/*
 * Copyright (c) 1982, 1986, 1988, 1993
 *      The Regents of the University of California.  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.
 * 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.
 *
 * $FreeBSD: src/sys/netinet/ip_divert.c,v 1.42.2.6 2003/01/23 21:06:45 sam Exp $
 */

#define _IP_VHL

#include "opt_inet.h"
#include "opt_ipdivert.h"

#ifndef INET
#error "IPDIVERT requires INET."
#endif

#include <sys/param.h>
#include <sys/kernel.h>
#include <sys/malloc.h>
#include <sys/mbuf.h>
#include <sys/socket.h>
#include <sys/protosw.h>
#include <sys/socketvar.h>
#include <sys/socketvar2.h>
#include <sys/sysctl.h>
#include <sys/systm.h>
#include <sys/proc.h>
#include <sys/caps.h>
#include <sys/in_cksum.h>
#include <sys/lock.h>
#include <sys/msgport.h>

#include <net/if.h>
#include <net/route.h>

#include <net/netmsg2.h>
#include <net/netisr2.h>

#include <netinet/in.h>
#include <netinet/in_systm.h>
#include <netinet/ip.h>
#include <netinet/in_pcb.h>
#include <netinet/in_var.h>
#include <netinet/ip_var.h>
#include <netinet/ip_divert.h>

/*
 * Divert sockets
 */

/*
 * Allocate enough space to hold a full IP packet
 */
#define DIVSNDQ         (65536 + 100)
#define DIVRCVQ         (65536 + 100)

#define DIV_IS_OUTPUT(sin)      ((sin) == NULL || (sin)->sin_addr.s_addr == 0)

#define DIV_OUTPUT      0x10000
#define DIV_INPUT       0x20000

/*
 * Divert sockets work in conjunction with ipfw, see the divert(4)
 * manpage for features.
 * Internally, packets selected by ipfw in ip_input() or ip_output(),
 * and never diverted before, are passed to the input queue of the
 * divert socket with a given 'divert_port' number (as specified in
 * the matching ipfw rule), and they are tagged with a 16 bit cookie
 * (representing the rule number of the matching ipfw rule), which
 * is passed to process reading from the socket.
 *
 * Packets written to the divert socket are again tagged with a cookie
 * (usually the same as above) and a destination address.
 * If the destination address is INADDR_ANY then the packet is
 * treated as outgoing and sent to ip_output(), otherwise it is
 * treated as incoming and sent to ip_input().
 * In both cases, the packet is tagged with the cookie.
 *
 * On reinjection, processing in ip_input() and ip_output()
 * will be exactly the same as for the original packet, except that
 * ipfw processing will start at the rule number after the one
 * written in the cookie (so, tagging a packet with a cookie of 0
 * will cause it to be effectively considered as a standard packet).
 */

/* Internal variables */
static struct inpcbinfo divcbinfo;
static struct inpcbportinfo divcbportinfo;

static u_long   div_sendspace = DIVSNDQ;        /* XXX sysctl ? */
static u_long   div_recvspace = DIVRCVQ;        /* XXX sysctl ? */

static struct mbuf *ip_divert(struct mbuf *, int, int);

/*
 * Initialize divert connection block queue.
 */
void
div_init(void)
{
        in_pcbinfo_init(&divcbinfo, 0, FALSE);
        in_pcbportinfo_init(&divcbportinfo, 1, 0);
        /*
         * XXX We don't use the hash list for divert IP, but it's easier
         * to allocate a one entry hash list than it is to check all
         * over the place for hashbase == NULL.
         */
        divcbinfo.hashbase = hashinit(1, M_PCB, &divcbinfo.hashmask);
        in_pcbportinfo_set(&divcbinfo, &divcbportinfo, 1);
        divcbinfo.wildcardhashbase = hashinit(1, M_PCB,
                                              &divcbinfo.wildcardhashmask);
        divcbinfo.ipi_size = sizeof(struct inpcb);
        ip_divert_p = ip_divert;
}

