/*
 *      X.25 Packet Layer release 002
 *
 *      This is ALPHA test software. This code may break your machine,
 *      randomly fail to work with new releases, misbehave and/or generally
 *      screw up. It might even work.
 *
 *      This code REQUIRES 2.1.15 or higher
 *
 *      This module:
 *              This module is free software; you can redistribute it and/or
 *              modify it under the terms of the GNU General Public License
 *              as published by the Free Software Foundation; either version
 *              2 of the License, or (at your option) any later version.
 *
 *      History
 *      X.25 001        Split from x25_subr.c
 *      mar/20/00       Daniela Squassoni Disabling/enabling of facilities
 *                                        negotiation.
 *      apr/14/05       Shaun Pereira - Allow fast select with no restriction
 *                                      on response.
 */

#define pr_fmt(fmt) "X25: " fmt

#include <linux/kernel.h>
#include <linux/string.h>
#include <linux/skbuff.h>
#include <net/sock.h>
#include <net/x25.h>

/**
 * x25_parse_facilities - Parse facilities from skb into the facilities structs
 *
 * @skb: sk_buff to parse
 * @facilities: Regular facilities, updated as facilities are found
 * @dte_facs: ITU DTE facilities, updated as DTE facilities are found
 * @vc_fac_mask: mask is updated with all facilities found
 *
 * Return codes:
 *  -1 - Parsing error, caller should drop call and clean up
 *   0 - Parse OK, this skb has no facilities
 *  >0 - Parse OK, returns the length of the facilities header
 *
 */
int x25_parse_facilities(struct sk_buff *skb, struct x25_facilities *facilities,
                struct x25_dte_facilities *dte_facs, unsigned long *vc_fac_mask)
{
        unsigned char *p;
        unsigned int len;

        *vc_fac_mask = 0;

        /*
         * The kernel knows which facilities were set on an incoming call but
         * currently this information is not available to userspace.  Here we
         * give userspace who read incoming call facilities 0 length to indicate
         * it wasn't set.
         */
        dte_facs->calling_len = 0;
        dte_facs->called_len = 0;
        memset(dte_facs->called_ae, '\0', sizeof(dte_facs->called_ae));
        memset(dte_facs->calling_ae, '\0', sizeof(dte_facs->calling_ae));

        if (!pskb_may_pull(skb, 1))
                return 0;

        len = skb->data[0];

        if (!pskb_may_pull(skb, 1 + len))
                return -1;

        p = skb->data + 1;

        while (len > 0) {
                switch (*p & X25_FAC_CLASS_MASK) {
                case X25_FAC_CLASS_A:
                        if (len < 2)
                                return -1;
                        switch (*p) {
                        case X25_FAC_REVERSE:
                                if((p[1] & 0x81) == 0x81) {
                                        facilities->reverse = p[1] & 0x81;
                                        *vc_fac_mask |= X25_MASK_REVERSE;
                                        break;
                                }

                                if((p[1] & 0x01) == 0x01) {
                                        facilities->reverse = p[1] & 0x01;
                                        *vc_fac_mask |= X25_MASK_REVERSE;
                                        break;
                                }

                                if((p[1] & 0x80) == 0x80) {
                                        facilities->reverse = p[1] & 0x80;
                                        *vc_fac_mask |= X25_MASK_REVERSE;
                                        break;
                                }

                                if(p[1] == 0x00) {
                                        facilities->reverse
                                                = X25_DEFAULT_REVERSE;
                                        *vc_fac_mask |= X25_MASK_REVERSE;
                                        break;
                                }

