samples: bpf: trivial eBPF program in C

this example does the same task as previous socket example
in assembler, but this one does it in C.

eBPF program in kernel does:
    /* assume that packet is IPv4, load one byte of IP->proto */
    int index = load_byte(skb, ETH_HLEN + offsetof(struct iphdr, protocol));
    long *value;

    value = bpf_map_lookup_elem(&my_map, &index);
    if (value)
        __sync_fetch_and_add(value, 1);

Corresponding user space reads map[tcp], map[udp], map[icmp]
and prints protocol stats every second

Signed-off-by: Alexei Starovoitov <ast@plumgrid.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/samples/bpf/Makefile b/samples/bpf/Makefile
index f46d3492d032ac46e28e803c98fa671001647053..770d145186c33b26145b033282149f630727a693 100644 (file)
--- a/samples/bpf/Makefile
+++ b/samples/bpf/Makefile
@@ -4,12 +4,26 @@ obj- := dummy.o
 # List of programs to build
 hostprogs-y := test_verifier test_maps
 hostprogs-y += sock_example
+hostprogs-y += sockex1
 
 test_verifier-objs := test_verifier.o libbpf.o
 test_maps-objs := test_maps.o libbpf.o
 sock_example-objs := sock_example.o libbpf.o
+sockex1-objs := bpf_load.o libbpf.o sockex1_user.o
 
 # Tell kbuild to always build the programs
 always := $(hostprogs-y)
+always += sockex1_kern.o
 
 HOSTCFLAGS += -I$(objtree)/usr/include
+
+HOSTCFLAGS_bpf_load.o += -I$(objtree)/usr/include -Wno-unused-variable
+HOSTLOADLIBES_sockex1 += -lelf
+
+# point this to your LLVM backend with bpf support
+LLC=$(srctree)/tools/bpf/llvm/bld/Debug+Asserts/bin/llc
+
+%.o: %.c
+       clang $(NOSTDINC_FLAGS) $(LINUXINCLUDE) $(EXTRA_CFLAGS) \
+               -D__KERNEL__ -Wno-unused-value -Wno-pointer-sign \
+               -O2 -emit-llvm -c $< -o -| $(LLC) -march=bpf -filetype=obj -o $@

diff --git a/samples/bpf/libbpf.h b/samples/bpf/libbpf.h
index cc62ad4d95decd0d6978cc744e99496e2dae401e..58c5fe1bdba1f08c278a750e69a7a32f706f819c 100644 (file)
--- a/samples/bpf/libbpf.h
+++ b/samples/bpf/libbpf.h
@@ -15,7 +15,7 @@ int bpf_prog_load(enum bpf_prog_type prog_type,
                  const struct bpf_insn *insns, int insn_len,
                  const char *license);
 
-#define LOG_BUF_SIZE 8192
+#define LOG_BUF_SIZE 65536
 extern char bpf_log_buf[LOG_BUF_SIZE];
 
 /* ALU ops on registers, bpf_add|sub|...: dst_reg += src_reg */

diff --git a/samples/bpf/sockex1_kern.c b/samples/bpf/sockex1_kern.c
new file mode 100644 (file)
index 0000000..0668926
--- /dev/null
+++ b/samples/bpf/sockex1_kern.c
@@ -0,0 +1,25 @@
+#include <uapi/linux/bpf.h>
+#include <uapi/linux/if_ether.h>
+#include <uapi/linux/ip.h>
+#include "bpf_helpers.h"
+
+struct bpf_map_def SEC("maps") my_map = {
+       .type = BPF_MAP_TYPE_ARRAY,
+       .key_size = sizeof(u32),
+       .value_size = sizeof(long),
+       .max_entries = 256,
+};
+
+SEC("socket1")
+int bpf_prog1(struct sk_buff *skb)
+{
+       int index = load_byte(skb, ETH_HLEN + offsetof(struct iphdr, protocol));
+       long *value;
+
+       value = bpf_map_lookup_elem(&my_map, &index);
+       if (value)
+               __sync_fetch_and_add(value, 1);
+
+       return 0;
+}
+char _license[] SEC("license") = "GPL";

diff --git a/samples/bpf/sockex1_user.c b/samples/bpf/sockex1_user.c
new file mode 100644 (file)
index 0000000..34a443f
--- /dev/null
+++ b/samples/bpf/sockex1_user.c
@@ -0,0 +1,49 @@
+#include <stdio.h>
+#include <assert.h>
+#include <linux/bpf.h>
+#include "libbpf.h"
+#include "bpf_load.h"
+#include <unistd.h>
+#include <arpa/inet.h>
+
+int main(int ac, char **argv)
+{
+       char filename[256];
+       FILE *f;
+       int i, sock;
+
+       snprintf(filename, sizeof(filename), "%s_kern.o", argv[0]);
+
+       if (load_bpf_file(filename)) {
+               printf("%s", bpf_log_buf);
+               return 1;
+       }
+
+       sock = open_raw_sock("lo");
+
+       assert(setsockopt(sock, SOL_SOCKET, SO_ATTACH_BPF, prog_fd,
+                         sizeof(prog_fd[0])) == 0);
+
+       f = popen("ping -c5 localhost", "r");
+       (void) f;
+
+       for (i = 0; i < 5; i++) {
+               long long tcp_cnt, udp_cnt, icmp_cnt;
+               int key;
+
+               key = IPPROTO_TCP;
+               assert(bpf_lookup_elem(map_fd[0], &key, &tcp_cnt) == 0);
+
+               key = IPPROTO_UDP;
+               assert(bpf_lookup_elem(map_fd[0], &key, &udp_cnt) == 0);
+
+               key = IPPROTO_ICMP;
+               assert(bpf_lookup_elem(map_fd[0], &key, &icmp_cnt) == 0);
+
+               printf("TCP %lld UDP %lld ICMP %lld packets\n",
+                      tcp_cnt, udp_cnt, icmp_cnt);
+               sleep(1);
+       }
+
+       return 0;
+}