bool callback(const PDU &pdu)
{
// The packet probably looks like this:
//
// EthernetII / IP / UDP / RawPDU
//
// So we retrieve each layer, and construct a
// DNS PDU from the RawPDU layer contents.
EthernetII eth = pdu.rfind_pdu<EthernetII>();
IP ip = eth.rfind_pdu<IP>();
UDP udp = ip.rfind_pdu<UDP>();
DNS dns = udp.rfind_pdu<RawPDU>().to<DNS>();
// Is it a DNS query?
if(dns.type() == DNS::QUERY) {
// Let's see if there's any query for an "A" record.
for(const auto &query : dns.queries()) {
if(query.type() == DNS::A) {
// Here's one! Let's add an answer.
dns.add_answer(
DNS::Resource(
query.dname(),
"127.0.0.1",
DNS::A,
query.query_class(),
// 777 is just a random TTL
777
)
);
}
}
// Have we added some answers?
if(dns.answers_count() > 0) {
// It's a response now
dns.type(DNS::RESPONSE);
// Recursion is available(just in case)
dns.recursion_available(1);
// Build our packet
auto pkt = EthernetII(eth.src_addr(), eth.dst_addr()) /
IP(ip.src_addr(), ip.dst_addr()) /
UDP(udp.sport(), udp.dport()) /
dns;
// Send it!
sender.send(pkt);
}
}
return true;
}
void DNSTest::test_equals(const DNS &dns1, const DNS &dns2) {
EXPECT_EQ(dns1.id(), dns2.id());
EXPECT_EQ(dns1.type(), dns2.type());
EXPECT_EQ(dns1.opcode(), dns2.opcode());
EXPECT_EQ(dns1.authoritative_answer(), dns2.authoritative_answer());
EXPECT_EQ(dns1.truncated(), dns2.truncated());
EXPECT_EQ(dns1.recursion_desired(), dns2.recursion_desired());
EXPECT_EQ(dns1.recursion_available(), dns2.recursion_available());
EXPECT_EQ(dns1.z(), dns2.z());
EXPECT_EQ(dns1.authenticated_data(), dns2.authenticated_data());
EXPECT_EQ(dns1.checking_disabled(), dns2.checking_disabled());
EXPECT_EQ(dns1.rcode(), dns2.rcode());
EXPECT_EQ(dns1.questions_count(), dns2.questions_count());
EXPECT_EQ(dns1.answers_count(), dns2.answers_count());
EXPECT_EQ(dns1.authority_count(), dns2.authority_count());
EXPECT_EQ(dns1.additional_count(), dns2.additional_count());
EXPECT_EQ(dns1.pdu_type(), dns2.pdu_type());
EXPECT_EQ(dns1.header_size(), dns2.header_size());
EXPECT_EQ(bool(dns1.inner_pdu()), bool(dns2.inner_pdu()));
}
TEST_F(DNSTest, Type) {
DNS dns;
dns.type(DNS::RESPONSE);
EXPECT_EQ(dns.type(), DNS::RESPONSE);
}