/*-
 * SPDX-License-Identifier: BSD-2-Clause
 *
 * Copyright (c) 2019 Isilon Systems, LLC.
 * Copyright (c) 2005-2014 Sandvine Incorporated. All rights reserved.
 * Copyright (c) 2000 Darrell Anderson
 * All rights reserved.
 *
 * 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.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR 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 AUTHOR 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.
 */

#include <sys/cdefs.h>
#include "opt_inet.h"

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/errno.h>
#include <sys/socket.h>
#include <sys/sysctl.h>

#include <net/ethernet.h>
#include <net/if.h>
#include <net/if_arp.h>
#include <net/if_dl.h>
#include <net/if_types.h>
#include <net/if_var.h>
#include <net/if_private.h>

#include <netinet/in.h>
#include <netinet/in_systm.h>
#include <netinet/in_var.h>
#include <netinet/ip.h>
#include <netinet/ip_var.h>
#include <netinet/ip_options.h>
#include <netinet/udp.h>

#include <machine/in_cksum.h>
#include <machine/pcb.h>

#include <net/debugnet.h>
#define DEBUGNET_INTERNAL
#include <net/debugnet_int.h>

int debugnet_arp_nretries = 3;
SYSCTL_INT(_net_debugnet, OID_AUTO, arp_nretries, CTLFLAG_RWTUN,
    &debugnet_arp_nretries, 0,
    "Number of ARP attempts before giving up");

/*
 * Handler for IP packets: checks their sanity and then processes any debugnet
 * ACK packets it finds.
 *
 * It needs to partially replicate the behaviour of ip_input() and udp_input().
 *
 * Parameters:
 *      pcb     a pointer to the live debugnet PCB
 *      mb      a pointer to an mbuf * containing the packet received
 *              Updates *mb if m_pullup et al change the pointer
 *              Assumes the calling function will take care of freeing the mbuf
 */
void
debugnet_handle_ip(struct debugnet_pcb *pcb, struct mbuf **mb)
{
        struct ip *ip;
        struct mbuf *m;
        unsigned short hlen;

        if (pcb->dp_state < DN_STATE_HAVE_GW_MAC)
                return;

        /* IP processing. */
        m = *mb;
        if (m->m_pkthdr.len < sizeof(struct ip)) {
                DNETDEBUG("dropping packet too small for IP header\n");
                return;
        }
        if (m->m_len < sizeof(struct ip)) {
                m = m_pullup(m, sizeof(struct ip));
                *mb = m;
                if (m == NULL) {
                        DNETDEBUG("m_pullup failed\n");
                        return;
                }
        }
        ip = mtod(m, struct ip *);

        /* IP version. */
        if (ip->ip_v != IPVERSION) {
                DNETDEBUG("bad IP version %d\n", ip->ip_v);
                return;
        }

        /* Header length. */
        hlen = ip->ip_hl << 2;
        if (hlen < sizeof(struct ip)) {
                DNETDEBUG("bad IP header length (%hu)\n", hlen);
                return;
        }
        if (hlen > m->m_len) {
                m = m_pullup(m, hlen);
                *mb = m;
                if (m == NULL) {
                        DNETDEBUG("m_pullup failed\n");
                        return;
                }
                ip = mtod(m, struct ip *);
        }
        /* Ignore packets with IP options. */
        if (hlen > sizeof(struct ip)) {
                DNETDEBUG("drop packet with IP options\n");
                return;
        }

#ifdef INVARIANTS
        if ((IN_LOOPBACK(ntohl(ip->ip_dst.s_addr)) ||
            IN_LOOPBACK(ntohl(ip->ip_src.s_addr))) &&
            (m->m_pkthdr.rcvif->if_flags & IFF_LOOPBACK) == 0) {
                DNETDEBUG("Bad IP header (RFC1122)\n");
                return;
        }
#endif

        /* Checksum. */
        if ((m->m_pkthdr.csum_flags & CSUM_IP_CHECKED) != 0) {
                if ((m->m_pkthdr.csum_flags & CSUM_IP_VALID) == 0) {
                        DNETDEBUG("bad IP checksum\n");
                        return;
                }
        } else {
                /* XXX */ ;
        }

