GOAL: write a new ebpf
example within samples/bpf
directory in the kernel source tree of 4.18.0, compile and execute it.
PROBLEM: after compiling it when I run sudo ./mine
it just terminates.
mine_kern.c
#include <uapi/linux/bpf.h>
#include <uapi/linux/if_ether.h>
#include <uapi/linux/ip.h>
#include <linux/in.h>
#include <linux/if_packet.h>
#include "bpf_helpers.h"
int icmp_filter(struct __sk_buff *skb){
int proto = load_byte(skb, ETH_HLEN + offsetof(struct iphdr, protocol));
if(proto == IPPROTO_ICMP && skb->pkt_type == PACKET_OUTGOING){
return -1;
} else {
return 0;
}
}
char _license[] SEC("license") = "GPL";
mine_user.c
#include <stdio.h>
#include <assert.h>
#include <linux/bpf.h>
#include <bpf/bpf.h>
#include "bpf_load.h"
#include "sock_example.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;
char buf[65535];
for(i=0; i<20; i++){
int res = recvfrom(sock, buf, sizeof(buf), 0, NULL, 0);
printf("res=%d\n", res);
}
return 0;
}
I've also modified the Makefile
inside samples/bpf
adding mine_user.c
and mine_kern.c
where required.
QUESTIONS: what is wrong with this code?