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31b12a4159
Currently, executing test_cgrp2_sock2 fails due to wrong section
header. This 'cgroup/sock1' style section is previously used at
'samples/bpf_load' (deprecated) BPF loader. Because this style isn't
supported in libbpf, this commit fixes this problem by correcting the
section header.
$ sudo ./test_cgrp2_sock2.sh
libbpf: prog 'bpf_prog1': missing BPF prog type, check ELF section name 'cgroup/sock1'
libbpf: prog 'bpf_prog1': failed to load: -22
libbpf: failed to load object './sock_flags_kern.o'
ERROR: loading BPF object file failed
In addition, this BPF program filters ping packets by comparing whether
the socket type uses SOCK_RAW. However, after the ICMP socket[1] was
developed, ping sends ICMP packets using SOCK_DGRAM. Therefore, in this
commit, the packet filtering is changed to use SOCK_DGRAM instead of
SOCK_RAW.
$ strace --trace socket ping -6 -c1 -w1 ::1
socket(AF_INET6, SOCK_DGRAM, IPPROTO_ICMPV6) = 3
[1]: https://lwn.net/Articles/422330/
Signed-off-by: Daniel T. Lee <danieltimlee@gmail.com>
Link: https://lore.kernel.org/r/20230115071613.125791-5-danieltimlee@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
49 lines
1.2 KiB
C
49 lines
1.2 KiB
C
#include <uapi/linux/bpf.h>
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#include <linux/socket.h>
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#include <linux/net.h>
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#include <uapi/linux/in.h>
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#include <uapi/linux/in6.h>
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#include <bpf/bpf_helpers.h>
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SEC("cgroup/sock")
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int bpf_prog1(struct bpf_sock *sk)
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{
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char fmt[] = "socket: family %d type %d protocol %d\n";
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char fmt2[] = "socket: uid %u gid %u\n";
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__u64 gid_uid = bpf_get_current_uid_gid();
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__u32 uid = gid_uid & 0xffffffff;
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__u32 gid = gid_uid >> 32;
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bpf_trace_printk(fmt, sizeof(fmt), sk->family, sk->type, sk->protocol);
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bpf_trace_printk(fmt2, sizeof(fmt2), uid, gid);
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/* block PF_INET6, SOCK_DGRAM, IPPROTO_ICMPV6 sockets
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* ie., make ping6 fail
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*/
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if (sk->family == PF_INET6 &&
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sk->type == SOCK_DGRAM &&
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sk->protocol == IPPROTO_ICMPV6)
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return 0;
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return 1;
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}
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SEC("cgroup/sock")
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int bpf_prog2(struct bpf_sock *sk)
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{
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char fmt[] = "socket: family %d type %d protocol %d\n";
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bpf_trace_printk(fmt, sizeof(fmt), sk->family, sk->type, sk->protocol);
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/* block PF_INET, SOCK_DGRAM, IPPROTO_ICMP sockets
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* ie., make ping fail
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*/
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if (sk->family == PF_INET &&
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sk->type == SOCK_DGRAM &&
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sk->protocol == IPPROTO_ICMP)
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return 0;
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return 1;
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}
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char _license[] SEC("license") = "GPL";
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