/*
 * IPPROTO_DIVERT is not a real IP protocol; don't allow any packets
 * with that protocol number to enter the system from the outside.
 */
int
div_input(struct mbuf **mp, int *offp, int proto)
{
        struct mbuf *m = *mp;

        ipstat.ips_noproto++;
        m_freem(m);
        return(IPPROTO_DONE);
}

/*
 * Divert a packet by passing it up to the divert socket at port 'port'.
 *
 * Setup generic address and protocol structures for div_input routine,
 * then pass them along with mbuf chain.
 */
static void
div_packet(struct mbuf *m, int incoming, int port)
{
        struct sockaddr_in divsrc = { sizeof divsrc, AF_INET };
        struct inpcb *inp;
        struct socket *sa;
        struct m_tag *mtag;
        struct divert_info *divinfo;
        u_int16_t nport;

        ASSERT_NETISR0;

        /* Locate the divert info */
        mtag = m_tag_find(m, PACKET_TAG_IPFW_DIVERT, NULL);
        divinfo = m_tag_data(mtag);
        divsrc.sin_port = divinfo->skipto;

        /*
         * Record receive interface address, if any.
         * But only for incoming packets.
         */
        divsrc.sin_addr.s_addr = 0;
        if (incoming) {
                struct ifaddr_container *ifac;

                /* Find IP address for receive interface */
                TAILQ_FOREACH(ifac, &m->m_pkthdr.rcvif->if_addrheads[mycpuid],
                              ifa_link) {
                        struct ifaddr *ifa = ifac->ifa;

                        if (ifa->ifa_addr == NULL)
                                continue;
                        if (ifa->ifa_addr->sa_family != AF_INET)
                                continue;
                        divsrc.sin_addr =
                            ((struct sockaddr_in *) ifa->ifa_addr)->sin_addr;
                        break;
                }
        }
        /*
         * Record the incoming interface name whenever we have one.
         */
        if (m->m_pkthdr.rcvif) {
                /*
                 * Hide the actual interface name in there in the
                 * sin_zero array. XXX This needs to be moved to a
                 * different sockaddr type for divert, e.g.
                 * sockaddr_div with multiple fields like
                 * sockaddr_dl. Presently we have only 7 bytes
                 * but that will do for now as most interfaces
                 * are 4 or less + 2 or less bytes for unit.
                 * There is probably a faster way of doing this,
                 * possibly taking it from the sockaddr_dl on the iface.
                 * This solves the problem of a P2P link and a LAN interface
                 * having the same address, which can result in the wrong
                 * interface being assigned to the packet when fed back
                 * into the divert socket. Theoretically if the daemon saves
                 * and re-uses the sockaddr_in as suggested in the man pages,
                 * this iface name will come along for the ride.
                 * (see div_output for the other half of this.)
                 */
                ksnprintf(divsrc.sin_zero, sizeof divsrc.sin_zero, "%s",
                          m->m_pkthdr.rcvif->if_xname);
        }

        /* Put packet on socket queue, if any */
        sa = NULL;
        nport = htons((u_int16_t)port);

        /*
         * Following loop to locate the inpcb is MPSAFE since the inpcb
         * insertion/removal happens on the same CPU (CPU0).
         */
        LIST_FOREACH(inp, &divcbinfo.pcblisthead, inp_list) {
                if (inp->inp_flags & INP_PLACEMARKER)
                        continue;
                if (inp->inp_lport == nport)
                        sa = inp->inp_socket;
        }
        if (sa) {
                lwkt_gettoken(&sa->so_rcv.ssb_token);
                if (ssb_appendaddr(&sa->so_rcv, (struct sockaddr *)&divsrc, m, NULL) == 0) {
                        m_freem(m);
                        soroverflow(sa);
                } else
                        sorwakeup(sa);
                lwkt_reltoken(&sa->so_rcv.ssb_token);
        } else {
                m_freem(m);
                ipstat.ips_noproto++;
                ipstat.ips_delivered--;
        }
}

static void
div_packet_handler(netmsg_t msg)
{
        struct mbuf *m;
        int port, incoming = 0;

        m = msg->packet.nm_packet;

        port = msg->lmsg.u.ms_result32 & 0xffff;
        if (msg->lmsg.u.ms_result32 & DIV_INPUT)
                incoming = 1;
        div_packet(m, incoming, port);
        /* no reply, msg embedded in mbuf */
}

static void
divert_packet(struct mbuf *m, int incoming)
{
        struct m_tag *mtag;
        struct divert_info *divinfo;
        int port;

