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