/* vi: set sw=4 ts=4: */
/*
 * Packet ops
 *
 * Rewrite by Russ Dill <Russ.Dill@asu.edu> July 2001
 *
 * Licensed under GPLv2, see file LICENSE in this source tree.
 */
#include "common.h"
#include "dhcpd.h"
#include <netinet/in.h>
#include <netinet/if_ether.h>
#include <netpacket/packet.h>

void FAST_FUNC udhcp_init_header(struct dhcp_packet *packet, char type)
{
        memset(packet, 0, sizeof(*packet));
        packet->op = BOOTREQUEST; /* if client to a server */
        switch (type) {
        case DHCPOFFER:
        case DHCPACK:
        case DHCPNAK:
                packet->op = BOOTREPLY; /* if server to client */
        }
        packet->htype = 1; /* ethernet */
        packet->hlen = 6;
        packet->cookie = htonl(DHCP_MAGIC);
        if (DHCP_END != 0)
                packet->options[0] = DHCP_END;
        udhcp_add_simple_option(packet, DHCP_MESSAGE_TYPE, type);
}

#if defined CONFIG_UDHCP_DEBUG && CONFIG_UDHCP_DEBUG >= 2
void FAST_FUNC udhcp_dump_packet(struct dhcp_packet *packet)
{
        char buf[sizeof(packet->chaddr)*2 + 1];

        if (dhcp_verbose < 2)
                return;

        bb_error_msg(
                //"op %x"
                //" htype %x"
                " hlen %x"
                //" hops %x"
                " xid %x"
                //" secs %x"
                //" flags %x"
                " ciaddr %x"
                " yiaddr %x"
                " siaddr %x"
                " giaddr %x"
                //" chaddr %s"
                //" sname %s"
                //" file %s"
                //" cookie %x"
                //" options %s"
                //, packet->op
                //, packet->htype
                , packet->hlen
                //, packet->hops
                , packet->xid
                //, packet->secs
                //, packet->flags
                , packet->ciaddr
                , packet->yiaddr
                , packet->siaddr_nip
                , packet->gateway_nip
                //, packet->chaddr[16]
                //, packet->sname[64]
                //, packet->file[128]
                //, packet->cookie
                //, packet->options[]
        );
        *bin2hex(buf, (void *) packet->chaddr, sizeof(packet->chaddr)) = '\0';
        bb_error_msg("chaddr %s", buf);
}
#endif

/* Read a packet from socket fd, return -1 on read error, -2 on packet error */
int FAST_FUNC udhcp_recv_kernel_packet(struct dhcp_packet *packet, int fd)
{
        int bytes;

        memset(packet, 0, sizeof(*packet));
        bytes = safe_read(fd, packet, sizeof(*packet));
        if (bytes < 0) {
                log1("packet read error, ignoring");
                return bytes; /* returns -1 */
        }

        if (bytes < offsetof(struct dhcp_packet, options)
         || packet->cookie != htonl(DHCP_MAGIC)
        ) {
                bb_error_msg("packet with bad magic, ignoring");
                return -2;
        }
        log1("received %s", "a packet");
        udhcp_dump_packet(packet);

        return bytes;
}

/* Construct a ip/udp header for a packet, send packet */
int FAST_FUNC udhcp_send_raw_packet(struct dhcp_packet *dhcp_pkt,
                uint32_t source_nip, int source_port,
                uint32_t dest_nip, int dest_port, const uint8_t *dest_arp,
                int ifindex)
{
        struct sockaddr_ll dest_sll;
        struct ip_udp_dhcp_packet packet;
        unsigned padding;
        int fd;
        int result = -1;
        const char *msg;

        fd = socket(PF_PACKET, SOCK_DGRAM, htons(ETH_P_IP));
        if (fd < 0) {
                msg = "socket(%s)";
                goto ret_msg;
        }

        memset(&dest_sll, 0, sizeof(dest_sll));
        memset(&packet, 0, offsetof(struct ip_udp_dhcp_packet, data));
        packet.data = *dhcp_pkt; /* struct copy */

        dest_sll.sll_family = AF_PACKET;
        dest_sll.sll_protocol = htons(ETH_P_IP);
        dest_sll.sll_ifindex = ifindex;
        dest_sll.sll_halen = 6;
        memcpy(dest_sll.sll_addr, dest_arp, 6);

        if (bind(fd, (struct sockaddr *)&dest_sll, sizeof(dest_sll)) < 0) {
                msg = "bind(%s)";
                goto ret_close;
        }

