/*
 * Copyright (C) 2012 by Darren Reed.
 *
 * See the IPFILTER.LICENCE file for details on licencing.
 *
 * $Id$
 *
 * Simple RCMD transparent proxy for in-kernel use.  For use with the NAT
 * code.
 */

#define IPF_RCMD_PROXY

typedef struct rcmdinfo {
        u_32_t  rcmd_port;      /* Port number seen */
        u_32_t  rcmd_portseq;   /* Sequence number where port is first seen */
        ipnat_t *rcmd_rule;     /* Template rule for back connection */
} rcmdinfo_t;

void ipf_p_rcmd_main_load(void);
void ipf_p_rcmd_main_unload(void);

int ipf_p_rcmd_init(void);
void ipf_p_rcmd_fini(void);
void ipf_p_rcmd_del(ipf_main_softc_t *, ap_session_t *);
int ipf_p_rcmd_new(void *, fr_info_t *, ap_session_t *, nat_t *);
int ipf_p_rcmd_out(void *, fr_info_t *, ap_session_t *, nat_t *);
int ipf_p_rcmd_in(void *, fr_info_t *, ap_session_t *, nat_t *);
u_short ipf_rcmd_atoi(char *);
int ipf_p_rcmd_portmsg(fr_info_t *, ap_session_t *, nat_t *);

static  frentry_t       rcmdfr;

static  int             rcmd_proxy_init = 0;


/*
 * RCMD application proxy initialization.
 */
void
ipf_p_rcmd_main_load(void)
{
        bzero((char *)&rcmdfr, sizeof(rcmdfr));
        rcmdfr.fr_ref = 1;
        rcmdfr.fr_flags = FR_INQUE|FR_PASS|FR_QUICK|FR_KEEPSTATE;
        MUTEX_INIT(&rcmdfr.fr_lock, "RCMD proxy rule lock");
        rcmd_proxy_init = 1;
}


void
ipf_p_rcmd_main_unload(void)
{
        if (rcmd_proxy_init == 1) {
                MUTEX_DESTROY(&rcmdfr.fr_lock);
                rcmd_proxy_init = 0;
        }
}


/*
 * Setup for a new RCMD proxy.
 */
int
ipf_p_rcmd_new(void *arg, fr_info_t *fin __unused, ap_session_t *aps, nat_t *nat)
{
        tcphdr_t *tcp = (tcphdr_t *)fin->fin_dp;
        rcmdinfo_t *rc;
        ipnat_t *ipn;

        KMALLOC(rc, rcmdinfo_t *);
        if (rc == NULL) {
#ifdef IP_RCMD_PROXY_DEBUG
                printf("ipf_p_rcmd_new:KMALLOCS(%d) failed\n", sizeof(*rc));
#endif
                return (-1);
        }
        aps->aps_sport = tcp->th_sport;
        aps->aps_dport = tcp->th_dport;

        ipn = ipf_proxy_rule_rev(nat);
        if (ipn == NULL) {
                KFREE(rc);
                return (-1);
        }

        aps->aps_data = rc;
        aps->aps_psiz = sizeof(*rc);
        bzero((char *)rc, sizeof(*rc));

        rc->rcmd_rule = ipn;

        return (0);
}


void
ipf_p_rcmd_del(ipf_main_softc_t *softc, ap_session_t *aps)
{
        rcmdinfo_t *rci;

        rci = aps->aps_data;
        if (rci != NULL) {
                rci->rcmd_rule->in_flags |= IPN_DELETE;
                ipf_nat_rule_deref(softc, &rci->rcmd_rule);
        }
}


/*
 * ipf_rcmd_atoi - implement a simple version of atoi
 */
u_short
ipf_rcmd_atoi(char *ptr)
{
        register char *s = ptr, c;
        register u_short i = 0;

        while (((c = *s++) != '\0') && ISDIGIT(c)) {
                i *= 10;
                i += c - '0';
        }
        return (i);
}


int
ipf_p_rcmd_portmsg(fr_info_t *fin, ap_session_t *aps, nat_t *nat)
{
        tcphdr_t *tcp, tcph, *tcp2 = &tcph;
        int off, dlen, nflags, direction;
        ipf_main_softc_t *softc;
        ipf_nat_softc_t *softn;
        char portbuf[8], *s;
        rcmdinfo_t *rc;
        fr_info_t fi;
        u_short sp;
        nat_t *nat2;
#ifdef USE_INET6
        ip6_t *ip6;
#endif
        int tcpsz;
        int slen = 0; /* silence gcc */
        ip_t *ip;
        mb_t *m;

        tcp = (tcphdr_t *)fin->fin_dp;

        m = fin->fin_m;
        ip = fin->fin_ip;
        tcpsz = TCP_OFF(tcp) << 2;
#ifdef USE_INET6
        ip6 = (ip6_t *)fin->fin_ip;
#endif
        softc = fin->fin_main_soft;
        softn = softc->ipf_nat_soft;
        off = (char *)tcp - (char *)ip + tcpsz + fin->fin_ipoff;

        dlen = fin->fin_dlen - tcpsz;
        if (dlen <= 0)
                return (0);

        rc = (rcmdinfo_t *)aps->aps_data;
        if ((rc->rcmd_portseq != 0) &&
            (tcp->th_seq != rc->rcmd_portseq))
                return (0);

        bzero(portbuf, sizeof(portbuf));
        COPYDATA(m, off, MIN(sizeof(portbuf), dlen), portbuf);

        portbuf[sizeof(portbuf) - 1] = '\0';
        s = portbuf;
        sp = ipf_rcmd_atoi(s);
        if (sp == 0) {
#ifdef IP_RCMD_PROXY_DEBUG
                printf("ipf_p_rcmd_portmsg:sp == 0 dlen %d [%s]\n",
                       dlen, portbuf);
#endif
                return (0);
        }

        if (rc->rcmd_port != 0 && sp != rc->rcmd_port) {
#ifdef IP_RCMD_PROXY_DEBUG
                printf("ipf_p_rcmd_portmsg:sp(%d) != rcmd_port(%d)\n",
                       sp, rc->rcmd_port);
#endif
                return (0);
        }

        rc->rcmd_port = sp;
        rc->rcmd_portseq = tcp->th_seq;

