tjh.dev
Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
kernel
os
linux
1// SPDX-License-Identifier: GPL-2.0
2#ifndef BPF_NO_PRESERVE_ACCESS_INDEX
3#define BPF_NO_PRESERVE_ACCESS_INDEX
4#endif
5#include <vmlinux.h>
6#include <bpf/bpf_core_read.h>
7#include <bpf/bpf_helpers.h>
8
9#define INLINE __always_inline
10
11#define skb_shorter(skb, len) ((void *)(long)(skb)->data + (len) > (void *)(long)skb->data_end)
12
13#define ETH_IPV4_TCP_SIZE (14 + sizeof(struct iphdr) + sizeof(struct tcphdr))
14
15static INLINE struct iphdr *get_iphdr(struct __sk_buff *skb)
16{
17 struct iphdr *ip = NULL;
18 struct ethhdr *eth;
19
20 if (skb_shorter(skb, ETH_IPV4_TCP_SIZE))
21 goto out;
22
23 eth = (void *)(long)skb->data;
24 ip = (void *)(eth + 1);
25
26out:
27 return ip;
28}
29
30SEC("tc")
31int main_prog(struct __sk_buff *skb)
32{
33 struct iphdr *ip = NULL;
34 struct tcphdr *tcp;
35 __u8 proto = 0;
36 int urg_ptr;
37 u32 offset;
38
39 if (!(ip = get_iphdr(skb)))
40 goto out;
41
42 proto = ip->protocol;
43
44 if (proto != IPPROTO_TCP)
45 goto out;
46
47 tcp = (void*)(ip + 1);
48 if (tcp->dest != 0)
49 goto out;
50 if (!tcp)
51 goto out;
52
53 urg_ptr = tcp->urg_ptr;
54
55 /* Checksum validation part */
56 proto++;
57 offset = sizeof(struct ethhdr) + offsetof(struct iphdr, protocol);
58 bpf_skb_store_bytes(skb, offset, &proto, sizeof(proto), BPF_F_RECOMPUTE_CSUM);
59
60 return urg_ptr;
61out:
62 return -1;
63}
64char _license[] SEC("license") = "GPL";