                        case X25_FAC_THROUGHPUT:
                                facilities->throughput = p[1];
                                *vc_fac_mask |= X25_MASK_THROUGHPUT;
                                break;
                        case X25_MARKER:
                                break;
                        default:
                                pr_debug("unknown facility "
                                       "%02X, value %02X\n",
                                       p[0], p[1]);
                                break;
                        }
                        p   += 2;
                        len -= 2;
                        break;
                case X25_FAC_CLASS_B:
                        if (len < 3)
                                return -1;
                        switch (*p) {
                        case X25_FAC_PACKET_SIZE:
                                facilities->pacsize_in  = p[1];
                                facilities->pacsize_out = p[2];
                                *vc_fac_mask |= X25_MASK_PACKET_SIZE;
                                break;
                        case X25_FAC_WINDOW_SIZE:
                                facilities->winsize_in  = p[1];
                                facilities->winsize_out = p[2];
                                *vc_fac_mask |= X25_MASK_WINDOW_SIZE;
                                break;
                        default:
                                pr_debug("unknown facility "
                                       "%02X, values %02X, %02X\n",
                                       p[0], p[1], p[2]);
                                break;
                        }
                        p   += 3;
                        len -= 3;
                        break;
                case X25_FAC_CLASS_C:
                        if (len < 4)
                                return -1;
                        pr_debug("unknown facility %02X, "
                               "values %02X, %02X, %02X\n",
                               p[0], p[1], p[2], p[3]);
                        p   += 4;
                        len -= 4;
                        break;
                case X25_FAC_CLASS_D:
                        if (len < p[1] + 2)
                                return -1;
                        switch (*p) {
                        case X25_FAC_CALLING_AE:
                                if (p[1] > X25_MAX_DTE_FACIL_LEN || p[1] <= 1)
                                        return -1;
                                if (p[2] > X25_MAX_AE_LEN)
                                        return -1;
                                dte_facs->calling_len = p[2];
                                memcpy(dte_facs->calling_ae, &p[3], p[1] - 1);
                                *vc_fac_mask |= X25_MASK_CALLING_AE;
                                break;
                        case X25_FAC_CALLED_AE:
                                if (p[1] > X25_MAX_DTE_FACIL_LEN || p[1] <= 1)
                                        return -1;
                                if (p[2] > X25_MAX_AE_LEN)
                                        return -1;
                                dte_facs->called_len = p[2];
                                memcpy(dte_facs->called_ae, &p[3], p[1] - 1);
                                *vc_fac_mask |= X25_MASK_CALLED_AE;
                                break;
                        default:
                                pr_debug("unknown facility %02X,"
                                        "length %d\n", p[0], p[1]);
                                break;
                        }
                        len -= p[1] + 2;
                        p += p[1] + 2;
                        break;
                }
        }

        return p - skb->data;
}

/*
 *      Create a set of facilities.
 */
int x25_create_facilities(unsigned char *buffer,
                struct x25_facilities *facilities,
                struct x25_dte_facilities *dte_facs, unsigned long facil_mask)
{
        unsigned char *p = buffer + 1;
        int len;

        if (!facil_mask) {
                /*
                 * Length of the facilities field in call_req or
                 * call_accept packets
                 */
                buffer[0] = 0;
                len = 1; /* 1 byte for the length field */
                return len;
        }

        if (facilities->reverse && (facil_mask & X25_MASK_REVERSE)) {
                *p++ = X25_FAC_REVERSE;
                *p++ = facilities->reverse;
        }

        if (facilities->throughput && (facil_mask & X25_MASK_THROUGHPUT)) {
                *p++ = X25_FAC_THROUGHPUT;
                *p++ = facilities->throughput;
        }

        if ((facilities->pacsize_in || facilities->pacsize_out) &&
            (facil_mask & X25_MASK_PACKET_SIZE)) {
                *p++ = X25_FAC_PACKET_SIZE;
                *p++ = facilities->pacsize_in ? : facilities->pacsize_out;
                *p++ = facilities->pacsize_out ? : facilities->pacsize_in;
        }

        if ((facilities->winsize_in || facilities->winsize_out) &&
            (facil_mask & X25_MASK_WINDOW_SIZE)) {
                *p++ = X25_FAC_WINDOW_SIZE;
                *p++ = facilities->winsize_in ? : facilities->winsize_out;
                *p++ = facilities->winsize_out ? : facilities->winsize_in;
        }

        if (facil_mask & (X25_MASK_CALLING_AE|X25_MASK_CALLED_AE)) {
                *p++ = X25_MARKER;
                *p++ = X25_DTE_SERVICES;
        }

