9cc873e858
Add a test that currently makes LLVM generate assembly code:
$ llvm-objdump -S skb_pkt_end.o
0000000000000000 <main_prog>:
; if (skb_shorter(skb, ETH_IPV4_TCP_SIZE))
0: 61 12 50 00 00 00 00 00 r2 = *(u32 *)(r1 + 80)
1: 61 14 4c 00 00 00 00 00 r4 = *(u32 *)(r1 + 76)
2: bf 43 00 00 00 00 00 00 r3 = r4
3: 07 03 00 00 36 00 00 00 r3 += 54
4: b7 01 00 00 00 00 00 00 r1 = 0
5: 2d 23 02 00 00 00 00 00 if r3 > r2 goto +2 <LBB0_2>
6: 07 04 00 00 0e 00 00 00 r4 += 14
; if (skb_shorter(skb, ETH_IPV4_TCP_SIZE))
7: bf 41 00 00 00 00 00 00 r1 = r4
0000000000000040 <LBB0_2>:
8: b4 00 00 00 ff ff ff ff w0 = -1
; if (!(ip = get_iphdr(skb)))
9: 2d 23 05 00 00 00 00 00 if r3 > r2 goto +5 <LBB0_6>
; proto = ip->protocol;
10: 71 12 09 00 00 00 00 00 r2 = *(u8 *)(r1 + 9)
; if (proto != IPPROTO_TCP)
11: 56 02 03 00 06 00 00 00 if w2 != 6 goto +3 <LBB0_6>
; if (tcp->dest != 0)
12: 69 12 16 00 00 00 00 00 r2 = *(u16 *)(r1 + 22)
13: 56 02 01 00 00 00 00 00 if w2 != 0 goto +1 <LBB0_6>
; return tcp->urg_ptr;
14: 69 10 26 00 00 00 00 00 r0 = *(u16 *)(r1 + 38)
0000000000000078 <LBB0_6>:
; }
15: 95 00 00 00 00 00 00 00 exit
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: John Fastabend <john.fastabend@gmail.com>
Link: https://lore.kernel.org/bpf/20201111031213.25109-3-alexei.starovoitov@gmail.com
54 lines
1,016 B
C
54 lines
1,016 B
C
// SPDX-License-Identifier: GPL-2.0
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#define BPF_NO_PRESERVE_ACCESS_INDEX
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#include <vmlinux.h>
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#include <bpf/bpf_core_read.h>
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#include <bpf/bpf_helpers.h>
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#define NULL 0
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#define INLINE __always_inline
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#define skb_shorter(skb, len) ((void *)(long)(skb)->data + (len) > (void *)(long)skb->data_end)
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#define ETH_IPV4_TCP_SIZE (14 + sizeof(struct iphdr) + sizeof(struct tcphdr))
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static INLINE struct iphdr *get_iphdr(struct __sk_buff *skb)
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{
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struct iphdr *ip = NULL;
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struct ethhdr *eth;
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if (skb_shorter(skb, ETH_IPV4_TCP_SIZE))
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goto out;
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eth = (void *)(long)skb->data;
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ip = (void *)(eth + 1);
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out:
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return ip;
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}
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SEC("classifier/cls")
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int main_prog(struct __sk_buff *skb)
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{
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struct iphdr *ip = NULL;
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struct tcphdr *tcp;
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__u8 proto = 0;
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if (!(ip = get_iphdr(skb)))
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goto out;
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proto = ip->protocol;
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if (proto != IPPROTO_TCP)
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goto out;
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tcp = (void*)(ip + 1);
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if (tcp->dest != 0)
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goto out;
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if (!tcp)
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goto out;
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return tcp->urg_ptr;
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out:
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return -1;
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}
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char _license[] SEC("license") = "GPL";
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