        /* Convert fields to host byte order. */
        ip->ip_len = ntohs(ip->ip_len);
        if (ip->ip_len < hlen) {
                DNETDEBUG("IP packet smaller (%hu) than header (%hu)\n",
                    ip->ip_len, hlen);
                return;
        }
        if (m->m_pkthdr.len < ip->ip_len) {
                DNETDEBUG("IP packet bigger (%hu) than ethernet packet (%d)\n",
                    ip->ip_len, m->m_pkthdr.len);
                return;
        }
        if (m->m_pkthdr.len > ip->ip_len) {
                /* Truncate the packet to the IP length. */
                if (m->m_len == m->m_pkthdr.len) {
                        m->m_len = ip->ip_len;
                        m->m_pkthdr.len = ip->ip_len;
                } else
                        m_adj(m, ip->ip_len - m->m_pkthdr.len);
        }

        ip->ip_off = ntohs(ip->ip_off);

        /* Check that the source is the server's IP. */
        if (ip->ip_src.s_addr != pcb->dp_server) {
                DNETDEBUG("drop packet not from server (from 0x%x)\n",
                    ip->ip_src.s_addr);
                return;
        }

        /* Check if the destination IP is ours. */
        if (ip->ip_dst.s_addr != pcb->dp_client) {
                DNETDEBUGV("drop packet not to our IP\n");
                return;
        }

        if (ip->ip_p != IPPROTO_UDP) {
                DNETDEBUG("drop non-UDP packet\n");
                return;
        }

        /* Do not deal with fragments. */
        if ((ip->ip_off & (IP_MF | IP_OFFMASK)) != 0) {
                DNETDEBUG("drop fragmented packet\n");
                return;
        }

        if ((m->m_pkthdr.csum_flags & CSUM_PSEUDO_HDR) != 0) {
                if ((m->m_pkthdr.csum_flags & CSUM_DATA_VALID) == 0) {
                        DNETDEBUG("bad UDP checksum\n");
                        return;
                }
        } else {
                /* XXX */ ;
        }

        /* UDP custom is to have packet length not include IP header. */
        ip->ip_len -= hlen;

        /* Checked above before decoding IP header. */
        MPASS(m->m_pkthdr.len >= sizeof(struct ipovly));

        /* Put the UDP header at start of chain. */
        m_adj(m, sizeof(struct ipovly));
        debugnet_handle_udp(pcb, mb);
}

/*
 * Builds and sends a single ARP request to locate the L2 address for a given
 * INET address.
 *
 * Return value:
 *      0 on success
 *      errno on error
 */
static int
debugnet_send_arp(struct debugnet_pcb *pcb, in_addr_t dst)
{
        struct ether_addr bcast;
        struct arphdr *ah;
        struct ifnet *ifp;
        struct mbuf *m;
        int pktlen;

        ifp = pcb->dp_ifp;

        /* Fill-up a broadcast address. */
        memset(&bcast, 0xFF, ETHER_ADDR_LEN);
        m = m_gethdr(M_NOWAIT, MT_DATA);
        if (m == NULL) {
                printf("%s: Out of mbufs\n", __func__);
                return (ENOBUFS);
        }
        pktlen = arphdr_len2(ETHER_ADDR_LEN, sizeof(struct in_addr));
        m->m_len = pktlen;
        m->m_pkthdr.len = pktlen;
        MH_ALIGN(m, pktlen);
        ah = mtod(m, struct arphdr *);
        ah->ar_hrd = htons(ARPHRD_ETHER);
        ah->ar_pro = htons(ETHERTYPE_IP);
        ah->ar_hln = ETHER_ADDR_LEN;
        ah->ar_pln = sizeof(struct in_addr);
        ah->ar_op = htons(ARPOP_REQUEST);
        memcpy(ar_sha(ah), IF_LLADDR(ifp), ETHER_ADDR_LEN);
        ((struct in_addr *)ar_spa(ah))->s_addr = pcb->dp_client;
        bzero(ar_tha(ah), ETHER_ADDR_LEN);
        ((struct in_addr *)ar_tpa(ah))->s_addr = dst;
        return (debugnet_ether_output(m, ifp, bcast, ETHERTYPE_ARP));
}