        /*
         * Initialise the packet info structure so we can search the NAT
         * table to see if there already is soemthing present that matches
         * up with what we want to add.
         */
        bcopy((char *)fin, (char *)&fi, sizeof(fi));
        fi.fin_flx |= FI_IGNORE;
        fi.fin_data[0] = 0;
        fi.fin_data[1] = sp;
        fi.fin_src6 = nat->nat_ndst6;
        fi.fin_dst6 = nat->nat_nsrc6;

        if (nat->nat_v[0] == 6) {
#ifdef USE_INET6
                if (nat->nat_dir == NAT_OUTBOUND) {
                        nat2 = ipf_nat6_outlookup(&fi, NAT_SEARCH|IPN_TCP,
                                                  nat->nat_pr[1],
                                                  &nat->nat_osrc6.in6,
                                                  &nat->nat_odst6.in6);
                } else {
                        nat2 = ipf_nat6_inlookup(&fi, NAT_SEARCH|IPN_TCP,
                                                 nat->nat_pr[0],
                                                 &nat->nat_osrc6.in6,
                                                 &nat->nat_odst6.in6);
                }
#else
                nat2 = (void *)-1;
#endif
        } else {
                if (nat->nat_dir == NAT_OUTBOUND) {
                        nat2 = ipf_nat_outlookup(&fi, NAT_SEARCH|IPN_TCP,
                                                 nat->nat_pr[1],
                                                 nat->nat_osrcip,
                                                 nat->nat_odstip);
                } else {
                        nat2 = ipf_nat_inlookup(&fi, NAT_SEARCH|IPN_TCP,
                                                nat->nat_pr[0],
                                                nat->nat_osrcip,
                                                nat->nat_odstip);
                }
        }
        if (nat2 != NULL)
                return (APR_ERR(1));

        /*
         * Add skeleton NAT entry for connection which will come
         * back the other way.
         */

        if (nat->nat_v[0] == 6) {
#ifdef USE_INET6
                slen = ip6->ip6_plen;
                ip6->ip6_plen = htons(sizeof(*tcp));
#endif
        } else {
                slen = ip->ip_len;
                ip->ip_len = htons(fin->fin_hlen + sizeof(*tcp));
        }

        /*
         * Fill out the fake TCP header with a few fields that ipfilter
         * considers to be important.
         */
        bzero((char *)tcp2, sizeof(*tcp2));
        tcp2->th_win = htons(8192);
        TCP_OFF_A(tcp2, 5);
        tcp_set_flags(tcp2, TH_SYN);

        fi.fin_dp = (char *)tcp2;
        fi.fin_fr = &rcmdfr;
        fi.fin_dlen = sizeof(*tcp2);
        fi.fin_plen = fi.fin_hlen + sizeof(*tcp2);
        fi.fin_flx &= FI_LOWTTL|FI_FRAG|FI_TCPUDP|FI_OPTIONS|FI_IGNORE;

        if (nat->nat_dir == NAT_OUTBOUND) {
                fi.fin_out = 0;
                direction = NAT_INBOUND;
        } else {
                fi.fin_out = 1;
                direction = NAT_OUTBOUND;
        }
        nflags = SI_W_SPORT|NAT_SLAVE|IPN_TCP;

        MUTEX_ENTER(&softn->ipf_nat_new);
        if (fin->fin_v == 4)
                nat2 = ipf_nat_add(&fi, rc->rcmd_rule, NULL, nflags,
                                   direction);
#ifdef USE_INET6
        else
                nat2 = ipf_nat6_add(&fi, rc->rcmd_rule, NULL, nflags,
                                    direction);
#endif
        MUTEX_EXIT(&softn->ipf_nat_new);

        if (nat2 != NULL) {
                (void) ipf_nat_proto(&fi, nat2, IPN_TCP);
                MUTEX_ENTER(&nat2->nat_lock);
                ipf_nat_update(&fi, nat2);
                MUTEX_EXIT(&nat2->nat_lock);
                fi.fin_ifp = NULL;
                if (nat2->nat_dir == NAT_INBOUND)
                        fi.fin_dst6 = nat->nat_osrc6;
                (void) ipf_state_add(softc, &fi, NULL, SI_W_SPORT);
        }
        if (nat->nat_v[0] == 6) {
#ifdef USE_INET6
                ip6->ip6_plen = slen;
#endif
        } else {
                ip->ip_len = slen;
        }
        if (nat2 == NULL)
                return (APR_ERR(1));
        return (0);
}


int
ipf_p_rcmd_out(void *arg, fr_info_t *fin, ap_session_t *aps, nat_t *nat)
{
        if (nat->nat_dir == NAT_OUTBOUND)
                return (ipf_p_rcmd_portmsg(fin, aps, nat));
        return (0);
}


int
ipf_p_rcmd_in(void *arg, fr_info_t *fin, ap_session_t *aps, nat_t *nat)
{
        if (nat->nat_dir == NAT_INBOUND)
                return (ipf_p_rcmd_portmsg(fin, aps, nat));
        return (0);
}