        M_ASSERTPKTHDR(m);

        /* Assure header */
        if (m->m_len < sizeof(struct ip) &&
            (m = m_pullup(m, sizeof(struct ip))) == NULL)
                return;

        mtag = m_tag_find(m, PACKET_TAG_IPFW_DIVERT, NULL);
        KASSERT(mtag != NULL, ("%s no divert tag!", __func__));
        divinfo = m_tag_data(mtag);

        port = divinfo->port;
        KASSERT(port != 0, ("%s: port=0", __func__));

        if (mycpuid != 0) {
                struct netmsg_packet *nmp;

                nmp = &m->m_hdr.mh_netmsg;
                netmsg_init(&nmp->base, NULL, &netisr_apanic_rport,
                            0, div_packet_handler);
                nmp->nm_packet = m;

                nmp->base.lmsg.u.ms_result32 = port; /* port is 16bits */
                if (incoming)
                        nmp->base.lmsg.u.ms_result32 |= DIV_INPUT;
                else
                        nmp->base.lmsg.u.ms_result32 |= DIV_OUTPUT;

                lwkt_sendmsg(netisr_cpuport(0), &nmp->base.lmsg);
        } else {
                div_packet(m, incoming, port);
        }
}

/*
 * Deliver packet back into the IP processing machinery.
 *
 * If no address specified, or address is 0.0.0.0, send to ip_output();
 * otherwise, send to ip_input() and mark as having been received on
 * the interface with that address.
 */
static int
div_output(struct socket *so, struct mbuf *m,
        struct sockaddr_in *sin, struct mbuf *control)
{
        int error = 0;
        struct m_tag *mtag;
        struct divert_info *divinfo;

        ASSERT_NETISR0;

        if (control)
                m_freem(control);               /* XXX */

        /*
         * Prepare the tag for divert info. Note that a packet
         * with a 0 tag in mh_data is effectively untagged,
         * so we could optimize that case.
         */
        mtag = m_tag_get(PACKET_TAG_IPFW_DIVERT, sizeof(*divinfo), M_NOWAIT);
        if (mtag == NULL) {
                error = ENOBUFS;
                goto cantsend;
        }
        m_tag_prepend(m, mtag);

        /* Loopback avoidance and state recovery */
        divinfo = m_tag_data(mtag);
        if (sin)
                divinfo->skipto = sin->sin_port;
        else
                divinfo->skipto = 0;

        /* Reinject packet into the system as incoming or outgoing */
        if (DIV_IS_OUTPUT(sin)) {
                struct ip *const ip = mtod(m, struct ip *);

                /* Don't allow packet length sizes that will crash */
                if ((u_short)ntohs(ip->ip_len) > m->m_pkthdr.len) {
                        error = EINVAL;
                        goto cantsend;
                }

                /* Send packet to output processing */
                ipstat.ips_rawout++;                    /* XXX */
                error = ip_output(m, NULL, NULL,
                            (so->so_options & SO_DONTROUTE) |
                            IP_ALLOWBROADCAST | IP_RAWOUTPUT,
                            NULL, NULL);
        } else {
                ip_input(m);
        }
        return error;

cantsend:
        m_freem(m);
        return error;
}

static void
div_attach(netmsg_t msg)
{
        struct socket *so = msg->attach.base.nm_so;
        int proto = msg->attach.nm_proto;
        struct pru_attach_info *ai = msg->attach.nm_ai;
        struct inpcb *inp;
        int error;

