/* vi: set sw=4 ts=4: */
/*
 * Copyright (C) 2011 Denys Vlasenko.
 *
 * Licensed under GPLv2, see file LICENSE in this source tree.
 */
#include "common.h"
#include "d6_common.h"
#include "dhcpd.h"
#include <netinet/in.h>
#include <netinet/if_ether.h>
#include <netpacket/packet.h>

#if defined CONFIG_UDHCP_DEBUG && CONFIG_UDHCP_DEBUG >= 2
void FAST_FUNC d6_dump_packet(struct d6_packet *packet)
{
        if (dhcp_verbose < 2)
                return;

        bb_error_msg(
                " xid %x"
                , packet->d6_xid32
        );
        //*bin2hex(buf, (void *) packet->chaddr, sizeof(packet->chaddr)) = '\0';
        //bb_error_msg(" chaddr %s", buf);
}
#endif

int FAST_FUNC d6_recv_kernel_packet(struct in6_addr *peer_ipv6
        UNUSED_PARAM
        , struct d6_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 d6_packet, d6_options)) {
                bb_error_msg("packet with bad magic, ignoring");
                return -2;
        }
        log1("received %s", "a packet");
        d6_dump_packet(packet);

        return bytes;
}

/* Construct a ipv6+udp header for a packet, send packet */
int FAST_FUNC d6_send_raw_packet(
                struct d6_packet *d6_pkt, unsigned d6_pkt_size,
                struct in6_addr *src_ipv6, int source_port,
                struct in6_addr *dst_ipv6, int dest_port, const uint8_t *dest_arp,
                int ifindex)
{
        struct sockaddr_ll dest_sll;
        struct ip6_udp_d6_packet packet;
        int fd;
        int result = -1;
        const char *msg;

        fd = socket(PF_PACKET, SOCK_DGRAM, htons(ETH_P_IPV6));
        if (fd < 0) {
                msg = "socket(%s)";
                goto ret_msg;
        }

        memset(&dest_sll, 0, sizeof(dest_sll));
        memset(&packet, 0, offsetof(struct ip6_udp_d6_packet, data));
        packet.data = *d6_pkt; /* struct copy */

        dest_sll.sll_family = AF_PACKET;
        dest_sll.sll_protocol = htons(ETH_P_IPV6);
        dest_sll.sll_ifindex = ifindex;
        /*dest_sll.sll_hatype = ARPHRD_???;*/
        /*dest_sll.sll_pkttype = PACKET_???;*/
        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;
        }

        packet.ip6.ip6_vfc = (6 << 4); /* 4 bits version, top 4 bits of tclass */
        if (src_ipv6)
                packet.ip6.ip6_src = *src_ipv6; /* struct copy */
        packet.ip6.ip6_dst = *dst_ipv6; /* struct copy */
        packet.udp.source = htons(source_port);
        packet.udp.dest = htons(dest_port);
        /* size, excluding IP header: */
        packet.udp.len = htons(sizeof(struct udphdr) + d6_pkt_size);
        packet.ip6.ip6_plen = packet.udp.len;
        /*
         * Someone was smoking weed (at least) while inventing UDP checksumming:
         * UDP checksum skips first four bytes of IPv6 header.
         * 'next header' field should be summed as if it is one more byte
         * to the right, therefore we write its value (IPPROTO_UDP)
         * into ip6_hlim, and its 'real' location remains zero-filled for now.
         */
        packet.ip6.ip6_hlim = IPPROTO_UDP;
        packet.udp.check = inet_cksum(
                                (uint16_t *)&packet + 2,
                                offsetof(struct ip6_udp_d6_packet, data) - 4 + d6_pkt_size
        );
        /* fix 'hop limit' and 'next header' after UDP checksumming */
        packet.ip6.ip6_hlim = 1; /* observed Windows machines to use hlim=1 */
        packet.ip6.ip6_nxt = IPPROTO_UDP;

        d6_dump_packet(d6_pkt);
        result = sendto(fd, &packet, offsetof(struct ip6_udp_d6_packet, data) + d6_pkt_size,
                        /*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 d6_send_kernel_packet(
                struct d6_packet *d6_pkt, unsigned d6_pkt_size,
                struct in6_addr *src_ipv6, int source_port,
                struct in6_addr *dst_ipv6, int dest_port,
                int ifindex)
{
        struct sockaddr_in6 sa;
        int fd;
        int result = -1;
        const char *msg;

        fd = socket(PF_INET6, SOCK_DGRAM, IPPROTO_UDP);
        if (fd < 0) {
                msg = "socket(%s)";
                goto ret_msg;
        }
        setsockopt_reuseaddr(fd);

        memset(&sa, 0, sizeof(sa));
        sa.sin6_family = AF_INET6;
        sa.sin6_port = htons(source_port);
        sa.sin6_addr = *src_ipv6; /* struct copy */
        if (bind(fd, (struct sockaddr *)&sa, sizeof(sa)) == -1) {
                msg = "bind(%s)";
                goto ret_close;
        }

        memset(&sa, 0, sizeof(sa));
        sa.sin6_family = AF_INET6;
        sa.sin6_port = htons(dest_port);
        sa.sin6_addr = *dst_ipv6; /* struct copy */
        sa.sin6_scope_id = ifindex;
        if (connect(fd, (struct sockaddr *)&sa, sizeof(sa)) == -1) {
                msg = "connect";
                goto ret_close;
        }

        d6_dump_packet(d6_pkt);
        result = safe_write(fd, d6_pkt, d6_pkt_size);
        msg = "write";
 ret_close:
        close(fd);
        if (result < 0) {
 ret_msg:
                bb_perror_msg(msg, "UDP");
        }
        return result;
}