/*
 * Handler for ARP packets: checks their sanity and then
 * 1. If the ARP is a request for our IP, respond with our MAC address
 * 2. If the ARP is a response from our server, record its MAC address
 *
 * It needs to replicate partially the behaviour of arpintr() and
 * in_arpinput().
 *
 * Parameters:
 *      pcb     a pointer to the live debugnet PCB
 *      mb      a pointer to an mbuf * containing the packet received
 *              Updates *mb if m_pullup et al change the pointer
 *              Assumes the calling function will take care of freeing the mbuf
 */
void
debugnet_handle_arp(struct debugnet_pcb *pcb, struct mbuf **mb)
{
        char buf[INET_ADDRSTRLEN];
        struct in_addr isaddr, itaddr;
        struct ether_addr dst;
        struct mbuf *m;
        struct arphdr *ah;
        struct ifnet *ifp;
        uint8_t *enaddr;
        int req_len, op;

        m = *mb;
        ifp = m->m_pkthdr.rcvif;
        if (m->m_len < sizeof(struct arphdr)) {
                m = m_pullup(m, sizeof(struct arphdr));
                *mb = m;
                if (m == NULL) {
                        DNETDEBUG("runt packet: m_pullup failed\n");
                        return;
                }
        }

        ah = mtod(m, struct arphdr *);
        if (ntohs(ah->ar_hrd) != ARPHRD_ETHER) {
                DNETDEBUG("unknown hardware address 0x%2D)\n",
                    (unsigned char *)&ah->ar_hrd, "");
                return;
        }
        if (ntohs(ah->ar_pro) != ETHERTYPE_IP) {
                DNETDEBUG("drop ARP for unknown protocol %d\n",
                    ntohs(ah->ar_pro));
                return;
        }
        req_len = arphdr_len2(ifp->if_addrlen, sizeof(struct in_addr));
        if (m->m_len < req_len) {
                m = m_pullup(m, req_len);
                *mb = m;
                if (m == NULL) {
                        DNETDEBUG("runt packet: m_pullup failed\n");
                        return;
                }
        }
        ah = mtod(m, struct arphdr *);

        op = ntohs(ah->ar_op);
        memcpy(&isaddr, ar_spa(ah), sizeof(isaddr));
        memcpy(&itaddr, ar_tpa(ah), sizeof(itaddr));
        enaddr = (uint8_t *)IF_LLADDR(ifp);

        if (memcmp(ar_sha(ah), enaddr, ifp->if_addrlen) == 0) {
                DNETDEBUG("ignoring ARP from myself\n");
                return;
        }

        if (isaddr.s_addr == pcb->dp_client) {
                printf("%s: %*D is using my IP address %s!\n", __func__,
                    ifp->if_addrlen, (u_char *)ar_sha(ah), ":",
                    inet_ntoa_r(isaddr, buf));
                return;
        }

        if (memcmp(ar_sha(ah), ifp->if_broadcastaddr, ifp->if_addrlen) == 0) {
                DNETDEBUG("ignoring ARP from broadcast address\n");
                return;
        }

        if (op == ARPOP_REPLY) {
                if (isaddr.s_addr != pcb->dp_gateway &&
                    isaddr.s_addr != pcb->dp_server) {
                        inet_ntoa_r(isaddr, buf);
                        DNETDEBUG("ignoring ARP reply from %s (not configured"
                            " server or gateway)\n", buf);
                        return;
                }
                if (pcb->dp_state >= DN_STATE_HAVE_GW_MAC) {
                        inet_ntoa_r(isaddr, buf);
                        DNETDEBUG("ignoring server ARP reply from %s (already"
                            " have gateway address)\n", buf);
                        return;
                }
                MPASS(pcb->dp_state == DN_STATE_INIT);
                memcpy(pcb->dp_gw_mac.octet, ar_sha(ah),
                    min(ah->ar_hln, ETHER_ADDR_LEN));
                
                DNETDEBUG("got server MAC address %6D\n",
                    pcb->dp_gw_mac.octet, ":");

                pcb->dp_state = DN_STATE_HAVE_GW_MAC;
                return;
        }

        if (op != ARPOP_REQUEST) {
                DNETDEBUG("ignoring ARP non-request/reply\n");
                return;
        }

        if (itaddr.s_addr != pcb->dp_client) {
                DNETDEBUG("ignoring ARP not to our IP\n");
                return;
        }

        memcpy(ar_tha(ah), ar_sha(ah), ah->ar_hln);
        memcpy(ar_sha(ah), enaddr, ah->ar_hln);
        memcpy(ar_tpa(ah), ar_spa(ah), ah->ar_pln);
        memcpy(ar_spa(ah), &itaddr, ah->ar_pln);
        ah->ar_op = htons(ARPOP_REPLY);
        ah->ar_pro = htons(ETHERTYPE_IP);
        m->m_flags &= ~(M_BCAST|M_MCAST);
        m->m_len = arphdr_len(ah);
        m->m_pkthdr.len = m->m_len;

        memcpy(dst.octet, ar_tha(ah), ETHER_ADDR_LEN);
        debugnet_ether_output(m, ifp, dst, ETHERTYPE_ARP);
        *mb = NULL;
}

