// See the file "COPYING" in the main distribution directory for copyright.

#include "zeek/packet_analysis/protocol/vxlan/VXLAN.h"

#include "zeek/packet_analysis/protocol/iptunnel/IPTunnel.h"
#include "zeek/packet_analysis/protocol/vxlan/events.bif.h"

using namespace zeek::packet_analysis::VXLAN;

VXLAN_Analyzer::VXLAN_Analyzer() : zeek::packet_analysis::Analyzer("VXLAN") {}

bool VXLAN_Analyzer::AnalyzePacket(size_t len, const uint8_t* data, Packet* packet) {
    // VXLAN always comes from a UDP connection, which means that session should always
    // be valid and always be a connection. Return a weird if we didn't have a session
    // stored.
    if ( ! packet->session ) {
        Analyzer::Weird("vxlan_missing_connection");
        return false;
    }
    else if ( AnalyzerViolated(packet->session) )
        return false;

    if ( packet->encap && packet->encap->Depth() >= BifConst::Tunnel::max_depth ) {
        packet->session->CheckHistory(zeek::session::detail::HIST_UNKNOWN_PKT, 'X');
        Weird("exceeded_tunnel_max_depth", packet);
        return false;
    }

    constexpr uint16_t hdr_size = 8;

    if ( hdr_size > len ) {
        AnalyzerViolation("VXLAN header truncation", packet->session, (const char*)data, len);
        return false;
    }

    if ( (data[0] & 0x08) == 0 ) {
        AnalyzerViolation("VXLAN 'I' flag not set", packet->session, (const char*)data, len);
        return false;
    }

    int vni = (data[4] << 16) + (data[5] << 8) + (data[6] << 0);

    len -= hdr_size;
    data += hdr_size;

    // We've successfully parsed the VXLAN part, so we might as well confirm this.
    AnalyzerConfirmation(packet->session);

    if ( len == 0 ) {
        // A VXLAN header that isn't followed by a tunnelled packet seems weird.
        Weird("vxlan_empty_packet", packet);
        return false;
    }

    int encap_index = 0;
    auto inner_packet = packet_analysis::IPTunnel::build_inner_packet(packet, &encap_index, nullptr, len, data, DLT_RAW,
                                                                      BifEnum::Tunnel::VXLAN, GetAnalyzerTag());

    bool analysis_succeeded = ForwardPacket(len, data, inner_packet.get());

    if ( analysis_succeeded && vxlan_packet ) {
        EncapsulatingConn* ec = inner_packet->encap->At(encap_index);
        if ( ec && ec->ip_hdr )
            inner_packet->session->EnqueueEvent(vxlan_packet, nullptr, packet->session->GetVal(),
                                                ec->ip_hdr->ToPktHdrVal(), val_mgr->Count(vni));
    }

    return analysis_succeeded;
}
