// SPDX-License-Identifier: GPL-2.0-or-later
/*
* 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
*
* 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;
}
/*fall through */
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));
memset(dte, 0, sizeof(*dte));
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");
}
}
}