Track routing decisions made by fib_validate_source

fibtrace.bt

kprobe:fib_validate_source {
    $skb = (struct sk_buff*) arg0;
    @skb[tid] = $skb;
    @ipheader[tid] = ((struct iphdr *) ($skb->head + $skb->network_header));
}

kretprobe:fib_validate_source {
    $skb = @skb[tid];
    $ipheader = @ipheader[tid];
    $version = $ipheader->version;

    // 0xe9051eac is "172.30.5.233" in little-endian byte order. Replace this with an appropriate
    // value.
    if ((uint32)$ipheader->daddr == 0xe9051eac) {
        printf("%dv%d | %s:%s -> %d\n", $ipheader->protocol, $version,
            ntop($ipheader->saddr), ntop($ipheader->daddr), retval);
    }

    delete(@ipheader[tid]);
    delete(@skb[tid]);
}

END {
    clear(@ipheader);
    clear(@skb);
}