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simplify tcp flag checks, fix stream_follower (#334)

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* simplify tcp flag checks, fix stream_follower

On various places was used simple comparison for checking state of flags.

tcp.flags() == (TCP::SYN | TCP::ACK)

This is not what you want usually, because this check is false
in case that another flag is set also. Correct check for syn-ack
packet should be:

(tcp.flags() & (TCP::SYN | TCP::ACK)) == (TCP::SYN | TCP::ACK)

To simplify this kind of check, add new has_flags method:

bool TCP::has_flags(small_uint<12> check_flags) const

* remove duplicate TCP::SYN flag check
This commit is contained in:
Lukáš Karas
2019-03-15 02:18:12 +01:00
committed by Matias Fontanini
parent 74e3d909e6
commit 22b4435c81
8 changed files with 32 additions and 11 deletions
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2
examples/portscan.cpp
View File

@@ -116,7 +116,7 @@ bool Scanner::callback(PDU& pdu) {
cout << "Port: " << setw(5) << tcp.sport() << " closed\n";
}
// Is SYN flag on? Then port is open!
else if(tcp.flags() == (TCP::SYN | TCP::ACK)) {
else if(tcp.has_flags(TCP::SYN | TCP::ACK)) {
cout << "Port: " << setw(5) << tcp.sport() << " open\n";
}
}

2
examples/tcp_connection_close.cpp
View File

@@ -68,7 +68,7 @@ private:
const IP& ip = pdu.rfind_pdu<IP>();
const TCP& tcp = pdu.rfind_pdu<TCP>();
// We'll only close a connection when seeing a SYN|ACK
if (tcp.flags() == (TCP::SYN | TCP::ACK)) {
if (tcp.has_flags(TCP::SYN | TCP::ACK)) {
// Create an ethernet header flipping the addresses
EthernetII packet(eth.src_addr(), eth.dst_addr());
// Do the same for IP