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add BSD ping detection

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Lain Iwakura 2025-07-17 12:31:20 +03:00
parent fa756500d3
commit f2b020d0a4
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GPG Key ID: C7C18257F2ADC6F8
1 changed files with 18 additions and 8 deletions
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xdp.c
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@ -94,18 +94,28 @@ int pinger(struct xdp_md* ctx) {
recalc_icmp_csum(icmphdr, 8, icmphdr->type);
__u64* ts_secs = (void*)(icmphdr + 1);
__u64* ts_nsecs = (void*)(icmphdr + 1) + sizeof(__u64);
if ((void*)ts_nsecs + sizeof(__u64) <= data_end) {
__u8* payload = (void*)(icmphdr + 1);
int is_bsd = 0;
if ((void*)(payload + 16) <= data_end) {
// Check for BSD ping signature: 0x08, 0x09, 0x0a, 0x0b, ...
if (payload[8] == 0x08 && payload[9] == 0x09 && payload[10] == 0x0a && payload[11] == 0x0b &&
payload[12] == 0x0c && payload[13] == 0x0d && payload[14] == 0x0e && payload[15] == 0x0f) {
is_bsd = 1;
}
}
if ((void*)(ts_secs + 1) <= data_end) {
__u64 old_secs = *ts_secs;
__u64 old_nsecs = *ts_nsecs;
*ts_secs -= bpf_get_prandom_u32() % 500;
*ts_nsecs -= bpf_get_prandom_u32();
recalc_icmp_csum(icmphdr, old_secs, *ts_secs);
}
if (!is_bsd) {
__u64* ts_nsecs = (void*)(icmphdr + 1) + sizeof(__u64);
if ((void*)ts_nsecs + sizeof(__u64) <= data_end) {
__u64 old_nsecs = *ts_nsecs;
*ts_nsecs -= bpf_get_prandom_u32();
recalc_icmp_csum(icmphdr, old_nsecs, *ts_nsecs);
}
}
__u8 old_ttl = iph->ttl;
iph->ttl = bpf_get_prandom_u32() % 200 + 40;