54 lines
989 B
C
54 lines
989 B
C
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// 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 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("tc")
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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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