/*
 * Copyright (c) 1992 Regents of the University of California.
 * All rights reserved.
 *
 * This software was developed by the Computer Systems Engineering group
 * at Lawrence Berkeley Laboratory under DARPA contract BG 91-66 and
 * contributed to Berkeley.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

/*
 * The send and receive functions were originally implemented in udp.c and
 * moved here. Also it is likely some more cleanup can be done, especially
 * once we will implement the support for tcp.
 */

#include <sys/param.h>
#include <sys/socket.h>
#include <sys/queue.h>

#include <string.h>
#include <stdbool.h>

#include <net/if.h>
#include <netinet/in.h>
#include <netinet/if_ether.h>
#include <netinet/in_systm.h>

#include <netinet/ip.h>
#include <netinet/ip_var.h>
#include <netinet/udp.h>
#include <netinet/udp_var.h>

#include "stand.h"
#include "net.h"

typedef STAILQ_HEAD(ipqueue, ip_queue) ip_queue_t;
struct ip_queue {
        void            *ipq_pkt;
        struct ip       *ipq_hdr;
        STAILQ_ENTRY(ip_queue) ipq_next;
};

/*
 * Fragment re-assembly queue.
 */
struct ip_reasm {
        struct in_addr  ip_src;
        struct in_addr  ip_dst;
        uint16_t        ip_id;
        uint8_t         ip_proto;
        uint8_t         ip_ttl;
        size_t          ip_total_size;
        ip_queue_t      ip_queue;
        void            *ip_pkt;
        struct ip       *ip_hdr;
        STAILQ_ENTRY(ip_reasm) ip_next;
};

STAILQ_HEAD(ire_list, ip_reasm) ire_list = STAILQ_HEAD_INITIALIZER(ire_list);

/* Caller must leave room for ethernet and ip headers in front!! */
ssize_t
sendip(struct iodesc *d, void *pkt, size_t len, uint8_t proto)
{
        ssize_t cc;
        struct ip *ip;
        u_char *ea;

        DEBUG_PRINTF(1, ("sendip: proto: %x d=%p called.\n", proto, (void *)d));
        DEBUG_PRINTF(1, ("saddr: %s:%d daddr: %s:%d\n",
            inet_ntoa(d->myip), ntohs(d->myport),
            inet_ntoa(d->destip), ntohs(d->destport)));

        ip = (struct ip *)pkt - 1;
        len += sizeof(*ip);

        bzero(ip, sizeof(*ip));

        ip->ip_v = IPVERSION;                   /* half-char */
        ip->ip_hl = sizeof(*ip) >> 2;           /* half-char */
        ip->ip_len = htons(len);
        ip->ip_p = proto;                       /* char */
        ip->ip_ttl = IPDEFTTL;                  /* char */
        ip->ip_src = d->myip;
        ip->ip_dst = d->destip;
        ip->ip_sum = in_cksum(ip, sizeof(*ip));  /* short, but special */

        if (ip->ip_dst.s_addr == INADDR_BROADCAST || ip->ip_src.s_addr == 0 ||
            netmask == 0 || SAMENET(ip->ip_src, ip->ip_dst, netmask))
                ea = arpwhohas(d, ip->ip_dst);
        else
                ea = arpwhohas(d, gateip);

        cc = sendether(d, ip, len, ea, ETHERTYPE_IP);
        if (cc == -1)
                return (-1);
        if (cc != len)
                panic("sendip: bad write (%zd != %zd)", cc, len);
        return (cc - sizeof(*ip));
}

static void
ip_reasm_free(struct ip_reasm *ipr)
{
        struct ip_queue *ipq;

        while ((ipq = STAILQ_FIRST(&ipr->ip_queue)) != NULL) {
                STAILQ_REMOVE_HEAD(&ipr->ip_queue, ipq_next);
                free(ipq->ipq_pkt);
                free(ipq);
        }
        free(ipr->ip_pkt);
        free(ipr);
}

static bool
ip_reasm_add(struct ip_reasm *ipr, void *pkt, struct ip *ip)
{
        struct ip_queue *ipq, *p;
        uint16_t off_q, off_ip;

        if ((ipq = calloc(1, sizeof(*ipq))) == NULL)
                return (false);

        ipq->ipq_pkt = pkt;
        ipq->ipq_hdr = ip;