        ASSERT_NETISR0;

        inp  = so->so_pcb;
        if (inp)
                panic("div_attach");
        error = caps_priv_check(ai->p_ucred, SYSCAP_RESTRICTEDROOT |
                                             __SYSCAP_NULLCRED);
        if (error)
                goto out;

        error = soreserve(so, div_sendspace, div_recvspace, ai->sb_rlimit);
        if (error)
                goto out;
        error = in_pcballoc(so, &divcbinfo);
        if (error)
                goto out;
        inp = (struct inpcb *)so->so_pcb;
        inp->inp_ip_p = proto;
        inp->inp_flags |= INP_HDRINCL;
        /*
         * The socket is always "connected" because
         * we always know "where" to send the packet.
         */
        sosetstate(so, SS_ISCONNECTED);
        error = 0;
out:
        lwkt_replymsg(&msg->attach.base.lmsg, error);
}

static void
div_detach(netmsg_t msg)
{
        struct socket *so = msg->detach.base.nm_so;
        struct inpcb *inp;

        ASSERT_NETISR0;

        inp = so->so_pcb;
        if (inp == NULL)
                panic("div_detach");
        in_pcbdetach(inp);
        lwkt_replymsg(&msg->detach.base.lmsg, 0);
}

static void
div_abort(netmsg_t msg)
{
        /*
         * Divert socket does not support listen(2),
         * so this should never be called.
         */
        panic("div_abort is called");
}

static void
div_disconnect(netmsg_t msg)
{
        struct socket *so = msg->disconnect.base.nm_so;
        int error;

        ASSERT_NETISR0;

        if (so->so_state & SS_ISCONNECTED) {
                soisdisconnected(so);
                error = 0;
        } else {
                error = ENOTCONN;
        }
        lwkt_replymsg(&msg->disconnect.base.lmsg, error);
}

static void
div_bind(netmsg_t msg)
{
        struct socket *so = msg->bind.base.nm_so;
        struct sockaddr *nam = msg->bind.nm_nam;
        int error;

        ASSERT_NETISR0;

        /*
         * in_pcbbind assumes that nam is a sockaddr_in
         * and in_pcbbind requires a valid address. Since divert
         * sockets don't we need to make sure the address is
         * filled in properly.
         * XXX -- divert should not be abusing in_pcbind
         * and should probably have its own family.
         */
        if (nam->sa_family != AF_INET) {
                error = EAFNOSUPPORT;
        } else {
                ((struct sockaddr_in *)nam)->sin_addr.s_addr = INADDR_ANY;
                error = in_pcbbind(so->so_pcb, nam, msg->bind.nm_td);
        }
        lwkt_replymsg(&msg->bind.base.lmsg, error);
}

static void
div_shutdown(netmsg_t msg)
{
        struct socket *so = msg->shutdown.base.nm_so;

        ASSERT_NETISR0;

        socantsendmore(so);

        lwkt_replymsg(&msg->shutdown.base.lmsg, 0);
}

static void
div_send(netmsg_t msg)
{
        struct socket *so = msg->send.base.nm_so;
        struct mbuf *m = msg->send.nm_m;
        struct sockaddr *nam = msg->send.nm_addr;
        struct mbuf *control = msg->send.nm_control;
        int error;

        /* Length check already done in ip_hashfn() */
        KASSERT(m->m_len >= sizeof(struct ip), ("IP header not in one mbuf"));

        /* Send packet */
        error = div_output(so, m, (struct sockaddr_in *)nam, control);
        lwkt_replymsg(&msg->send.base.lmsg, error);
}

SYSCTL_DECL(_net_inet_divert);
SYSCTL_PROC(_net_inet_divert, OID_AUTO, pcblist, CTLFLAG_RD, &divcbinfo, 1,
            in_pcblist_range, "S,xinpcb", "List of active divert sockets");

struct pr_usrreqs div_usrreqs = {
        .pru_abort = div_abort,
        .pru_accept = pr_generic_notsupp,
        .pru_attach = div_attach,
        .pru_bind = div_bind,
        .pru_connect = pr_generic_notsupp,
        .pru_connect2 = pr_generic_notsupp,
        .pru_control = in_control_dispatch,
        .pru_detach = div_detach,
        .pru_disconnect = div_disconnect,
        .pru_listen = pr_generic_notsupp,
        .pru_peeraddr = in_setpeeraddr_dispatch,
        .pru_rcvd = pr_generic_notsupp,
        .pru_rcvoob = pr_generic_notsupp,
        .pru_send = div_send,
        .pru_sense = pru_sense_null,
        .pru_shutdown = div_shutdown,
        .pru_sockaddr = in_setsockaddr_dispatch,
        .pru_sosend = sosend,
        .pru_soreceive = soreceive
};

static struct mbuf *
ip_divert_out(struct mbuf *m, int tee)
{
        struct mbuf *clone = NULL;
        //struct ip *ip = mtod(m, struct ip *);