        /* We were sending full-sized DHCP packets (zero padded),
         * but some badly configured servers were seen dropping them.
         * Apparently they drop all DHCP packets >576 *ethernet* octets big,
         * whereas they may only drop packets >576 *IP* octets big
         * (which for typical Ethernet II means 590 octets: 6+6+2 + 576).
         *
         * In order to work with those buggy servers,
         * we truncate packets after end option byte.
         *
         * However, RFC 1542 says "The IP Total Length and UDP Length
         * must be large enough to contain the minimal BOOTP header of 300 octets".
         * Thus, we retain enough padding to not go below 300 BOOTP bytes.
         * Some devices have filters which drop DHCP packets shorter than that.
         */
        padding = DHCP_OPTIONS_BUFSIZE - 1 - udhcp_end_option(packet.data.options);
        if (padding > DHCP_SIZE - 300)
                padding = DHCP_SIZE - 300;

        packet.ip.protocol = IPPROTO_UDP;
        packet.ip.saddr = source_nip;
        packet.ip.daddr = dest_nip;
        packet.udp.source = htons(source_port);
        packet.udp.dest = htons(dest_port);
        /* size, excluding IP header: */
        packet.udp.len = htons(UDP_DHCP_SIZE - padding);
        /* for UDP checksumming, ip.len is set to UDP packet len */
        packet.ip.tot_len = packet.udp.len;
        packet.udp.check = inet_cksum((uint16_t *)&packet,
                        IP_UDP_DHCP_SIZE - padding);
        /* but for sending, it is set to IP packet len */
        packet.ip.tot_len = htons(IP_UDP_DHCP_SIZE - padding);
        packet.ip.ihl = sizeof(packet.ip) >> 2;
        packet.ip.version = IPVERSION;
        packet.ip.ttl = IPDEFTTL;
        packet.ip.check = inet_cksum((uint16_t *)&packet.ip, sizeof(packet.ip));

        udhcp_dump_packet(dhcp_pkt);
        result = sendto(fd, &packet, IP_UDP_DHCP_SIZE - padding, /*flags:*/ 0,
                        (struct sockaddr *) &dest_sll, sizeof(dest_sll));
        msg = "sendto";
 ret_close:
        close(fd);
        if (result < 0) {
 ret_msg:
                bb_perror_msg(msg, "PACKET");
        }
        return result;
}

/* Let the kernel do all the work for packet generation */
int FAST_FUNC udhcp_send_kernel_packet(struct dhcp_packet *dhcp_pkt,
                uint32_t source_nip, int source_port,
                uint32_t dest_nip, int dest_port)
{
        struct sockaddr_in sa;
        unsigned padding;
        int fd;
        int result = -1;
        const char *msg;

        fd = socket(PF_INET, SOCK_DGRAM, IPPROTO_UDP);
        if (fd < 0) {
                msg = "socket(%s)";
                goto ret_msg;
        }
        setsockopt_reuseaddr(fd);

        memset(&sa, 0, sizeof(sa));
        sa.sin_family = AF_INET;
        sa.sin_port = htons(source_port);
        sa.sin_addr.s_addr = source_nip;
        if (bind(fd, (struct sockaddr *)&sa, sizeof(sa)) == -1) {
                msg = "bind(%s)";
                goto ret_close;
        }

        memset(&sa, 0, sizeof(sa));
        sa.sin_family = AF_INET;
        sa.sin_port = htons(dest_port);
        sa.sin_addr.s_addr = dest_nip;
        if (connect(fd, (struct sockaddr *)&sa, sizeof(sa)) == -1) {
                msg = "connect";
                goto ret_close;
        }

        udhcp_dump_packet(dhcp_pkt);
        padding = DHCP_OPTIONS_BUFSIZE - 1 - udhcp_end_option(dhcp_pkt->options);
        if (padding > DHCP_SIZE - 300)
                padding = DHCP_SIZE - 300;
        result = safe_write(fd, dhcp_pkt, DHCP_SIZE - padding);
        msg = "write";
 ret_close:
        close(fd);
        if (result < 0) {
 ret_msg:
                bb_perror_msg(msg, "UDP");
        }
        return result;
}