mirror of
https://github.com/xdp-project/bpf-examples.git
synced 2024-05-06 15:54:53 +00:00
5f3898ca61
This makes it easier to see/decode packets via tcpdump. Borrowing part of ../encap-forward/encap.h. Signed-off-by: Jesper Dangaard Brouer <brouer@redhat.com>
34 lines
713 B
C
34 lines
713 B
C
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static __always_inline __u16 csum_fold_helper(__u32 csum)
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{
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__u32 sum;
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sum = (csum >> 16) + (csum & 0xffff);
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sum += (sum >> 16);
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return ~sum;
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}
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static void encap_ipv4_ipip(volatile void *data, volatile void *data_end)
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{
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volatile struct iphdr *iph;
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size_t len;
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struct iphdr encap_hdr = {
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.version = 4,
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.ihl = 5,
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.protocol = IPPROTO_IPIP,
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.ttl = 16,
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.saddr = bpf_htonl(0x0a0b0202),
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.daddr = bpf_htonl(0x0a0b0201),
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};
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iph = data + sizeof(struct ethhdr);
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if (iph + 1 > data_end)
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return;
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*iph = encap_hdr;
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len = (data_end - data);
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iph->tot_len = bpf_htons(len - sizeof(struct ethhdr));
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iph->check = csum_fold_helper(bpf_csum_diff((__be32 *)iph, 0, (__be32 *)iph, sizeof(*iph), 0));
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}
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