        /* Clone packet if we're doing a 'tee' */
        if (tee)
                clone = m_dup(m, M_NOWAIT);

        /*
         * XXX
         * delayed checksums are not currently compatible
         * with divert sockets.
         */
        if (m->m_pkthdr.csum_flags & CSUM_DELAY_DATA) {
                in_delayed_cksum(m);
                m->m_pkthdr.csum_flags &= ~CSUM_DELAY_DATA;
        }

        /* Deliver packet to divert input routine */
        divert_packet(m, 0);

        /* If 'tee', continue with original packet */
        return clone;
}

static struct mbuf *
ip_divert_in(struct mbuf *m, int tee)
{
        struct mbuf *clone = NULL;
        struct ip *ip = mtod(m, struct ip *);
        struct m_tag *mtag;

        if (ip->ip_off & htons(IP_MF | IP_OFFMASK)) {
                const struct divert_info *divinfo;
                u_short frag_off;
                int hlen;

                /*
                 * Only trust divert info in the fragment
                 * at offset 0.
                 */
                frag_off = ntohs(ip->ip_off) << 3;
                if (frag_off != 0) {
                        mtag = m_tag_find(m, PACKET_TAG_IPFW_DIVERT, NULL);
                        m_tag_delete(m, mtag);
                }

                /*
                 * Attempt reassembly; if it succeeds, proceed.
                 * ip_reass() will return a different mbuf.
                 */
                m = ip_reass(m);
                if (m == NULL)
                        return NULL;
                ip = mtod(m, struct ip *);

                /* Caller need to redispatch the packet, if it is for us */
                m->m_pkthdr.fw_flags |= FW_MBUF_REDISPATCH;

                /*
                 * Get the header length of the reassembled
                 * packet
                 */
                hlen = IP_VHL_HL(ip->ip_vhl) << 2;

                /*
                 * Restore original checksum before diverting
                 * packet
                 */
                ip->ip_len = htons(ntohs(ip->ip_len) + hlen);
                ip->ip_sum = 0;
                if (hlen == sizeof(struct ip))
                        ip->ip_sum = in_cksum_hdr(ip);
                else
                        ip->ip_sum = in_cksum(m, hlen);

                /*
                 * Only use the saved divert info
                 */
                mtag = m_tag_find(m, PACKET_TAG_IPFW_DIVERT, NULL);
                if (mtag == NULL) {
                        /* Wrongly configured ipfw */
                        kprintf("ip_input no divert info\n");
                        m_freem(m);
                        return NULL;
                }
                divinfo = m_tag_data(mtag);
                tee = divinfo->tee;
        }

        /*
         * Divert or tee packet to the divert protocol if
         * required.
         */

        /* Clone packet if we're doing a 'tee' */
        if (tee)
                clone = m_dup(m, M_NOWAIT);

        /* Deliver packet to divert input routine */
        divert_packet(m, 1);

        /* Catch invalid reference */
        m = NULL;
        ip = NULL;

        ipstat.ips_delivered++;

        /* If 'tee', continue with original packet */
        if (clone != NULL) {
                /*
                 * Complete processing of the packet.
                 * XXX Better safe than sorry, remove the DIVERT tag.
                 */
                mtag = m_tag_find(clone, PACKET_TAG_IPFW_DIVERT, NULL);
                KKASSERT(mtag != NULL);
                m_tag_delete(clone, mtag);
        }
        return clone;
}

static struct mbuf *
ip_divert(struct mbuf *m, int tee, int incoming)
{
        struct mbuf *ret;

        if (incoming)
                ret = ip_divert_in(m, tee);
        else
                ret = ip_divert_out(m, tee);
        return ret;
}