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Linux/net/x25/x25_dev.c

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  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                 return 0;
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 #if IS_ENABLED(CONFIG_LLC)
164         case ARPHRD_ETHER:
165                 return;
166 #endif
167         default:
168                 return;
169         }
170 
171         skb->protocol = htons(ETH_P_X25);
172         skb->dev      = nb->dev;
173 
174         dev_queue_xmit(skb);
175 }
176 
177 void x25_terminate_link(struct x25_neigh *nb)
178 {
179         struct sk_buff *skb;
180         unsigned char *ptr;
181 
182 #if IS_ENABLED(CONFIG_LLC)
183         if (nb->dev->type == ARPHRD_ETHER)
184                 return;
185 #endif
186         if (nb->dev->type != ARPHRD_X25)
187                 return;
188 
189         skb = alloc_skb(1, GFP_ATOMIC);
190         if (!skb) {
191                 pr_err("x25_dev: out of memory\n");
192                 return;
193         }
194 
195         ptr  = skb_put(skb, 1);
196         *ptr = X25_IFACE_DISCONNECT;
197 
198         skb->protocol = htons(ETH_P_X25);
199         skb->dev      = nb->dev;
200         dev_queue_xmit(skb);
201 }
202 
203 void x25_send_frame(struct sk_buff *skb, struct x25_neigh *nb)
204 {
205         unsigned char *dptr;
206 
207         skb_reset_network_header(skb);
208 
209         switch (nb->dev->type) {
210         case ARPHRD_X25:
211                 dptr  = skb_push(skb, 1);
212                 *dptr = X25_IFACE_DATA;
213                 break;
214 
215 #if IS_ENABLED(CONFIG_LLC)
216         case ARPHRD_ETHER:
217                 kfree_skb(skb);
218                 return;
219 #endif
220         default:
221                 kfree_skb(skb);
222                 return;
223         }
224 
225         skb->protocol = htons(ETH_P_X25);
226         skb->dev      = nb->dev;
227 
228         dev_queue_xmit(skb);
229 }
230 

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