net/x25/x25_dev.c

   1 // SPDX-License-Identifier: GPL-2.0-or-later
   2 /*
   3  *      X.25 Packet Layer release 002
   4  *
   5  *      This is ALPHA test software. This code may break your machine, randomly fail to work with new
   6  *      releases, misbehave and/or generally screw up. It might even work.
   7  *
   8  *      This code REQUIRES 2.1.15 or higher
   9  *
  10  *      History
  11  *      X.25 001        Jonathan Naylor Started coding.
  12  *      2000-09-04      Henner Eisen    Prevent freeing a dangling skb.
  13  */
  14
  15 #define pr_fmt(fmt) "X25: " fmt
  16
  17 #include <linux/kernel.h>
  18 #include <linux/netdevice.h>
  19 #include <linux/skbuff.h>
  20 #include <linux/slab.h>
  21 #include <net/sock.h>
  22 #include <linux/if_arp.h>
  23 #include <net/x25.h>
  24 #include <net/x25device.h>
  25
  26 static int x25_receive_data(struct sk_buff *skb, struct x25_neigh *nb)
  27 {
  28         struct sock *sk;
  29         unsigned short frametype;
  30         unsigned int lci;
  31
  32         if (!pskb_may_pull(skb, X25_STD_MIN_LEN))
  33                 return 0;
  34
  35         frametype = skb->data[2];
  36         lci = ((skb->data[0] << 8) & 0xF00) + ((skb->data[1] << 0) & 0x0FF);
  37
  38         /*
  39          *      LCI of zero is always for us, and its always a link control
  40          *      frame.
  41          */
  42         if (lci == 0) {
  43                 x25_link_control(skb, nb, frametype);
  44                 return 0;
  45         }
  46
  47         /*
  48          *      Find an existing socket.
  49          */
  50         if ((sk = x25_find_socket(lci, nb)) != NULL) {
  51                 int queued = 1;
  52
  53                 skb_reset_transport_header(skb);
  54                 bh_lock_sock(sk);
  55                 if (!sock_owned_by_user(sk)) {
  56                         queued = x25_process_rx_frame(sk, skb);
  57                 } else {
  58                         queued = !sk_add_backlog(sk, skb, READ_ONCE(sk->sk_rcvbuf));
  59                 }
  60                 bh_unlock_sock(sk);
  61                 sock_put(sk);
  62                 return queued;
  63         }
  64
  65         /*
  66          *      Is is a Call Request ? if so process it.
  67          */
  68         if (frametype == X25_CALL_REQUEST)
  69                 return x25_rx_call_request(skb, nb, lci);
  70
  71         /*
  72          *      Its not a Call Request, nor is it a control frame.
  73          *      Can we forward it?
  74          */
  75
  76         if (x25_forward_data(lci, nb, skb)) {
  77                 if (frametype == X25_CLEAR_CONFIRMATION) {
  78                         x25_clear_forward_by_lci(lci);
  79                 }
  80                 kfree_skb(skb);
  81                 return 1;
  82         }
  83
  84 /*
  85         x25_transmit_clear_request(nb, lci, 0x0D);
  86 */
  87
  88         if (frametype != X25_CLEAR_CONFIRMATION)
  89                 pr_debug("x25_receive_data(): unknown frame type %2x\n",frametype);
  90
  91         return 0;
  92 }
  93
  94 int x25_lapb_receive_frame(struct sk_buff *skb, struct net_device *dev,
  95                            struct packet_type *ptype, struct net_device *orig_dev)
  96 {
  97         struct sk_buff *nskb;
  98         struct x25_neigh *nb;
  99
 100         if (!net_eq(dev_net(dev), &init_net))
 101                 goto drop;
 102
 103         nskb = skb_copy(skb, GFP_ATOMIC);
 104         if (!nskb)
 105                 goto drop;
 106         kfree_skb(skb);
 107         skb = nskb;
 108
 109         /*
 110          * Packet received from unrecognised device, throw it away.
 111          */
 112         nb = x25_get_neigh(dev);
 113         if (!nb) {
 114                 pr_debug("unknown neighbour - %s\n", dev->name);
 115                 goto drop;
 116         }
 117
 118         if (!pskb_may_pull(skb, 1)) {
 119                 x25_neigh_put(nb);
 120                 goto drop;
 121         }
 122
 123         switch (skb->data[0]) {
 124
 125         case X25_IFACE_DATA:
 126                 skb_pull(skb, 1);
 127                 if (x25_receive_data(skb, nb)) {
 128                         x25_neigh_put(nb);
 129                         goto out;
 130                 }
 131                 break;
 132
 133         case X25_IFACE_CONNECT:
 134                 x25_link_established(nb);
 135                 break;
 136
 137         case X25_IFACE_DISCONNECT:
 138                 x25_link_terminated(nb);
 139                 break;
 140         }
 141         x25_neigh_put(nb);
 142 drop:
 143         kfree_skb(skb);
 144 out:
 145         return 0;
 146 }
 147
 148 void x25_establish_link(struct x25_neigh *nb)
 149 {
 150         struct sk_buff *skb;
 151         unsigned char *ptr;
 152
 153         switch (nb->dev->type) {
 154         case ARPHRD_X25:
 155                 if ((skb = alloc_skb(1, GFP_ATOMIC)) == NULL) {
 156                         pr_err("x25_dev: out of memory\n");
 157                         return;
 158                 }
 159                 ptr  = skb_put(skb, 1);
 160                 *ptr = X25_IFACE_CONNECT;
 161                 break;
 162
 163         default:
 164                 return;
 165         }
 166
 167         skb->protocol = htons(ETH_P_X25);
 168         skb->dev      = nb->dev;
 169
 170         dev_queue_xmit(skb);
 171 }
 172
 173 void x25_terminate_link(struct x25_neigh *nb)
 174 {
 175         struct sk_buff *skb;
 176         unsigned char *ptr;
 177
 178         if (nb->dev->type != ARPHRD_X25)
 179                 return;
 180
 181         skb = alloc_skb(1, GFP_ATOMIC);
 182         if (!skb) {
 183                 pr_err("x25_dev: out of memory\n");
 184                 return;
 185         }
 186
 187         ptr  = skb_put(skb, 1);
 188         *ptr = X25_IFACE_DISCONNECT;
 189
 190         skb->protocol = htons(ETH_P_X25);
 191         skb->dev      = nb->dev;
 192         dev_queue_xmit(skb);
 193 }
 194
 195 void x25_send_frame(struct sk_buff *skb, struct x25_neigh *nb)
 196 {
 197         unsigned char *dptr;
 198
 199         skb_reset_network_header(skb);
 200
 201         switch (nb->dev->type) {
 202         case ARPHRD_X25:
 203                 dptr  = skb_push(skb, 1);
 204                 *dptr = X25_IFACE_DATA;
 205                 break;
 206
 207         default:
 208                 kfree_skb(skb);
 209                 return;
 210         }
 211
 212         skb->protocol = htons(ETH_P_X25);
 213         skb->dev      = nb->dev;
 214
 215         dev_queue_xmit(skb);
 216 }