        STAILQ_FOREACH(p, &ipr->ip_queue, ipq_next) {
                off_q = ntohs(p->ipq_hdr->ip_off) & IP_OFFMASK;
                off_ip = ntohs(ip->ip_off) & IP_OFFMASK;

                if (off_q == off_ip) {  /* duplicate */
                        free(pkt);
                        free(ipq);
                        return (true);
                }

                if (off_ip < off_q) {
                        /*
                         * Everything in queue has larger offset,
                         * drop out of loop and insert to HEAD.
                         */
                        break;
                }

                /*
                 * p in queue is smaller than ip, check if we need to put
                 * ip after p or after p->next.
                 */
                struct ip_queue *next = STAILQ_NEXT(p, ipq_next);
                if (next == NULL) {
                        /* insert after p */
                        STAILQ_INSERT_AFTER(&ipr->ip_queue, p, ipq, ipq_next);
                        return (true);
                }

                off_q = ntohs(next->ipq_hdr->ip_off) & IP_OFFMASK;
                if (off_ip < off_q) {
                        /* next fragment offset is larger, insert after p. */
                        STAILQ_INSERT_AFTER(&ipr->ip_queue, p, ipq, ipq_next);
                        return (true);
                }
                /* next fragment offset is smaller, loop */
        }
        STAILQ_INSERT_HEAD(&ipr->ip_queue, ipq, ipq_next);
        return (true);
}

/*
 * Receive a IP packet and validate it is for us.
 */
static ssize_t
readipv4(struct iodesc *d, void **pkt, void **payload, ssize_t n)
{
        struct ip *ip = *payload;
        size_t hlen;
        struct ether_header *eh;
        struct udphdr *uh;
        char *ptr = *pkt;
        struct ip_reasm *ipr;
        struct ip_queue *ipq, *last;
        bool morefrag, isfrag;
        uint16_t fragoffset;

        if (n < sizeof(*ip)) {
                free(ptr);
                errno = EAGAIN; /* Call me again. */
                return (-1);
        }

        hlen = ip->ip_hl << 2;
        if (hlen < sizeof(*ip) ||
            in_cksum(ip, hlen) != 0) {
                DEBUG_PRINTF(1, ("%s: short hdr or bad cksum.\n", __func__));
                free(ptr);
                errno = EAGAIN; /* Call me again. */
                return (-1);
        }

        if (n < ntohs(ip->ip_len)) {
                DEBUG_PRINTF(1, ("readip: bad length %zd < %d.\n",
                       n, ntohs(ip->ip_len)));
                free(ptr);
                errno = EAGAIN; /* Call me again. */
                return (-1);
        }

        fragoffset = (ntohs(ip->ip_off) & IP_OFFMASK) * 8;
        morefrag = (ntohs(ip->ip_off) & IP_MF) == 0 ? false : true;
        isfrag = morefrag || fragoffset != 0;

        uh = (struct udphdr *)((uintptr_t)ip + sizeof(*ip));

        if (d->myip.s_addr && ip->ip_dst.s_addr != d->myip.s_addr) {
                DEBUG_PRINTF(1, ("%s: not for us: saddr %s (%d) != %s (%d)\n",
                    __func__, inet_ntoa(d->myip), ntohs(d->myport),
                    inet_ntoa(ip->ip_dst), ntohs(uh->uh_dport)));
                free(ptr);
                errno = EAGAIN; /* Call me again. */
                return (-1);
        }

        /* Unfragmented packet. */
        if (!isfrag) {
                DEBUG_PRINTF(1, ("%s: unfragmented saddr %s:%d -> %s:%d\n",
                    __func__,
                    inet_ntoa(ip->ip_src), ntohs(uh->uh_sport),
                    inet_ntoa(ip->ip_dst), ntohs(uh->uh_dport)));
                /* If there were ip options, make them go away */
                if (hlen != sizeof(*ip)) {
                        bcopy(((u_char *)ip) + hlen, uh,
                            ntohs(uh->uh_ulen) - hlen);
                        ip->ip_len = htons(sizeof(*ip));
                        n -= hlen - sizeof(*ip);
                }

                n = (n > (ntohs(ip->ip_len) - sizeof(*ip))) ?
                    ntohs(ip->ip_len) - sizeof(*ip) : n;
                *pkt = ptr;
                *payload = (void *)((uintptr_t)ip + sizeof(*ip));
                return (n);
        }