        if (dte_facs->calling_len && (facil_mask & X25_MASK_CALLING_AE)) {
                unsigned int bytecount = (dte_facs->calling_len + 1) >> 1;
                *p++ = X25_FAC_CALLING_AE;
                *p++ = 1 + bytecount;
                *p++ = dte_facs->calling_len;
                memcpy(p, dte_facs->calling_ae, bytecount);
                p += bytecount;
        }

        if (dte_facs->called_len && (facil_mask & X25_MASK_CALLED_AE)) {
                unsigned int bytecount = (dte_facs->called_len % 2) ?
                dte_facs->called_len / 2 + 1 :
                dte_facs->called_len / 2;
                *p++ = X25_FAC_CALLED_AE;
                *p++ = 1 + bytecount;
                *p++ = dte_facs->called_len;
                memcpy(p, dte_facs->called_ae, bytecount);
                p+=bytecount;
        }

        len       = p - buffer;
        buffer[0] = len - 1;

        return len;
}

/*
 *      Try to reach a compromise on a set of facilities.
 *
 *      The only real problem is with reverse charging.
 */
int x25_negotiate_facilities(struct sk_buff *skb, struct sock *sk,
                struct x25_facilities *new, struct x25_dte_facilities *dte)
{
        struct x25_sock *x25 = x25_sk(sk);
        struct x25_facilities *ours = &x25->facilities;
        struct x25_facilities theirs;
        int len;

        memset(&theirs, 0, sizeof(theirs));
        memcpy(new, ours, sizeof(*new));

        len = x25_parse_facilities(skb, &theirs, dte, &x25->vc_facil_mask);
        if (len < 0)
                return len;

        /*
         *      They want reverse charging, we won't accept it.
         */
        if ((theirs.reverse & 0x01 ) && (ours->reverse & 0x01)) {
                SOCK_DEBUG(sk, "X.25: rejecting reverse charging request\n");
                return -1;
        }

        new->reverse = theirs.reverse;

        if (theirs.throughput) {
                int theirs_in =  theirs.throughput & 0x0f;
                int theirs_out = theirs.throughput & 0xf0;
                int ours_in  = ours->throughput & 0x0f;
                int ours_out = ours->throughput & 0xf0;
                if (!ours_in || theirs_in < ours_in) {
                        SOCK_DEBUG(sk, "X.25: inbound throughput negotiated\n");
                        new->throughput = (new->throughput & 0xf0) | theirs_in;
                }
                if (!ours_out || theirs_out < ours_out) {
                        SOCK_DEBUG(sk,
                                "X.25: outbound throughput negotiated\n");
                        new->throughput = (new->throughput & 0x0f) | theirs_out;
                }
        }

        if (theirs.pacsize_in && theirs.pacsize_out) {
                if (theirs.pacsize_in < ours->pacsize_in) {
                        SOCK_DEBUG(sk, "X.25: packet size inwards negotiated down\n");
                        new->pacsize_in = theirs.pacsize_in;
                }
                if (theirs.pacsize_out < ours->pacsize_out) {
                        SOCK_DEBUG(sk, "X.25: packet size outwards negotiated down\n");
                        new->pacsize_out = theirs.pacsize_out;
                }
        }

        if (theirs.winsize_in && theirs.winsize_out) {
                if (theirs.winsize_in < ours->winsize_in) {
                        SOCK_DEBUG(sk, "X.25: window size inwards negotiated down\n");
                        new->winsize_in = theirs.winsize_in;
                }
                if (theirs.winsize_out < ours->winsize_out) {
                        SOCK_DEBUG(sk, "X.25: window size outwards negotiated down\n");
                        new->winsize_out = theirs.winsize_out;
                }
        }

        return len;
}

/*
 *      Limit values of certain facilities according to the capability of the
 *      currently attached x25 link.
 */
void x25_limit_facilities(struct x25_facilities *facilities,
                          struct x25_neigh *nb)
{

        if (!nb->extended) {
                if (facilities->winsize_in  > 7) {
                        pr_debug("incoming winsize limited to 7\n");
                        facilities->winsize_in = 7;
                }
                if (facilities->winsize_out > 7) {
                        facilities->winsize_out = 7;
                        pr_debug("outgoing winsize limited to 7\n");
                }
        }
}