Created
November 1, 2021 08:41
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trace_dns_drops traces DNS drops by ip_vs_in and ipt_do_table.
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#!/usr/bin/env bpftrace | |
/* | |
* trace_dns_drops traces DNS drops by ip_vs_in and ipt_do_table. | |
* | |
* Background: | |
* 1. Before 5.9, ip_vs_in can cause UDP packets drops when IPVS RS deleted | |
* and source port reused, See https://github.com/kubernetes/kubernetes/issues/71514 for more details. | |
* 2. Misconfiguration of iptables can cause DNS drops. | |
* | |
* Usage: | |
* trace_dns_drops.bt | |
*/ | |
#include <linux/skbuff.h> | |
#include <linux/ip.h> | |
#include <linux/udp.h> | |
BEGIN | |
{ | |
printf("Tracing DNS drops. Hit Ctrl-C to end.\n"); | |
printf("%-8s %-8s %-16s %-25s %20s %21s\n", "TIME", "PID", "SKB", "FUNC", "LADDR:LPORT", "RADDR:RPORT"); | |
} | |
kprobe:ip_vs_remote_request4 | |
{ | |
@skb[tid] = (struct sk_buff *)arg1; | |
@func[tid] = "ip_vs_remote_request4"; | |
} | |
kprobe:ip_vs_local_request4 | |
{ | |
@skb[tid] = (struct sk_buff *)arg1; | |
@func[tid] = "ip_vs_local_request4"; | |
} | |
kprobe:ipt_do_table | |
{ | |
@skb[tid] = (struct sk_buff *)arg0; | |
@func[tid] = "ipt_do_table"; | |
} | |
kretprobe:ip_vs_remote_request4, | |
kretprobe:ip_vs_local_request4, | |
kretprobe:ipt_do_table | |
/@skb[tid]/ | |
{ | |
if (retval != NF_DROP) { | |
return; | |
} | |
$skb = @skb[tid]; | |
$func = @func[tid]; | |
$iph = (struct iphdr *)($skb->head + $skb->network_header); | |
$proto = $iph->protocol; | |
if ($proto != IPPROTO_UDP) { | |
return; | |
} | |
$sip = ntop(AF_INET, $iph->saddr); | |
$dip = ntop(AF_INET, $iph->daddr); | |
$udphdr = (struct udphdr *)($skb->head + $skb->transport_header); | |
$sport = (($udphdr->source & 0x00ff) << 8) | (($udphdr->source & 0xff00) >> 8); | |
$dport = (($udphdr->dest & 0x00ff) << 8) | (($udphdr->dest & 0xff00) >> 8); | |
time("%H:%M:%S "); | |
printf("%-8d %-16lx %-25s %14s:%-6d %14s:%-6d\n", pid, $skb, $func, $sip, $sport, $dip, $dport); | |
return; | |
} | |
END | |
{ | |
clear(@skb); | |
clear(@func); | |
} |
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