        STAILQ_FOREACH(ipr, &ire_list, ip_next) {
                if (ipr->ip_src.s_addr == ip->ip_src.s_addr &&
                    ipr->ip_dst.s_addr == ip->ip_dst.s_addr &&
                    ipr->ip_id == ip->ip_id &&
                    ipr->ip_proto == ip->ip_p)
                        break;
        }

        /* Allocate new reassembly entry */
        if (ipr == NULL) {
                if ((ipr = calloc(1, sizeof(*ipr))) == NULL) {
                        free(ptr);
                        return (-1);
                }

                ipr->ip_src = ip->ip_src;
                ipr->ip_dst = ip->ip_dst;
                ipr->ip_id = ip->ip_id;
                ipr->ip_proto = ip->ip_p;
                ipr->ip_ttl = MAXTTL;
                STAILQ_INIT(&ipr->ip_queue);
                STAILQ_INSERT_TAIL(&ire_list, ipr, ip_next);
                DEBUG_PRINTF(1, ("%s: new reassembly ID=%d %s -> %s\n",
                    __func__, ntohs(ip->ip_id), inet_ntoa(ip->ip_src),
                    inet_ntoa(ip->ip_dst)));
        }

        /*
         * NOTE: with ip_reasm_add() ptr will be stored in reassembly
         * queue and we can not free it without destroying the queue.
         */
        if (!ip_reasm_add(ipr, ptr, ip)) {
                STAILQ_REMOVE(&ire_list, ipr, ip_reasm, ip_next);
                free(ipr);
                free(ptr);
                return (-1);
        }

        /*
         * Walk the packet list in reassembly queue, if we got all the
         * fragments, build the packet.
         */
        n = 0;
        last = NULL;
        STAILQ_FOREACH(ipq, &ipr->ip_queue, ipq_next) {
                fragoffset = (ntohs(ipq->ipq_hdr->ip_off) & IP_OFFMASK) * 8;
                if (fragoffset != n) {
                        DEBUG_PRINTF(1, ("%s: need more fragments %d %s -> ",
                            __func__, ntohs(ipq->ipq_hdr->ip_id),
                            inet_ntoa(ipq->ipq_hdr->ip_src)));
                        DEBUG_PRINTF(1, ("%s offset=%d MF=%d\n",
                            inet_ntoa(ipq->ipq_hdr->ip_dst),
                            fragoffset,
                            (ntohs(ipq->ipq_hdr->ip_off) & IP_MF) != 0));
                        errno = EAGAIN;
                        return (-1);
                }

                n += ntohs(ipq->ipq_hdr->ip_len) - (ipq->ipq_hdr->ip_hl << 2);
                last = ipq;
        }

        /* complete queue has last packet with MF 0 */
        if ((ntohs(last->ipq_hdr->ip_off) & IP_MF) != 0) {
                DEBUG_PRINTF(1, ("%s: need more fragments %d %s -> ",
                    __func__, ntohs(last->ipq_hdr->ip_id),
                    inet_ntoa(last->ipq_hdr->ip_src)));
                DEBUG_PRINTF(1, ("%s offset=%d MF=%d\n",
                    inet_ntoa(last->ipq_hdr->ip_dst),
                    (ntohs(last->ipq_hdr->ip_off) & IP_OFFMASK) * 8,
                    (ntohs(last->ipq_hdr->ip_off) & IP_MF) != 0));
                errno = EAGAIN;
                return (-1);
        }

        ipr->ip_total_size = n + sizeof(*ip) + sizeof(struct ether_header);
        ipr->ip_pkt = malloc(ipr->ip_total_size + 2);
        if (ipr->ip_pkt == NULL) {
                STAILQ_REMOVE(&ire_list, ipr, ip_reasm, ip_next);
                ip_reasm_free(ipr);
                return (-1);
        }

        ipq = STAILQ_FIRST(&ipr->ip_queue);
        /* Fabricate ethernet header */
        eh = (struct ether_header *)((uintptr_t)ipr->ip_pkt + 2);
        bcopy((void *)((uintptr_t)ipq->ipq_pkt + 2), eh, sizeof(*eh));

