/*-*- Mode: C; c-basic-offset: 8; indent-tabs-mode: nil -*-*/

/***
  This file is part of systemd.

  Copyright (C) 2013 Intel Corporation. All rights reserved.
  Copyright (C) 2014 Tom Gundersen

  systemd is free software; you can redistribute it and/or modify it
  under the terms of the GNU Lesser General Public License as published by
  the Free Software Foundation; either version 2.1 of the License, or
  (at your option) any later version.

  systemd is distributed in the hope that it will be useful, but
  WITHOUT ANY WARRANTY; without even the implied warranty of
  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
  Lesser General Public License for more details.

  You should have received a copy of the GNU Lesser General Public License
  along with systemd; If not, see <http://www.gnu.org/licenses/>.
***/

#include <sys/ioctl.h>

#include "sd-dhcp-server.h"
#include "dhcp-server-internal.h"
#include "dhcp-internal.h"

sd_dhcp_server *sd_dhcp_server_ref(sd_dhcp_server *server) {
        if (server)
                assert_se(REFCNT_INC(server->n_ref) >= 2);

        return server;
}

sd_dhcp_server *sd_dhcp_server_unref(sd_dhcp_server *server) {
        if (server && REFCNT_DEC(server->n_ref) <= 0) {
                log_dhcp_server(server, "UNREF");

                sd_dhcp_server_stop(server);

                sd_event_unref(server->event);
                free(server);
        }

        return NULL;
}

int sd_dhcp_server_new(sd_dhcp_server **ret, int ifindex) {
        _cleanup_dhcp_server_unref_ sd_dhcp_server *server = NULL;

        assert_return(ret, -EINVAL);
        assert_return(ifindex > 0, -EINVAL);

        server = new0(sd_dhcp_server, 1);
        if (!server)
                return -ENOMEM;

        server->n_ref = REFCNT_INIT;
        server->fd = -1;
        server->index = ifindex;

        *ret = server;
        server = NULL;

        return 0;
}

int sd_dhcp_server_attach_event(sd_dhcp_server *server, sd_event *event, int priority) {
        int r;

        assert_return(server, -EINVAL);
        assert_return(!server->event, -EBUSY);

        if (event)
                server->event = sd_event_ref(event);
        else {
                r = sd_event_default(&server->event);
                if (r < 0)
                        return r;
        }

        server->event_priority = priority;

        return 0;
}

int sd_dhcp_server_detach_event(sd_dhcp_server *server) {
        assert_return(server, -EINVAL);

        server->event = sd_event_unref(server->event);

        return 0;
}

sd_event *sd_dhcp_server_get_event(sd_dhcp_server *server) {
        assert_return(server, NULL);

        return server->event;
}

int sd_dhcp_server_stop(sd_dhcp_server *server) {
        assert_return(server, -EINVAL);

        server->receive_message =
                sd_event_source_unref(server->receive_message);

        server->fd = safe_close(server->fd);

        log_dhcp_server(server, "STOPPED");

        return 0;
}

static int server_receive_message(sd_event_source *s, int fd,
                                  uint32_t revents, void *userdata) {
        _cleanup_free_ uint8_t *message = NULL;
        uint8_t cmsgbuf[CMSG_LEN(sizeof(struct in_pktinfo))];
        sd_dhcp_server *server = userdata;
        struct iovec iov = {};
        struct msghdr msg = {
                .msg_iov = &iov,
                .msg_iovlen = 1,
                .msg_control = cmsgbuf,
                .msg_controllen = sizeof(cmsgbuf),
        };
        struct cmsghdr *cmsg;
        int buflen = 0, len, r;

        assert(server);

        r = ioctl(fd, FIONREAD, &buflen);
        if (r < 0)
                return r;
        if (buflen < 0)
                return -EIO;

        message = malloc0(buflen);
        if (!message)
                return -ENOMEM;

        iov.iov_base = message;
        iov.iov_len = buflen;

        len = recvmsg(fd, &msg, 0);
        if (len < buflen)
                return 0;

        for (cmsg = CMSG_FIRSTHDR(&msg); cmsg; cmsg = CMSG_NXTHDR(&msg, cmsg)) {
                if (cmsg->cmsg_level == IPPROTO_IP &&
                    cmsg->cmsg_type == IP_PKTINFO &&
                    cmsg->cmsg_len == CMSG_LEN(sizeof(struct in_pktinfo))) {
                        struct in_pktinfo *info = (struct in_pktinfo*)CMSG_DATA(cmsg);

                        /* TODO figure out if this can be done as a filter on the socket, like for IPv6 */
                        if (server->index != info->ipi_ifindex)
                                return 0;

                        break;
                }
        }

        log_dhcp_server(server, "received message");

        return 1;
}

int sd_dhcp_server_start(sd_dhcp_server *server) {
        int r;

        assert_return(server, -EINVAL);
        assert_return(server->event, -EINVAL);
        assert_return(!server->receive_message, -EBUSY);
        assert_return(server->fd == -1, -EBUSY);

        r = dhcp_network_bind_udp_socket(INADDR_ANY, DHCP_PORT_SERVER);
        if (r < 0) {
                sd_dhcp_server_stop(server);
                return r;
        }
        server->fd = r;

        r = sd_event_add_io(server->event, &server->receive_message,
                            server->fd, EPOLLIN,
                            server_receive_message, server);
        if (r < 0) {
                sd_dhcp_server_stop(server);
                return r;
        }

        r = sd_event_source_set_priority(server->receive_message,
                                         server->event_priority);
        if (r < 0) {
                sd_dhcp_server_stop(server);
                return r;
        }

        log_dhcp_server(server, "STARTED");

        return 0;
}