chapter8 - exercises1 failure

I am doing the first exercise in chapter8, modifying hello.bpf.c to print different content depending on the ping request message or response message. Here is my source program:

#include "vmlinux.h"
#include <bpf/bpf_endian.h>
#include <bpf/bpf_helpers.h>
#include "packet.h"

int ping(struct xdp_md *ctx){

    long protocol = lookup_protocol(ctx);  
    if (protocol == 1) // ICMP  
    {  
        void *data = (void *)(long)ctx->data;      

        struct icmphdr *icmp = data + sizeof(struct ethhdr) + sizeof(struct iphdr);

        if(icmp->type == 8)  //  8 for ping request
            bpf_printk("i'm a ping request packet");

        if(icmp->type == 0)  // 0 for ping response
            bpf_printk("i'm a ping response packet");
    }  

    return XDP_PASS;
}

Then I executed thesudo make command, then:


$ sudo make
clang \
    -target bpf \
    -D __BPF_TRACING__ \
        -I/usr/include/x86_64-linux-gnu \
    -Wall \
    -O2 -o hello.bpf.o -c hello.bpf.c
bpftool net detach xdp dev lo
rm -f /sys/fs/bpf/hello
bpftool prog load hello.bpf.o /sys/fs/bpf/hello
libbpf: prog 'ping': BPF program load failed: Permission denied
libbpf: prog 'ping': -- BEGIN PROG LOAD LOG --
0: R1=ctx(off=0,imm=0) R10=fp0
0: (61) r2 = *(u32 *)(r1 +4)          ; R1=ctx(off=0,imm=0) R2_w=pkt_end(off=0,imm=0)
1: (61) r1 = *(u32 *)(r1 +0)          ; R1_w=pkt(off=0,r=0,imm=0)
2: (bf) r3 = r1                       ; R1_w=pkt(off=0,r=0,imm=0) R3_w=pkt(off=0,r=0,imm=0)
3: (07) r3 += 14                      ; R3_w=pkt(off=14,r=0,imm=0)
4: (2d) if r3 > r2 goto pc+19         ; R2_w=pkt_end(off=0,imm=0) R3_w=pkt(off=14,r=14,imm=0)
5: (69) r3 = *(u16 *)(r1 +12)         ; R1_w=pkt(off=0,r=14,imm=0) R3_w=scalar(umax=65535,var_off=(0x0; 0xffff))
6: (55) if r3 != 0x8 goto pc+17       ; R3_w=8
7: (bf) r6 = r1                       ; R1_w=pkt(off=0,r=14,imm=0) R6_w=pkt(off=0,r=14,imm=0)
8: (07) r6 += 34                      ; R6=pkt(off=34,r=14,imm=0)
9: (2d) if r6 > r2 goto pc+14         ; R2=pkt_end(off=0,imm=0) R6=pkt(off=34,r=34,imm=0)
10: (71) r1 = *(u8 *)(r1 +23)         ; R1_w=scalar(umax=255,var_off=(0x0; 0xff))
11: (55) if r1 != 0x1 goto pc+12      ; R1_w=1
12: (71) r1 = *(u8 *)(r6 +0)
invalid access to packet, off=34 size=1, R6(id=0,off=34,r=34)
R6 offset is outside of the packet
processed 13 insns (limit 1000000) max_states_per_insn 0 total_states 1 peak_states 1 mark_read 1
-- END PROG LOAD LOG --
libbpf: prog 'ping': failed to load: -13
libbpf: failed to load object 'hello.bpf.o'
Error: failed to load object file
make: *** [Makefile:13：hello] 错误 255

I want to know what went wrong and how to correct it. thanks

lizrice / learning-ebpf

chapter8 - exercises1 failure #32