        /* Fabricate IP header */
        ipr->ip_hdr = (struct ip *)((uintptr_t)eh + sizeof(*eh));
        bcopy(ipq->ipq_hdr, ipr->ip_hdr, sizeof(*ipr->ip_hdr));
        ipr->ip_hdr->ip_hl = sizeof(*ipr->ip_hdr) >> 2;
        ipr->ip_hdr->ip_len = htons(n);
        ipr->ip_hdr->ip_sum = 0;
        ipr->ip_hdr->ip_sum = in_cksum(ipr->ip_hdr, sizeof(*ipr->ip_hdr));

        n = 0;
        ptr = (char *)((uintptr_t)ipr->ip_hdr + sizeof(*ipr->ip_hdr));
        STAILQ_FOREACH(ipq, &ipr->ip_queue, ipq_next) {
                char *data;
                size_t len;

                hlen = ipq->ipq_hdr->ip_hl << 2;
                len = ntohs(ipq->ipq_hdr->ip_len) - hlen;
                data = (char *)((uintptr_t)ipq->ipq_hdr + hlen);

                bcopy(data, ptr + n, len);
                n += len;
        }

        *pkt = ipr->ip_pkt;
        ipr->ip_pkt = NULL;     /* Avoid free from ip_reasm_free() */
        *payload = ptr;

        /* Clean up the reassembly list */
        while ((ipr = STAILQ_FIRST(&ire_list)) != NULL) {
                STAILQ_REMOVE_HEAD(&ire_list, ip_next);
                ip_reasm_free(ipr);
        }
        DEBUG_PRINTF(1, ("%s: completed fragments ID=%d %s -> %s\n",
            __func__, ntohs(ip->ip_id), inet_ntoa(ip->ip_src),
            inet_ntoa(ip->ip_dst)));
        return (n);
}

/*
 * Receive a IP packet.
 */
ssize_t
readip(struct iodesc *d, void **pkt, void **payload, time_t tleft,
    uint8_t proto)
{
        time_t t;
        ssize_t ret = -1;

        t = getsecs();
        while ((getsecs() - t) < tleft) {
                ssize_t n;
                uint16_t etype; /* host order */
                void *ptr = NULL;
                void *data = NULL;

                errno = 0;
                n = readether(d, &ptr, &data, tleft, &etype);
                if (n == -1) {
                        free(ptr);
                        continue;
                }
                /* Ethernet address checks are done in readether() */

                /* Need to respond to ARP requests. */
                if (etype == ETHERTYPE_ARP) {
                        struct arphdr *ah = data;

                        DEBUG_PRINTF(1, ("%s: ARP request\n", __func__));

                        if (ah->ar_op == htons(ARPOP_REQUEST)) {
                                /* Send ARP reply */
                                arp_reply(d, ah);
                        }
                        free(ptr);
                        continue;       /* Get next packet */
                }

                if (etype == ETHERTYPE_IP) {
                        struct ip *ip = data;

                        if (ip->ip_v == IPVERSION &&    /* half char */
                            ip->ip_p == proto) {
                                errno = 0;
                                ret = readipv4(d, &ptr, &data, n);
                                if (ret >= 0) {
                                        *pkt = ptr;
                                        *payload = data;
                                        return (ret);
                                }

                                /*
                                 * Bubble up the error if it wasn't successful
                                 */
                                if (errno != EAGAIN)
                                        return (-1);
                                continue;
                        }
                        DEBUG_PRINTF(1, ("%s: IP version or proto. "
                            "ip_v=%d ip_p=%d\n",
                            __func__, ip->ip_v, ip->ip_p));
                        free(ptr);
                        continue;
                }
                free(ptr);
        }
        /* We've exhausted tleft; timeout */
        errno = ETIMEDOUT;
        DEBUG_PRINTF(1, ("%s: timeout\n", __func__));
        return (-1);
}