/*
 * Sends ARP requests to locate the server and waits for a response.
 * We first try to ARP the server itself, and fall back to the provided
 * gateway if the server appears to be off-link.
 *
 * Return value:
 *      0 on success
 *      errno on error
 */
int
debugnet_arp_gw(struct debugnet_pcb *pcb)
{
        in_addr_t dst;
        int error, polls, retries;

        dst = pcb->dp_server;
restart:
        for (retries = 0; retries < debugnet_arp_nretries; retries++) {
                error = debugnet_send_arp(pcb, dst);
                if (error != 0)
                        return (error);
                for (polls = 0; polls < debugnet_npolls &&
                    pcb->dp_state < DN_STATE_HAVE_GW_MAC; polls++) {
                        debugnet_network_poll(pcb);
                        DELAY(500);
                }
                if (pcb->dp_state >= DN_STATE_HAVE_GW_MAC)
                        break;
                printf("(ARP retry)");
        }
        if (pcb->dp_state >= DN_STATE_HAVE_GW_MAC)
                return (0);
        if (dst == pcb->dp_server) {
                printf("\nFailed to ARP server");
                if (pcb->dp_gateway != INADDR_ANY) {
                        printf(", trying to reach gateway...\n");
                        dst = pcb->dp_gateway;
                        goto restart;
                } else
                        printf(".\n");
        } else
                printf("\nFailed to ARP gateway.\n");

        return (ETIMEDOUT);
}

/*
 * Unreliable IPv4 transmission of an mbuf chain to the debugnet server
 * Note: can't handle fragmentation; fails if the packet is larger than
 *       ifp->if_mtu after adding the UDP/IP headers
 *
 * Parameters:
 *      pcb     The debugnet context block
 *      m       mbuf chain
 *
 * Returns:
 *      int     see errno.h, 0 for success
 */
int
debugnet_ip_output(struct debugnet_pcb *pcb, struct mbuf *m)
{
        struct udphdr *udp;
        struct ifnet *ifp;
        struct ip *ip;

        MPASS(pcb->dp_state >= DN_STATE_HAVE_GW_MAC);

        ifp = pcb->dp_ifp;

        M_PREPEND(m, sizeof(*ip), M_NOWAIT);
        if (m == NULL) {
                printf("%s: out of mbufs\n", __func__);
                return (ENOBUFS);
        }

        if (m->m_pkthdr.len > ifp->if_mtu) {
                printf("%s: Packet is too big: %d > MTU %u\n", __func__,
                    m->m_pkthdr.len, ifp->if_mtu);
                m_freem(m);
                return (ENOBUFS);
        }

        ip = mtod(m, void *);
        udp = (void *)(ip + 1);

        memset(ip, 0, offsetof(struct ip, ip_p));
        ip->ip_p = IPPROTO_UDP;
        ip->ip_sum = udp->uh_ulen;
        ip->ip_src = (struct in_addr) { pcb->dp_client };
        ip->ip_dst = (struct in_addr) { pcb->dp_server };

        /* Compute UDP-IPv4 checksum. */
        udp->uh_sum = in_cksum(m, m->m_pkthdr.len);
        if (udp->uh_sum == 0)
                udp->uh_sum = 0xffff;

        ip->ip_v = IPVERSION;
        ip->ip_hl = sizeof(*ip) >> 2;
        ip->ip_tos = 0;
        ip->ip_len = htons(m->m_pkthdr.len);
        ip->ip_id = 0;
        ip->ip_off = htons(IP_DF);
        ip->ip_ttl = 255;
        ip->ip_sum = 0;
        ip->ip_sum = in_cksum(m, sizeof(struct ip));

        return (debugnet_ether_output(m, ifp, pcb->dp_gw_mac, ETHERTYPE_IP));
}