// Copyright 2026 Google LLC

//

// Licensed under the Apache License, Version 2.0 (the "License");

// you may not use this file except in compliance with the License.

// You may obtain a copy of the License at

//

//      http://www.apache.org/licenses/LICENSE-2.0

//

// Unless required by applicable law or agreed to in writing, software

// distributed under the License is distributed on an "AS IS" BASIS,

// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.

// See the License for the specific language governing permissions and

// limitations under the License.

#include <cstddef>

#include <cstdint>

#include <cstring>

#include <sys/socket.h>

#include <netinet/in.h>

#include <arpa/inet.h>

#include <unistd.h>

#include "event2/event.h"

#include "event2/dns.h"

// Callback for DNS server - just respond to every request and drop it

static void dns_server_cb(struct evdns_server_request *req, void *data) {

    // Respond with NOERROR to exercise the response path too

    evdns_server_request_respond(req, 0);

}

extern "C" int LLVMFuzzerTestOneInput(const uint8_t *data, size_t size) {

    if (size < 12 || size > 1500)

        return 0;

    // Create a UDP socketpair

    int fds[2];

    if (socketpair(AF_UNIX, SOCK_DGRAM, 0, fds) < 0)

        return 0;

    struct event_base *base = event_base_new();

    if (!base) {

        close(fds[0]);

        close(fds[1]);

        return 0;

    }

    // Create DNS server port on fds[0]

    struct evdns_server_port *port =

        evdns_add_server_port_with_base(base, fds[0], 0, dns_server_cb, nullptr);

    if (!port) {

        event_base_free(base);

        close(fds[0]);

        close(fds[1]);

        return 0;

    }

    // Send the fuzz data as a DNS packet to the server via fds[1]

    send(fds[1], data, size, 0);

    // Run the event loop briefly to process the packet

    event_base_loop(base, EVLOOP_NONBLOCK);

    // Clean up

    evdns_close_server_port(port);

    event_base_free(base);

    close(fds[0]);

    close(fds[1]);

    return 0;

}