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

#include "zeek/PacketFilter.h"

#include "zeek/IP.h"

namespace zeek::detail {

void PacketFilter::DeleteFilter(void* data) {
    auto f = static_cast<Filter*>(data);
    delete f;
}

PacketFilter::PacketFilter(bool arg_default) {
    default_match = arg_default;
    src_filter.SetDeleteFunction(PacketFilter::DeleteFilter);
    dst_filter.SetDeleteFunction(PacketFilter::DeleteFilter);
}

void PacketFilter::AddSrc(const IPAddr& src, uint32_t tcp_flags, double probability) {
    Filter* f = new Filter;
    f->tcp_flags = tcp_flags;
    f->probability = probability * static_cast<double>(util::detail::max_random());
    auto prev = static_cast<Filter*>(src_filter.Insert(src, 128, f));
    delete prev;
}

void PacketFilter::AddSrc(Val* src, uint32_t tcp_flags, double probability) {
    Filter* f = new Filter;
    f->tcp_flags = tcp_flags;
    f->probability = probability * static_cast<double>(util::detail::max_random());
    auto prev = static_cast<Filter*>(src_filter.Insert(src, f));
    delete prev;
}

void PacketFilter::AddDst(const IPAddr& dst, uint32_t tcp_flags, double probability) {
    Filter* f = new Filter;
    f->tcp_flags = tcp_flags;
    f->probability = probability * static_cast<double>(util::detail::max_random());
    auto prev = static_cast<Filter*>(dst_filter.Insert(dst, 128, f));
    delete prev;
}

void PacketFilter::AddDst(Val* dst, uint32_t tcp_flags, double probability) {
    Filter* f = new Filter;
    f->tcp_flags = tcp_flags;
    f->probability = probability * static_cast<double>(util::detail::max_random());
    auto prev = static_cast<Filter*>(dst_filter.Insert(dst, f));
    delete prev;
}

bool PacketFilter::RemoveSrc(const IPAddr& src) {
    auto f = static_cast<Filter*>(src_filter.Remove(src, 128));
    delete f;
    return f != nullptr;
}

bool PacketFilter::RemoveSrc(Val* src) {
    auto f = static_cast<Filter*>(src_filter.Remove(src));
    delete f;
    return f != nullptr;
}

bool PacketFilter::RemoveDst(const IPAddr& dst) {
    auto f = static_cast<Filter*>(dst_filter.Remove(dst, 128));
    delete f;
    return f != nullptr;
}

bool PacketFilter::RemoveDst(Val* dst) {
    auto f = static_cast<Filter*>(dst_filter.Remove(dst));
    delete f;
    return f != nullptr;
}

bool PacketFilter::Match(const std::shared_ptr<IP_Hdr>& ip, int len, int caplen) {
    Filter* f = reinterpret_cast<Filter*>(src_filter.Lookup(ip->SrcAddr(), 128));
    if ( f )
        return MatchFilter(*f, *ip, len, caplen);

    f = reinterpret_cast<Filter*>(dst_filter.Lookup(ip->DstAddr(), 128));
    if ( f )
        return MatchFilter(*f, *ip, len, caplen);

    return default_match;
}

bool PacketFilter::MatchFilter(const Filter& f, const IP_Hdr& ip, int len, int caplen) {
    if ( ip.NextProto() == IPPROTO_TCP && f.tcp_flags ) {
        // Caution! The packet sanity checks have not been performed yet
        int ip_hdr_len = ip.HdrLen();
        len -= ip_hdr_len; // remove IP header
        caplen -= ip_hdr_len;

        if ( static_cast<unsigned int>(len) < sizeof(struct tcphdr) ||
             static_cast<unsigned int>(caplen) < sizeof(struct tcphdr) )
            // Packet too short, will be dropped anyway.
            return false;

        const struct tcphdr* tp = reinterpret_cast<const tcphdr*>(ip.Payload());

        if ( tp->th_flags & f.tcp_flags )
            // At least one of the flags is set, so don't drop
            return false;
    }

    return util::detail::random_number() < f.probability;
}

} // namespace zeek::detail
