + /* Metadata will be in the perf event before the packet data. */ > + struct S { > + u16 cookie; > + u16 pkt_len; > + } __packed metadata; > + > + if (data < data_end) { > + /* The XDP perf_event_output handler will use the upper 32 > bits > + * of the flags argument as a number of bytes to include of > the > + * packet payload in the event data. If the size is too big, > the > + * call to bpf_perf_event_output will fail and return -EFAULT. > + * > + * See bpf_xdp_event_output in net/core/filter.c. > + * > + * The BPF_F_CURRENT_CPU flag means that the event output fd > + * will be indexed by the CPU number in the event map. > + */ > + u64 flags = BPF_F_CURRENT_CPU; > + u16 sample_size; > + int ret; > + > + metadata.cookie = 0xdead; > + metadata.pkt_len = (u16)(data_end - data); > + sample_size = min(metadata.pkt_len, SAMPLE_SIZE); > + flags |= (u64)sample_size << 32; > + > + ret = bpf_perf_event_output(ctx, &my_map, flags, > + &metadata, sizeof(metadata)); > + if (ret) > + bpf_printk("perf_event_output failed: %d\n", ret); > + } > + > + return XDP_PASS; > +} > + > +char _license[] SEC("license") = "GPL"; > +u32 _version SEC("version") = LINUX_VERSION_CODE; > diff --git a/samples/bpf/xdp_sample_pkts_user.c > b/samples/bpf/xdp_sample_pkts_user.c > new file mode 100644 > index 000000000000..8dd87c1eb560 > --- /dev/null > +++ b/samples/bpf/xdp_sample_pkts_user.c > @@ -0,0 +1,169 @@ > +// SPDX-License-Identifier: GPL-2.0 > +#include <stdio.h> > +#include <stdlib.h> > +#include <string.h> > +#include <linux/perf_event.h> > +#include <linux/bpf.h> > +#include <net/if.h> > +#include <errno.h> > +#include <assert.h> > +#include <sys/sysinfo.h> > +#include <sys/ioctl.h> > +#include <signal.h> > +#include <libbpf.h> > +#include <bpf/bpf.h> > + > +#include "perf-sys.h" > +#include "trace_helpers.h" > + > +#define MAX_CPUS 128 > +static int pmu_fds[MAX_CPUS], if_idx; > +static struct perf_event_mmap_page *headers[MAX_CPUS]; > +static char *if_name; > + > +static int do_attach(int idx, int fd, const char *name) > +{ > + int err; > + > + err = bpf_set_link_xdp_fd(idx, fd, 0); > + if (err < 0) > + printf("ERROR: failed to attach program to %s\n", name); > + > + return err; > +} > + > +static int do_detach(int idx, const char *name) > +{ > + int err; > + > + err = bpf_set_link_xdp_fd(idx, -1, 0); > + if (err < 0) > + printf("ERROR: failed to detach program from %s\n", name); > + > + return err; > +} > + > +#define SAMPLE_SIZE 64 > + > +static int print_bpf_output(void *data, int size) > +{ > + struct { > + __u16 cookie; > + __u16 pkt_len; > + __u8 pkt_data[SAMPLE_SIZE]; > + } __packed *e = data; > + int i; > + > + if (e->cookie != 0xdead) { > + printf("BUG cookie %x sized %d\n", > + e->cookie, size); > + return LIBBPF_PERF_EVENT_ERROR; > + } > + > + printf("Pkt len: %-5d bytes. Ethernet hdr: ", e->pkt_len); > + for (i = 0; i < 14 && i < e->pkt_len; i++) > + printf("%02x ", e->pkt_data[i]); > + printf("\n"); > + > + return LIBBPF_PERF_EVENT_CONT; > +} > + > +static void test_bpf_perf_event(int map_fd, int num) > +{ > + struct perf_event_attr attr = { > + .sample_type = PERF_SAMPLE_RAW, > + .type = PERF_TYPE_SOFTWARE, > + .config = PERF_COUNT_SW_BPF_OUTPUT, > + .wakeup_events = 1, /* get an fd notification for every event > */ > + }; > + int i; > + > + for (i = 0; i < num; i++) { > + int key = i; > + > + pmu_fds[i] = sys_perf_event_open(&attr, -1/*pid*/, i/*cpu*/, > + -1/*group_fd*/, 0); > + > + assert(pmu_fds[i] >= 0); > + assert(bpf_map_update_elem(map_fd, &key, > + &pmu_fds[i], BPF_ANY) == 0); > + ioctl(pmu_fds[i], PERF_EVENT_IOC_ENABLE, 0); > + } > +} > + > +static void sig_handler(int signo) > +{ > + do_detach(if_idx, if_name); > + exit(0); > +} > + > +int main(int argc, char **argv) > +{ > + struct bpf_prog_load_attr prog_load_attr = { > + .prog_type = BPF_PROG_TYPE_XDP, > + }; > + struct bpf_object *obj; > + struct bpf_map *map; > + int prog_fd, map_fd; > + char filename[256]; > + int ret, err, i; > + int numcpus; > + > + if (argc < 2) { > + printf("Usage: %s <ifname>\n", argv[0]); > + return 1; > + } > + > + numcpus = get_nprocs(); > + if (numcpus > MAX_CPUS) > + numcpus = MAX_CPUS; > + > + snprintf(filename, sizeof(filename), "%s_kern.o", argv[0]); > + prog_load_attr.file = filename; > + > + if (bpf_prog_load_xattr(&prog_load_attr, &obj, &prog_fd)) > + return 1; > + > + if (!prog_fd) { > + printf("load_bpf_file: %s\n", strerror(errno)); > + return 1; > + } > + > + map = bpf_map__next(NULL, obj); > + if (!map) { > + printf("finding a map in obj file failed\n"); > + return 1; > + } > + map_fd = bpf_map__fd(map); > + > + if_idx = if_nametoindex(argv[1]); > + if (!if_idx) > + if_idx = strtoul(argv[1], NULL, 0); > + > + if (!if_idx) { > + fprintf(stderr, "Invalid ifname\n"); > + return 1; > + } > + if_name = argv[1]; > + err = do_attach(if_idx, prog_fd, argv[1]); > + if (err) > + return err; > + > + if (signal(SIGINT, sig_handler) || > + signal(SIGHUP, sig_handler) || > + signal(SIGTERM, sig_handler)) { > + perror("signal"); > + return 1; > + } > + > + test_bpf_perf_event(map_fd, numcpus); > + > + for (i = 0; i < numcpus; i++) > + if (perf_event_mmap_header(pmu_fds[i], &headers[i]) < 0) > + return 1; > + > + ret = perf_event_poller_multi(pmu_fds, headers, numcpus, > + print_bpf_output); > + kill(0, SIGINT); > + return ret; > +} >
