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                 return 0;
 120
 121         switch (skb->data[0]) {
 122
 123         case X25_IFACE_DATA:
 124                 skb_pull(skb, 1);
 125                 if (x25_receive_data(skb, nb)) {
 126                         x25_neigh_put(nb);
 127                         goto out;
 128                 }
 129                 break;
 130
 131         case X25_IFACE_CONNECT:
 132                 x25_link_established(nb);
 133                 break;
 134
 135         case X25_IFACE_DISCONNECT:
 136                 x25_link_terminated(nb);
 137                 break;
 138         }
 139         x25_neigh_put(nb);
 140 drop:
 141         kfree_skb(skb);
 142 out:
 143         return 0;
 144 }
 145
 146 void x25_establish_link(struct x25_neigh *nb)
 147 {
 148         struct sk_buff *skb;
 149         unsigned char *ptr;
 150
 151         switch (nb->dev->type) {
 152         case ARPHRD_X25:
 153                 if ((skb = alloc_skb(1, GFP_ATOMIC)) == NULL) {
 154                         pr_err("x25_dev: out of memory\n");
 155                         return;
 156                 }
 157                 ptr  = skb_put(skb, 1);
 158                 *ptr = X25_IFACE_CONNECT;
 159                 break;
 160
 161 #if IS_ENABLED(CONFIG_LLC)
 162         case ARPHRD_ETHER:
 163                 return;
 164 #endif
 165         default:
 166                 return;
 167         }
 168
 169         skb->protocol = htons(ETH_P_X25);
 170         skb->dev      = nb->dev;
 171
 172         dev_queue_xmit(skb);
 173 }
 174
 175 void x25_terminate_link(struct x25_neigh *nb)
 176 {
 177         struct sk_buff *skb;
 178         unsigned char *ptr;
 179
 180 #if IS_ENABLED(CONFIG_LLC)
 181         if (nb->dev->type == ARPHRD_ETHER)
 182                 return;
 183 #endif
 184         if (nb->dev->type != ARPHRD_X25)
 185                 return;
 186
 187         skb = alloc_skb(1, GFP_ATOMIC);
 188         if (!skb) {
 189                 pr_err("x25_dev: out of memory\n");
 190                 return;
 191         }
 192
 193         ptr  = skb_put(skb, 1);
 194         *ptr = X25_IFACE_DISCONNECT;
 195
 196         skb->protocol = htons(ETH_P_X25);
 197         skb->dev      = nb->dev;
 198         dev_queue_xmit(skb);
 199 }
 200
 201 void x25_send_frame(struct sk_buff *skb, struct x25_neigh *nb)
 202 {
 203         unsigned char *dptr;
 204
 205         skb_reset_network_header(skb);
 206
 207         switch (nb->dev->type) {
 208         case ARPHRD_X25:
 209                 dptr  = skb_push(skb, 1);
 210                 *dptr = X25_IFACE_DATA;
 211                 break;
 212
 213 #if IS_ENABLED(CONFIG_LLC)
 214         case ARPHRD_ETHER:
 215                 kfree_skb(skb);
 216                 return;
 217 #endif
 218         default:
 219                 kfree_skb(skb);
 220                 return;
 221         }
 222
 223         skb->protocol = htons(ETH_P_X25);
 224         skb->dev      = nb->dev;
 225
 226         dev_queue_xmit(skb);
 227 }