1. 08 Mar, 2016 1 commit
  2. 02 Apr, 2015 1 commit
    • Alexei Starovoitov's avatar
      samples/bpf: Add simple non-portable kprobe filter example · b896c4f9
      Alexei Starovoitov authored
      tracex1_kern.c - C program compiled into BPF.
      It attaches to kprobe:netif_receive_skb()
      When skb->dev->name == "lo", it prints sample debug message into
      trace_pipe via bpf_trace_printk() helper function.
      tracex1_user.c - corresponding user space component that:
        - loads BPF program via bpf() syscall
        - opens kprobes:netif_receive_skb event via perf_event_open()
        - attaches the program to event via ioctl(event_fd,
          PERF_EVENT_IOC_SET_BPF, prog_fd);
        - prints from trace_pipe
      Note, this BPF program is non-portable. It must be recompiled
      with current kernel headers. kprobe is not a stable ABI and
      BPF+kprobe scripts may no longer be meaningful when kernel
      internals change.
      No matter in what way the kernel changes, neither the kprobe,
      nor the BPF program can ever crash or corrupt the kernel,
      assuming the kprobes, perf and BPF subsystem has no bugs.
      The verifier will detect that the program is using
      bpf_trace_printk() and the kernel will print 'this is a DEBUG
      kernel' warning banner, which means that bpf_trace_printk()
      should be used for debugging of the BPF program only.
      $ sudo tracex1
                  ping-19826 [000] d.s2 63103.382648: : skb ffff880466b1ca00 len 84
                  ping-19826 [000] d.s2 63103.382684: : skb ffff880466b1d300 len 84
                  ping-19826 [000] d.s2 63104.382533: : skb ffff880466b1ca00 len 84
                  ping-19826 [000] d.s2 63104.382594: : skb ffff880466b1d300 len 84
      Signed-off-by: default avatarAlexei Starovoitov <ast@plumgrid.com>
      Cc: Arnaldo Carvalho de Melo <acme@infradead.org>
      Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
      Cc: Daniel Borkmann <daniel@iogearbox.net>
      Cc: David S. Miller <davem@davemloft.net>
      Cc: Jiri Olsa <jolsa@redhat.com>
      Cc: Linus Torvalds <torvalds@linux-foundation.org>
      Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
      Cc: Namhyung Kim <namhyung@kernel.org>
      Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
      Cc: Peter Zijlstra <peterz@infradead.org>
      Cc: Steven Rostedt <rostedt@goodmis.org>
      Link: http://lkml.kernel.org/r/1427312966-8434-7-git-send-email-ast@plumgrid.comSigned-off-by: default avatarIngo Molnar <mingo@kernel.org>
  3. 06 Dec, 2014 1 commit
    • Alexei Starovoitov's avatar
      samples: bpf: example of stateful socket filtering · 03f4723e
      Alexei Starovoitov authored
      this socket filter example does:
      - creates arraymap in kernel with key 4 bytes and value 8 bytes
      - loads eBPF program which assumes that packet is IPv4 and loads one byte of
        IP->proto from the packet and uses it as a key in a map
        r0 = skb->data[ETH_HLEN + offsetof(struct iphdr, protocol)];
        *(u32*)(fp - 4) = r0;
        value = bpf_map_lookup_elem(map_fd, fp - 4);
        if (value)
             (*(u64*)value) += 1;
      - attaches this program to raw socket
      - every second user space reads map[IPPROTO_TCP], map[IPPROTO_UDP], map[IPPROTO_ICMP]
        to see how many packets of given protocol were seen on loopback interface
      $sudo samples/bpf/sock_example
      TCP 0 UDP 0 ICMP 0 packets
      TCP 187600 UDP 0 ICMP 4 packets
      TCP 376504 UDP 0 ICMP 8 packets
      TCP 563116 UDP 0 ICMP 12 packets
      TCP 753144 UDP 0 ICMP 16 packets
      Signed-off-by: default avatarAlexei Starovoitov <ast@plumgrid.com>
      Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>