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Linux/net/x25/x25_dev.c

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  1 /*
  2  *      X.25 Packet Layer release 002
  3  *
  4  *      This is ALPHA test software. This code may break your machine, randomly fail to work with new
  5  *      releases, misbehave and/or generally screw up. It might even work.
  6  *
  7  *      This code REQUIRES 2.1.15 or higher
  8  *
  9  *      This module:
 10  *              This module is free software; you can redistribute it and/or
 11  *              modify it under the terms of the GNU General Public License
 12  *              as published by the Free Software Foundation; either version
 13  *              2 of the License, or (at your option) any later version.
 14  *
 15  *      History
 16  *      X.25 001        Jonathan Naylor Started coding.
 17  *      2000-09-04      Henner Eisen    Prevent freeing a dangling skb.
 18  */
 19 
 20 #define pr_fmt(fmt) "X25: " fmt
 21 
 22 #include <linux/kernel.h>
 23 #include <linux/netdevice.h>
 24 #include <linux/skbuff.h>
 25 #include <linux/slab.h>
 26 #include <net/sock.h>
 27 #include <linux/if_arp.h>
 28 #include <net/x25.h>
 29 #include <net/x25device.h>
 30 
 31 static int x25_receive_data(struct sk_buff *skb, struct x25_neigh *nb)
 32 {
 33         struct sock *sk;
 34         unsigned short frametype;
 35         unsigned int lci;
 36 
 37         if (!pskb_may_pull(skb, X25_STD_MIN_LEN))
 38                 return 0;
 39 
 40         frametype = skb->data[2];
 41         lci = ((skb->data[0] << 8) & 0xF00) + ((skb->data[1] << 0) & 0x0FF);
 42 
 43         /*
 44          *      LCI of zero is always for us, and its always a link control
 45          *      frame.
 46          */
 47         if (lci == 0) {
 48                 x25_link_control(skb, nb, frametype);
 49                 return 0;
 50         }
 51 
 52         /*
 53          *      Find an existing socket.
 54          */
 55         if ((sk = x25_find_socket(lci, nb)) != NULL) {
 56                 int queued = 1;
 57 
 58                 skb_reset_transport_header(skb);
 59                 bh_lock_sock(sk);
 60                 if (!sock_owned_by_user(sk)) {
 61                         queued = x25_process_rx_frame(sk, skb);
 62                 } else {
 63                         queued = !sk_add_backlog(sk, skb, sk->sk_rcvbuf);
 64                 }
 65                 bh_unlock_sock(sk);
 66                 sock_put(sk);
 67                 return queued;
 68         }
 69 
 70         /*
 71          *      Is is a Call Request ? if so process it.
 72          */
 73         if (frametype == X25_CALL_REQUEST)
 74                 return x25_rx_call_request(skb, nb, lci);
 75 
 76         /*
 77          *      Its not a Call Request, nor is it a control frame.
 78          *      Can we forward it?
 79          */
 80 
 81         if (x25_forward_data(lci, nb, skb)) {
 82                 if (frametype == X25_CLEAR_CONFIRMATION) {
 83                         x25_clear_forward_by_lci(lci);
 84                 }
 85                 kfree_skb(skb);
 86                 return 1;
 87         }
 88 
 89 /*
 90         x25_transmit_clear_request(nb, lci, 0x0D);
 91 */
 92 
 93         if (frametype != X25_CLEAR_CONFIRMATION)
 94                 pr_debug("x25_receive_data(): unknown frame type %2x\n",frametype);
 95 
 96         return 0;
 97 }
 98 
 99 int x25_lapb_receive_frame(struct sk_buff *skb, struct net_device *dev,
100                            struct packet_type *ptype, struct net_device *orig_dev)
101 {
102         struct sk_buff *nskb;
103         struct x25_neigh *nb;
104 
105         if (!net_eq(dev_net(dev), &init_net))
106                 goto drop;
107 
108         nskb = skb_copy(skb, GFP_ATOMIC);
109         if (!nskb)
110                 goto drop;
111         kfree_skb(skb);
112         skb = nskb;
113 
114         /*
115          * Packet received from unrecognised device, throw it away.
116          */
117         nb = x25_get_neigh(dev);
118         if (!nb) {
119                 pr_debug("unknown neighbour - %s\n", dev->name);
120                 goto drop;
121         }
122 
123         if (!pskb_may_pull(skb, 1))
124                 return 0;
125 
126         switch (skb->data[0]) {
127 
128         case X25_IFACE_DATA:
129                 skb_pull(skb, 1);
130                 if (x25_receive_data(skb, nb)) {
131                         x25_neigh_put(nb);
132                         goto out;
133                 }
134                 break;
135 
136         case X25_IFACE_CONNECT:
137                 x25_link_established(nb);
138                 break;
139 
140         case X25_IFACE_DISCONNECT:
141                 x25_link_terminated(nb);
142                 break;
143         }
144         x25_neigh_put(nb);
145 drop:
146         kfree_skb(skb);
147 out:
148         return 0;
149 }
150 
151 void x25_establish_link(struct x25_neigh *nb)
152 {
153         struct sk_buff *skb;
154         unsigned char *ptr;
155 
156         switch (nb->dev->type) {
157         case ARPHRD_X25:
158                 if ((skb = alloc_skb(1, GFP_ATOMIC)) == NULL) {
159                         pr_err("x25_dev: out of memory\n");
160                         return;
161                 }
162                 ptr  = skb_put(skb, 1);
163                 *ptr = X25_IFACE_CONNECT;
164                 break;
165 
166 #if IS_ENABLED(CONFIG_LLC)
167         case ARPHRD_ETHER:
168                 return;
169 #endif
170         default:
171                 return;
172         }
173 
174         skb->protocol = htons(ETH_P_X25);
175         skb->dev      = nb->dev;
176 
177         dev_queue_xmit(skb);
178 }
179 
180 void x25_terminate_link(struct x25_neigh *nb)
181 {
182         struct sk_buff *skb;
183         unsigned char *ptr;
184 
185 #if IS_ENABLED(CONFIG_LLC)
186         if (nb->dev->type == ARPHRD_ETHER)
187                 return;
188 #endif
189         if (nb->dev->type != ARPHRD_X25)
190                 return;
191 
192         skb = alloc_skb(1, GFP_ATOMIC);
193         if (!skb) {
194                 pr_err("x25_dev: out of memory\n");
195                 return;
196         }
197 
198         ptr  = skb_put(skb, 1);
199         *ptr = X25_IFACE_DISCONNECT;
200 
201         skb->protocol = htons(ETH_P_X25);
202         skb->dev      = nb->dev;
203         dev_queue_xmit(skb);
204 }
205 
206 void x25_send_frame(struct sk_buff *skb, struct x25_neigh *nb)
207 {
208         unsigned char *dptr;
209 
210         skb_reset_network_header(skb);
211 
212         switch (nb->dev->type) {
213         case ARPHRD_X25:
214                 dptr  = skb_push(skb, 1);
215                 *dptr = X25_IFACE_DATA;
216                 break;
217 
218 #if IS_ENABLED(CONFIG_LLC)
219         case ARPHRD_ETHER:
220                 kfree_skb(skb);
221                 return;
222 #endif
223         default:
224                 kfree_skb(skb);
225                 return;
226         }
227 
228         skb->protocol = htons(ETH_P_X25);
229         skb->dev      = nb->dev;
230 
231         dev_queue_xmit(skb);
232 }
233 

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